Food Research International 89 (2016) 90–116

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Food Research International

journal homepage: www.elsevier.com/locate/foodres

Review

Chemical constituents and health effects of sweet potato

Sunan Wang a,b, Shaoping Nie c, Fan Zhu b,⁎
a
Canadian Food and Wine Institute, Niagara College, 135 Taylor Road, Niagara-on-the-Lake, Ontario, Canada L0S 1J0
b
School of Chemical Sciences, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
c
State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang 330047, China

a r t i c l e i n f o a b s t r a c t

Article history: Sweet potatoes are becoming a research focus in recent years due to their unique nutritional and functional prop-
Received 8 July 2016 erties. Bioactive carbohydrates, proteins, lipids, carotenoids, anthocyanins, conjugated phenolic acids, and min-
Received in revised form 20 August 2016 erals represent versatile nutrients in different parts (tubers, leaves, stems, and stalks) of sweet potato. The
Accepted 23 August 2016
unique composition of sweet potato contributes to their various health benefits, such as antioxidative, hepato-
Available online 27 August 2016
protective, antiinflammatory, antitumor, antidiabetic, antimicrobial, antiobesity, antiaging effects. Factors affect-
Keywords:
ing the nutritional composition and bio-functions of sweet potato include the varieties, plant parts, extraction
Sweet potato time and solvents, postharvest storage, and processing. The assays for bio-function evaluation also contribute
Chemical composition to the variations among different studies. This review summarizes the current knowledge of the chemical com-
Functional food position of sweet potato, and their bio-functions studied in vitro and in vivo. Leaves, stems, and stalks of sweet
Health effect potato remain much underutilized on commercial levels. Sweet potato can be further developed as a sustainable
Polyphenol crop for diverse nutritionally enhanced and value-added food products to promote human health.
Crown Copyright © 2016 Published by Elsevier Ltd. All rights reserved.

Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
2. Chemical composition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
2.1. Proximate composition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
2.1.1. Roots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
2.1.2. Leaves and other parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
2.2. Carbohydrates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
2.2.1. Starch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
2.2.2. Monosaccharides and oligosaccharides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
2.2.3. Dietary fiber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
2.3. Protein . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
2.3.1. Roots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
2.3.2. Leaves and other parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
2.4. Lipids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
2.4.1. Roots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
2.4.2. Leaves and other parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
2.5. Minerals and vitamins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
2.5.1. Roots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
2.5.2. Leaves and other underutilized parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
2.6. Phenolic compounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
2.6.1. Total phenolic content . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
2.6.2. Phenolic acids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
2.6.3. Flavonoids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
2.6.4. Anthocyanins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
2.7. Carotenoids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

⁎ Corresponding author.
E-mail address: fzhu5@yahoo.com (F. Zhu).

http://dx.doi.org/10.1016/j.foodres.2016.08.032
0963-9969/Crown Copyright © 2016 Published by Elsevier Ltd. All rights reserved.
 S. Wang et al. / Food Research International 89 (2016) 90–116 91

2.7.1. Roots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

2.7.2. Leaves and other parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
2.8. Undesirable/anti-nutrient components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
2.8.1. Roots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
2.8.2. Leaves and other parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
3. Bioactivities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
3.1. In vitro models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
3.1.1. Antioxidant activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
3.1.2. Antimicrobial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
3.1.3. Resistance to enzyme hydrolysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
3.1.4. Antigenotoxicity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
3.1.5. Antiangiogenesis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
3.1.6. Anticancer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
3.1.7. Antihepatotoxic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
3.1.8. Antiobesity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
3.1.9. Antiinflammatory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
3.2. In vivo models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
3.2.1. Hepatoprotection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
3.2.2. Prevention of damage by exercise-induced oxidative stress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
3.2.3. Antiaging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
3.2.4. Hypoglycemic and antihyperglycemic effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
3.2.5. Inhibitory effect on low-density lipoprotein oxidation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
3.2.6. Regulation of liver lipid profiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
3.2.7. Antitumor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
3.2.8. Immunomodulatory activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
3.2.9. Antiobesity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
3.3. Bioactive synergy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
3.4. Relationships between in vitro and in vivo model systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
3.5. Impact of processing and health concerns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
3.5.1. High-fructose syrup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
3.5.2. Formation of acrylamide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
3.5.3. Pro-angiogenetic components. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
4. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113

1. Introduction Chakraborty, 2015). The main sweet potato producers are China, Indo-
nesia, Vietnam, India, Philippines, and Japan in Asia; Brazil and USA in
Ipomoea batatas, commonly called sweet potato, belongs to the the Americas; and Nigeria, Uganda, Tanzania, Rwanda, Burundi, Mada-
Convolvulaceae family (morning glory). Diverse sweet potato varieties gascar, Angola, and Mozambique in Africa (FAO, 2012). Sweet potato
are widely cultivated between 40°N and 32°S, up to an altitude of is cultivated extensively for its nutritious and health-promoting values
2000 m (and up to 2800 m in equatorial regions) (FAO, 2012). Sweet (FAO, 2012; Lee et al., 2012). It also plays an important role in food se-
potato is ranked the most important food crop after rice, wheat, potato, curity. The world production of sweet potatoes saw a steady drop
maize, and cassava (Shekhar, Mishra, Buragohain, Chakraborty, & from 1993 to 2004, but has been stable for the past decade (Fig. 1).

Fig. 1. World production of sweet potatoes from 1993 to 2014 (FAOSTAT, 2016). Dashed line presents the general trend.
92 S. Wang et al. / Food Research International 89 (2016) 90–116

The production reached over 100 million tonnes in 2014 (FAOSTAT, Gari, Lacto-Pickles) (El Sheikha & Montet, 2014; Panda, Naskar,
2016). Shivakumar, & Ray, 2009), beverages (i.e., nonalcoholic lacto-juices and
Roots, stems, and leaves of sweet potatoes are edible parts with alcoholic wine and beer) (Panda, Panda, ShivaKumar, & Ray, 2009),
varying composition of nutrients, bioactives, non-nutrients, and anti- dairy products (i.e., acidophilus milk, curd and yogurt) (Panda, Naskar,
nutrients. In addition to genetic diversity, variable chemical composi- & Ray, 2006; Perez & Tan, 2006; Mohapatra, Panda, Sahoo, Sivakumar, &
tions of sweet potatoes can also be attributed to the pre- and post-stor- Ray, 2007), major condiments (i.e., red vinegar) (Terahara et al., 2003),
age conditions, extraction and analytic methods applied, and processing and food additives [organic acids (i.e., citric acids) (Bindumole,
parameters (Anastácio & Carvalho, 2013). Sweet potato root starch with Sasikiran, & Balagopalan, 2000) and sugar syrups (i.e., high-fructose
unique physicochemical properties is particularly valued as a functional syrup)] (Johnson, Padmaja, & Moorthy, 2009). The food applications of
food ingredient (Zhu & Wang, 2014). Yellow- and orange-fleshed sweet sweet potato roots have diversified considerably. Sweet potato leaves,
potatoes contain a blend of phenolic acids (i.e., hydroxycinnamic acids) stems, and stalks remain underutilized in food industry. Understanding
and have relatively high levels of carotenoids (i.e., β-carotene). Purple- the chemical composition and health effects of sweet potatoes provides
fleshed sweet potato has high levels of acylated anthocyanins and other a basis for their better utilization and commercialization.
phenolics with antioxidant and anti-inflammatory activities (Grace et Sweet potato starch (Zhu & Wang, 2014) has been recently reviewed
al., 2014). Anthocyanins of purple sweet potatoes possess aromatic acyl- in detail. Bovell-Benjamin (2007) overviewed the studies (prior to
ated glycosyl groups, and exhibit relatively high pH tolerance and ther- 2006) on chemical composition and utilization of sweet potato (mainly
mostability (Kim, Kim, et al., 2012). Sweet potato leaves are a good on starch). Johnson and Pace (2010) summarized the studies (until
source of minerals (K, P, Ca, Mg, Fe, Mn, Cu), dietary fibers, and dietary 2009) on sweet potato leaves. The lack of the latest information on the
antioxidants (Johnson & Pace, 2010; Sun, Mu, Xi, Zhang & Chen, 2014). chemical composition and health benefits hinders the novel application
The concentration of sweet potato leaf polyphenols was 7–9 times as of sweet potatoes (especially commercially underutilized parts) as sus-
much as those of grape seeds (Xi, Mu, & Sun, 2015). tainable foods. Focusing on publications of the recent 5 years (until
Unique chemical constituents enable sweet potatoes to prevent and 2016), this mini-review updates the current knowledge of the chemical
treat a variety of disorders as revealed in vitro and in vivo. Recently re- composition of sweet potatoes, and the health impacts from both in
ported bioactivities included antioxidative (Ahmed, Akter, & Eun, vitro and in vivo studies.
2010a, 2010b; Anastácio & Carvalho, 2013; Chan, Khong, Iqbal, Umar,
& Ismail, 2012; Ding, Ni, & Kokot, 2015; Donado-Pestana, Salgado, 2. Chemical composition
Oliveira Rios, Santos, & Jablonski, 2012; Gan et al., 2012; Grace,
Truong, Truong, Raskin, & Lila, 2015; Grace et al., 2014; Huang et al., 2.1. Proximate composition
2012; Huang et al., 2013; Hu et al., 2016; Islam & Everette, 2012; Jiao,
Yang, Jiang, & Zhai, 2012; Kuan, Thoo, & Siow, 2016; Lee et al., 2012; 2.1.1. Roots
Liao, Lai, Yuan, Hsu, & Chan, 2011; Lim et al., 2013; Maloney, Truong, Carbohydrates are the predominant component of sweet potato
& Allen, 2014; Motsa, Modi, & Mabhaudhi, 2015; Panda, Swain, Singh, roots, which are followed by protein, ash, and fat (Table 1). The starch,
& Ray, 2013; Park et al., 2015; Peng, Li, Guan, & Zhao, 2013; crude fiber, protein, ash, and fat of tubes from 80 sweet potatoes varie-
Rautenbach, Faber, Laurie, & Laurie, 2010; Salawu, Udi, Akindahunsi, ties had ranges of 42.4–77.3, 1.9–6.4, 1.3–9.5, 1.1–4.9, and 0.2–3.0/100 g
Boligon, & Athayde, 2015; Soison et al., 2014; Sun, Mu, Xi, Zhang, et of dry matter, respectively (Oboh, Ologhobo, & Tewe, 1989; Ravindran,
al., 2014; Taira, Taira, Ohmine, & Nagata, 2013; Wang et al., 2012; Wu, Ravindran, Sivakanesan, & Rajaguru, 1995; Ishida et al., 2000; Mei, Mu,
Tsai, Hwang, & Chiu, 2012; Wu et al., 2015; Xi et al., 2015; Xu et al., & Han, 2010; Dincer et al., 2011). Decrease in protein contents occurred
2010; Zhang, Mu, & Sun, 2012; Zhao, Yan, Zhang, & Zhang, 2014; Zhu, in baked sweet potato tubers (but not in boiled tubers) as compared
Cai, Yang, Ke, & Corke, 2010, hepatoprotective (Choi, Hwang, Choi, with fresh tubers. This may be associated with the involvement of pro-
Chung, & Jeong, 2010; Wang et al., 2014; Hwang, Choi, Choi, Chung, & teins in non-enzymatic browning reaction during the thermal process.
Jeong, 2011; Hwang, Choi, Han, et al., 2011; Jung, Shin, Kim, & Kwon,
2015; Zhang, Pan, Jiang, & Mo, 2016), anticancer (Lim et al., 2013; Wu 2.1.2. Leaves and other parts
et al., 2015), antidiabetic (Zhao, Yan, Lu, & Zhang, 2013), and Leaves of 42 sweet potato varieties had higher levels of ash and pro-
antiinflammatory (Wang et al., 2014). Awareness of the relationships tein, when compared with tubers, and had higher levels of dietary fiber
between sweet potato and human health has promoted efforts to in- than stalks and stems (Table 1) (Ishida et al., 2000; Sun, Mu, Xi, Zhang,
crease the levels of certain bioactive constituents in sweet potatoes. Ge- et al., 2014). The contents of carbohydrate, dietary fiber, protein, ash,
netic approaches, such as molecular breeding, hold great potential to and fat of leaves from 42 sweet potato varieties had ranges of 42.0–
increase the antioxidant and specific nutrient concentrations of sweet 61.3, 5.9–14.3, 3.7–31.1, 1.5–14.7, and 0.3–5.3 g/100 g of dry matter, re-
potatoes (Park et al., 2015; Kubow et al., 2016). For example, by control- spectively (Ishida et al., 2000; Sun, Mu, Xi, Zhang, et al., 2014). Accord-
ling either the storage roots-specific SPO1 promoter or the oxidative ing to Ishida et al. (2000), the contents of dietary fiber, protein, ash and
stress-inducible peroxidase anion 2 (SWPA2) promoters, transgenic fat of 2 sweet potato varieties were 2.4–4.6, 0.5–0.7, 0.9–1.7, and 0.1–
IbMYB1 gene, dual-pigmented sweet potatoes were developed 0.3 g/100 g (dry matter), respectively, for stalks; and were 10.4–11.3,
and exhibited increased levels of anthocyanins and flavonoids, and 0.9–1.4, 0.8–1.3, and 0.5–0.6 g/100 g (dry matter), respectively, for
DPPH (1,1-diphenyl-2-picyl-hydrazyl) radical scavenging activity stems (Ishida et al., 2000).
(Park et al., 2015).
Sweet potatoes are versatile ingredients in the food industry. Leaves 2.2. Carbohydrates
of sweet potato are commonly consumed as nutrient-dense and health-
promoting green leafy vegetables (Johnson & Pace, 2010). Roots of 2.2.1. Starch
sweet potato are consumed in a variety of means. Baking, boiling,
dehydrating, and frying represent world-wide cooking methods. Com- 2.2.1.1. Roots
mercially processed sweet potato starches (Zhu & Wang, 2014) and Being a major carbohydrate of sweet potato root, starch accounts for
bioproducts (El Sheikha & Ray, 2015) have been addressed recently. up to approximately 80% of the dry matter. Sweet potato root remains
As shown in Supplementary Table 1, representatives of commercial one of the cheap raw materials for starch industries worldwide. Diversi-
sweet potato-related products fall into a few broad categories, including ty in the composition, granular, and molecular structures of sweet pota-
pasta (i.e., noodles) (Lee, Kim, Lee, & Lim, 2006; Lee, Woo, Lim, Kim, & to starch have been reviewed recently (Zhu & Wang, 2014). In brief,
Lim, 2005; Tan, Gu, Zhou, Wu, & Xie, 2006), pickled vegetables (i.e., amylose content of sweet potato starch varies between 0% and 34.16%
 S. Wang et al. / Food Research International 89 (2016) 90–116 93

among 930 genotypes (Zhu & Wang, 2014). The starch granules are 2001). The structures of the transitory starches in the leaves remain to
round, polygonal, and oval or semi-oval. The granules vary in diameter be explored.
size from 2 to 45 μm. The granules possess either A-type or C-type poly-
morph (a mixture of both A- and B-types). The structural characteristics 2.2.2. Monosaccharides and oligosaccharides
of sweet potato starch have been correlated with physiochemical prop-
erties and applications (Zhu & Wang, 2014). Molecular/physical struc- 2.2.2.1. Roots
tures of sweet potato starches due to genetic diversity remain to be The total sugar content in sweet potato roots (3.8%) was higher than
studied (Zhu & Wang, 2014). For novel properties, native sweet potato that of cassava roots (1.2%) (Johnson et al., 2009). Sucrose, maltose, and
starch has been modified enzymatically (4-α-glucanotransferase), glucose represent predominant free sugars, which result in the sweet
chemically (cross-linking, acid hydrolysis, oxidation, acetylation, taste of sweet potato root. Variety, length of storage, and cooking meth-
hydroxypropylation, hydroxypropylation-acetylation, and od affect the sugar composition of sweet potato (Dincer et al., 2011;
hydroxylpropylation cross-linking), physically (electrolysis, annealing, Laurie et al., 2013). Sweetness in stored and cooked sweet potato is
and heat-moisture treatment) (Zhu & Wang, 2014). due to the hydrolysis of starch to maltose and oligosaccharides by α-
and β-amylases. The activities of α- and β-amylases in roots changed
2.2.1.2. Leaves and other parts during storage and cooking (Morrison, Pressey, & Kays, 1993). The ini-
The circadian regulations of starch synthetic rate or starch accumu- tial sugar concentration in fresh roots (depending on the cultivars)
lation were observed in sweet potato leaves (Wang, Yeh, & Tsai, and starch hydrolytic activity (depending on the α- and β-amylase

Fig. 2. Representative chemical compounds of sweet potatoes. (A) Ipomotaosides 1, 2, 3, and 4 in ethyl acetate extract of the aerial parts of sweet potato cultivated in Japan (Yoshikawa et
al., 2010). Deca, dodca, and cin refer to n-decanoic, n-dodecanoic, and trans-cinnamic acids, respectively. (B) Five colourless caffeoyl compounds in purple sweet potato (Zhao et al., 2014).
(C) Cyanidin 3-caffeoyl sophoroside-5-glucoside, peonidin 3-caffeoyl sophoroside-5 glucoside, and pelargonidin 3-dicaffeoyl sophoroside-5 glucoside in purple-fleshed sweet potatoes
identified by HPLC-DAD and HPLC-ESI-QTOF-MS/MS (Lee et al., 2013). Reprinted with permissions from the publishers.
94 S. Wang et al. / Food Research International 89 (2016) 90–116

Fig. 2 (continued).

activities) determined the sweetness of the final products (e.g., baked followed by glucose (2.7–4.7 mg/g of dry weight), fructose (1.4–
roots) (Morrison et al., 1993). Of the fresh roots of 3 varieties, the con- 4.0 mg/g of dry weight), and non-detectable maltose (Dincer et al.,
tent of sucrose was the highest (56.9–60.0 mg/g of dry weight), 2011). Maltose became the second predominant sugar in the cooked

Table 1
Proximate composition of various parts of sweet potato.

Number of Moisture Ash Crude protein Crude fat Carbohydrate Dietary fiber Reference
Plant parts cultivars (g/100 g, DM) (g/100 g, DM) (g/100 g, DM) (g/100 g, DM) (g/100 g, DM) (g/100 g, DM)

Root 49 63.2–82.2 3.6–4.9 1.4–9.5 0.3–3.0 ether extractable N/A 3.5–6.4 crude fiber Oboh et al. (1989)
16 62.8–69.4 2.4–4.2 3.2–7.2 1.1–2.1 63.1–77.3 1.9–3.5 crude fiber Ravindran et al. (1995)
2 69.9–70.9 1.1–1.4 1.3–2.1 0.2–0.3 21.9–25.1sugar 7.6–11.8 Ishida et al. (2000)
10 N/A 1.6–3.0 3.4–6.1 0.2–0.6 42.4–60.9 starch 17.2–26.6 Mei et al. (2010)
3 66.2–68.9 2.1–2.5 4.3–5.1 N/A 63.9–64.9 starch 2.3–2.7 crude fiber Dincer et al. (2011)
3boiled 62.3–67.0 2.2–2.6 4.7–5.0 N/A 49.2–57.4 starch 2.5–2.8 crude fiber Dincer et al. (2011)
3baked 59.4–63.5 2.3–2.6 3.5–4.6 N/A 55.8–60.2 starch 2.1–2.7 crude fiber Dincer et al. (2011)
Leaf 2 84.9–69.9 1.5–1.9 3.7–3.8 0.3–1.0 0.9–2.0sugar 5.9–6.9 Ishida et al. (2000)
40 84.1–88.9 7.4–14.7 16.7–31.1 2.1–5.3 42.0–61.3 9.2–14.3 Sun, Mu, Xi, Zhang and Chen (2014)
Stalk 2 88.9–94.4 0.9–1.7 0.5–0.7 0.1–0.3 0.9–4.5sugar 2.4–4.6 Ishida et al. (2000)
Stem 2 79.2–83.7 0.8–1.3 0.9–1.4 0.5–0.6 3.2–6.7sugar 10.4–11.3 Ishida et al. (2000)
 S. Wang et al. / Food Research International 89 (2016) 90–116 95

(1) (2) (3)

Fig. 3. Sweet potato varieties (1) white-fleshed cultivar Yulmi, (2) orange-fleshed cultivar Juhwangmi, and (3) purple-fleshed cultivar Sinjami (Park et al., 2016). Reprinted with
permission from the publisher.

sweet potatoes (Mei et al., 2010; Dincer et al., 2011). The maltose con- fiber content was 2.7 g/100 g fresh weight for 18 varieties (Huang,
tent was correlated with the sweetness of cooked sweet potato Picha, Kilili, & Johnson, 1999) and 19.9% (residue of starch extraction)
(Laurie et al., 2013). For boiled roots, the contents of sucrose, glucose, for 2 varieties (Salvador, Suganuma, Kitahara, Tanoue, & Ichiki, 2000).
fructose, and maltose of 3 varieties had ranges of 49.0–61.5, 1.3–3.9, The non-starch polysaccharides, including cellulose, lignin, hemicellu-
2.0–3.8, and 48.1–122.8 mg/g of dry weight, respectively. For baked lose, and pectin contribute towards the dietary fiber fractions of sweet
roots, the contents of sucrose, glucose, fructose, and maltose of 3 varie- potato roots. Average contents of cellulose (31.2%), lignin (16.9%), pec-
ties had ranges of 55.6–64.3, 1.7–4.9, 1.2–3.4 and 48.5–56.2 mg/g, dry tin (15.7%), and hemicellulose (11.3%) were measured in 10 varieties
weight, respectively (Dincer et al., 2011). The content of reducing sugars (Mei et al., 2010). Averages of cellulose (40.1%) and hemicellulose
in different sweet potato flour ranged from 1.2% to 24.4% of dry weight (9.7%) were found in another 2 varieties (Salvador et al., 2000). The
(Van Hal, 2000). In fresh orange sweet potato (Covington), total reduc- cell wall material of sweet potato root had the highest amount of the
ing sugar (a sum of glucose and fructose) accounts for 3.2% (Truong et pectin fraction and consequently the highest galacturonic acid content
al., 2014). Glucose and fructose are the most abundant reducing sugars (Salvador et al., 2000). Monosaccharides of dietary fiber from 10 varie-
in raw sweet potato roots (Mei et al., 2010). ties of sweet potato residues were rhamnose (1.4%–2.5%), arabinose
The increase in maltose content of cooked sweet potato was associ- (2.9%–4.3%), galactose (7.5%–14.2%), glucose (46.7%–65.7%), xylose
ated with the hydrolysis of starch (Waramboi, Dennien, Gidley, & (2.6%–4.1%), mannose (0.5%–2.1%), and two uronic acids (14.8%–
Sopade, 2011). Liquefaction and saccharification of sweet potato starch 34.7%) (galacturonic and glucuronic acids) (Mei et al., 2010). Dietary fi-
have been employed for the production of glucose and high-fructose bers of 10 sweet potato varieties differed in swelling, water-holding, oil-
syrup (a sweetener that is twice as sweet as glucose) for the food and holding, and glucose absorption capacities due to the differences in
beverage industries (Johnson et al., 2009; Johnson, Moorthy, & chemical composition (ratios of cellulose, pectin, hemicellulose, and
Padmaja, 2010; Dominque, Gichuhi, Rangari, & Bovell-Benjamin, lignin) to form different cross-linked structures (Mei et al., 2010).
2013). The fructose yield depended on the glucose content prior to
isomerization, and in turn was dependent on the initial starch content 2.2.3.2. Leaves and other parts
of sweet potato (Johnson et al., 2009). The level of dietary fiber in sweet potato leaves was approximately
3.2 and 1.3 times higher than those in the stems and stalks, respectively
2.2.2.2. Leaves and other parts (Ishida et al., 2000). Dietary fiber contents of dried leaves from sweet
Sucrose from sweet potato leaves functions as a stimulator for the potatoes cultivated in Japan and Africa were on average of 6% (Ishida
transcription of starch granule-bound starch synthase I gene (Wang et et al., 2000) and 38% (Mosha, Pace, Adeyeye, Mtebe, & Laswai, 1995), re-
al., 2001). Galactose in sweet potato leaves is a sugar component of ga- spectively. The crude fibers in leaves from 40 varieties grown in China
lactolipids (Napolitano, Carbone, Saggese, Takagaki, & Pizza, 2007). The ranged from 9.2 to 14.3 g/100 g (dry weight) (Sun, Mu, Xi, Zhang, et
monogalactosyldiacylglycerol and digalactosyldiacylglycerol fractions al., 2014). Total dietary fiber content ranged from 9.4% to 19.2% of the
of the galactolipids contribute to the formation of polyunsaturated es- fresh weight of sweet potato leaves (Almazan & Zhou, 1995). The phys-
sential fatty acids in sweet potato leaves (Napolitano et al., 2007). icochemical properties and food uses of dietary fibers in leaves remain
Four ipomotaosides (Fig. 2A) (resin glycosides) were found in ethyl to be studied. Obviously, sweet potato stems and stalks are
acetate extract of the aerial parts of sweet potato cultivated in Japan underutilized sources of dietary fibers.
(Yoshikawa et al., 2010). These ipomotaosides derived from the aerial
parts of sweet potato were anti-inflammatory against cyclooxygenase 2.3. Protein
(COX)-1 and -2 in vitro using COX-1- and COX-2-catalyzed prostaglan-
din biosynthesis assay (Yoshikawa et al., 2010). 2.3.1. Roots
Sporamins (sporamins A and B), being the major storage proteins in
2.2.3. Dietary fiber sweet potato roots, account for approximately 60%–80% of the total pro-
tein. Sporamin A N-terminal sequence was Ser-Glu-Thr-Pro-Val.
2.2.3.1. Roots Sprouting decreased the total soluble protein and sporamin levels in
The dietary fiber contents in sweet potato cultivars are variable, de- whole, outer, and inner flesh of sweet potato roots (Chen, Lai, Hung, &
pending on the genetics and growing conditions of the crops as well as Liu, 2013). Asparaginyl endopeptidase SPAE and papain-like cysteine
the analytical methods (sieving or enzymatic method). Using the siev- protease SPCP2 are possibly involved in the degradation of sporamin
ing method, the average content of dietary fiber in sweet potato resi- (Chen et al., 2013).
dues (after starch extraction) of 10 varieties was 75.2% (Mei et al., Sporamins resist the actions of digestive enzymes (pepsin, trypsin,
2010). Using the enzymatic–gravimetric method, the average dietary and chymotrypsin) (Maloney et al., 2014), stabilize emulsifiers (Guo &
96 S. Wang et al. / Food Research International 89 (2016) 90–116

Mu, 2011), and are antioxidative (Zhang, Mu, & Sun, 2014). Sporamins were anti-inflammatory and had a higher bioavailability than free
from outer peels and the extract of white-skinned Caiapo sweet potato fatty acids (Christensen, 2009).
were more resistant to pepsin digestion than sporamin from blanched In sweet potato leaves of 4 chilling-tolerant genotypes, the fatty acid
peels of orange sweet potatoes (Maloney et al., 2014). Moist heat treat- components in the glycolipids included linolenic (18:3, 47%–58%),
ment at temperatures above 80 °C eliminated trypsin inhibitors in palmitic (16:0, 23%–29%), linoleic (18:2, 12%–17%), stearic (18:0, 2%–
sweet potatoes (Zhang & Corke, 2001). The emulsifying property of 6%), and oleic (18:1, 0%–2%) acids (Garner et al., 2012). The fatty acid
sweet potato was the result of intermolecular disulfide linkage between components of phospholipid fraction of the leaves included palmitic
saporamin A, saporamin B, and some high-molecular-weight aggrega- (16:0, 41%–45%), linoleic (18:2, 20%–26%), linolenic (18:3, 19%–29%),
tions at the oil–water interface (Guo & Mu, 2011). Sweet potato pro- stearic (18:0, 3%–7%), and oleic (18:1, 1%–5%) acids (Garner et al.,
tein-stabilized emulsions represent shear-thinning non-Newtonian 2012). Linoleic, α-linolenic acids, and β-sitosterol are also present in
fluids (Mu, Tan, Chen, & Xue, 2009). sweet potato leaves (Johnson & Pace, 2010).
With aims to obtain better quality sweet potato protein isolates/con-
centrates, some studies worked on the protein extraction and the im- 2.5. Minerals and vitamins
pact of anti-browning agents on sweet potato protein solubility and
recovery (Mu et al., 2009; Arogundade & Mu, 2012). 2.5.1. Roots
According to Arogundade and Mu (2012), ultrafiltration/ Contents of minerals Ca, P, Fe, Na, K, Mg, Zn, Cu in 2 sweet potato
diafiltration-processed sweet potato protein (at pH 4, 6, and 7) was su- roots had ranges of 68.0–73.3, 40.0–42.7, 1.64–2.27, 22.3–26.6, 235–
perior to isoelectrically precipitated sweet potato protein (at pH 4). The 502, 26.7–27.0 (mg/100 g), 249–389, and 152–304 μg/100 g, respective-
former gave a better yield, purity, solubility, and thermal stability. Iso- ly (Ishida et al., 2000). Except for Na, contents of Ca, Fe, K, Mg, Zn, and Cu
leucine, valine, methionine, cysteine, phenylalanine, and tyrosine repre- in sweet potato roots were lower than that those of sweet potato leaves
sent the major amino acids of the root protein (Arogundade & Mu, (Ishida et al., 2000; Sun, Mu, Xi, Zhang, et al., 2014). Roots of 2 sweet po-
2012). tato varieties contained β-carotene (273–400 μg/100 g), vitamins B1
Acidic glycoprotein (22 kDa) and arabinogalactan protein (53–128 μg/100 g), B2 (248–254 μg/100 g), B6 (120–329 μg/100 g), ni-
(126.8 kDa) from Caiapo powder (a protein extract from a white- acin (856–1498 μg/100 g), pantotenic acid (320–660 μg/100 g), biotin
skinned sweet potato cultivar) were antidiabetic in vivo (Kusano, (3–8 μg/100 g), and vitamins C (62.7–81 mg/100 g) and E (1.39–
Tamasu, & Nakatsugawa, 2005; Ludvik, Hanefeld, & Pacini, 2008; 2.84 mg/100 g) (Ishida et al., 2000).
Ozaki, Oki, Suzuki, & Kitamura, 2010). In sweet potato roots, 20S protea-
some was involved in the regulation catalytic activity of plastidial starch 2.5.2. Leaves and other underutilized parts
phosphorylase (Pho1), which is associated with starch biosynthesis (Lin Sweet potato leaves contained essential minerals of Fe, Ca, and Mg
et al., 2012). Invertase inhibitors (10 and 22 kDa) in sweet potato roots and the essential trace elements of Cr, Co, Ni, Cu, and Zn (Taira et al.,
had lectin-like properties, which were antimicrobial (Huang, Sheu, 2013). The minerals presented in sweet potato leaves of 40 varieties in-
Chang, Lu, Chang, Huang & Lin, 2008). The contents of protein 3-hy- cluded macro-elements K (the highest), Ca, P, Mg, and Na with ranges of
droxy-3-methylglutaryl coenzyme A reductase (HMGR) in sweet potato 479.3–4280.6, 229.7–1958.1, 131.1–2639.8, 220.2–910.5, and 8.06–
root with cutting and fungal infection were much higher than that in the 832.31 mg/100 g DW, respectively, while the micro-elements Fe, Mn,
fresh sweet potato root (Kondo, Uritani, & Oba, 2003). Zn, and Cu had ranges of 1.9–21.8, 1.7–10.9, 1.2–3.2, and 0.7–1.9 mg/
100 g DW, respectively (Sun, Mu, Xi, Zhang, et al., 2014). Increasing cer-
2.3.2. Leaves and other parts tain mineral components of sweet potato leaves can be achieved by cul-
Proteins (10 and 22 kDa) in sweet potato leaves possessed antimi- tivar selection (Sun, Mu, Xi, Zhang, et al., 2014). Among 40 sweet potato
crobial properties (Wang, Wu, Chang, & Sung, 2003). Antidiabetic pro- varieties, the cultivar Jishu had the highest K (4280.6 mg/100 g DW). A
teins (22 and 58 kDa) found in Caiapo powder (Kusano, Abe, & high K content is critically important to prevent hypokalemia stimulat-
Tamura, 2001) were also detected in a peel mixture of three orange- ed cardiac arrhythmias and acute respiratory failure (Sun, Mu, Xi,
fleshed sweet potato cultivars (Beauregard, Jewel, and Covington) Zhang, et al., 2014). Leaves of 2 sweet potato varieties contained β-car-
(Maloney, Truong, & Allen, 2012). Peel protein functions as a trypsin in- otene (273–400 μg/100 g), vitamins B1 (53–128 μg/100 g), B2 (248–
hibitor. Mixing blanched peels with 59.7 mL of NaCl (0.025 mM per 254 μg/100 g), B6 (120–329 μg/100 g), niacin (856–1498 μg/100 g),
gram peel) before precipitating with CaCl2 (6.8 mM) was recommended pantotenic acid (320–660 μg/100 g), biotin (3–8 μg/100 g), and vitamins
for effectively extracting protein from sweet potato peels with maxi- C (62.7–81 mg/100 g) and E (1.39–2.84 mg/100 g). Compared with
mum protein solubility and minimum solvent usage (Maloney et al., stems and stalks, leaves had higher contents of β-carotene, vitamins
2012). B2, C and E, and biotin (Ishida et al., 2000).

2.4. Lipids 2.6. Phenolic compounds

2.4.1. Roots 2.6.1. Total phenolic content

There is a small amount of lipids associated with root starch (e.g.,
0.12%) (Deng, Mu, Zhang, & Abegunde, 2013). The starch's physico- 2.6.1.1. Roots
chemical properties may be affected by the presence of these lipids The total phenolic content (TPC) of flour from roots has been much
(Zhu & Wang, 2014). reported, including 10.68–15.69 g gallic acid equivalent (GAE)/100 g
(DW) for maltodextrin and α-amylase-treated purple sweet potato
2.4.2. Leaves and other parts flour (Ahmed et al., 2010a), 13.78–57.23 g GAE/100 g (DW) for encap-
The crude fat content ranged between 2.08 and 5.28 g/100 g dry sulated and non-encapsulated flours (Ahmed et al., 2010b), and 14.9–
leaves from 40 sweet potato cultivars (Sun, Mu, Xi, Zhang, et al., 36.2 g GAE/100 g (DW) for steamed sweet potato flours (Rumbaoa,
2014). From the leaves of sweet potatoes cultivated in Japan, 26 galacto- Cornago, & Geronimo, 2009).
lipids identified by Napolitano et al. (2007) are comprised of
monogalactosyldiacylglycerols (MGDG) and digalactosyldiacylglycerol 2.6.1.2. Leaves and other parts
(DGDG). Fatty acids (C16:0, C18:0, C18:1, C18:2, C18:3, and C19:2) The TPC of leaves of 8 sweet potato varieties from Japan ranged from
were attached to the two carbons of the glycerol galactolipid backbones 6.3 to 13.5 g/100 g GAE (DW) (Nagai et al., 2011). The TPC of leaves of
(Napolitano et al., 2007; Garner, Izekor, & Islam, 2012). Galactolipids 116 sweet potato varieties cultivated in China ranged from 8.94 to
 S. Wang et al. / Food Research International 89 (2016) 90–116 97

Table 2
Phytochemicals and antioxidants in various parts of sweet potato.

Plant parts
(No.) Parameters postharvest storage
Country origin and extraction Phytochemical composition Antioxidant capacities Reference

Root Storage 10 °C, 85% RH Total phenolic content DPPH [IC50 (mg/mL) of sample] Dincer et al. (2011)
(3) Cooked Boiled, baked (mg gallic acid/g, DW)
Turkey Drying Freeze-dried
⋅ Raw: 92.0–132.3
Method No
⋅ Fresh: 0.9–1.0 ⋅ Boiled: 74.1–88.2
Acidified No
⋅ Boiled: 3.4–4.2 ⋅ Baked: 62.2–86.3
Time 10 h
⋅ Baked: 3.0–3.8
Temperature 80 °C
β-carotene content (mg/100 g, DW)
Solvent 80% methanol

⋅ Fresh: 5.6–128.5
⋅ Boiled: 3.3–12.6
⋅ Baked: 1.2–10.1

Root Storage 5 °C, 40 days Total phenolic content (mg gallic DPPH (mM trolox equivalents/100 g, DW) Donado-Pestana et al.
(4) Cooked Boiled, roasted, steamed, or acid/g, DW) (2012)
Orange-fresh flour processed
⋅ Raw: 12.8–19.5
Brazil Drying Freeze-dried
⋅ Fresh: 1.30–1.93 ⋅ Boiled: 10.3–14.0
Method No
⋅ Boiled: 1.33–2.05 ⋅ Roasted: 9.8–12.5
Acidified No
⋅ Roasted: 1.07–1.70 ⋅ Steamed: 7.8–13.8
Time No
⋅ Steamed: 1.05–1.56 ⋅ Flour: 2.5–7.5
Temperature No
⋅ Flour: 0.96–1.77
Solvent 100% acetone
ABTS (M trolox equivalents/100 g, DW)
(for carotenoid extract)
Total trans-β carotene (mg/100 g,
100% ethanol
DW)
(for phenolic extract) ⋅ Raw: 16.0–18.8
⋅ Boiled: 13.5–16.5
⋅ Fresh: 79.1–128.5 ⋅ Roasted: 8.5–14.3
⋅ Boiled: 68.9–133.3 ⋅ Steamed: 8.8–13.5
⋅ Roasted: 64.6–127.0 ⋅ Flour: 5.3–14.5
⋅ Steamed: 69.4–131.0
⋅ Flour: 45.4–79.7

Root Storage Sliced, 4 °C, 3 days Total phenolic content (mg gallic ABTS (μmol trolox equivalents/100 g, Kuan et al. (2016)
(3) Cooked No acid/100 g, DW) DW)
Orange, Yellow, Drying Convection, 55 °C, 3 h
Purple Vacuum, 55 °C, 6 h
⋅ Fresh: 138.2–757.4 ⋅ Fresh: 1586.0–3014.4
Japan Method No
⋅ Convention: 56.5–348.7 ⋅ Convention: 100.4–334.3
Acidified Yes
⋅ Vacuum: 139.0–255.0 ⋅ Vacuum: 371.4–1924.0
Time No
Temperature No
β-carotene content (mg/100 g, DW)
Solvent 2% citric acid solution
(for phenolic extract)
Hexane:acetone (7:3) ⋅ Fresh: 12.0–121.6
(for β-carotene extract) ⋅ Convention: 12.4–121.3
Hydrochloric acid ⋅ Vacuum:12.4–127.3
(37%):methanol (15:85)
(for anthocyanin extract) Anthocyanin content (mg/100 g,
DW)

⋅ Fresh: 0–57.9
⋅ Convention: 0–5.7
⋅ Vacuum: 0–8.1

Leaf Storage No Total phenolic content (mg gallic Not applicable Carvalho et al. (2010)
(1) Cooked No acid/100 g, FW)
Portugal Drying Hot air Photoperiods (10–30 days)
Method Stirring
⋅ Short day: 4.94–5.76
Acidified No
⋅ Long day: 8.63–25.0
Time 24 h
Temperature No
Solvent 100% methanol

Leaf Storage No Total phenolic content (mg gallic Hydrophilic-ORAC (μmol trolox/g, FW) Isabelle et al. (2010)
(2) Cooked No acid/g, FW)
Malaysia, Vietnam Drying Freeze
⋅ 16.37–67.29
Method Sonication
⋅ 0.59–3.57
Acidified Yes
Time 0.25 h
Temperature 37–39 °C
Solvent 70% acetone

Leaf Storage No Total phenolic content (mg gallic DPPH [EC50 (mg/mL) of sample] Liao et al. (2011)
(4) Cooked No acid/g sample)
Taiwan Drying Air-dried

(continued on next page)

98 S. Wang et al. / Food Research International 89 (2016) 90–116

Table 2 (continued)

Plant parts
(No.) Parameters postharvest storage
Country origin and extraction Phytochemical composition Antioxidant capacities Reference

Method Boiling ⋅ 28.1–130 ⋅ 0.11–0.41

Acidified No Total flavonoid content (mg Reducing power [EC50 (mg/mL) of
Time 0.33 h quercetin/g sample) sample]
Temperature 100 °C
Solvent 100% water
⋅ 18.0–72.7 ⋅ 0.27–0.47
Superoxide radical [EC50 (mg/mL) of
sample]

⋅ 0.10–0.61
Iron-chelating activity

⋅ 3.9–12.6% (0.125 mg/mL)

⋅ 10.1–23.3% (0.5 mg/mL)
⋅ 14.9–22.0% (1.0 mg/mL)

Leaf Storage Not applicable Total phenolic content (mg DPPH (mM ascorbic acid equivalents/mg) Nagai et al. (2011)
(8) Cooked Not applicable chlorogenic acid/100 g, DW)
Japan Drying Freeze-dried
⋅ 4.3–8.1
Method Stirring
⋅ 6.3–13.5
Acidified No
LDL oxidizability (lag time assay, min)
Time 1h
Temperature Ambient
Solvent 70% methanol ⋅ 22–114

Leaf Storage 48 h, 10 °C, 95% RH Total phenolic content (mg gallic Total antioxidant activity (mg ascorbic acid Anastácio and Carvalho
(1) Cooked No acid/100 g, DW) equivalents/100 g, DW) (2013)
Portugal Drying Hot air
Method Stirring
⋅ Acidified:1.20–1.32 ⋅ Acidified:1.64–2.83
Acidified With and without
⋅ Non-acidified:1.18–1.30 ⋅ Non-acidified:1.06–1.45
Time 24, 48, 72 h
Temperature 37 °C
Total flavonoid content (mg Reducing power (mg gallic acid/100 g,
Solvent 80% methanol
quercetin/g sample) DW)

⋅ Acidified: 0.52–0.56 ⋅ Acidified: 63.0–89.2

⋅ Non-acidified: 0.56–0.66 ⋅ Non-acidified: 1.06–1.45

FRAP (mM trolox equivalents/g, DW)

⋅ Acidified: 29.7–32.0
⋅ Non-acidified: 27.0–29.3

DPPH (mM trolox equivalents/g, DW)

⋅ Acidified: 23.2–58.8
⋅ Non-acidified: 7.9–36.7

Leaf Storage No Total phenolic content (mg Free radical scavenging (mg ascorbic acid Sun, Mu, Xi, Zhang and
(40) Cooked No chlorogenic acid/100 g, DW) equivalents/mg, DW) Chen (2014)
China Drying Freeze-dried
Method No
⋅ 2.73–12.46 ⋅ 0.08–0.82
Acidified No
Time 0.5 h
Temperature 50 °C
Solvent 70% ethanol

Tip Storage −40 °C until analysis Individual phenolic content (mg/g DPPH (10–50 mg/mL) (100% scavenging Cui et al. (2011)
(1) Cooked Fermented, boiled, steamed DW) ability)
15 cm from the Drying Freeze-dried Chlorogenic acid
growing end Method Sonication
⋅ Untreated: 60–90%
China Acidified Yes
⋅ Untreated: 2.34 ⋅ Steamed: 60–90%
Time 0.5 h
⋅ Steamed: 7.99 ⋅ Boiled: 60–90%
Temperature No
⋅ Boiled: 5.16 ⋅ Fermented: 10–60%
Solvent 80% ethanol
⋅ Fermented: 0.09 FRAP (mmol/100 g, DW)
Quercetin

⋅ Untreated: not detected ⋅ Untreated: 22.7

⋅ Steamed: not detected ⋅ Steamed: 27.5
⋅ Boiled: not detected ⋅ Boiled: 30
⋅ Fermented: 0.89 ⋅ Fermented:15
Rutin

⋅ Untreated: 0.24
⋅ Steamed: 0.48
 S. Wang et al. / Food Research International 89 (2016) 90–116 99

Table 2 (continued)

Plant parts
(No.) Parameters postharvest storage
Country origin and extraction Phytochemical composition Antioxidant capacities Reference

⋅ Boiled: 0.46
⋅ Fermented: 0.26
Stem Storage 48 h, 10 °C, 95% RH Total phenolic content (mg gallic Total antioxidant activity (mg ascorbic acid Anastácio and Carvalho
15–38 cm of Cooked No acid/100 g, DW) equivalents/100 g, DW) (2013)
bottom section Drying Hot air
Portugal Method Stirring
⋅ Acidified: 0.42–0.47 ⋅ Acidified: 1.63–2.70
Acidified Yes/No
⋅ Non-acidified: 0.57–0.60 ⋅ Non-acidified: 1.08–1.35
Time 24, 48, 72 h
Total flavonoid content (mg Reducing power (mg gallic acid/100 g,
Temperature 37 °C
quercetin/g sample) DW)
Solvent 80% methanol

⋅ Acidified: 0.064–0.068 ⋅ Acidified: 28.8–35.3

⋅ Non-acidified: 0.050–0.068 ⋅ Non-acidified: 37.0–39.6
FRAP (mM trolox equivalents/g, DW)

⋅ Acidified: 13.5–16.2
⋅ Non-acidified: 17.6–18.3
DPPH (mM trolox equivalents/g, DW)

⋅ Acidified: 23.7–62.4
⋅ Non-acidified: 9.1–38.3

ABTS: 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid); DPPH: 1,1-diphenyl-2-picryl-hydrazyl; DW: dry weight; FW: fresh weight; FRAP: ferric reducing antioxidant power; EC50
(or IC50): concentration providing 50% inhibition; No.: number of cultivars; ORAC: oxygen radical absorbance capacity; RH: relative humidity.

27.33 mg chlorogenic acid equivalent (CHAE)/g DW (Xu et al., 2010). sweet potato (Sinjami, 579.5 μg/ g) ranked the highest, followed
The leaf TPC of 5 sweet potato varieties cultivated in Fiji ranged from by orange-fleshed (Juhwangmi, 127.12 μg/ g) and white-fleshed
2.4 to 2.8 g GAE/100 g (DW). Among various polyphenols, quercetin (Yulmi, 45.41 μg/ g) varieties (Fig. 3) (Park et al., 2016). Four flavo-
contents of 5 varieties were 0.4–0.9 g/100 g of DM (Lako et al., 2007). noids, including quercetin (dominant flavonoid), myricetin,
The leaf TPC of 4 varieties cultivated in Taiwan ranged from 0.3 to kaempferol, and luteolin were identified in orange- or purple-
1.3 g GAE/100 g DW. Under different storage and extraction conditions, fleshed sweet potatoes, but luteolin was not detected in the white-
the leaf TPC of 1 variety from Portugal ranged from 1.20 to 1.32 g GAE/ fleshed variety (Park et al., 2016). The conversion of kaempferol to
100 g of DW, while the stem of this sweet potato had a much lower TPC quercetin and myricetin resulted in a low kaempferol content in
(0.42–0.60 GAE/100 g, DW) (Anastácio & Carvalho, 2013). The stem end sweet potato roots, as dihydrokaempferol is a precursor of
of the root contained significantly more phenolics than the other parts dihydroquercetin and dihydromyricetin in sweet potato roots
of sweet potato (Jung, Lee, Kozukue, Levin, & Friedman, 2011). (Ojong et al., 2008). A flavonoid yield of 27.81–40.54 mg quercetin
equivalent/100 g dry weight has been reported in purple sweet potato
2.6.2. Phenolic acids roots using conventional, ultrasound-assisted, and accelerated-solvent
extractions (Cai et al., 2016).
2.6.2.1. Roots
Using liquid chromatography–mass spectrometry (LC–MS), proton 2.6.3.2. Leaves and other parts
nuclear magnetic resonance (1H NMR), and 13C NMR, five caffeoyl com- The flavonoid content (18–73 mg quercetin equivalents/100 g,
pounds identified from purple sweet potato (Ayamurasaki) contained DW) varied among 4 Taiwan sweet potato varieties (Liao et al.,
caffeoyl quinic acid and caffeoyl diglucoside. Caffeoylquinic acid 2011). A flavonoid content range of 5–7 mg quercetin equivalents/
derivatives, including 5-caffeoylquinic acid (chlorogenic acid), 6-O- 100 g (DW) has been reported in acidified and non-acidified extracts
caffeoyl-β-D-fructofuranosyl-(2–1)-α-D-glucopyranoside, trans-4,5- of purple sweet potato stem (Anastácio & Carvalho, 2013). The flavo-
dicaffeoylquinic acid, 3,5-dicaffeoylquinic acid, and 4,5-dicaffeoylquinic noid composition varies greatly among different colored sweet pota-
acid, represent the major types of polyphenols in the roots of purple to leaves. Quercetin, myricetin, and luteolin have only been detected
sweet potato (Fig. 2B) (Zhao et al., 2014). in purple sweet potato leaves. Apigenin has only been detected in
green sweet potato leaves (Anastácio & Carvalho, 2013). Quercetin
2.6.2.2. Leaves and other parts (89 mg /100 g, DW) has been identified only in fermented Chinese
Hydroxycinnamic acids [p-coumaric acid conjugates (415 g/ g) and Cuilü sweet potato tips (15 cm from the growing end) (Cui, Liu, Li,
sinapic acid (480 g/ g)], and hydroxybenzoic acids [benzoic (106 g/ g) & Song, 2011).
and p-anisic acids (48.0 g/ g)] were present in higher amounts in leaves
under a long day than those in leaves exposed to a short photoperiod for 2.6.4. Anthocyanins
30 days (Carvalho et al., 2010).
2.6.4.1. Roots
2.6.3. Flavonoids The anthocyanin content of purple-fleshed sweet potatoes is varie-
ty-dependent, ranging from 32 to 1390 mg/100 g DW as measured by
2.6.3.1. Roots pH differential-spectrophotometry (cyanidin-3-glucoside or
The content of flavonoids varies greatly among different colour- pelargonidin-3-glucoside equivalents)- or HPLC (cyanidin-3-glucoside
fleshed sweet potatoes. The flavonoid content for purple-fleshed or peonidin 3-caffeoylsophoroside-5 glucoside equivalents)-based
100 S. Wang et al. / Food Research International 89 (2016) 90–116

methods (Xu et al., 2015). A total of 27 anthocyanins have been identi- in carotenoid composition (Maoka, Akimoto, Ishiguro, Yoshinaga, &
fied. These anthocyanins are predominantly acylated glucosides of Yoshimoto, 2007; O'Connell, Ryan, & O'Brien, 2007; Bengtsson,
cyanidin and peonidin, which are diversified by acrylating with ferulic Namutebi, Larsson-Alminger, & Svanberg, 2008; Donado-Pestana et al.,
acid, diferulic acid, caffeic acid, or hydroxybenzoic acid moieties (Fig. 2012). Among them, orange-fleshed sweet potato had the highest
2C) (Montilla et al., 2010; Wang et al., 2004; Kim, Ahn, Ahn, Lee, & amount of carotenoids with trans β-carotene being dominant. Lipophilic
Kwak, 2012; Kim, Kim, et al., 2012; Lee, Park, Choi, & Jung, 2013; Xu et β-carotene had pro-vitamin A activity (Bovell-Benjamin, 2007;
al., 2015; Hu et al., 2016). Delphin chloride, cyanidin chloride, Donado-Pestana et al., 2012). Selected orange fleshed sweet potatoes
pelargonidin chloride, malvidin chloride, and peonidin chloride were could be 20–30 times higher in β-carotene content than golden rice.
found in Chingshey purple sweet potato, while only cyanidin chloride The trans-β-carotene content of 4 orange-fleshed varieties ranged
and delphinidin chloride were the main anthocyanins in fermented from 79.1 to 128.5 mg/100 g DW (Donado-Pestana et al., 2012). Xantho-
Chingshey purple sweet potato (Wu et al., 2012). In 12 purple-fleshed phylls, lutein, and zeaxanthin were identified as minor carotenoids in
sweet potato cultivars, 13 acylated anthocyanins were tentatively raw and processed sweet potato roots (O'Connell et al., 2007;
identified, including 2 new anthocyanins, cyanidin 3-caffeoyl-vanilloyl Donado-Pestana et al., 2012). Lutein and zeaxanthin of raw roots form
sophoroside-5-glucoside, and peonidin 3-caffeoyl-vanilloyl 4 orange-fleshed varieties had ranges of 0.1–0.4 and 0.1–0.2 mg/100 g
sophoroside-5-glucoside, using a combination of ultra-performance DW, respectively (Donado-Pestana et al., 2012).
liquid chromatography–photodiode array detection, quadrupole-time-
of-flight mass spectrometry, and tandem mass spectrometry analyses 2.7.2. Leaves and other parts
(He et al., 2016). Increases in the content of anthocyanins occurred in leaves of sweet
Acylation enhances hydrophilicity, thermal stability, and pH sensi- potato under longer day photoperiods (Carvalho et al., 2010). Sweet po-
tivity of sweet potato anthocyanins (Tsukui, 1996). Li, Li, et al. (2013) tato leaves are excellent source of lutein, ranging from 34 to 68 mg/
and Li, Mu and Deng (2013) studied the thermal stability of anthocya- 100 mg among different varieties (Lim, 2014).
nins extracted from purple sweet potato in aqueous solutions with var-
ious pH values (2–6) and fruit juices (apple, pear, grapefruit, orange,
2.8. Undesirable/anti-nutrient components
tangerine, kiwifruit, lemon juices). At pH 3 and 4, purple sweet potato
anthocyanins achieved the highest stability. During heating (80 °C–
2.8.1. Roots
100 °C), purple sweet potato anthocyanins, colored apple juice, and
Phytic acid and tannins represent anti-nutrients in sweet potato
pear juice had the highest stability (Li, Li, et al., 2013; Li, Mu, et al.,
roots. Phytic acid is involved in mineral chelation and protein complex-
2013). Acetic acid, malic acid, or other organic acid produced by
ation, thus reducing mineral and protein bioavailability. A b 10 phytate/
fermenting sweet potato may increase the stability of anthocyanins
Zn molar ratio indicates a good Zn bioavailability. Protein–tannin com-
(Wu et al., 2012). On the other hand, storage (Grace et al., 2014) and
plex formation reduces the protein digestibility (Arogundade & Mu,
maltodextrin treatment (Ahmed, Akter, & Eun, 2009; Ahmed et al.,
2012). Also, the tannins can reduce the starch digestion by interacting
2010a) decreased the anthocyanin content of sweet potato. Thermal
with starch and amylases (Zhu, 2015).
degradation of anthocyanins occurred in both convection and vacu-
Mycotoxins may be found in sweet potato roots. Ingestion of myco-
um-dried purple sweet potato, although the anthocyanin retention in
toxins (i.e., ipomeamarone and ipomeamaronol) in moldy roots leads to
vacuum-dried samples was better than that of the convection-dried
mycotoxicosis. The toxic furanoterpenoids, including 4-ipomeanol (1-
(Kuan et al., 2016). This may be attributed to the decreased oxidation
(3-furyl)-4-hydroxy-1-pentanone), the isomeric 1-ipomeanol (1-(3-
in the vacuum system. Baking gave better retention of anthocyanins in
furyl)-1-hydroxy-4-pentanone), the corresponding diketone
purple-fleshed sweet potato (Shinzami) than steaming. This may be be-
(ipomeanine (1-(3-furyl)-1,4-pentanedione), and the diol (1,4-
cause acylated phenolic acids and sugars were more degraded in steam-
ipomeadiol (1-(3-furyl)-1,4-pentanediol)) were in microbially infected
cooked sweet potato than in baked sweet potato (Kim, Kim, et al., 2012).
sweet potato roots (Boyd, Burka, Harris, & Willson, 1974). 4-Ipomeanol
Suitable processing techniques may be used for maximum anthocyanin
[1-(3-furyl)-4-hydroxypentanone] is particularly toxic to lung (Boyd,
retention in sweet potato products.
1982; Boyd, Burka, & Wilson, 1975; Boyd & Wilson, 1972; Boyd et al.,
1974; Doster, Farrell, & Wilson, 1983). Black-rotted sweet potatoes con-
2.6.4.2. Leaves and other parts
tain ipomeanine as a result of the secondary oxidation of ipomeamaron.
According to Karna et al. (2011), the anthocyanin content of metha-
Approximately 80% and 90% of the ipomeamarone was eliminated by
nol extracts of sweet potato leaves were 2.5-fold higher than that of
microwave cooking for 2 min and baking at 204 °C for 2 min, respective-
spinach. Using high-speed countercurrent chromatography (HSCCC),
ly. 4-Ipomeanol is more heat stable than ipomeamarone (Cody & Haard,
non-, mono-, and diacylated glucosides of cyanidin and peonidin were
1976; Kubota, 1958). Processing methods to eliminate mycotoxins in
found in 4 Japanese purple sweet potato cultivars (Chiran Murasaki,
sweet potato roots are essential.
Tanegashima Murasaki, Naka Murasaki, and Purple Sweet) (Montilla
et al., 2010). The cyanidin derivatives was predominant in the cultivars
Tanegashima Murasaki and Naka Murasaki. The other two cultivars 2.8.2. Leaves and other parts
(Chiran Murasaki and Purple Sweet) contained mostly peonidin deriva- Several chemicals in sweet potato leaves, such as phytic acid, cya-
tives (Montilla et al., 2010). Previous researchers reported that cyanidin nide, tannins, oxalates, alkaloids, and anthraquinones are anti-nutrients.
types (not peonidin types) represented the major anthocyanin compo- Caffeoylquinic acid derivatives isolated from leaves were antimutagenic
sition of sweet potato leaves (Huang, Wang, Eaves, Shikany, & Pace, (Pochapski et al., 2011). The total contents of alkaloids and anthraqui-
2007; Islam, Yoshimoto, Terahara, & Yamakawa, 2002). nones were 345.7 and 328.4 mg/100 g of dry leaves, respectively
(Pochapski et al., 2011).
2.7. Carotenoids
3. Bioactivities
2.7.1. Roots
Sweet potato can be an excellent source of carotenoids. The caroten- 3.1. In vitro models
oid contents of 11 sweet potato varieties, including 5 orange-fleshed, 2
yellow-fleshed, and 4 white-fleshed varieties, ranged from 0.4 to Diverse in vitro assays have been used to probe the bioactivities of
72.5 μg/g fresh weight (Tomlins, Owori, Bechoff, Menya, & Westby, sweet potato. The experimental designs and major findings of these
2011). Orange, yellow, cream, white, and purple sweet potatoes differed studies are summarized in Table 2.
 S. Wang et al. / Food Research International 89 (2016) 90–116 101

3.1.1. Antioxidant activity dependently decreased the DPPH radical scavenging activity of sweet
The most measured bioactivity is the in vitro antioxidant and free potato roots (Grace et al., 2014). Therefore, it becomes clear that suit-
radical scavenging activities by various chemical assays such as DPPH, able processing methods and conditions should be selected to maximize
ORAC, FRAP, ABTS, and reducing power, Fe2+-chelating, hydroxyl radi- the antioxidant activity of sweet potato products.
cal scavenging activity, linoleic acid autoxidation inhibition activity,
and photo-chemiluminescence assays (Ahmed et al., 2010a, 2010b; 3.1.1.2. Leaves and other parts
Gan et al., 2012; Rautenbach et al., 2010; Xu et al., 2010; Zhu et al., The free radical scavenging ability (determined by the
2010; Liao et al., 2011; Chan et al., 2012; Donado-Pestana et al., 2012; photochemiluminescent method) of leaves from 40 sweet potato culti-
Islam & Everette, 2012; Lee et al., 2012; Huang et al., 2012; Taira et al., vars ranged from 0.08 to 0.82 mg ascorbic acid equivalents/mg (Table 2)
2013; Wu et al., 2012; Zhang et al., 2012; Panda et al., 2013; Wang et (Sun, Mu, Xi, Zhang, et al., 2014). The free radical scavenging ability was
al., 2012; Anastácio & Carvalho, 2013; Jiao et al., 2012; Huang et al., correlated with the contents of total polyphenols and carbohydrates.
2013; Lim et al., 2013; Peng et al., 2013; Maloney et al., 2014; Grace et This indicated a possible involvement of carbohydrates in preventing
al., 2014; Salawu et al., 2015; Zhao et al., 2014; Sun, Mu, Xi, Zhang, et polyphenol oxidation (Sun, Mu, Xi, Zhang, et al., 2014). Antioxidants
al., 2014; Soison et al., 2014; Motsa et al., 2015; Park et al., 2015; Xi et of 4 varieties of water extracts from sweet potato leaves from Taiwan
al., 2015; Ding et al., 2015; Grace et al., 2015; Wu et al., 2015; Hu et were studied by DPPH scavenging (EC50, 0.11–0.41 mg/mL of sample),
al., 2016; Kuan et al., 2016). Cell line-based antioxidant capacity assays reducing power (EC50, 0.27–0.47 mg/mL of sample), superoxide radical
were also applied by evaluating the cytoprotective activity of antioxi- scavenging (EC50, 0.10–0.61 mg/mL of sample), and iron-chelating ac-
dant components in sweet potato using RAW264.7 cells (Wu et al., tivity (10.1−23.3%, 0.5 mg/mL). Flavonoids appeared to be a key con-
2012), SH-SY5Y human neuroblastoma cells (Grace et al., 2014), tributor for the tested antioxidant capacities (Liao et al., 2011). DPPH
human keratinocyte HaCaT cells (Liao et al., 2011), and human liver scavenging abilities of the leaves of 8 sweet potato cultivars ranged
HepG2 cells (Huang et al., 2012; Hwang, Choi, Choi, et al., 2011). Cell in- from 4.3 to 8.1 mM ascorbic acid equivalents/mg, DW (Nagai et al.,
juries were due to intracellular production of reactive oxygen species 2011). DPPH values were positively correlated with total phenolic con-
induced by tert-butyl hydroperoxide and hydrogen peroxide (Hwang, tents of these leaves (Nagai et al., 2011). According to Isabelle et al.
Choi, Choi, et al., 2011). Different chemical and cell-based assays differ (2010), TPC and hydrophilic-ORAC of 2 sweet potato cultivars ranged
in substrate/probe, free radical source, underlying chemical reaction, from 0.59 to 3.57 mg GAE/g FW and 16.37 to 67.29 μmol trolox/g FW.
and measurement technique. Comparison of antioxidant properties of leaves across the studies be-
Various parts (e.g., roots, leaves) of sweet potatoes varying in geno- came difficult due to the different quantification methods used for eval-
types and product forms (e.g., cooked, flour, emulsion) exhibited differ- uating antioxidant activity in each study (Table 2).
ent antioxidant activities. Extraction variables (solvent–solid ratio, time,
pH, solid particle size, temperature, solvent type) also influence the an- 3.1.2. Antimicrobial
tioxidant capacities of the resulting crude exacts or fractions of sweet Antimicrobial activities of various parts of sweet potato varied de-
potatoes (Anastácio & Carvalho, 2013). The antioxidant activities were pending on the strains of bacterial type, sweet potato varieties, extract
attributed to the various bioactive compounds present in sweet pota- characteristics (water or ethanol-based extract), and in vitro evaluating
toes. For example, antioxidant activities were positively correlated to methods for antimicrobial activity. Diffusion assays (i.e., agar disk-
the contents of total phenolics (Rautenbach et al., 2010; Xu et al., diffusion, agar well diffusion) and dilution assays (i.e., broth dilution)
2010; Zhu et al., 2010), hydroxycinnamic acid derivatives (Zhu et al., were used for the in vitro investigation of sweet potato as potential an-
2010) and total anthocyanins (Zhu et al., 2010; Gan et al., 2012; Ding timicrobial agents (Pochapski et al., 2011; Boo et al., 2012; Lee et al.,
et al., 2015), anthocyanins and phenolic acids combined (Grace et al., 2012). In the agar disk-diffusion method, filter paper discs (about
2014), hydrophobic amino acids (Zhang et al., 2012), and caffeoyl com- 6 mm in diameter), containing the test compound at a desired concen-
pounds (Zhao et al., 2014). Antioxidant activities have also been related tration, are placed on the surface of agar containing the inoculum of the
to the number and structure of caffeoyl compounds present in sweet test microorganism. The antimicrobial activity was measured as the size
potatoes (Zhao et al., 2014). Combining quinic acids with di-caffeoyl of the clear zone of growth inhibition. In agar well diffusion method, a
had much stronger antioxidant activities than combining quinic acids volume (20–100 μL) of the extract solution at a test concentration is in-
with mono-caffeoyl, while cis-dicaffeoyl quinic acid had a much greater troduced into the well (hole) of agar containing the inoculum of the test
antioxidant capacity than trans-dicaffeoyl quinic acid (Zhao et al., microorganism. The well (hole, 6 to 8 mm in diameter) was punched
2014). The antioxidative synergy among various components possibly aseptically with a sterile cork. The antimicrobial agent diffuses into the
yields the antioxidant activity of sweet potato extracts (Wang & Zhu, agar medium and inhibits the growth of the microbial strain tested
2015). (Balouiri, Sadiki, & Ibnsouda, 2016). The dilution method quantitatively
determines the minimal inhibitory concentration of sweet potato (Lee
3.1.1.1. Roots et al., 2012; Balouiri et al., 2016). The use of standardized antimicrobial
The DPPH scavenging activity of raw and cooked flour of 4 orange- activity screening and evaluating methods is necessary to ensure an ac-
fleshed sweet potato roots ranged from 2.5 to 19.5 mM trolox equiva- curate experimental approach and to allow the researchers to compare
lents/100 g, DW, while ABTS scavenging activity of raw, cooked, and results.
flour of sweet potato roots ranged from 5.3 to 18.8 M trolox equiva-
lent/100 g, DW. The DPPH values were correlated with total carotenoid 3.1.2.1. Roots
content (but not with total phenolic content) of roots, while ABTS In a study of bactericidal activity against 2 g positive bacteria (Bacil-
values were correlated with total phenolic (but not total carotenoid) lus subtilis, Micrococcus luteus) and 4 g negative bacteria (Escherichia
content (Donado-Pestana et al., 2012). Cooking, including boiling, coli, Salmonella typhymurium, Vibrio parahaemolyticus, Proteus mirabilis),
steaming, baking, roasting, and frying, in general decreased the antiox- water extract of Korean purple sweet potato root powder were com-
idant capacities (DPPH, ABTS) of sweet potato roots (Donado-Pestana et pared to water extracts from 12 plant dietary materials, including
al., 2012; Lee et al., 2012). Extrusion (feed moisture content 10%) and black rice, yellow bitter melon, yellow paprika, red cabbage, yellow gar-
drum-drying (140 °C) achieved the maximum antioxidant activity of denia, blue gardenia, Chinese foxglove, mulberry leaves, onion peel,
flours (Soison et al., 2014). Fermentation increased the superoxide dis- grape peel, mulberry, and red beet. By comparing the size of the clear
mutase activity of sweet potato in RAW264.7 cells to various extents, zone formation of growth inhibition in agar disk diffusion test, the anti-
depending on the lactic acid bacteria (LAB) species (Wu et al., 2012). microbial activities of sweet potato water extract in E. coli was found to
On the other hand, postharvest storages (4 or 8 months) time- be comparable to those of red cabbage, blue gardenia, mulberry leaves,
102 S. Wang et al. / Food Research International 89 (2016) 90–116

grape peel, and mulberry (Boo et al., 2012). In the case of B. subtilis, sweet potato tips possibly functions as an ACE inhibitor (Ishiguro,
sweet potato water extracts were comparable to immature bitter Yoshimoto, Tsubata, & Takagaki, 2007). Thermal processes induced phe-
melon, paprika, blue gardenia, Chinese foxglove, mulberry leave, grape nolic polymerization or oxidation, possibly contributing to the increased
peel, mulberry and red beet (Boo et al., 2012). In the case of V. ACE inhibitory activity (Cui et al., 2011).
parahaemolyticus, sweet potato water extract was comparable to that
of immature bitter melon and Chinese foxglove (Boo et al., 2012). In 3.1.4. Antigenotoxicity
the case of M. luteus, sweet potato extracts were comparable to that of Antigenotoxicity evaluations focused on the involvement of sweet
immature bitter melon, paprika, mulberry leaves, and mulberry (Boo potato in the protection against free radical (i.e., hydroxyl radicals)-in-
et al., 2012). Water extracts of sweet potato did not exhibit the growth duced oxidative damages of DNA, such as plasmid pBR322 DNA
of S. typhymurium and P. mirabilis. The main antibacterial components (Zhang et al., 2012) and calf thymus DNA (Huang et al., 2012). Oxidative
in sweet potato extracts are hydrophilic pigments (i.e., anthocyanin DNA damages can be reflected by base oxidation, deoxyribose damage,
pigments) (Boo et al., 2012). According to Lee et al. (2012), the strand breaks, apurinic/apyrimidinic sites, and DNA–protein cross-links.
ethanol extract of Sinjami Korean sweet potato (not Yeonhwangmi, The mechanisms behind the protection of sweet potato different types
Jinhongmi, and Juhwangmi varieties) were antimicrobial against of oxidative (or non-oxidative) DNA damages remain to be studied.
E. coli, S. typhimurium, and Staphylococcus aureus using the broth di-
lution assay. The different results of these two studies are possibly 3.1.4.1. Roots
due to the differences in the phytochemical composition (as a result Enzymatic hydrolysates of sweet potato protein extracted from fresh
of extract solvent) of the extracts and the methodology of the anti- roots in vitro protected DNA from hydroxyl radical damages (Zhang et
microbial tests. Steaming and roasting decreased the antimicrobial al., 2012). Among the hydrolysates produced by different enzymes
activities of unprocessed Sinjami sweet potatoes (Lee et al., 2012). (alcalase, neutrase, proleather FG-F (a protease), AS1.398, papain, and
This may be due to the loss of polyphenols during thermal processing pepsin), alcalase hydrolysate fractions (b 3 kDa) showed the highest
with antimicrobial activity. DNA-protecting effect. The protective effects of enzymatic hydrolysates
could be attributed to their hydroxyl radical scavenging and chelating of
3.1.2.2. Leaves and other parts iron (a catalyst in the Fenton reaction) (Zhang et al., 2012). The DNA-
Islam (2008) found that the lyophilized leaf powder of three sweet protective bioactive in the enzymatic hydrolysates of sweet potato
potato cultivars effectively suppressed several foodborne pathogens could be antioxidant amino acids (i.e., His, Met, Cys, Tyr, and Phe) and
including E. coli O157:H7, Bacillus cereus, and S. aureus. The leaf extracts the hydrophobic amino acids (Zhang et al., 2012). Defensin protein (5
exhibited minimal effects on growth of health-promoting bifidobacterium or 10 mg/mL) from Taiwan sweet potato roots protected against hy-
(B. adolescentis, B. bifidum, B. breve, B. longum, B. infuntis). Polysaccha- droxyl radical-induced damages of calf thymus DNA (1 mg/mL), during
rides were considered as major antibacterial agents in lyophilized leaf a 15-min reaction (Huang et al., 2012). Hydrolytic peptides were anti-
extracts (Islam, 2008). Inconsistently, in both agar disk diffusion and oxidative in defensin protein (Huang et al., 2012).
agar well diffusion tests, 70% ethanol leaf extract of Brazilian sweet po-
tato minimally influenced the growth of Streptococcus mutans, S. mitis, 3.1.5. Antiangiogenesis
Staphylococcus aureus, and Candida albicans (Pochapski et al., 2011). Angiogenesis is a complex process of forming new blood vessels
Again, extraction solvents represent a factor influencing the antibacteri- from existing blood vessels. This process contributes to the develop-
al ability of the sweet potato samples. To improve food quality and safe- ment and progression of several neoplastic and non-neoplastic diseases,
ty, novel food products containing sweet potato with antibacterial including cancers and atherosclerosis. Angiogenesis results in the deg-
properties against foodborne spoilage and pathogenic bacteria are radation of extracellular matrices, migration, and proliferation of endo-
expected. thelial cells and maturation of new blood vessels (tube formation). In
vitro effects of purple sweet potatoes on angiogenesis were evaluated
3.1.3. Resistance to enzyme hydrolysis in the human umbilical vascular endothelial cells (HUVECs) with prom-
ising results (Chen et al., 2011).
3.1.3.1. Roots
A unique amino acid sequence or compact structure of sweet potato 3.1.5.1. Leaves and other parts
protein represents possible barriers against digestive enzymes to recog- In VEGF165-stimulated HUVECs, 70% methanol extracts (0.2 to
nize cleavage sites in protein. Sweet potato sporamins (23 and 24 kDa) 0.8 mM gallic acid equivalent polyphenols per gram of dry weight)
contained numerous potential cleavage sites for pepsin, trypsin, and from purple sweet potato leaves dose-dependently decreased cell pro-
chymotrypsin. However, the compact structure of sporamins possibly liferation and migration, tube formation, and the activity of secreted
reduced their accessibility to these digestive enzymes such as pepsin MMP-2 (Chen et al., 2011). Leaf extracts containing 0.8 mM gallic acid
(Maloney et al., 2014). Caiapo sweet potato protein (60 kDa) exhibited equivalent polyphenols achieved the maximum effects (Chen et al.,
resistance to trypsin and chymotrypsin digestion (Maloney et al., 2014). 2011). Key antiangiogenesis bioactives (polyphenols or other com-
Peel sporamins from orange- and white-fleshed sweet potatoes varied pounds) in methanol leaf extracts deserve further identification.
in the inhibitory activities on digestive enzymes (trypsin and chymo-
trypsin) (Maloney et al., 2014). Processes, such as blanching and gastric 3.1.6. Anticancer
digestion, possibly eliminated the inhibitory activities of sweet potato Cancer cells have accelerated proliferative capacity and resistance to
peels against amylase and chymotrypsin, but minimally influenced the apoptosis (programmed cell death), although the clinical relevance of
function of peel sporamins as trypsin inhibitors (Maloney et al., 2014). these in vitro preclinical models deserves further research (Gillet,
Varma, & Gottesman, 2013). In vitro studies using cancer cells indicate
3.1.3.2. Leaves and other parts that sweet potato had anticancer properties via inhibiting cancer cell
An angiotensin-converting-enzyme inhibitor (ACE inhibitor) is used proliferation and stimulating apoptosis (Karna et al., 2011; Li, Mu, &
primarily for the control of hypertension and congestive heart failure. Deng, 2013; Lim et al., 2013; Zhang, Mu, & Zhang, 2013; Wu et al.,
Angiotensin-converting enzyme inhibition activities were found in 2015; Wu et al., 2015). Factors influencing antiproliferations of sweet
freeze-dried powders of Chinese Cuilü sweet potato tips (leaves and potatoes against cancer cells include material type (i.e., crude extract,
stem,15 cm from the growing end) (Cui et al., 2011). Processes, such fraction, or purified components), treatment doses, plant parts, and can-
as boiling, fermentation, and steaming increased the ACE inhibitory ac- cer cell types (Karna et al., 2011; Li, Li, et al., 2013; Li, Mu and Deng,
tivity of sweet potato products (Cui et al., 2011). Caffeoyl quinic acid in 2013; Lim et al., 2013; Zhang et al., 2013; Wu et al., 2015; Wu et al.,
 S. Wang et al. / Food Research International 89 (2016) 90–116 103

Table 3
Health effects of sweet potato: in vitro studies.

Parts
Bio-functions used Sample type (No.) Experimental design Major findings References

Antioxidative Root Methanolic crude extracts of peel, Antioxidant activities were measured by The extracts exhibited genotype-dependent Zhu et al.
peel flesh, and whole root of purple ABTS, FRAP and DPPH assays antioxidant activities (2010)
fleshed sweet potatoes (10) Anthocyanins and hydroxycinnamic acid Antioxidant activities positively correlated
derivatives were identified by total phenolics, hydroxycinnamic acid
LC–PDA–APCI–MS derivatives and total anthocyanins contents
Antioxidative Root Hydrophilic fractions of raw and Antioxidant activities were measured by Boiling increased antioxidant activities and Rautenbach et
cooked sweet potatoes (4) ORAC, FRAP and ABTS assays chlorogenic acid content al. (2010)
Effects of thermal treatment (boiling water, Boiling decreased carotenoid and vitamin C
12 min) and drought stress on levels of contents
β-carotene, chlorogenic acid, and vitamin C Drought stress genotype-dependently
were studied increased antioxidant activities, and
contents of carotenoid, vitamin C, and
polyphenols
Antioxidative Root Hydro- and lipo-philic fractions Antioxidant activities were measured by Hydrophilic fractions had higher antioxidant Islam and
of orange-fleshed sweet potatoes ABTS, DPPH, and ORAC assays activities than lipophilic fractions Everette (2012)
(5)
Antioxidative Root Steamed and roasted sweet Antioxidant activities were measured by Antioxidant activities of steamed sweet Wang et al.
potatoes DPPH and FRAP assays potato were higher than those of roasted (2012)
Effects of steaming (140 °C) and roasting sweet potatoes
(240 °C, 60 min) on antioxidant activities
were studied
Antioxidative Root Orange-fleshed sweet potato Antioxidant activities were measured by Antioxidant activities were Donado-Pestana
roots (4) DPPH and ABTS assays cultivar-dependent et al. (2012)
Effects of various thermal treatments Thermal treatments and flour processing
(boiling at 95 °C for 40 or 60 min; or roasting decreased antioxidant activities
at 220 °C for 30 or 45 min; or steaming at 95 The carotenoids were positively correlated
°C for 45 or 65 min), or flour processing on with DPPH values, and phenolic contents
antioxidant activities were studied positively correlated with ABTS values
Antioxidative Root Sweet potato peel Antioxidant activity was measured by FRAP Solvent solid ratio and root cut depth are Anastácio and
Peel assays two key influencing factors to determine Carvalho (2013)
Effects of nine extraction variables (solvent total phenolic content and FRAP value
solid ratio, time, pH, peeling cut depth,
particle size, temperature, solvent, sample
amount, and agitation) on total phenolic
content and antioxidant activity were
studied
Antioxidative Root Anthocyanins extracts of powder Antioxidant activities were measured by Anthocyanin extracts exhibited Jiao et al. (2012)
of purple sweet potato (1) inhibition of peroxidation of linoleic acid, dose-dependent DPPH radical and
DPPH, and superoxide radical-scavenging superoxide anion scavenging activities
assays DPPH values of anthocyanin extracts were
higher than that of BHT
Reducing power of anthocyanin extracts
were higher than that of L-ascorbic acid and
BHT
Antioxidative Root Purple-flesh sweet potato flours Antioxidant activities were measured by Extruded (feed moisture contents 10%) and Soison et al.
(1) DPPH and ABTS assays drum-dried (140 °C) flour achieved the (2014)
Effects of extrusions (feed moisture maximum phenolic content and antioxidant
contents: 10%, 13%, 16%; screw speeds 250, activities
325, 400 rpm.), and drum-drying (120 °C,
130 °C, 140 °C) on the antioxidant activities
were studied
Antioxidative Root Pure and adulterated mixtures of Antioxidant activities were measured by Pure purple sweet potato flour had the Ding et al.
commercial available white and DPPH, ferrous ion binding capacity and ABTS highest antioxidant activity; pure white (2015)
purple sweet potato flours (2) assays sweet potato flour had the lowest
Adulterated flour sample were prepared by antioxidant activity
mixing purple sweet potato flour with the Total antioxidant activity positively
white sweet potato flour at various correlated with the total anthocyanin
concentration (20, 40, 60, 80%) contents of flours
Adulterated flour sample had antioxidant
activity between the highest and lowest
amounts found in the pure samples
Antioxidative Root Orange, yellow, and purple sweet Antioxidant activities were measured by Vacuum-dried sweet potato powder Kuan et al.
potato powder ABTS and DPPH assays retained higher antioxidant activity than (2016)
Effects of vacuum drying (55 °C for 6 h) and convection-dried powder
convectional drying (55 °C for 3 h) on the Purple sweet potato powder exhibited
antioxidant activities were studied higher antioxidant activity than orange or
yellow sweet potato powder
Antioxidative Root Anthocyanin fractions of purple Antioxidant activities of anthocyanin Anthocyanin fractions exhibited Hu et al. (2016)
sweet potato (30) fractions were evaluated by reducing power cultivar-dependent antioxidant activities
activity, DPPH, hydroxyl radical scavenging due to their cultivar-dependent anthocyanin
activity and linoleic acid autoxidation compositions
inhibition assays 7 of 13 identified anthocyanins were
Individual anthocyanins were identified by antioxidative
HPLC Number or type of the acylated groups in

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Table 3 (continued)

Parts
Bio-functions used Sample type (No.) Experimental design Major findings References
Effects of anthocyanin type on antioxidant anthocyanins are not correlated to their
activity were studied antioxidant activities
Antioxidative Leaf Chloroform, ethyl acetate, Antioxidant activities were measured by Leaf extracts exhibited variety-dependent Xu et al. (2010)
n-butanol or water extract from DPPH, ABTS, and FRAP assays and antioxidant activities. Ethyl acetate
sweet potato leaves (116) extracts had the highest antioxidant
activities
Antioxidant activities were positively
correlated with the total polyphenol
contents. Caffeoylquinic acid derivatives are
antioxidants in leaves
Antioxidative Leaf Methanol extract of sweet potato Antioxidant activities were measured by Antioxidant activities of sweet potato vines Anastácio and
stem vines (stems and leaves) (1) total antioxidant activity, reducing power, varied due to the antioxidant evaluated Carvalho (2013)
FRAP, and DPPH assays assay applied, parts of vein (stems or leaves),
Effects of plant parts, extraction time, and extraction time, and solvent
solvents on antioxidant activities were Parts of the vine were the most influential
studied factor in all studied antioxidant assays. Time
of extraction was the most influential factor
in the reducing power value
Antioxidative Leaf Crude and purified flavonoids Antioxidant activities were evaluated by The dynamic high-pressure Huang et al.
from sweet potato leaves (1) DPPH, superoxide anion, and hydroxyl microfluidization-assisted extracts exhibited (2013)
radical scavenging assays higher dose-dependent antioxidant
Effects of dynamic high-pressure activities than traditional ethanol extracts
microfluidization-assisted extractions on The dynamic high-pressure
antioxidant activities flavonoid levels were microfluidization-assisted extraction
studied accelerated the dissolution of antioxidant
compounds, leading to higher antioxidant
activities
Antioxidative Leaf Fresh sweet potato leaves (1) An antioxidant activity was measured by Steaming, baking, and frying increased Sun, Mu, Liu,
ORAC assay antioxidant capacity of leaves. Steaming Zhang and Chen
Effects of boiling, steaming, microwaving, increased total polyphenol contents (2014)
baking, and frying on proximate Antioxidant activity could be mainly
compositions, total and individual attributed to 4,5-di-O-caffeoylquinic,
polyphenol contents, and antioxidant 3,4-di-O-caffeoylquinic,
activity were studied 3,5-di-O-caffeoylquinic, and
3,4,5-tri-O-caffeoylquinic acids in leaves
Antioxidative Leaf Ethanol extracts of sweet potato Antioxidant activity was measured Antioxidant activity of 40 leaves ranged from Sun, Mu, Xi,
leaves (40) photo-chemiluminescent assay 0.08 to 0.82 mg ascorbic acid Zhang, et al.
equivalents/mg, DW (2014)
Antioxidant activity were positively correlated
with TPC and carbohydrate content, while
negatively correlating with crude protein,
crude fat, and crude fiber contents
Antioxidative Root Sweet potato roots and leaf (3) Antioxidant activities were evaluated by Antioxidant activities of roots and leaves are Motsa et al.
leaf DPPH and FRAP assays cultivar-dependent (2015)
DPPH values of roots were higher than that
of leaves; FRAP values of leaves were higher
than that of roots
Antioxidative Leaf Ethanol extract sweet potato leaf Antioxidant activities were determined by Leaf polyphenols showed dose-dependent Xi et al. (2015)
polyphenols (2) photochemiluminescence and oxygen scavenging activity against oxygen radical
radical absorbance capacity assays absorbance capacity
Caffeoylquinic acids, especially three types of
di-caffeoylquinic acids are polyphenols in
leaves
Antimicriobial Root Water extract of purple sweet Antimicrobial activities was evaluated (using Water extracts showed antimicrobial Boo et al.
potato (1) agar diffusion) against Gram-positive activity in E. coli, B. subtilis, V. (2012)
bacteria (Bacillus subtilis, Micrococcus luteus) parahaemolyticus, and M. luteus
and Gram-negative bacteria (Escherichia coli,
Salmonella typhymurium, Proteus mirabilis,
Vibrio parahaemolyticus)
Antimicrobial and Root Ethanol extracts of sweet potato Antioxidant activities were evaluated by Ethanol extracts exhibited Lee et al. (2012)
antioxidative (4) ABTS and DPPH assays cultivar-dependent ABTS and DPPH
Antimicrobial activities were evaluated scavenging activities, and superoxide
against Staphylococcus aureus, Salmonella dismutase-like activity
typhimurium, Escherichia coli Only the Sinjami variety was antimicrobial
Effects of steaming (121 °C) and roasting against S. aureus, S. typhimurium, and E. coli
(200 °C) on antioxidative, and antimicrobial Steaming and roasting decreased the
activities were studied antioxidative and antimicrobial activities
Inhibitory activity Tip Ethanol extract of fresh Cuilü Antioxidant activities were measured by Fermentation reduced the levels of free Cui et al. (2011)
against enzymes sweet potato tips (15 cm from DPPH and FRAP assays amino acids, total phenolic, DPPH and FRAP,
and antioxidative the growing end) undergo Free amino acids, organic acids, phenolics while increasing organic acids,
untreated, fermented, boiled, and (chlorogenic acid, rutin, and quercetin) and angiotensin-converting enzyme inhibition
steamed (1) angiotensin-converting enzyme inhibition activity
activities were determined Boiling reduced the levels of free amino
acids, organic acids while increasing total
phenolic, FRAP values,
 S. Wang et al. / Food Research International 89 (2016) 90–116 105

Table 3 (continued)

Parts
Bio-functions used Sample type (No.) Experimental design Major findings References
angiotensin-converting enzyme inhibition
activity
Steaming reduced the levels of free amino
acids, organic acids while increasing total
phenolic, FRAP values,
angiotensin-converting enzyme inhibition
activity
Steaming had a better retention of taste
qualities and health-relevant functions than
boiling
Inhibitory activity Root Protein fractions of orange-flesh, Trypsin, amylase, or chymotrypsin inhibitory Peel protein fractions had trypsin-inhibitory Maloney et al.
against enzymes peel white-skinned root peels (3) activities were evaluated activity before and after simulated gastric (2014)
digestion
Peel protein fractions lost amylase and
chymotrypsin inhibitory activity after gastric
digestion
Antiinflammatory Root Extracts from lyophilized Antioxidant activity was measured by DPPH Freshly harvested sweet potato extracts Grace et al.
and antioxidative powders of sweet-potatoes (4) assay showed DPPH radical scavenging and (2014)
Anti-inflammatory capacity was evaluated inhibited the LPS-induced reactive oxygen
using LPS-induced inflammation of SH-SY5Y species accumulation in neuronal cells
human neuroblastoma cells Combination of high levels of anthocyanins
Effects of post storage (4, 8 months) on and phenolic acids are key contributors for a
contents of phenolics, anthocyanins, ascorbic high DPPH value
acid, and carotenoids, antioxidative and Anti-inflammatory capacity was positively
anti-inflammatory properties were studied correlated with the DPPH value and phenolic
contents
Post storages time-dependently decreased
antioxidative, anti-inflammatory and
ascorbic acid levels of sweet potatoes
Anti-lipid oxidation Root Extract of purple-fleshed sweet Emulsions were made by blending extracts Both oil-in-water emulsions containing Gan et al.
potato (1) (200, 500, 1000 ppm) physically with lipid sweet potato extract (1000 ppm) had the (2012)
and fish oil–soybean oil structured lipid highest anti-lipid oxidation
(soybean oil: fish oil =3:1, w/w). Anthocyanins acted as free radical
Antioxidant capacities were evaluated by scavengers in the water phase of emulsion
measuring lipid peroxides and thiobarbituric
acid reactive substances
Anti-LDL oxidation Leaf Sweet potato leaves and Antioxidant activity was measured in a Leaves and caffeoylquinic acid derivatives Taira et al.
and antioxidative caffeoylquinic acid derivatives LDL-oxidation induction system (15 μM) were anti-LDL oxidation (2013)
(11) Antioxidant activity of sweet potato leaves
was correlated with the amounts of
caffeoylquinic acid derivatives in leaves
Antioxidative and Root Enzymatic hydrolysates of sweet Hydroxyl radical-scavenging activity and Alcalase hydrolysates had the highest Zhang et al.
protection of potato protein (1) Fe2+-chelating activity of hydrolysates were hydroxyl radical-scavenging and (2012)
DNA damage studied Fe2+-chelating activities
Alcalase hydrolysates had the strongest
protection of hydroxyl radical-induced DNA
damages
Antioxidative and Root Sweet potato defensin protein Antioxidant activities were measured by Defensin exhibited dose-dependent Huang et al.
protection of (1) ABTS, DPPH, reducing power, Fe2+-chelating antioxidant activities (2012)
DNA damage ability, FTC (ferric thiocyanate) assays Defensin (5, 10 mg/ mL) protected against
Protection of defensin on calf thymus DNA hydroxyl radical induced calf thymus DNA
against hydroxyl radical-induced damage in damage during 15-min reactions
HepG2 cells were studied Defensin (12.5, 25, 50, 100 μg/ mL)
dose-dependently decreased the production
of intracellular peroxide in HepG2 cells
Antiproliferation in Root Anthocyanin extracts of Human colonic SW480 cancer cells were Anthocyanin extracts induced Lim et al. (2013)
cancer cells purple-fleshed sweet potato (2) treated with anthocyanin extracts at 0–40 dose-dependent inhibition of proliferation in
μM of peonidin-3-glucoside equivalent SW480 cancer cells
Anthocyanin extracts induced cytostatic
arrest of cell cycle at G1 phase
Antiproliferation in Root Polysaccharides from purple Antioxidant activities were evaluated by Three polysaccharides exhibited Wu et al. (2015)
cancer cells and sweet potato (1) DPPH, chelating ferrous ions, and reducing dose-dependently antioxidant activities.
antioxidative power assays PSPP2–1 had the highest DPPH value,
Human stomach cancer SGC7901 and human reducing and Fe2+ chelating capacity
colonic carcinoma SW620 cells were treated Three polysaccharides induced
with various doses of polysaccharides (100, dose-dependent inhibition of proliferation in
200, 300, 400, or 500 μg/mL for SGC7901; cancer cells. PSPP-1 had the highest
200, 400, 600, 800, or 1000 μg/mL for antiproliferative effects
SW620) for 48 h PSPP1-1 (33.3 kDa) were composed of
rhamnose, xylose, glucose, and galactose.
PSPP2-1 (17.8 kDa) were composed of
rhamnose and galactose
Anticytotoxic and Leaf Water extract from sweet potato Antioxidant activities were measured by Antioxidative activities of water extracts was Liao et al.
2+
antioxidative leaves (4) reducing power, Fe chelating, and cultivar-dependent (2011)

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106 S. Wang et al. / Food Research International 89 (2016) 90–116

Table 3 (continued)

Parts
Bio-functions used Sample type (No.) Experimental design Major findings References
superoxide anion scavenging assays H2O2 (250 μM)-induced cytotoxicity in
Effect of water extracts on protecting human HaCaT cells was attenuated by water extract
keratinocytes (HaCaT cells) from at 1 mg/mL
H2O2-induced cytotoxicity were studied
Hepatoprotection Root Anthocyanin fractions from Antioxidant activities were measured in Anthocyanin fractions suppressed tert-butyl Hwang, Choi,
and antioxidative aqueous extract of whole tert-butyl hydroperoxide-induced HepG2 hydroperoxide-induced ROS formation, GSH Choi, et al.
purple-fleshed sweet potatoes cells depletion and caspase-3 activation (2011)
Cells were treated with anthocyanin Anthocyanin fractions dose-dependently
fractions at 0–800 μg/mL increased expression of the ARE-Luc reporter
gene (HO-1-ARE, NQO1-ARE, and GST-ARE)
Anthocyanin fractions involved in PI3K/Akt
and ERK1/2 survival pathways to control cell
death, at least in part, by inducing HO-1
expression
Hepatoprotection Root Anthocyanin fractions of Rat hepatic stellate HSC-T6 cells were Anthocyanin fractions induced Choi et al.
and antioxidative purple-fleshed sweet potatoes treated with anthocyanin fraction at 0–200 dose-dependent inhibition of proliferation in (2011)
μg/mL HSC-T6 cells
Anthocyanin fractions blocked PDGFR-β
signaling, and inhibited Akt and ERK1/2
activation and α-SMA expression
Antiobesity Root Anthocyanin fractions from HepG2 cells were incubated in serum-free Anthocyanin fractions dose-dependently Hwang, Choi,
purple sweet potato (1) DMEM containing D-glucose (30 mmol/L) increased the phosphorylation of AMPK and Han, et al.,
and anthocyanin fraction (0, 50, 100, 200 acetyl-coenzyme A carboxylase in HepG2 (2011)
μg/mL) hepatocytes
Anthocyanin fractions promoted antiobesity
via regulating AMPK pathway to reduce the
expression of lipid metabolism-related
proteins (such as SREBP-1 and FAS) in
HepG2 hepatocytes
Antiangiogenesis Leaf 70% methanol extract of purple Effect of leaf extracts on angiogenesis in Leaf extracts (0.2 to 0.8 mM gallic acid Chen et al.
sweet potato leaves human umbilical vascular endothelial cells equivalent polyphenols) decreased (2011)
(HUVECs) were evaluated proliferation, migration, tube formation, and
MMP-2 activity of vascular endothelial
growth factor-treated HUVECs
Antiproliferation in Leaf 100% methanol leaf extract Effect of methanolic leaf extracts on human Leaf extracts dose-dependently inhibited Karna et al.
cancer cells prostate cancer cells (LNCaP, DU145, PC-3, growth of all cancer cells with IC50 values in (2011)
C4-2, C4-2B) and normal prostate epithelial the range of 145–315 μg/mL
cells (PrE and RWPE-1) were evaluated IC50 of leaf extracts in normal cells ranged
from 1000 to 1250 μg/mL
Antiproliferation in Root Pectin Effects of sweet potato pectin on human Root pectin (at doses of 0.01, 0.10, 0.25, 0.50, Zhang et al.
cancer cells colon cancer cells (HT-29) and human breast 1.00 mg/mL) dose-dependently inhibited (2013)
cancer cells (Bcap-37) were evaluated cancer cell proliferation
Antiproliferation in Root Purified protein (about 25 kDa) Effects of sweet potato proteins on Root protein inhibited cancer cell Li, Mu and Deng
cancer cells proliferation, migration, invasion of human proliferation (dose–dependently, at doses of (2013)
colorectal cancer cells (SW480) were 2, 4, 10, 20, 40 μmol/L), migration (at doses
evaluated of 0.8, 8, 40 μmol protein/L), and invasion( at
doses of 0.8, 8. 40 μmol protein/L)

ABTS: 2,20-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid); BHT: butylated hydroxytoluene; DPPH: 2,2-diphenyl-1-picrylhydrazyl; FTC: (ferric thiocyanate); FRAP: ferric reducing
ability of plasma; IC50: a concentration required for scavenging 50% activity; LC–PDA–APCI–MS: liquid chromatography–photodiode array detector–atmospheric pressure chemical ion-
ization–mass spectrometry; LAAO: linoleic acid autoxidation; LDL: low-density lipoprotein; No.: number of cultivars; MMP: matrix metalloproteinase; MTT: 3-(4,5-dimethylthiazol-2-yl)-
2,5-diphenyltetrazolium bromide; ORAC: oxygen radical absorbance capacity; RPA: reducing power activity.

2015). The in vitro molecular mechanisms behind anticancer cell prolif- effects of PSPP2-1 and PSPP3-1 on apoptosis were not studied (Wu et
eration of sweet potatoes have rarely been studied. al., 2015). PSPP2-1 (not PSPP1-1) exhibited the highest reducing
power, DPPH radical scavenging and chelating capability. These findings
3.1.6.1. Roots provide evidence indicating that in vitro antioxidant capacities of die-
In human gastric carcinoma SGC7901 and colon cancer SW620 cells, tary materials is not always correlated to their in vitro anticancer activ-
3 polysaccharides, PSPP1-1 (17.8 kDa), PSPP2-1 (33.3 kDa), and PSPP3- ities (Wang & Zhu, 2015). In human colon cancer HT-29 and breast
1 (75.3 kDa) isolated purple sweet potato root dose-dependently cancer Bcap-37 cells, sweet potato root pectin (at doses of 0.01, 0.10,
inhibited proliferation of cancer cells (Wu et al., 2015). The antiprolifer- 0.25, 0.50, 1.00 mg/ mL) dose-dependently inhibited cancer cell prolif-
ative activities of polysaccharides against SGC7901 cells followed the eration (Zhang et al., 2013). In addition to polysaccharides, purified pro-
order of PSPP1-1 N PSPP2-1 N PSPP3-1 (at doses of 100, 200, 300, 400, tein (about 25 kDa) from fresh sweet potato roots dose-dependently
500 μg/ mL). The antiproliferative activities of polysaccharides against inhibited the proliferation (at doses of 2, 4, 10, 20, 40 μmol protein/ L),
SW620 cells are in the order of PSPP1-1 N PSPP3-1 N PSPP2-1 (at migration (at doses of 0.8, 8, 40 μmol protein/ L), and invasion (at
doses of 200, 400, 600, 800, 1000 μg/ mL). PSPP1-1 exhibited the highest doses of 0.8, 8, 40 μmol protein/ L) in human colorectal SW480 cancer
antiproliferative effects on both cell lines, probably due to its lower mo- cells (Li, Mu, & Deng, 2013). Purple sweet potato anthocyanin was
lecular weight and higher sulfate contents than PSPP2-1 and PSPP3-1 also antiproliferative against cancer cells. In human colonic SW480 can-
(Wu et al., 2015). PSPP1-1has been found to induce apoptosis, but the cer cells, anthocyanin extracts (at varying concentrations up to 40 μM of
 S. Wang et al. / Food Research International 89 (2016) 90–116 107

Table 4
Health effects of sweet potato: in vivo studies.

Sample type
Parts (No.)
Bio-functions used Country of origin Experimental design Major findings References

Prevention of Leaf Cooked purple sweet 15 healthy male human subjects daily consumed a 1 Sweet potato leaves decreased exercise-induced Chang et
exercise-induced potato leaves (stir-fried week diet containing 200 g cooked purple sweet plasma lipid peroxidation (plasma thiobarbituric al. (2010)
oxidative stress for 3–5 min) potato leaves and the control diet, respectively acid-reactive substance production), protein
(1) Sweet potato leaves diet referred to polyphenol-rich oxidation (protein carbonyl production), and
Taiwan diet (5.7 mg gallic acid equivalent/g diet, DW, of total inflammation (pro-inflammatory cytokine plasma
polyphenols) IL-6 concentration)
Control diet refers to low-polyphenol diet (5.7 mg Sweet potato leaves increased plasma total
gallic acid equivalent/g diet, DW, of total polyphenol concentrations and ferric reducing
polyphenols) ability of plasma
Hepatoprotective Root Anthocyanin fractions Rats (male Sprague–Dawley) received dimethyl Anthocyanin fractions exhibited Choi et al.
and antifibrotic form aqueous extract of nitrosamine (DMN, 10 mg/ kg BW intraperitoneal dose-dependent hepatoprotective and (2010)
whole purple-fleshed injection, 3 times, weekly) for 4 weeks antifibrotic effects against liver injuries induced
sweet potato DMN-induced rats were intragastrically administered by DMN
50, 100, 200 mg/kg of anthocyanin fraction (6 times,Anthocyanin fractions acted as antioxidants
daily) for 4 weeks) Anthocyanin fractions decreased DMN-induced
increases in expression levels of a-smooth muscle
actin and collagen type I and III, platelet-derived
growth factor receptors-β, tumor necrosis
factor-α and transforming growth factor-β
Hepatoprotective Root Anthocyanin fractions Rats (male Sprague–Dawley) received DMN Anthocyanin fractions had dose-dependent Hwang,
and antioxidative from whole purple sweet (10 mg/kg, BW intraperitoneal injection, 3 times, hepatoprotective and antifibrotic in heptic Choi, Yun,
potato weekly) for 4 weeks DMN-induced injured rats et al.
(1) DMN-induced rats were fed intragastrically Anthocyanin fractions decreased serum alanine (2011)
Korea anthocyanin (50, 100, 200 mg/kg, daily, 6 times) for 4 aminotransferase and aspartate aminotransferase
weeks activities, and liver malondialdehyde
Anthocyanin fractions increased the expression of
the antioxidant enzymes (NADPH:quinine,
oxidoreductase-1, heme oxygenase-1, and GSTα),
via activating nuclear erythroid 2-related factor 2
Anthocyanin fractions decreased inflammatory
mediators (COX-2 and iNOS gene expression) via
inhibiting NF-κB
Hepatoprotective Root Anthocyanin fractions Rat (male Sprague–Dawley) received tert-butyl Anthocyanin fractions protected rats against Hwang,
and antioxidative from aqueous extract of hydroperoxide (0.2 mmol/kg, BW) by intraperitoneal tert-butyl hydroperoxide-induced hepatic injury Choi, Choi,
whole purple-fleshed injection Anthocyanin fractions decreased serum alanine et al.
sweet potatoes Rats were administered intragastrically anthocyanin aminotransferase and aspartate aminotransferase (2011)
(1) fraction (10–200 mg/kg BW, once, daily) for 3 days activities, but increased glutathione-S-transferase
Korea activity
Anthocyanin fractions decreased
malondialdehyde, pyknosis, cytolysis, necrosis,
cell swelling, and DNA damage of liver
Anthocyanin fractions increased the expression
levels of the antioxidant enzymes
(NADPH:quinine oxidoreductase-1, heme
oxygenase-1, and glutathione S-transferase via
Nrf2 nuclear translocation and Akt and ERK1/2
activation pathways
Hepatoprotective Root Purple sweet potato Acute liver injured rats (male Kunming) were Sweet potato anthocyanins dose-dependently Wang et
and antioxidative anthocyanin powder (1) induced by single peritoneal injection of tert-butyl decreased serum alanine aminotransferase and al. (2014)
hydroperoxide (0.1%, 10 mL/kg, BW) aspartate aminotransferase activities, liver index
Chronic liver injured rats (male Wistar) were in tert-butyl hydroperoxide induced acute and
induced by peritoneal injecting of tert-butyl chronic liver-injured rats
hydroperoxide (25%, 2 mL/kg BW, twice, weekly) for Sweet potato anthocyanins attenuated tert-butyl
12 weeks hydroperoxide induced ballooning degeneration,
Acute liver injured rats were fed anthocyanin (375, macrovesicular steatosis, fibrous tissue
750, 1500 mg/kg, daily) for 7 days hyperplasia and even spotty necrosis,
Chronic liver injured rats were fed anthocyanins inflammatory cell infiltrate
(32.5, 75, 150 mg/kg, daily) for 45 days
Hepatoprotective Root Crude water extracts and Ischaemia–reperfusion rats (male, Sprague–Dawley) Water extracts had better hepatoprotective Jung et al.
and antioxidative anthocyanins from orally fed extracts (10 g/kg BW) or anthocyanins effects than purified anthocyanins (2015)
Shinzam purple sweet (180.3 mg/ kg BW, twice, daily) for 14 days Water extracts decreased serum aspirate
potato aminotransferase and alanine aminotransferase
(1) activities
Korea Water extracts increased liver glutathione levels
and activities of superoxide dismutase and
glutathione peroxidase. Anthocyanins fractions
only increased liver superoxide dismutase activity
Both water extracts and anthocyanins attenuated
hepatic pathological changes (hepatic distortion,
haemorrhage, necrosis and inflammatory cell

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Table 4 (continued)

Sample type
Parts (No.)
Bio-functions used Country of origin Experimental design Major findings References

infiltration)
Hepatoprotective Root Anthocyanin fractions Rats (male Kunmin) were orally administered Anthocyanin fractions exhibited dose-dependent Zhang et
and antioxidative from ethanol extract of intragastrically anthocyanin fractions (227.5, 455, DPPH and hydroxyl radical-scavenging capacities al. (2016)
purple-fleshed sweet 910 mg/kg) and 0.8% CCl4 for 3 weeks Anthocyanin fractions dose-dependently
potatoes Antioxidant activities were measured by DPPH and increased relative liver weights, and activities of
(1) hydroxyl radical-scavenging assays superoxide dismutase and glutathione peroxidase
China in carbon tetrachloride-induced rats
Anthocyanin fractions decreased serum aspartate
aminotransferase and alanine aminotransferase,
and hepatic lipid peroxidation (malondialdehyde
production)
Anthocyanin fraction suppressed vacuolization,
necrosis, and congestion in carbon
tetrachloride-induced rats
Anti-LDL oxidation Leaf Sweet potato leaves Healthy volunteers (6 males and 7 females, 22–49 Sweet potato leaves prolonged a lag time for Nagai et
(8) years old) consumed 18 g of raw “Suioh” leaves starting LDL oxidation and prevented al. (2011)
containing about 1000 mg polyphenols thiobarbituric acid reactive substance production
at 0.5 h and 4 h after leaf consumption
Sweet potato leaves decreased LDL mobility at 2 h
and 4 h after leaf consumption
Anti-LDL oxidation were due to the combination
of hydrophilic and hydrophobic antioxidants in
leaves
Antihyperglycemic Root Purple sweet potato Kunming mice fed anthocyanin extract powder (100, Anthocyanin reduced plasma glucose levels Zhao et al.
anthocyanin extracts 1000 mg/kg, BW) for 4 weeks before streptozocin Anthocyanins treated rats had normal (2013)
(100 mg/kg, BW) injection microscopic appearance of the pancreatic cells
Streptozocin-induced Kunming mice fed anthocyanin Anthocyanin diet inhibited body weight loss of
extract powder (100, 1000 mg/kg, BW) for another 1 streptozocin-induced diabetic rats
week
Antihyperglycemic Leaf Sweet potato leaf extract Male KK-Ay mice were fed diets containing 3% sweet Leaf extracts attenuated hyperglycaemia in type 2 Nagamine
powder potato leaf extract powder for 5 weeks diabetic mice et al.
(1) Leaf extracts stimulated glucagon-like peptide-1 (2014)
secretion
Caffeoylquinic acid derivatives were
antihyperglycaemia bioactives in leaves
Antiaging Root Anthocyanin extracts Kunming ablactation mice (male) were fed Anthocyanin extracts-treated mice Zhao et al.
from purple sweet anthocyanin extract powder (100, 500, 1000 mg/kg, dose-dependently decreased serum (2013)
potatoes BW) malondialdehyde levels, and increased
(1) superoxide dismutase and glutathione peroxidase
Anthocyanin extracts (100 mg/kg) were similar to
vitamin C in their antiaging effects
Inhibition of Root Anthocyanin-enriched CF-1 mice were fed a diet containing dietary Anthocyanins-enriched sweet potatoes Lim et al.
carcinogenesis purple fleshed sweet anthocyanin-enriched purple-fleshed sweet potato suppressed zoxymethane-induced formation of (2013)
potatoes (10%–30%) aberrant crypt foci in the colons of CF-1 mice
(2) Anthocyanins-enriched sweet potatoes inhibited
cell nuclear antigen and promoted apoptotic
caspase-3 expression in the colon mucosal
epithelial cells
Inhibition of Root Anthocyanin extracts Specific pathogen-free (SPF)-grade ICR mice (males Anthocyanins inhibited implanted S180 cell Zhao et al.
carcinogenesis from purple sweet and females) were implanted with S180 sarcoma growth (2013)
potatoes cells Anthocyanins decreased in serum
(1) S180 implanted rats were fed anthocyanin extracts malondialdehyde levels and increased superoxide
(100, 500, 1000 mg/kg, BW) dismutase and glutathione peroxidase activities
Inhibition of Root Purified protein from Human colorectal cancer HCT-8 cells were inoculated Sweet potato proteins were antiproliferative and Li, Mu and
carcinogenesis fresh sweet potatoes into the peritoneal cavity of 15 BALB/c nude mice antimetastatic Deng
(1) Murine Lewis lung carcinoma 3LL cells inoculated (2013)
subcutaneously into the hind legs of C57BL/6 mice
Sweet potato protein was administered
intraperitoneally (2 μmol/L per kg, daily) or
intragastrically (80 μmol/L per kg, daily)
Inhibition of Leaf Freeze-dried methanol Human prostate cells PC3Luc were implanted 400 mg/kg of leaf extract was non-toxic to normal Karna et
carcinogenesis leaf extracts of sweet subcutaneouslyinto male nude mice tissues, such as gut and bone marrow al. (2011)
potatoes The mice received freeze-dried methanol leaf 400 mg/kg leaf extracts inhibited growth and
(1) extracts (400 mg/kg, BW, daily) by oral gavage progression of prostate tumor xenografts by ∼69%
in nude mice
Immunomodulatory Root Water, ethanol (10% and LP-BM5 murine leukemia virus (MuLV)-induced Water extracts increased activities of serum Kim, Nam,
activity 80%) extracts from immune deficient mice was fed dietary antioxidant enzymes (superoxide dismutase, et al.
purple sweet potatoes supplementation with water, ethanol (10% or 80%) catalase, glutathione peroxidase) (2015),
(1) extracts (300 mg/kg, BW) for 12 weeks Water extracts attenuated the decreases in T- and
B-cell proliferation, proinflammatory cytokine
(TNF-a) production, and imbalance of the
Th1-type and Th2-type cytokine productions in
mitogen-stimulated splenocytes of LP-BM5 MuLV
infected mice
 S. Wang et al. / Food Research International 89 (2016) 90–116 109

Table 4 (continued)

Sample type
Parts (No.)
Bio-functions used Country of origin Experimental design Major findings References

Antiobesity Root Anthocyanin fractions ICR male mice were fed orally high-fat diet (45% kcal Anthocyanin fractions reduced body and liver Hwang,
from purple sweet fat) with anthocyanin fractions (200 mg/kg, daily) for weights, levels of serum aspartate Choi, Han,
potatoes 4 weeks aminotransferase serum alanine et al.
(1) aminotransferase, and serum glucose in obese (2011)
mice
Anthocyanin fractions increased the
phosphorylation of AMPK and acetyl-coenzyme A
carboxylase in the liver
Anthocyanin fractions increased the levels of
sterol regulatory element-binding protein 1,
acetyl-coenzyme A carboxylase, and fatty acid
synthase
Antiobesity Root Purple sweet potato C57BL/6 J male rats were fed high-fat diet (45% kcal Purple sweet potato extracts dose-dependently Shin et al.
extracts fat) containing sweet potato extracts (100, 250, 500 decreased body and adipose tissue weights, (2013)
mg/kg) for 16 weeks hepatic steatosis in obese rats
Purple sweet potato extracts modulated
lipogenesis-related genes; purple sweet potato
extracts suppressed the expressions of sterol
regulatory element-binding protein-1, acyl-CoA
synthetase, glycerol-3-phosphate acyltransferase,
HMG-CoA reductase, and fatty acid synthase in
liver of obese rats

BW: body weight; DW: dry weight; LDL: low-density lipoprotein.

peonidin-3-glucoside equivalent) dose-dependently inhibited cancer hepatocyte HL7702 cells (Wang et al., 2014). The mechanisms
cell proliferation. In fact, purple sweet potato anthocyanin induced cyto- responding to hepatotoxicity varied among the cell lines applied. Sweet
static arrest of cell cycle at G1 phase (Lim et al., 2013). The molecular potato anthocyanin (100, 200, 400 μg/ mL) dose-dependently inhibited
mechanism of action of the in vitro anticancer properties of sweet potato the accumulation of reactive oxygen species in HL7702 cells induced by
crude extracts, fractions, and purified components remains to be carbon tetrachloride (Wang et al., 2014). Anthocyanin fraction prevented
investigated. t-BHP-induced cell death in HepG2 cells by dose-dependently reducing
the levels of intracellular reactive oxygen species, lipid peroxidation,
3.1.6.2. Leaves and other parts and caspase-3 activity. Anthocyanin fraction increased the levels of
In human prostate cancer cells (LNCaP, DU145, PC-3, C4-2, C4-2B), cytoprotective enzymes in HepG2 cells via Akt and ERK1/2/Nrf2 signaling
methanol extracts of sweet potato leaves (cultivated in the USA) pathways (Hwang, Choi, Choi, et al., 2011). Anthocyanin fractions also
inhibited cellular proliferation of all studied cancer cells (with IC50 dose-dependently inhibited rat hepatic stellate HSC-T6 cell proliferation
values in the range of 145–315 μg/mL). In normal prostate epithelial via blocking PDGFR-β signaling, inhibiting Akt and ERK1/2 activation
cells (PrEC and RWPE-1), methanol extracts of sweet potato leaves min- and α-SMA expression (Choi et al., 2011). These mechanisms found in
imally influenced normal cells (with IC50 values 1000 and 1250 μg/mL for vitro have been confirmed in the section of in vivo anti-hepatoprotection.
PrEC and RWPE-1 cells, respectively). Molecular mechanism underlying
the anticancer effect of leaf extracts in PC-3 prostate cancer cells (cancer 3.1.8. Antiobesity
cell representative) was related to their interferences of cell cycle pro- The antiobesity potential of sweet potatoes was evaluated in HepG2
gression, reductions of clonogenic survival, modulations of cell cycle cells (human hepatocellular liver carcinoma cell line). However, it re-
and apoptosis regulatory molecules, and inductions of apoptosis (Karna mains to be determined in terms of the relevance between HepG2
et al., 2011). Previously, caffeoylquinic acid derivatives, 3,4,5-tri-O- cells and human physiological functions related to obesity.
caffeoylquinic acid, in particular, dose-dependently and cell line-depen-
dently inhibited the proliferation of human stomach Kato III cancer 3.1.8.1. Roots
cells, colon cancer DLD-1 cells, and promyelocytic leukemia HL-60 cells HepG2 cells were treated with glucose (30 mM) to induce hepatic
(Kurata, Adachi, Yamakawa, & Yoshimoto, 2007). At the molecular lipid accumulation (Hwang, Choi, Han, et al., 2011). Anthocyanin frac-
level, 3,4,5-tri-O-caffeoylquinic acid induced apoptosis by increasing cas- tions (at doses of 50, 100, 200 μg/mL) were nontoxic, but dose-depen-
pase-3 activity and expression of c-Jun (Kurata et al., 2007). More efforts dently reduced the accumulation of the intracellular lipid, the
are needed to identify the key bioactive or bioactive mixtures with poten- triglyceride and total cholesterols in glucose-treated HepG2 cells and,
tial for cancer prevention. The molecular mechanism of the growth sup- at the molecular level, anthocyanin fractions reduced levels of lipid me-
pression in cancer cells induced by sweet potatoes remains to be clarified. tabolism-related proteins (FAS and SREBP-1), which was associated
with adenosine monophosphate-activated protein kinase (AMPK) sig-
3.1.7. Antihepatotoxic naling pathways (Hwang, Choi, Han, et al., 2011). Anthocyanin fractions
HepG2 (human hepatocellular liver carcinoma cells), HSC-T6 (rat inhibited hepatic lipid accumulation via activating of AMPK signaling
hepatic stellate cells), HL7702 (human normal hepatocyte cells) repre- pathways. The involvement of AMPK signaling pathways in antiobesity
sented the recently used cell lines to test the hepatoprotective potential of sweet potato root anthocyanin was further confirmed using obese
of sweet potatoes. rats in the in vivo antiobesity section below.

3.1.7.1. Roots 3.1.9. Antiinflammatory

The protective effects of anthocyanin fractions from purple sweet
potato were studied using rat hepatic stellate HSC-T6 cells, tert-butyl 3.1.9.1. Roots
hydroperoxide (t-BHP)-treated HepG2 cells (Choi et al., 2011; Hwang, In lipopolysaccharide-stimulated human neuroblastoma cells (SH-
Choi, Choi, et al., 2011), and carbon tetrachloride-treated human normal SY5Y), extracts from lyophilized powders of 4 sweet potato varieties
110 S. Wang et al. / Food Research International 89 (2016) 90–116

(NCPUR06-020, Covington, Yellow Covington, and NC07-847) had ge- et al., 2011). In another study, anthocyanins (50–200 mg/ kg) decreased
notype-dependent anti-inflammatory properties. The molecular mech- the levels of inflammatory mediators (COX-2 and iNOS gene expres-
anism behind these extracts was not probed (Grace et al., 2014). sion) by inhibiting NF-κB in hepatic DMN-induced injured rats
Postharvest storage time-dependently decreased the anti-inflammatory (Hwang, Choi, Yun, et al., 2011). Daily Chinese sweet potato anthocya-
capacity of sweet potatoes. Anti-inflammatory capacity has been con- nin (at doses up to 910 mg/kg for 3 weeks) diet were antifibrotic in
nected to the DPPH radical scavenging activity and phenolic contents mice with hepatic CCl4-induced injury (Zhang et al., 2016). Crude ex-
(Grace et al., 2014). Molecular mechanisms behind anti-inflammatory tracts and purified anthocyanins from purple sweet potato attenuated
capacity of sweet potatoes have been rarely reported. hepatic pathological changes. These changes included hepatic distor-
tion, haemorrhage, necrosis, and inflammatory cell infiltration in is-
3.2. In vivo models chaemia–reperfusion-induced hepatic injured rats (Jung et al., 2015),
vacuolization, necrosis, and congestion in hepatic CCl4-induced injured
Diverse health benefits of sweet potato and its components have rats (Zhang et al., 2016), disordered arrangement of cells and cellular
been observed in animal and clinical models in vivo (Table 3). In respec- edema in hepatic alcohol-induced injured rats (Sun, Mu, Liu, et al.,
tive studies, sweet potato cultivars, plant parts used, animal model char- 2014), and ballooning degeneration, macrovesicular steatosis, fibrous
acteristics, dosage ranges, dietary intervention period, and cellular and tissue, hyperplasia and spotty necrosis, and inflammatory cell infiltrate
molecular biomarkers evaluated were the variables. Although antioxi- in hepatic CCl4-induced injured rats (Wang et al., 2014). According to
dant activity has been linked to several bio-functions of sweet potato, Jung et al. (2015), sweet potato crude extracts were more hepatoprotec-
such as hepatoprotection, antitumor, and immunomodulatory activi- tive than the purified anthocyanins. Therefore, additive and synergistic
ties, it should be noted that there may be no correlation between effects of different hepatoprotective bioactives, rather than a single
them (Wang & Zhu, 2015). component (anthocyanin), possibly contributed to this effect of crude
extracts.
3.2.1. Hepatoprotection
Hepatoprotection of sweet potato has been identified in rats with 3.2.2. Prevention of damage by exercise-induced oxidative stress
hepatic injuries which were induced by various agents such as car- Sweet potato has the ability to prevent physiological abnormali-
bon tetrachloride (CCl4) (Wang et al., 2014; Zhang et al., 2016), acet- ties induced by oxidative stress, and the effect is correlated with
aminophen (Wang et al., 2014), ischaemia–reperfusion (Jung et al., the levels of biomarkers indicating oxidative damage, inflammation,
2015), dimethylnitrosamine (DMN) (Choi et al., 2010; Hwang, and antioxidant status. The markers of oxidative damages include in-
Choi, Yun, et al., 2011), tert-butyl hydroperoxide (t-BHP) (Hwang, creases in plasma TBARS and protein carbonyl content (as a marker
Choi, Choi, et al., 2011), and ethanol (Sun, Mu, Liu, et al., 2014; of protein oxidation) (Chang, Hu, Huang, Yeh, & Liu, 2010). The
Wang et al., 2014). markers of antioxidant status include plasma total polyphenol con-
centration and total antioxidant power (i.e., the ferric reducing abil-
3.2.1.1. Roots ity of plasma) (Chang et al., 2010). The markers of inflammation
Crude extracts or purified anthocyanins from purple sweet potato include plasma IL-6 concentration and HSP72 protein expression
roots act via diverse mechanisms in response to liver injury in animal (Chang et al., 2010).
models. Korean Shinzami purple sweet potato extracts (10 g/kg rat
body weight) and purified anthocyanins (180.3 mg/ kg rat body weight)
decreased the activities of serum aspirate aminotransferase (AST) and 3.2.2.1. Leaves and other parts
alanine aminotransferase(ALT) in the hepatic ischaemia reperfusion in- Fifteen healthy male human subjects consumed 200 g of cooked
jured rats (Jung et al., 2015). Anthocyanins purified from the aqueous sweet potato leaves (high-polyphenol diet with 5.7 mg gallic acid
extracts of Korean whole purple sweet potato (50, 100, 200 mg/ kg rat equivalents of total polyphenols/g diet) or the control (a low-polyphe-
body weight, 6 times, weekly) attenuated the AST and ALT activities in nol diet with 0.63 mg gallic acid equivalent of total polyphenols/g
hepatic DMN-induced injured rats after 4 weeks of feeding (Hwang, diet) daily for 7 days. During this dietary intervention, all subjects per-
Choi, Yun, et al., 2011). A 3-day diet containing anthocyanin extract formed treadmill running for 1 h at a speed corresponding to 70% of
(10–200 mg/ kg rat body weight, once, daily) attenuated AST and ALT each subject's individual maximal oxygen uptake (Chang et al., 2010).
activities in hepatic t-BHP-induced injured rats (Hwang, Choi, Choi, et Compared with the control, the purple sweet potato leaves group in-
al., 2011). Chinese purple sweet potato anthocyanins (for 7 days) atten- creased the total polyphenol concentration and ferric reducing ability
uated the AST and ALT activities in rats with hepatic injury induced by of plasma, decreased the plasma levels of thiobarbituric acid-reactive
ethanol, acetaminophen, and CCl4 (Wang et al., 2014). In male C57BL/ substance and protein carbonyl, and IL-6 concentration (pro-inflamma-
6 mice with hepatic injury by alcohol, Chinese purple sweet potato an- tory cytokine) (Chang et al., 2010).
thocyanins (3.02 × 104 mg cyanidin 3-glucoside equivalents /100 g of
total anthocyanins) at daily doses of up to 375 mg/ kg rat body weight 3.2.3. Antiaging
(30 days) attenuated the AST and ALT activities, in addition to decreas- Few studies have used male Kunming mouse models to provide
ing the levels of serum triglyceride, total cholesterol, low-density lipo- certain mechanistic information related to antiaging property of sweet
protein cholesterol, and lactate dehydrogenase (Sun, Mu, Xi, Zhang, et potatoes (Lu, Wu, Zheng, Hu, & Zhang, 2010; Zhao et al., 2013). In the
al., 2014). Sweet potato extracts or purified anthocyanins acted as anti- study by Lu et al. (2010), the effect of sweet potato anthocyanins on
oxidants to regulate impaired oxidative balance by suppressing reactive the survival of neurons was tested on Kunming mice with D-galactose-
oxygen species generation in hepatic CCl4-induced injured rats (Zhang induced oxidative stress damage. In a study by Zhao et al. (2013), a
et al., 2016), by inhibiting lipid peroxidation (malondialdehyde level possible involvement of antioxidant mechanism in antiaging property
as an indicator) in hepatic injured rats induced by t-BHP and CCl4 or al- of purple sweet potato anthocyanins was confirmed in Kunming mice.
cohol (Hwang, Choi, Choi, et al., 2011; Sun, Mu, Liu, et al., 2014; Sun, Mu, One of the concerns surrounding the animal models used here is their
Xi and Song, 2014; Sun, Mu, Xi, Zhang and Chen, 2014; Zhang et al., relevance to the human aging process. These animal models only
2016), or by increasing the activities of superoxide dismutase and gluta- reflected a defined range of pathology of aging. Diverse animal aging
thione peroxidase in hepatic CCl4-induced injured rats (Zhang et al., models have been established (Mitchell, Scheibye-Knudsen, Longo, &
2016). In hepatic t-BHP-induced injured rats, daily anthocyanin (10– De Cabo, 2015). Appropriate selections of animal models to explore
200 mg/ kg) diet for 3 days up-regulated antioxidant enzyme HO-1 the molecular mechanisms behind the antiaging property of sweet
via the Akt and ERK1/2/Nrf2 signaling pathways (Hwang, Choi, Choi, potato remain to be justified.
 S. Wang et al. / Food Research International 89 (2016) 90–116 111

3.2.3.1. Roots 3.2.4.2. Leaves and other parts

Purple sweet potato anthocyanins were fed to D-galactose-treated Hot water extracts of sweet potato leaves and stems were hypogly-
male Kunming mice on a daily basis for 4 weeks (Lu et al., 2010). Purple cemic in normoglycemic model, and antihyperglycemic in STZ-induced
sweet potato anthocyanins, at a dose of 100 mg/ kg rat body weight, diabetic model (Olowu, Adeneye, & Adeyemi, 2011). Healthy or diabetic
protected brain function of mice against D-galactose-induced oxidative rats were orally fed leaf and stem extracts, at doses of 100, 200, and
stress. Sweet potato anthocyanins increased the open-field activity, spa- 400 mg/ kg of rat body weight for 14 days. Leaf and stem extracts
tial learning and memory ability, and decreased the step-through laten- (100–400 mg/kg) dose-dependently decreased the fasting blood glu-
cy of D-galactose-treated mice (Lu et al., 2010). Sweet potato cose levels of both healthy and diabetic rats. The maximum hypoglyce-
anthocyanins decreased the formation of advanced glycation end-prod- mic effects of the extracts in both healthy and STZ-induced
ucts (AGEs) and the AGE receptor expression. Sweet potato anthocya- hyperglycemic rats were achieved at a dose of 400 mg/ kg, which
nins increased the expression and activities of Cu, Zn-superoxide were comparable to that of glibenclamide (an antidiabetic drug refer-
dismutase, and catalase. Sweet potato anthocyanins increased neuronal ence) at a dose of 1 mg/ kg. Non-cytotoxicity of the aqueous leaf and
survival (indictor of brain learning–memory function) and cognitive stem extracts (up to 1000 mg/kg) was proven (Olowu et al., 2011);
performance. At the molecular level, phosphorylation of Bad at Ser136 however, the molecular mechanism of their effects remains unclear.
and Ser112 associated with the activation of PI3K/Akt and ERK path- The diversity of chemical constitutes, such as phytochemicals (i.e., phe-
ways, respectively, was involved in these observed effects (Lu et al., nolic acids, anthocyanins) and polysaccharide, are possible antidiabetic
2010). bioactives in these leaf and stem extracts. Male KK-Ay mice (type 2 di-
In another study, antiaging activity of anthocyanin extracts from abetic mice) were fed with a diet containing 3% of sweet potato leaf ex-
purple sweet potato was proved in 12-month-old male Kunming mice tract powder for 5 weeks (Nagamine et al., 2014). As a result, sweet
that were fed anthocyanins (doses of 100, 500, 1000 mg/ kg rat body potato leaf attenuated hyperglycemia in KK-Ay mice, via stimulating
weight). In terms of the capacity to retard the aging of the mice, antho- glucagon-like peptide-1 (GLP-1) secretion. Caffeoylquinic acid deriva-
cyanin extract (100 mg/ kg) was similar to vitamin C (100 mg/kg) (Zhao tives were one of the key hypoglycemic contributors in sweet potato
et al., 2013). No difference in antiaging index was observed in 12- leaves (Nagamine et al., 2014).
month-old mice fed with 1000 mg/kg anthocyanin extracts and 5-
month-old rats fed with normal diet without anthocyanin extracts. 3.2.5. Inhibitory effect on low-density lipoprotein oxidation
The levels of superoxide dismutase and glutathione peroxidase and
malondialdehyde production of 12-month-old rats fed with 1000 mg/ 3.2.5.1. Leaves and other parts
kg anthocyanin extracts were similar to the normally fed 5-month-old In a clinical trial, 6 male and 7 female healthy volunteers (ages of 22
rats (Zhao et al., 2013). These findings showed that the antioxidant and 49) consumed 18 g of raw sweet potato leaves containing 1000 mg
mechanism was behind the antiaging property of sweet potato anthocy- polyphenols (Nagai et al., 2011). A prolonged lag time for starting LDL
anins. The involvement of other mechanisms remains to be determined. oxidation and inhibition of thiobarbituric acid reactive substances
were observed at 0.5 and 4 h after consumption of sweet potato leaves.
Decreases in LDL mobility were observed at 2 and 4 h after consumption
3.2.4. Hypoglycemic and antihyperglycemic effects
of the leaves. One of the major anti-LDL contributors were a combina-
Hyperglycemia (exceptionally high blood glucose) represents one of
tion of hydrophilic and hydrophobic antioxidants in leaves (Nagai et
the typical diabetic complications. Diabetes has become listed as a major
al., 2011). No recent studies reported the inhibitory effect of sweet po-
health concern due to its ever-increasing occurrence worldwide
tato roots on LDL oxidation, though it may be expected that the bioac-
(Schwarz et al., 2013). Sweet potato-derived dietary materials demon-
tives in the roots possess this function.
strated their potential as cost-efficient antidiabetic agents. Numerous
diabetic animal models have been established to clarify the pathogene-
3.2.6. Regulation of liver lipid profiles
sis and progression in human diabetes. Well-designed experiments,
varying in dose, dose schedules, and routes of administration and ani-
3.2.6.1. Leaves and other parts
mal model types, are critical to elucidate the molecular mechanisms be-
Alterations in lipid profiles were observed in hypertensive rats with
hind hypoglycemic activity of sweet potatoes (Wang & Zhu, 2016).
sweet potato diet. Male spontaneously hypertensive rats were fed with
AIN-76A diet containing 4% sweet potato greens (Tuskegee) for
3.2.4.1. Roots 4 weeks. Sweet potato greens decreased the concentration of
Anthocyanins of purple sweet potato root were hypoglycemic in pentadecanoic and lauric acids (saturated fatty acids), while increasing
normoglycemic models and antihyperglycemic in diabetic models in- the concentrations of oleic acid (monounsaturated omega-9 fatty acid),
duced by high-saturated fat/sugar or streptozotocin (STZ) (Zhao et al., total eicosapentaenoic and docosahexaenoic acids (a sum of EHA and
2013). Molecular mechanisms behind these effects have been rarely DHA), and total omega-3 fatty acids (a sum of linolenic acid, EHA and
reported. In the study by Zhao et al. (2013), male Kunming mice were DHA) (Johnson, Pace, Dawkins, & Willian, 2013). The health impacts
fed with a diet containing purple sweet potato root anthocyanins (1 or of sweet potato greens induced alterations in liver fatty acid profiles
10 g/kg rat body weight) for 4 weeks prior to injecting STZ (at dose of were not further defined.
100 mg/kg rat body weight). The diabetic rats were then fed with purple
sweet potato anthocyanins for another 1 week. The hypoglycemic prop- 3.2.7. Antitumor
erty of purple sweet potato was reflected by lowering plasma glucose Antitumor activity of sweet potatoes was observed in mice im-
levels in Kunming mice with pre-treatment (4 weeks) of purple sweet planted with tumor cells, and in the colon of mice with carcinogen-in-
potato anthocyanins. In Kunming mice with diabetes induced by high- duced aberrant crypt foci (Zhao et al., 2013; Lim et al., 2013).
saturated fat/sugar, pre-treatment (4 weeks) of purple sweet potato an- Mechanisms by which sweet potato exerts antitumor activity are not
thocyanins decreased the plasma glucose levels. Five weeks of treat- yet fully understood.
ment (4 weeks of pre-treatment and 1 week post-treatment) with
purple sweet potato anthocyanins dose-dependently inhibited the in- 3.2.7.1. Roots
crease in the plasma glucose levels, abnormal pancreatic morphology In sarcoma 180 (S180) implanted ICR male mice, anthocyanin ex-
(i.e., hemorrhagic necrosis, interstitial vascular lesions or fibrosis, cell tract powder (doses of 100, 500, 1000 mg/kg rat body weight) dose-de-
degeneration, lymphocytic infiltration), and body weight loss in STZ- pendently inhibited the growth of implanted cells. Anthocyanin extract
treated mice (Zhao et al., 2013). powder increased the levels of serum antioxidant enzymes (superoxide
112 S. Wang et al. / Food Research International 89 (2016) 90–116

dismutase and glutathione peroxidase), and decreased serum free radical scavenging, singlet oxygen quenching, metal chelation,
malondialdehyde levels (Zhao et al., 2013). In the study by Lim et al. and inhibition of oxidative enzymes (Campbell & Campbell, 2005). An-
(2013), purple-fleshed sweet potato anthocyanin extracts (10%–30%) tioxidant synergies derived from a combination of antioxidative com-
suppressed the formation of azoxymethane-induced aberrant crypt pounds have been rarely reported.
foci in the colon of CF-1 mice. Anthocyanin extracts inhibited the prolif- Maximizing health potential starts with the use of whole sweet pota-
eration of cell nuclear antigen and stimulated the apoptotic caspase-3 to plant, which refers to every part of the food, including root, root peels,
expression in the colon mucosal epithelial cells (Lim et al., 2013). stems, and leaves. Use of all parts of the sweet potato can also be a new
approach to minimize the amount of food waste. As shown in Tables 3
3.2.8. Immunomodulatory activity and 4, different parts (i.e., roots and leaves) of sweet potato varied in
The immunomodulatory activity of sweet potato was studied in health benefits. Mixed different parts of sweet potato may target multi-
mice infected by virus. For example, C57BL/6 mice with LP-BM5 murine ple molecular processes and potentially result in more powerful therapy
leukemia virus infection develops a disease that has many features in for the prevention and treatment of human diseases, than that of root or
common with human immune-deficiency (Kim, Nam, et al., 2015). leaf used alone. Up to date, few studies have tested this hypothesis.
Noticeably, the biological interactions among bioactive components in
3.2.8.1. Roots different parts may be synergistic, additive, and antagonistic (Wang & Zhu,
Water, 10% and 80% ethanol extracts of purple sweet potato root 2015). Whether health-promoting synergisms or antagonisms existed
powder at a concentration of 300 mg/kg were individually given to among mixed different parts of sweet potatoes is still to be discovered.
LP-BM5 virus-infected mice (Kim, Nam, et al., 2015). Among all the test- Methods to effectively evaluate these interactions are not well established.
ed extracts, water extract has the highest immunomodulatory activity. In addition, the consumption of sweet potato may possibly affect the me-
In mitogen-stimulated splenocytes of LP-BM5 virus-infected mice, tabolism of a variety of other foods in the daily diet or pharmaceutical
water extract increased the levels of serum antioxidant enzymes (su- drugs (e.g., antidiabetic drugs). Little information is available about inter-
peroxide dismutase, catalase glutathione peroxidase). Water extract actions between sweet potato-derived dietary materials and food/drug.
stimulated T- and B-cell proliferation and the pro-inflammatory cyto- Overall, sweet potato-derived synergisms remain to be developed.
kine (TNF-a) production. Water extract restricted the production imbal-
ance of the Th1-type and Th2-type cytokine (Kim, Nam, et al., 2015).
3.4. Relationships between in vitro and in vivo model systems
Antioxidant mechanism of immunomodulatory activity of sweet potato
was proved; however, other mechanisms are to be explored.
Few studies simply demonstrated a positive correlation between in
vitro and in vivo study. For example, anthocyanin fractions obtained
3.2.9. Antiobesity
from the purple sweet potato exhibited hepatoprotective effect on
Obesity represents a key contributor to the development of type 2
tert-butyl hydroperoxide-induced damage in HepG2 cells line (in vitro
diabetes, high blood pressure, heart disease, stroke, arthritis, and cancer
model) and haptic injury of rat (in vivo model). Protective effects of an-
(Hwang, Choi, Han, et al., 2011; Shin et al., 2013). Purple sweet potato
thocyanin fractions from purple sweet potato were attributed to their
anthocyanins have been found to be of antiobesity.
reactive oxygen species scavenging and regulation of the antioxidant
enzyme HO-1 via the Akt and ERK1/2/Nrf2 signaling pathways both in
3.2.9.1. Roots
vitro and in vivo (Hwang, Choi, Choi, et al., 2011). On the other hand,
A 4-week diet containing purple sweet potato anthocyanin fractions
the in vitro and ex vivo effects of purple sweet potato leaves on angio-
(at a concentration of 200 mg/kg) reduced weight gain and hepatic tri-
genesis were not correlated (Chen et al., 2011). Leaf methanol extract
glyceride accumulation, and improved the serum lipid profile in obese
containing polyphenols (0.2 to 0.8 mM gallic acid equivalent) were
ICR male mice induced by a high-fat diet (45% kcal fat) (Hwang, Choi,
antiangiogenesis in vitro. However, the results of ex vivo human serum
Han, et al., 2011). Focusing on the molecular targets, anthocyanin frac-
collected from the subjects who consumed 200 g of cooked sweet pota-
tions increased the levels of phosphorylation of AMPK and acetyl-coen-
to leaves showed pro-angiogenetic. The difference in the chemical com-
zyme A carboxylase in the liver. Anthocyanin fractions down-regulated
position between leaf methanol extract and leaf metabolites in human
the levels of sterol regulatory element-binding protein 1, acetyl-coen-
serum resulted in conflicting results. No studies provide mathematical
zyme A carboxylase, and fatty acid synthase. Anthocyanin fractions
models that describe in vitro and in vivo correlation (IVIVC). IVIVC re-
inhibited hepatic lipid accumulation via AMPK signaling pathway. In an-
flects connections between an in vitro property of a dosage form and
other study, a 16-week diet containing aqueous extracts of purple sweet
an in vivo response (Lua, Kima, & Parka, 2011; Sakore & Chakraborty,
potato (doses of 100, 250 and 500 mg/kg) dose-dependently improved
2011). For example, IVIVC can predict the in vivo performance of bioac-
the signs and symptoms of obesity in obese C57BL/6 J male rats treated
tives based on their antiproliferative activity in vitro. Well-characterized
by a high-fat diet (Shin et al., 2013). In obese rats, sweet potato extracts
physicochemical, biopharmaceutical, and pharmacokinetic properties
decreased the weights of rat body and adipose tissues. Sweet potato ex-
are crucial for developing an IVIVC focusing on physiological functions
tracts decreased the occurrence of hepatic steatosis (fatty liver). At the
of sweet potatoes.
molecular level, sweet potato extracts modulated lipogenesis-related
genes by multiply suppressing the expression of sterol regulatory ele-
ment-binding protein-1, acyl-CoA synthase, glycerol-3-phosphate acyl- 3.5. Impact of processing and health concerns
transferase, HMG-CoA reductase, and fatty acid synthase in liver tissue
(Shin et al., 2013). 3.5.1. High-fructose syrup
Sweet potatoes are potential raw materials for economic production
3.3. Bioactive synergy of high-fructose syrup, which is a sweetener used in food and beverage
industries (Johnson et al., 2009; Johnson et al., 2010; Dominque et al.,
Health-promoting synergism related to sweet potatoes deserves 2013). Concerns have been raised about the intake of sweeteners, par-
great research effects. Whole sweet potato plants have diverse chemical ticularly high-fructose syrup, which may be associated with many dis-
components with different physiological activities as shown above. The orders (i.e., obesity, diabetes, cardiovascular disease, hypertension,
combination of in vivo stimulatory and inhibitory effects of these com- cancer, and metabolic syndrome) (Bray, Nielsen, & Popkin, 2004;
ponents possibly results in particular physiological effects. In terms of White, 2013). A recent a systematic review and meta-analysis, however,
antioxidative responses, natural antioxidants in sweet potatoes possibly showed no correlation between hypercaloric fructose and glucose diets
applied different modes of action to response oxidative stress, such as and occurrence of non-alcoholic fatty liver disease (Chung et al., 2014).
 S. Wang et al. / Food Research International 89 (2016) 90–116 113

Impact of the sweet potato-related high-fructose syrup and other sugars Almazan, A. M., & Zhou, X. (1995). Total dietary fibre content of some green and root veg-
etables obtained at different ethanol concentrations. Food Chemistry, 53, 215–218.
(i.e., glucose) intake on human health remains to be better investigated. Anastácio, A., & Carvalho, I. S. (2013). Spotlight on PGI sweet potato from Europe: Study of
plant part, time and solvent effects on antioxidant activity. Journal of Food
3.5.2. Formation of acrylamide Biochemistry, 37, 628–637.
Arogundade, L. A., & Mu, T. -H. (2012). Influence of oxidative browning inhibitors and iso-
Reducing monosaccharides (glucose and fructose) and reducing di- lation techniques on sweet potato protein recovery and composition. Food Chemistry,
saccharide (maltose) represent reducing sugars in raw and cooked 134, 1374–1384.
sweet potato roots (Mei et al., 2010; Waramboi et al., 2011). During Balouiri, M., Sadiki, M., & Ibnsouda, S. K. (2016). Methods for in vitro evaluating antimicro-
bial activity: A review. Journal of Pharmaceutical Analysis, 6, 71–79.
thermal processing, the Maillard reaction of reducing sugars (free alde- Bengtsson, A., Namutebi, A., Larsson-Alminger, M., & Svanberg, U. (2008). Effects of vari-
hyde or ketone group) and amino acids results in the formation of acryl- ous traditional processing methods on the all-trans-β-carotene content of orange-
amide (a potential carcinogen and neurotoxin). According to limited fleshed sweet potato. Journal of Food Composition and Analysis, 21, 134–143.
Bindumole, V. R., Sasikiran, K., & Balagopalan, C. (2000). Production of citric acid by the
studies, the concentrations of reducing sugars (either glucose or
fermentation of sweet potato using Aspergillus niger. Journal of Root Crops, 26, 38–42.
fructose) did not correlate with the acrylamide formation in sweet pota- Boo, H. O., Hwang, S. J., Bae, C. S., Park, S. H., Heo, B. G., & Gorinstein, S. (2012). Extraction
to-related products, such as fried crisps (Truong et al., 2014). Roles of and characterization of some natural plant pigments. Industrial Crops and Products,
reducing sugars of sweet potato in acrylamide formation remain to be 40, 129–135.
Bovell‐Benjamin, A. C. (2007). Sweet potato: A review of its past, present, and future role
clarified. Selecting sweet potato varieties with reduced amounts of re- in human nutrition. Advances in Food and Nutrition Research, 52, 1–59.
ducing sugars and amino acids may help to reduce the acrylamide Boyd, M. R. (1982). Metabolic activation of pulmonary toxins. Mechanisms in respiratory
formation. toxicology (pp. 85–112). Boca Raton, FL: CRC Press.
Boyd, M. R., & Wilson, B. J. (1972). Isolation and characterization of 4-ipomeanol, a lung-
toxic furanoterpenoid produced by sweet potatoes (Ipomoea batatas). Journal of
3.5.3. Pro-angiogenetic components Agricultural and Food Chemistry, 20, 428–430.
In vitro data has shown the inhibitory effect of sweet potato leaf ex- Boyd, M. R., Burka, L. T., Harris, T. M., & Willson, B. J. (1974). Lung-toxic furanoterpenoids
produced by sweet potatoes (Ipomoea batatas) following microbial infection.
tracts on angiogenesis in human umbilical vascular endothelial cells. Biochimica et Biophysica Acta (BBA)/Lipids and Lipid Metabolism, 337, 184–195.
However, ex vivo, sweet potato leaf was pro-angiogenetic in serum col- Boyd, M. R., Burka, L. T., & Wilson, B. J. (1975). Distribution, excretion, and binding of ra-
lected from healthy humans (Chen et al., 2011). The difference may be dioactivity in the rat after intraperitoneal administration of the lung-toxic furan, [14C]
4 ipomeanol. Toxicology and Applied Pharmacology, 32, 147–157.
because the chemical composition of leaf extracts differed from those Bray, G. A., Nielsen, S. J., & Popkin, B. M. (2004). Consumption of high-fructose corn syrup
of leaf metabolites from human consumption. Metabolites of sweet po- in beverages may play a role in the epidemic of obesity. American Journal of Clinical
tato in relation to human health should be clarified. Nutrition, 79, 537–543.
Cai, Z., Qu, Z., Lan, Y., Zhao, S., Ma, X., Wan, Q., ... Li, P. (2016). Conventional, ultrasound-
assisted, and accelerated-solvent extractions of anthocyanins from purple sweet po-
4. Conclusions tatoes. Food Chemistry, 197, 266–272.
Campbell, C. T., & Campbell, T. M. (2005). The China study. Dallas, TX, USA: Ben Bella.
Various parts of the sweet potato (i.e., leaf, root, root peel, stem) in Carvalho, I. S., Cavaco, T., Carvalho, L. M., & Duque, P. (2010). Effect of photoperiod on fla-
vonoid pathway activity in sweet potato (Ipomoea batatas (L.) Lam.) leaves. Food
various forms (extracts, anthocyanin fractions, flours, powders) have Chemistry, 118, 384–390.
their unique chemical compositions. The chemical constituents possibly Chan, K. W., Khong, N. M. H., Iqbal, S., Umar, I. M., & Ismail, M. (2012). Antioxidant prop-
have unique physiological responses in vitro and in vivo, and sweet po- erty enhancement of sweet potato flour under simulated gastrointestinal pH.
International Journal of Molecular Sciences, 13, 8987–8997.
tato thus has great potential to influence human health. Health-promot- Chang, W. H., Hu, S. P., Huang, Y. F., Yeh, T. S., & Liu, J. F. (2010). Effect of purple sweet po-
ing bio-functions of sweet potatoes include antioxidation, antibacterial, tato leaves consumption on exercise-induced oxidative stress and IL-6 and HSP72
anti-inflammation, antidiabetic, anticancer, antihepatotoxicity, and an- levels. Journal of Applied Physiology, 109, 1710–1715.
Chen, C. M., Li, S. C., Chen, C. Y. O., Au, H. K., Shih, C. K., Hsu, C. Y., & Liu, J. F. (2011). Con-
tiaging. Results of in vitro and in vivo studies share common discrepan- stituents in purple sweet potato leaves inhibit in vitro angiogenesis with opposite ef-
cies. Factors affecting the bioactivities of sweet potato include the fects ex vivo. Nutrition, 27, 1177–1182.
genetics, growing conditions and processing methods of samples, ana- Chen, Y. Y., Lai, M. H., Hung, H. Y., & Liu, J. F. (2013). Sweet potato Ipomoea batatas (L.)
Lam. “Tainong 57” starch improves insulin sensitivity in high-fructose diet-fed rats
lytical methods, and chemical/biological models. The use of molecular by ameliorating adipocytokine levels, pro-inflammatory status, and insulin signaling.
breeding has great potential to increase nutritional and functional con- Journal of Nutritional Science and Vitaminology, 59, 272–280.
stituents in economically important sweet potatoes, thus allowing de- Choi, J. H., Hwang, Y. P., Choi, C. Y., Chung, Y. C., & Jeong, H. G. (2010). Anti-fibrotic effects
of the anthocyanins isolated from the purple-fleshed sweet potato on hepatic fibrosis
velopment in nutritionally improved varieties. Limited understanding
induced by dimethylnitrosamine administration in rats. Food and Chemical Toxicology,
of molecular mechanisms behind certain bio-functions is available and 48, 3137–3143.
remains to be better explored. The bio-accessibility and bioavailability Choi, J. H., Hwang, Y. P., Park, B. H., Choi, C. Y., Chung, Y. C., & Jeong, H. G. (2011). Antho-
of bioactives in sweet potato deserve attention in the future. Bridging cyanins isolated from the purple-fleshed sweet potato attenuate the proliferation of
hepatic stellate cells by blocking the PDGF receptor. Environmental Toxicology and
the gaps between animal studies and human clinic studies continues Pharmacology, 31, 212–219.
to be expected. Concerning possible interactions among various sweet Christensen, L. P. (2009). Galactolipids as potential health promoting compounds in veg-
potato bioactives in physiological conditions, proper assessing methods etable foods. Recent Patents on Food, Nutrition & Agriculture, 1, 50–58.
Chung, M., Ma, J., Patel, K., Berger, S., Lau, J., & Lichtenstein, A. H. (2014). Fructose, high-
for exploring the mechanisms of action behind those interactions are fructose corn syrup, sucrose, and nonalcoholic fatty liver disease or indexes of liver
critical for the applications of sweet potato in the control of human dis- health: A systematic review and meta-analysis. American Journal of Clinical
eases. Practical applications of underutilized parts of sweet potatoes Nutrition, 100, 833–849.
Cody, M., & Haard, N. F. (1976). Influence of cooking on toxic stress metabolites in sweet
should be diversified, focusing on optimization in formulations and pro- potato root. Journal of Food Science, 41, 469–470.
cessing techniques to maximize the retention of bioactives. Cui, L., Liu, C., Li, D., & Song, J. (2011). Effect of processing on taste quality and health-rel-
Supplementary data to this article can be found online at http://dx. evant functionality of sweet potato tips. Agricultural Sciences in China, 10, 456–462.
Deng, F. M., Mu, T. H., Zhang, M., & Abegunde, O. K. (2013). Composition, structure, and
doi.org/10.1016/j.foodres.2016.08.032. physicochemical properties of sweet potato starches isolated by sour liquid process-
ing and centrifugation. Starch/Stärke, 65, 162–171.
References Dincer, C., Karaoglan, M., Erden, F., Tetik, N., Topuz, A., & Ozdemir, F. (2011). Effects
of baking and boiling on the nutritional and antioxidant properties of sweet po-
Ahmed, M., Akter, M. S., & Eun, J. B. (2009). Effect of maltodextrin concentration and dry- tato [ Ipomoea batatas (L.) Lam.] cultivars. Plant Foods for Human Nutrition, 66,
ing temperature on quality properties of purple sweet potato flour. Food Science and 341–347.
Biotechnology, 18, 1487–1494. Ding, X., Ni, Y., & Kokot, S. (2015). NIR spectroscopy and chemometrics for the discrimi-
Ahmed, M., Akter, M. S., & Eun, J. B. (2010a). Impact of α-amylase and maltodextrin on nation of pure, powdered, purple sweet potatoes and their samples adulterated
physicochemical, functional and antioxidant capacity of spray-dried purple sweet po- with the white sweet potato flour. Chemometrics and Intelligent Laboratory Systems,
tato flour. Journal of the Science of Food and Agriculture, 90, 494–502. 144, 17–23.
Ahmed, M., Akter, M. S., & Eun, J. B. (2010b). Encapsulation by spray drying of bioactive Dominque, B., Gichuhi, P. N., Rangari, V. R., & Bovell-Benjamin, A. C. (2013). Sugar profile,
components, physicochemical and morphological properties from purple sweet pota- mineral content, and rheological and thermal properties of an isomerized sweet po-
to. LWT - Food Science and Technology, 43, 1307–1312. tato starch syrup. International Journal of Food Science, 243412.
114 S. Wang et al. / Food Research International 89 (2016) 90–116

Donado-Pestana, C., Salgado, J., Oliveira Rios, A., Santos, P., & Jablonski, A. (2012). Stability Jiao, Y., Yang, Z., Jiang, Y., & Zhai, W. (2012). Study on chemical constituents and antiox-
of carotenoids, total phenolics and in vitro antioxidant capacity in the thermal pro- idant activity of anthocyanins from purple sweet potato (Ipomoea batatas L.).
cessing of orange-fleshed sweet potato (Ipomoea batatas Lam.) cultivars grown in International Journal of Food Engineering, 8, 1–16.
Brazil. Plant Foods for Human Nutrition, 67, 262–270. Johnson, M., & Pace, R. D. (2010). Sweet potato leaves: Properties and synergistic interac-
Doster, A. R., Farrell, R. L., & Wilson, B. J. (1983). An ultrastructural study of bronchiolar tions that promote health and prevent disease. Nutrition Reviews, 68, 604–615.
lesions in rats induced by 4-ipomeanol, a product from mold-damaged sweet pota- Johnson, R., Padmaja, G., & Moorthy, S. N. (2009). Comparative production of glucose and
toes. The American Journal of Pathology, 111, 56–61. high fructose syrup from cassava and sweet potato roots by direct conversion tech-
El Sheikha, A. F., & Montet, D. (2014). African fermented foods: Historical roots and real niques. Innovative Food Science & Emerging Technologies, 10, 616–620.
benefits. In R. C. Ray, & D. Montet (Eds.), Microorganisms and fermentation of tradition- Johnson, R., Moorthy, S. N., & Padmaja, G. (2010). Production of high fructose syrup from
al foods (pp. 246–280). Florida: CRC Press/Taylor & Francis Group. cassava and sweet potato flours and their blends with cereal flours. Food Science and
El Sheikha, A. F., & Ray, R. C. (2015). Potential impacts of bio-processing of sweet potato: Technology International, 16, 251–258.
Review. Critical Reviews in Food Science and Nutrition. http://dx.doi.org/10.1080/ Johnson, M., Pace, R. D., Dawkins, N. L., & Willian, K. R. (2013). Diets containing traditional
10408398.2014.960909. and novel green leafy vegetables improve liver fatty acid profiles of spontaneously
FAO (Food and Agriculture Organization of the United Nations) (2012). http://www. hypertensive rats. Lipids in Health and Disease, 12, 168–175.
feedipedia.org/node/745. Jung, J. -K., Lee, S. -U., Kozukue, N., Levin, C. E., & Friedman, M. (2011). Distribution of phe-
FAOSTAT (Statistics division of Food and Agriculture Organization of the United Nations) nolic compounds and antioxidative activities in parts of sweet potato ( Ipomoea
(2016). http://faostat3.fao.org/browse/Q/*/E. batata L.) plants and in home processed roots. Journal of Food Composition and
Gan, L. J., Yang, D., Shin, J. A., Kim, S. J., Hong, S. T., Lee, J. H., ... Lee, K. T. (2012). Oxidative Analysis, 24, 29–37.
comparison of emulsion systems from fish oil-based structured lipid versus physical- Jung, S. -B., Shin, J. -H., Kim, J. Y., & Kwon, O. (2015). Shinzami Korean purple‐fleshed
ly blended lipid with purple-fleshed sweet potato (Ipomoea batatas L.) extracts. sweet potato extract prevents ischaemia–reperfusion‐induced liver damage in rats.
Journal of Agricultural and Food Chemistry, 60, 467–475. Journal of the Science of Food and Agriculture, 95, 2818–2823.
Garner, J. O., Izekor, E., & Islam, S. (2012). Lipid and fatty acid compositions of chilling tol- Karna, P., Gundala, S. R., Gupta, M. V., Shamsi, S. A., Pace, R. D., Yates, C., ... Aneja, R.
erant sweet potato (Ipomoea batatas L.) genotypes. American Journal of Plant (2011). Polyphenol-rich sweet potato greens extract inhibits proliferation and
Physiology, 7, 252–260. induces apoptosis in prostate cancer cells in vitro and in vivo. Carcinogenesis, 32,
Gillet, J. P., Varma, S., & Gottesman, M. M. (2013). The clinical relevance of cancer cell 1872–1880.
lines. Journal of the National Cancer Institute, 105, 452–458. Kim, S. H., Ahn, Y. O., Ahn, M. J., Lee, H. S., & Kwak, S. S. (2012a). Down-regulation of β-
Grace, M. H., Yousef, G. G., Gustafson, S. J., Truong, V. D., Yencho, G. C., & Lila, M. A. (2014). carotene hydroxylase increases β-carotene and total carotenoids enhancing salt
Phytochemical changes in phenolics, anthocyanins, ascorbic acid, and carotenoids as- stress tolerance in transgenic cultured cells of sweet potato. Phytochemistry, 74,
sociated with sweet potato storage and impacts on bioactive properties. Food 69–78.
Chemistry, 145, 717–724. Kim, H. W., Kim, J. B., Cho, S. M., Chung, M. N., Lee, Y. M., Chu, S. M., ... Lee, D. J. (2012b).
Grace, M. H., Truong, A. N., Truong, V. D., Raskin, I., & Lila, M. A. (2015). Novel value-added Anthocyanin changes in the Korean purple-fleshed sweet potato, Shinzami, as affect-
uses for sweet potato juice and flour in polyphenol- and protein-enriched functional ed by steaming and baking. Food Chemistry, 130, 966–972.
food ingredients. Food Science & Nutrition, 3, 415–424. Kim, O. -K., Nam, D. -E., Yoon, H. -G., Baek, S. J., Jun, W., & Lee, J. (2015a). Immunomodu-
Guo, Q., & Mu, T. H. (2011). Emulsifying properties of sweet potato protein: Effect of pro- latory and antioxidant effects of purple sweet potato extract in LP-BM5 murine leu-
tein concentration and oil volume fraction. Food Hydrocolloids, 25, 98–106. kemia virus-induced murine acquired immune deficiency syndrome. Journal of
He, W., Zeng, M., Chen, J., Jiao, Y., Niu, F., Tao, G., ... He, Z. (2016). Identification and quan- Medicinal Food, 18, 882–889.
titation of anthocyanins in purple-fleshed sweet potatoes cultivated in China by Kim, H. J., Park, W. S., Bae, J. Y., Kang, S. Y., Yang, M. H., Lee, S., ... Ahn, M. J. (2015b). Var-
UPLC-PDA and UPLC-QTOF-MS/MS. Journal of Agricultural and Food Chemistry, 64, iations in the carotenoid and anthocyanin contents of Korean cultural varieties and
171–177. home-processed sweet potatoes. Journal of Food Composition and Analysis, 41,
Hu, Y., Deng, L., Chen, J., Zhou, S., Liu, S., Fu, Y., ... Chen, M. (2016). An analytical pipeline to 188–193.
compare and characterize the anthocyanin antioxidant activities of purple sweet po- Kondo, K., Uritani, I., & Oba, K. (2003). Induction mechanism of 3-hydroxy-3-methylglu-
tato cultivars. Food Chemistry, 194, 46–54. taryl-CoA reductase in potato tuber and sweet potato root tissues. Bioscience,
Huang, Y. H., Picha, D. H., Kilili, A. W., & Johnson, C. E. (1999). Changes in invertase activ- Biotechnology, and Biochemistry, 67, 1007–1017.
ities and reducing sugar content in sweetpotato stored at different temperatures. Kuan, L. -Y., Thoo, Y. -Y., & Siow, L. -F. (2016). Bioactive components, ABTS radical scav-
Journal of Agricultural and Food Chemistry, 47, 4927–4931. enging capacity and physical stability of orange, yellow and purple sweet potato
Huang, Z., Wang, B., Eaves, D. H., Shikany, J. M., & Pace, R. D. (2007). Phenolic compound (Ipomoea batatas) powder processed by convection‐ or vacuum‐drying methods.
profile of selected vegetables frequently consumed by African Americans in the International Journal of Food Science and Technology, 51, 700–709.
southeast United States. Food Chemistry, 103, 1395–1402. Kubota, T. (1958). Volatile constituents of black-rotted sweet potato and related sub-
Huang, G. J., Sheu, M. J., Chang, Y. S., Lu, T. L., Chang, H. Y., Huang, S. S., & Lin, Y. H. (2008). stances. Tetrahedron, 4, 68–86.
Isolation and characterization of invertase inhibitor from sweet potato storage roots. Kubow, S., Iskandar, M. M., Sabally, K., Azadi, B., Sadeghi Ekbatan, S., Kumarathasan, P., ...
Journal of the Science of Food and Agriculture, 88, 2615–2621. Zum Felde, T. (2016). Biotransformation of anthocyanins from two purple-fleshed
Huang, G. J., Deng, J. S., Chen, H. J., Huang, S. S., Liao, J. C., Hou, W. C., & Lin, Y. H. (2012). sweet potato accessions in a dynamic gastrointestinal system. Food Chemistry, 192,
Defensin protein from sweet potato (Ipomoea batatas [L.] Lam ‘Tainong 57’) stor- 171–177.
age roots exhibits antioxidant activities in vitro and ex vivo. Food Chemistry, 135, Kurata, R., Adachi, M., Yamakawa, O., & Yoshimoto, M. (2007). Growth suppression of
861–867. human cancer cells by polyphenolics from sweet potato (Ipomoea batatas L.) leaves.
Huang, X., Tu, Z., Xiao, H., Li, Z., Zhang, Q., Wang, H., ... Zhang, L. (2013). Dynamic high pres- Journal of Agricultural and Food Chemistry, 55, 185–190.
sure microfluidization-assisted extraction and antioxidant activities of sweet potato Kusano, S., Abe, H., & Tamura, H. (2001). Isolation of antidiabetic components from white-
(Ipomoea batatas L.) leaves flavonoid. Food and Bioproducts Processing, 91, 1–6. skinned sweet potato (Ipomoea batatas L.). Bioscience, Biotechnology, and
Hwang, Y. P., Choi, J. H., Choi, J. M., Chung, Y. C., & Jeong, H. G. (2011a). Protective mech- Biochemistry, 65, 109–114.
anisms of anthocyanins from purple sweet potato against tert-butyl hydroperoxide- Kusano, S., Tamasu, S., & Nakatsugawa, S. (2005). Effects of the white-skinned sweet po-
induced hepatotoxicity. Food and Chemical Toxicology, 249, 2081–2089. tato (Ipomoea batatas L.) on the expression of adipocytokine in adipose tissue of ge-
Hwang, Y. P., Choi, J. H., Han, E. H., Kim, H. G., Wee, J. H., Jung, K. O., ... Jeong, H. G. (2011b). netic type 2 diabetic mice. Food Science and Technology Research, 11, 369–372.
Purple sweet potato anthocyanins attenuate hepatic lipid accumulation through acti- Lako, J., Trenerry, V. C., Wahlqvist, M., Wattanapenpaiboon, N., Sotheeswaran, S., &
vating adenosine monophosphate-activated protein kinase in human HepG2 cells Premier, R. (2007). Phytochemical flavonols, carotenoids and the antioxidant proper-
and obese mice. Nutrition Research, 31, 896–906. ties of a wide selection of Fijian fruit, vegetables and other readily available foods.
Hwang, Y. P., Choi, J. H., Yun, H. J., Han, E. H., Kim, H. G., Kim, J. Y., ... Jeong, H. G. (2011c). Food Chemistry, 101, 1727–1741.
Anthocyanins from purple sweet potato attenuate dimethylnitrosamine-induced Laurie, S. M., Faber, M., Calitz, F. J., Moelich, E. I., Muller, N., & Labuschagne, M. T. (2013).
liver injury in rats by inducing Nrf2-mediated antioxidant enzymes and reducing The use of sensory attributes, sugar content, instrumental data and consumer accept-
COX-2 and iNOS expression. Food and Chemical Toxicology, 49, 93–99. ability in selection of sweet potato varieties. Journal of the Science of Food and
Isabelle, M., Lee, B. L., Lim, M. T., Koh, W., Huang, D., & Ong, C. N. (2010). Antioxidant ac- Agriculture, 93, 1610–1619.
tivity and profiles of common vegetables in Singapore. Food Chemistry, 120, Lee, S. Y., Woo, K. S., Lim, J. K., Kim, H. I., & Lim, S. T. (2005). Effect of processing variables
993–1003. on texture of sweet potato starch noodles prepared in a nonfreezing process. Cereal
Ishida, H., Suzuno, H., Sugiyama, N., Innami, S., Tadokoro, T., & Maekawa, A. (2000). Nutri- Chemistry, 82, 475–478.
tive evaluation on chemical components of leaves, stalks and stems of sweet potatoes Lee, S. Y., Kim, J. Y., Lee, S. J., & Lim, S. T. (2006). Textural improvement of sweet potato
(Ipomoea batatas poir). Food Chemistry, 68, 359–367. starch noodles prepared without freezing using gums and other starches. Food
Ishiguro, K., Yoshimoto, M., Tsubata, M., & Takagaki, K. (2007). Hypotensice effect of Science and Biotechnology, 15, 986–989.
sweet potato tops. Nippon Shokuhin Kagaku Kogaku Kaishi, 54, 45–49. Lee, Y. -M., Bae, J. -H., Kim, J. -B., Kim, S. -Y., Chung, M. -N., Park, M. -Y., ... Kim, J. -H. (2012).
Islam, S. (2008). Antimicrobial activities of Ipomoea batatas (L.) leaf. Journal of Food, Changes in the physiological activities of four sweet potato varieties by cooking con-
Agriculture and Environment, 6, 14–17. dition. Korean Journal of Nutrition, 45, 12–19.
Islam, S., & Everette, J. D. (2012). Effect of extraction procedures, genotypes and screening Lee, M. J., Park, J. S., Choi, D. S., & Jung, M. Y. (2013). Characterization and quantitation
methods to measure the antioxidant potential and phenolic content of orange- of anthocyanins in purple-fleshed sweet potatoes cultivated in Korea by HPLC-
fleshed sweet potatoes (Ipomoea batatas L.). American Journal of Food Technology, 7, DAD and HPLC-ESI-QTOF-MS/MS. Journal of Agricultural and Food Chemistry, 61,
50–61. 3148–3158.
Islam, M. S., Yoshimoto, M., Terahara, N., & Yamakawa, O. (2002). Anthocyanin composi- Li, J., Li, X. D., Zhang, Y., Zheng, Z. D., Qu, Z. Y., Liu, M., ... Qu, L. (2013a). Identification and
tions in sweet potato (Ipomoea batatas L.) leaves. Bioscience, Biotechnology, and thermal stability of purple-fleshed sweet potato anthocyanins in aqueous solutions
Biochemistry, 66, 2483–2486. with various pH values and fruit juices. Food Chemistry, 136, 1429–1434.
 S. Wang et al. / Food Research International 89 (2016) 90–116 115

Li, P. G., Mu, T. H., & Deng, L. (2013b). Anticancer effects of sweet potato protein on Panda, S. H., Panda, S., ShivaKumar, P. S., & Ray, R. C. (2009b). Anthocyanin-rich sweet po-
human colorectal cancer cells. World Journal of Gastroenterology, 19, 3300–3308. tato lacto-pickle: Production, nutritional and proximate composition. International
Liao, W. C., Lai, Y. C., Yuan, M. C., Hsu, Y. L., & Chan, C. F. (2011). Antioxidative activity of Journal of Food Science and Technology, 44, 445–455.
water extract of sweet potato leaves in Taiwan. Food Chemistry, 127, 1224–1228. Panda, S. K., Swain, M. R., Singh, S., & Ray, R. C. (2013). Proximate compositions of a herbal
Lim, S., Xu, J., Kim, J., Chen, T.‐Y., Su, X., Standard, J., ... Wang, W. (2013). Role of anthocy- purple sweet potato (Ipomoea batatas L.) wine. Journal of Food Processing and
anin‐enriched purple‐fleshed sweet potato p40 in colorectal cancer prevention. Preservation, 37, 596–605.
Molecular Nutrition & Food Research, 57, 1908–1917. Park, S. C., Kim, Y. -H., Kim, S. H., Jeong, Y. J., Kim, C. Y., Lee, J. S., ... Kwak, S. -S. (2015).
Lim, T. K. (2014). Edible medicinal and non-medicinal plants. Flowers, Vol. 8, Springer. Overexpression of the IbMYB1 gene in an orange-fleshed sweet potato cultivar pro-
Lin, Y. C., Chen, H. M., Chou, I. M., Chen, A. N., Chen, C. P., Young, G. H., ... Juang, R. H. duces a dual-pigmented transgenic sweet potato with improved antioxidant activity.
(2012). Plastidial starch phosphorylase in sweet potato roots is proteolytically mod- Physiologia Plantarum, 153, 525–537.
ified by protein-protein interaction with the 20S proteasome. PLoS ONE, 7, e35336. Park, S. Y., Lee, S., Yang, J., Lee, J. S., Oh, S. -D., Oh, S., ... Yeo, Y. (2016). Comparative analysis
Lu, J., Wu, D. M., Zheng, Y. L., Hu, B., & Zhang, Z. F. (2010). Purple sweet potato color alle- of phytochemicals and polar metabolites from colored sweet potato (Ipomoea batatas
viates D-galactose-induced brain aging in old mice by promoting survival of neurons L.) tubers. Food Science and Biotechnology, 25, 283–291.
via PI3K pathway and inhibiting cytochrome C-mediated apoptosis. Brain Pathology, Peng, Z., Li, J., Guan, Y., & Zhao, G. (2013). Effect of carriers on physicochemical properties,
20, 598–612. antioxidant activities and biological components of spray-dried purple sweet potato
Lua, Y., Kima, S., & Parka, K. (2011). In vitro–in vivo correlation: Perspectives on model de- flours. LWT - Food Science and Technology, 51, 348–355.
velopment. International Journal of Pharmaceutics, 418, 142–148. Perez, R. H., & Tan, J. D. (2006). Production of acidophilus milk enriched with purees from
Ludvik, B., Hanefeld, M., & Pacini, G. (2008). Improved metabolic control by Ipomoea coloured sweet potato (Ipomoea batatas L.) varieties. Annals of Tropical Research, 28,
batatas (Caiapo) is associated with increased adiponectin and decreased fibrinogen 70–85.
levels in type 2 diabetic subjects. Diabetes, Obesity and Metabolism, 10, 586–592. Pochapski, M., Fosquiera, E., Esmerino, L., dos Santos, E., Farago, P., Santos, F., & Groppo, F.
Maloney, K. P., Truong, V. D., & Allen, J. C. (2012). Chemical optimization of protein extrac- (2011). Phytochemical screening, antioxidant, and antimicrobial activities of the
tion from sweet potato (Ipomoea batatas) peel. Journal of Food Science, 77, E307–E312. crude leaves' extract from Ipomoea batatas (L.) Lam. Pharmacognosy Magazine, 7,
Maloney, K. P., Truong, V. D., & Allen, J. C. (2014). Susceptibility of sweet potato (Ipomoea 165–170.
batatas) peel proteins to digestive enzymes. Food Science & Nutrition, 2, 351–360. Rautenbach, F., Faber, M., Laurie, S., & Laurie, R. (2010). Antioxidant capacity and antiox-
Maoka, T., Akimoto, N., Ishiguro, K., Yoshinaga, M., & Yoshimoto, M. (2007). Carotenoids idant content in roots of 4 sweet potato varieties. Journal of Food Science, 75,
with a 5,6-dihydro-5,6-dihydroxy-β-end group, from yellow sweet potato C400–C405.
“Benimasari”, Ipomoea batatas LAM. Phytochemistry, 68, 1740–1745. Ravindran, V., Ravindran, G., Sivakanesan, R., & Rajaguru, S. B. (1995). Biochemical assess-
Mei, X., Mu, T. H., & Han, J. J. (2010). Composition and physicochemical properties of di- ment of tubers from 16 cultivars of sweetpotato (Ipomoea batatas L.). Journal of
etary fiber extracted from residues of 10 varieties of sweet potato by a sieving meth- Agricultural and Food Chemistry, 43, 2646–2651.
od. Journal of Agricultural and Food Chemistry, 58, 7305–7310. Rumbaoa, R. G. O., Cornago, D. F., & Geronimo, I. M. (2009). Phenolic content and antiox-
Mitchell, S. J., Scheibye-Knudsen, M., Longo, D. L., & De Cabo, R. (2015). Animal models of idant capacity of Philippine sweet potato (Ipomoea batatas) varieties. Food Chemistry,
aging research: Implications for human aging and age-related diseases. Annual 113, 1133–1138.
Review of Animal Biosciences, 3, 283–303. Sakore, S., & Chakraborty, B. S. (2011). In-vitro–in-vivo correlation (IVIVC): A strategic
Mohapatra, S., Panda, S. H., Sahoo, A. K., Sivakumar, P. S., & Ray, R. C. (2007). β-Carotene tool in drug development. Journal of Bioequivalence & Bioavailability, S3, S3–001.
rich sweet potato curd: Production, nutritional and proximate composition. Salawu, S. O., Udi, E., Akindahunsi, A. A., Boligon, A. A., & Athayde, M. A. (2015). Antioxi-
International Journal of Food Science and Technology, 42, 1305–1314. dant potential, phenolic profile and nutrient composition of flesh and peels from Ni-
Montilla, E. C., Hillebrand, S., Butschbach, D., Baldermann, S., Watanabe, N., & gerian white and purple skinned sweet potato (Ipomea batatas L.). Asian Journal of
Winterhalter, P. (2010). Preparative isolation of anthocyanins from Japanese purple Plant Science and Research, 5, 14–23.
sweet potato (Ipomoea batatas L.) varieties by high-speed countercurrent chromatog- Salvador, L. D., Suganuma, T., Kitahara, K., Tanoue, H., & Ichiki, M. (2000). Monosaccharide
raphy. Journal of Agricultural and Food Chemistry, 58, 9899–9904. composition of sweet potato fiber and cell wall polysaccharides from sweet potato,
Morrison, T. A., Pressey, R., & Kays, S. J. (1993). Changes in alpha and beta-amylase during cassava, and potato analyzed by the high-performance anion exchange chromatogra-
storage of sweet potato lines with varying starch hydrolysis potential. Journal of the phy with pulsed amperometric detection method. Journal of Agricultural and Food
American Society for Horticultural Science, 118, 236–242. Chemistry, 48, 3448–3454.
Mosha, T. C., Pace, R. D., Adeyeye, S., Mtebe, K., & Laswai, H. (1995). Proximate composi- Schwarz, P. E. H., Gallein, G., Ebermann, D., Müller, A., Lindner, A., Rothe, U., ... Müller, G.
tion and mineral content of selected Tanzanian vegetables and the effect of tradition- (2013). Global diabete survey—An annual report on quality of diabetes care.
al processing on the retention of ascorbic acid, riboflavin and thiamine. Plant Foods for Diabetes Research and Clinical Practice, 100, 11–18.
Human Nutrition, 48, 235–245. Shekhar, S., Mishra, D., Buragohain, A. K., Chakraborty, S., & Chakraborty, N. (2015). Com-
Motsa, N. M., Modi, A. T., & Mabhaudhi, T. (2015). Influence of agro-ecological production parative analysis of phytochemicals and nutrient availability in two contrasting culti-
areas on antioxidant activity, reducing sugar content, and selected phytonutrients of vars of sweet potato (Ipomoea batatas L.). Food Chemistry, 173, 957–965.
orange-fleshed sweet potato cultivars. Ciência e Tecnologia de Alimentos, 35, 32–37. Shin, S. J., Bae, U. J., Ahn, M., Ka, S. O., Woo, S. J., Noh, S. O., ... Park, B. H. (2013). Aqueous
Mu, T. -H., Tan, S. -S., Chen, J. -W., & Xue, Y. -L. (2009). Effect of pH and NaCl/CaCl2 on the extracts of purple sweet potato attenuate weight gain in high fat-fed mice.
solubility and emulsifying properties of sweet potato protein. Journal of the Science of International Journal of Pharmacology, 9, 42–49.
Food and Agriculture, 89, 337–342. Soison, B., Jangchud, K., Jangchud, A., Harnsilawat, T., Piyachomkwan, K., Charunuch, C., &
Nagai, M., Tani, M., Kishimoto, Y., Iizuka, M., Saita, E., Toyozaki, M., ... Kondo, K. (2011). Prinyawiwatkul, W. (2014). Physico-functional and antioxidant properties of purple-
Sweet potato (Ipomoea batatas L.) leaves suppressed oxidation of low density lipo- flesh sweet potato flours as affected by extrusion and drum-drying treatments.
protein (LDL) in vitro and in human subjects. Journal of Clinical Biochemistry and International Journal of Food Science and Technology, 49, 2067–2075.
Nutrition, 48, 203–208. Sun, H., Mu, T., Liu, X., Zhang, M., & Chen, J. (2014a). Purple sweet potato (Ipomoea batatas
Nagamine, R., Ueno, S., Tsubata, M., Yamaguchi, K., Takagaki, K., Hira, T., ... Tsuda, T. L.) snthocyanins: Preventive effect on acute and sub-acute alcoholic liver damage and
(2014). Dietary sweet potato (Ipomoea batatas L.) leaf extract attenuates dealcoholic effect. Journal of Agricultural and Food Chemistry, 62, 2364–2373.
hyperglycaemia by enhancing the secretion of glucagon-like peptide-1 (GLP-1). Sun, H., Mu, T., Xi, L., & Song, Z. (2014b). Effects of domestic cooking methods on polyphe-
Food & Function, 5, 2309–2316. nols and antioxidant activity of sweet potato leaves. Journal of Agricultural and Food
Napolitano, A., Carbone, V., Saggese, P., Takagaki, K., & Pizza, C. (2007). Novel galactolipids Chemistry, 62, 8982–8989.
from the leaves of Ipomoea batatas L.: Characterization by liquid chromatography Sun, H., Mu, T., Xi, L., Zhang, M., & Chen, J. (2014c). Sweet potato (Ipomoea batatas L.)
coupled with electrospray ionization-quadrupole time-of-flight tandem mass spec- leaves as nutritional and functional foods. Food Chemistry, 156, 380–389.
trometry. Journal of Agricultural and Food Chemistry, 5, 10289–10297. Taira, J., Taira, K., Ohmine, W., & Nagata, J. (2013). Mineral determination and anti-LDL ox-
O'Connell, O. F., Ryan, L., & O'Brien, N. M. (2007). Xanthophyll carotenoids are more idation activity of sweet potato (Ipomoea batatas L.) leaves. Journal of Food
bioaccessible from fruits than dark green vegetables. Nutrition Research, 27, Composition and Analysis, 29, 117–125.
258–264. Tan, H. Z., Gu, W. Y., Zhou, J. P., Wu, W. G., & Xie, Y. L. (2006). Comparative study on the
Oboh, S., Ologhobo, A., & Tewe, O. (1989). Some aspects of the biochemistry and nutri- starch noodle structure of sweet potato and mung bean. Journal of Food Science, 71,
tional value of the sweetpotato (Ipomoea batatas). Food Chemistry, 31, 9–18. C447–C455.
Ojong, P. B., Njiti, V., Guo, Z., Gao, M., Besong, S., & Barnes, S. L. (2008). Variation of flavo- Terahara, N., Matsui, T., Fukui, K., Matsugano, K., Sugita, K., & Matsumoto, K. (2003).
noid content among sweet potato accessions. Journal of the American Society for Caffeoylsophorose in a red vinegar produced through fermentation with purple
Horticultural Science, 133, 819–824. sweet potato. Journal of Agricultural and Food Chemistry, 51, 2539–2543.
Olowu, A., Adeneye, A., & Adeyemi, O. (2011). Hypoglycaemic effect of Ipomoea batatas Tomlins, K., Owori, C., Bechoff, A., Menya, G., & Westby, A. (2011). Relationship among the
aqueous leaf and stem extract in normal and streptozotocin-induced hyperglycaemic carotenoid content, dry matter content and sensory attributes of sweet potato. Food
rats. Journal of Natural Pharmaceuticals, 2, 56–61. Chemistry, 121, 14–21.
Ozaki, S., Oki, N., Suzuki, S., & Kitamura, S. (2010). Structural characterization and hypo- Truong, V. D., Pascua, Y. T., Reynolds, R., Thompson, R. L., Palazoğlu, T. K., Mogol, R. A., &
glycemic effects of arabinogalactan-protein from the tuberous cortex of the white- Gökmen, V. (2014). Processing treatments for mitigating acrylamide formation in
skinned sweet potato (Ipomoea batatas L.). Journal of Agricultural and Food sweet potato French fries. Journal of Agricultural and Food Chemistry, 62, 310–316.
Chemistry, 58, 11593–11599. Tsukui, A. (1996). Stability of anthocyanins in various vegetables and fruits. Food Science
Panda, S. H., Naskar, S. K., & Ray, R. C. (2006). Production, proximate and nutritional and Technology International, 2, 30–33.
evaluation of sweet potato curd. Journal of Food, Agriculture and Environment, 4, Van Hal, M. (2000). Quality of sweetpotato flour during processing and storage. Food
124–127. Reviews International, 16, 1–37.
Panda, S. H., Naskar, S. K., Shivakumar, P. S., & Ray, R. C. (2009a). Lactic acid fermentation Wang, S., & Zhu, F. (2015). Dietary antioxidant synergy in chemical and biological sys-
of anthocyanin-rich sweet potato (Ipomoea batatas L.) into lacto-juice. International tems. Critical Reviews in Food Science and Nutrition. http://dx.doi.org/10.1080/
Journal of Food Science and Technology, 44, 288–296. 10408398.2015.1046546.
116 S. Wang et al. / Food Research International 89 (2016) 90–116

Wang, S., & Zhu, F. (2016). Antidiabetic dietary materials and animal models. Food Xu, J., Su, X., Lim, S., Griffin, J., Carey, E., Katz, B., ... Wang, W. (2015). Characterisation and
Research International, 85, 315–331. stability of anthocyanins in purple-fleshed sweet potato P40. Food Chemistry, 186,
Wang, S. J., Yeh, K. W., & Tsai, C. Y. (2001). Regulation of starch granule-bound starch syn- 90–96.
thase I gene expression by circadian clock and sucrose in the source tissue of sweet Yoshikawa, K., Yagi, C., Hama, H., Tanaka, M., Arihara, S., & Hashimoto, T. (2010).
potato. Plant Science, 161, 635–644. Ipomotaosides A-D, resin glycosides from the aerial parts of Ipomoea batatas and
Wang, Y. L., Wu, C. Y., Chang, C. T., & Sung, H. Y. (2003). Invertase inhibitors from sweet their inhibitory activity against COX-1 and COX-2. Journal of Natural Products, 73,
potato (Ipomoea batatas): Purification and biochemical characterization. Journal of 1763–1766.
Agricultural and Food Chemistry, 51, 4804–4809. Zhang, Z., & Corke, H. (2001). Trypsin inhibitor activity in vegetative tissue of sweet pota-
Wang, S. J., Yeh, K. W., & Tsai, C. Y. (2004). Circadian control of sweet potato granule- to plants and its response to heat treatment. Journal of the Science of Food and
bound starch synthase I gene in Arabidopsis plants. Plant Growth Regulation, 42, Agriculture, 81, 1358–1363.
161–168. Zhang, M., Mu, T. H., & Sun, M. J. (2012). Sweet potato protein hydrolysates: Antioxidant
Wang, T. C., Chen, B. Y., Shen, Y. P., Wong, J. J., Yang, C. C., & Lin, T. C. (2012). Influences of activity and protective effects on oxidative DNA damage. International Journal of Food
superheated steaming and roasting on the quality and antioxidant activity of cooked Science and Technology, 47, 2304–2310.
sweet potatoes. International Journal of Food Science and Technology, 47, 1720–1727. Zhang, Y. Y., Mu, T. H., & Zhang, M. (2013). Optimization of acid extraction of pectin from
Wang, W., Li, J., Wang, Z., Gao, H., Su, L., Xie, J., ... Han, Y. (2014). Oral hepatoprotective sweet potato residues by response surface methodology and its antiproliferation ef-
ability evaluation of purple sweet potato anthocyanins on acute and chronic chemical fect on cancer cells. International Journal of Food Science and Technology, 48, 778–785.
liver injuries. Cell Biochemistry and Biophysics, 69, 539–549. Zhang, M., Mu, T. H., & Sun, M. J. (2014). Purification and identification of antioxidant pep-
Waramboi, J. G., Dennien, S., Gidley, M. J., & Sopade, P. A. (2011). Characterization of sweet tides from sweet potato protein hydrolysates by alcalase. Journal of Functional Foods,
potato from Papua New Guinea and Australia physicochemical, pasting and gelatini- 7, 191–200.
zation properties. Food Chemistry, 126, 1759–1770. Zhang, M., Pan, L. J., Jiang, S. T., & Mo, Y. W. (2016). Protective effects of anthocyanins from
White, J. S. (2013). Challenging the fructose hypothesis: New perspectives on fructose purple sweet potato on acute carbon tetrachloride-induced oxidative hepatotoxicity
consumption and metabolism. Advances in Nutrition, 4, 246–256. fibrosis in mice. Food and Agricultural Immunology, 27, 157–170.
Wu, T. Y., Tsai, C. C., Hwang, Y. T., & Chiu, T. H. (2012). Effect of antioxidant activity and Zhao, J. G., Yan, Q. Q., Lu, L. Z., & Zhang, Y. Q. (2013). In vivo antioxidant, hypoglycemic,
functional properties of Chingshey purple sweet potato fermented milk by Lactobacil- and anti-tumor activities of anthocyanin extracts from purple sweet potato.
lus acidophilus, L. delbrueckii subsp. lactis, and L. gasseri strains. Journal of Food Science, Nutrition Research and Practice, 7, 359–365.
77, M2–M8. Zhao, J. G., Yan, Q. Q., Zhang, J., & Zhang, Y. Q. (2014). Isolation and identification of
Wu, Q., Qu, H., Jia, J., Kuang, C., Wen, Y., Yan, H., & Gui, Z. (2015). Characterization, antiox- colourless caffeoyl compounds in purple sweet potato by HPLC-DAD–ESI/MS and
idant and antitumor activities of polysaccharides from purple sweet potato. their antioxidant activities. Food Chemistry, 161, 22–26.
Carbohydrate Polymers, 132, 31–41. Zhu, F. (2015). Interactions between starch and phenolic compound. Trends in Food
Xi, L., Mu, T., & Sun, H. (2015). Preparative purification of polyphenols from sweet potato Science & Technology, 43, 129–143.
(Ipomoea batatas L.) leaves by AB-8 macroporous resins. Food Chemistry, 172, Zhu, F., & Wang, S. (2014). Physicochemical properties, molecular structure, and uses of
166–174. sweet potato starch. Trends in Food Science & Technology, 36, 68–78.
Xu, W., Liu, L., Hu, B., Sun, Y., Ye, H., Ma, D., & Zeng, X. (2010). TPC in the leaves of 116 Zhu, F., Cai, Y. Z., Yang, X. S., Ke, J., & Corke, H. (2010). Anthocyanins, hydroxycinnamic
sweet potato (Ipomoea batatas L.) varieties and Pushu 53 leaf extracts. Journal of acid derivatives, and antioxidant activity in roots of different Chinese purple fleshed
Food Composition and Analysis, 23, 599–604. sweetpotato genotypes. Journal of Agricultural and Food Chemistry, 58, 7588–7596.