International Food Research Journal 22(2): 798-806 (2015)

Journal homepage: http://www.ifrj.upm.edu.my

Nutritional potential of nine underexploited legumes in Southwest Nigeria

Ade-Omowaye, B.I.O,, 1Tucker, G.A. and 3Smetanska, I.

123*

Division of Nutritional Sciences, School of Biosciences, University of Nottingham,

1

Sutton Bonington Campus, Loughborough, Leics LE12 5RD, UK

2
Department of Food Science and Engineering, Ladoke Akintola University of Technology, PMB
4000, Ogbomoso, Nigeria
3
Department of Plant Food Processing, University of Applied Science Weihenstephan- Triesdorf,
Steingruber Str. 2, Weidenbach 91746, Germany

Article history Abstract

Received: 17 June 2014 There is increasing interest in finding new food sources to alleviate malnutrition in developing
Received in revised form: countries. Nine little known legumes (Mallotus subulatus (white variety), Cassia hirsutta,
26 August 2014
Accepted: 3 September 2014
Canavalia ensiformis, Vignea subterranean (checkered variety), Vigna racemosa, Mallotus
subulatus (red variety), Vignea subterranean (cream variety), Sphenostylis sterocarpa
Keywords and Cajanus cajan in the South western Nigeria were studied to highlight their nutritional
significance. The proximate composition, fatty acid composition, total phenolic content,
Underutilized legumes antioxidant activity and amino acid profile of the legumes were evaluated using standard
Chemical composition methods in the literature. Significant (p<0.05) variations existed among the legumes with
Amino acid profile respect to their proximate composition, fatty acid profile, total phenolic content, antioxidant
Antioxidant properties activity and amino acid composition. Mallotus subulatus (red variety) rated highest in protein,
Fatty acid composition
Vigna racemosa and Sphenostylis sterocarpa had high starch contents, while Cajanus cajan
rated best in dietary fibre (non starch polysaccharides) among the legumes tested. The total
unsaturated fatty acids were much higher than the total saturated fatty acids in all the legumes.
Linoleic acid (C18:2) was the most abundant polyunsaturated fatty acid (PUFA) identified, at
varying levels, in all the legumes studied. All the legumes had varying levels of linolenic acid
(C18:3). Sphenostylis sterocarpa had the least essential fatty acid contents (32.73%) and the
highest (57.25%) was found in Cassia hirsutta. Cajanus cajan had the highest total phenolic
content (293.23 mg/100g) and also rated best in its antioxidant activity. The percentage total
essential amino acids were between 45.53 and 48.44 which are considered adequate for ideal
protein foods. All the legumes were good sources of total phenolics and possess moderate
to high antioxidant activities suggesting that these lesser known legumes are promising
commodities in combating food and nutrition insecurity in Nigeria and other countries where
they are known and consumed. © All Rights Reserved
Introduction chronic diseases, mainly cardiovascular diseases,
but also obesity and type 2 diabetes (Schröder, 2007;
The nutritional value of legumes is gaining Sievenpiper et al., 2009). Legumes contain a range of
considerable interest globally because of the demand nutrients and bioactive components that may explain
for healthy foods. Consumed regularly, legumes their protective effect. Legumes are an important food
contribute to a healthy diet, and would help to crop in Nigeria and all over the world because they
control metabolic diseases such as diabetes mellitus provide a vast number of the population with a cheap
(Nestel et al., 2004). In general, legumes are sources alternate source of protein. Cowpea, groundnut and
of complex carbohydrates, protein and dietary fibre, soybeans are the major legumes consumed in Nigeria.
have significant amounts of vitamins and minerals, Bean production increased from 2.14 million hectares
and high energetic value (Almeida- Costa et al., 2006). in 1994/1995 to 3.47 million hectares in 2005/2006
Legumes are an affordable source of protein and have (Akinyele, 2009). In order to secure food supply for
the advantage of having low glycemic index, and the Nigerian population, research efforts are being
significant antioxidant activity (Granito et al., 2008). directed towards the study of underexploited legumes
Legumes have been demonstrated to help manage that are well adapted to adverse environmental
both cholesterol and blood glucose (Olmedilla- conditions and highly resistant to disease and pests.
Alonso et al., 2013). Legume consumption has been For instance, Fasoyiro et al. (2006) evaluated and
associated with a lower risk of developing several reported the proximate, mineral and anti-nutritional

*Corresponding author.
Email: adeomowaye@yahoo.com, bioade-omowaye@lautech.edu.ng
Tel: 00234-8034-947-340
799 Ade-Omowaye et al./IFRJ 22(2): 798-806

factors found in four minor grain legumes found in conductivity detector. Quantitation was achieved
Nigeria. The crude protein contents in the legumes with Eager 300 software using an L-aspartic acid
was found to range between 22 and 37 % suggesting standard. Total protein was determined using the
the potentials of these underutilized legumes as N*6.25 conversion factor (Igbal et al., 2006). The fat
protein sources for the Nigerian populace. Oboh content was determined using a Soxtherm Gerhardt
(2006) also evaluated the antioxidant properties rapid Soxhlet extraction system. The extraction was
of some commonly consumed and underutilized performed using the Soxhlet method with petroleum
tropical legumes in Nigeria. It is documented that ether (AOAC, 1990). Moisture was determined
there are thousands of underutilized crops which from sample weight loss after oven drying at 105 °C
have desirable nutritional profiles compared to major for 5 h (AOAC 1990). Non-starch polysaccharides
crops and have the potential to alleviate ‘hidden (NSP) were determined by the method of Englyst
hunger’ of the poor communities (Nah and Chau, and Cummings (1988). Starch was measured using
2010). The aim of this present study was to evaluate a starch Assay kit- HK (SA-20) following the
the nutritional profile of some underutilized legumes manufacturer’s protocol (Sigma-Aldrich, St. Louis,
in Nigeria to provide enlightenment on their potential MO, USA).
as food sources for a wider populace in the country.
Preparation of fatty acid methyl ester (FAMEs)
Materials And Methods Oil extracted with soxhlet extractor using
petroleum ether was dissolved in chloroform to a
Materials concentration of 10 mg/mL (i.e. 0.01 g lipid mixed
Freshly harvested whole legume seeds were with 1.0 ml chloroform). For every 1.0 ml of sample,
purchased from peasant farmers in Atisbo and Saki 200 µL of trimethylsulfonium hydroxide (TMSH)
West Local Government areas of Oyo State in Nigeria. was added. After waiting for at least 10 min (to allow
The nine (9) legume seed samples studied in this work the fatty acids to convert to methyl esters), 2.0 µL
were: Mallotus subulatus (white variety); Cassia was injected into the GC/MS for analysis.
hirsutta; Canavalia ensiformis; Vignea subterranean
(checkered variety); Vigna racemosa; Mallotus Determination of fatty acid composition
subulatus (red variety); Vignea subterranean (cream Fatty acid analysis on GC/MS was performed
variety); Sphenostylis sterocarpa and Cajanus cajan. using a CTS Analytics PAL system auto sampler
and a DSQ and TRACE GC Ultra (Thermo Electron
Sample preparation Corporation). The sample was injected into the SSL
The legumes were manually cleaned to remove injector (split flow 50 mL min-1) at a temperature
foreign material, immature and damaged seeds. The of 250˚C. Compounds were separated using a
legumes were milled using a coffee grinder and polyethylene glycol (BP20 ID 0.22 mm × 25 m)
sieved to obtain a flour fraction of less than 699 µm. gas chromatography column (Milton Keynes, UK)
The milled samples were sealed in polyethylene bags with 30 mL min-1 nitrogen. Oven temperatures were
and stored at -140C for two months. controlled at 120˚C (1 min) then ramped (5˚C min-
1) to 260˚C. Identification of chromatographic peaks
Proximate composition was carried out by comparison of their retention times
Chemical analysis to determine proximate using appropriate fatty acid methyl esters standards
composition of each sample was carried out using (Merck, Sigma) (Carvalho and Malcata, 2005).
standard procedures. A Thermo Flash Nitrogen
Analyser (Flash EA1112 Nitrogen Analyzer) was Determination of total phenolic content and
used to determine the protein content of the samples antioxidant capacity
according to the Dumas method (AOAC, 1990). 0ne gram of the legume flour sample was
A 50 mg sample was sealed in a tin capsule and homogenized with 50 mL acetone and then
combusted at approximately 1800°C. Combustion centrifuged for 10 min at 2,000×g. Supernatant was
gases were passed into a reduction reactor (at 680°C collected and kept in an ice bath. Total phenolic
containing reduced copper) where nitrogen oxides content was assayed using the method described
are converted to elemental nitrogen. Carbon dioxide, by Slinkard and Singleton (1977). Total phenolic
sulphur dioxide and water were removed via filters content was expressed in terms of milligrammes of
of soda lime, magnesium perchlorate and a molecular gallic acid per 100 g of dry weight (mg gallic acid
sieve. The effluent stream was passed through a 100 g−1 DW). Antioxidant capacity of the sample was
nitrogen separation column (50°C) and into a thermal determined using ferric reducing antioxidant potential
 Ade-Omowaye et al./IFRJ 22(2): 798-806 800

(FRAP) assay according to the method described by confirmed. This observation agrees with the findings
Benzie and Strain (1996). Antioxidant capacity was of Almeida Costa et al. (2006) who reported protein
expressed as millimoles of Trolox equivalents per in pea, common bean, chickpea and lentil to be in
gram of dry weight (millimoles TE g−1 DW). the range of 18.5 to 24%. The results are also close
to those reported by Bravo et al. (1999) for lesser
Statistical analysis known pulses in India which were in the range of
Statistical analysis of all data of the two 20.7 to 25%. Mamiro et al. (2011) reported protein
replicates was done with Statistical Analysis System contents in local and improved cowpea varieties (a
(SAS) (version 9.2). Analysis of variance (ANOVA) legume widely consumed in Nigeria and several
procedure was used to determine statistical significant other parts of the world) to be in the range of 22-
difference (p<0.05) in all data. Means were separated 26% suggesting the potential of these lesser known
with least significant difference using Fisher’s legumes as alternative sources of protein for the
procedure. seemingly increasing population in Nigeria. The
similar protein content might suggest a comparable
Results and Discussion nutritional value for these underexploited legumes in
terms of protein digestibility, in-depth studies of this
Proximate composition of the legumes are underway.
The proximate composition of all the studied Starch content varied between 13.02 and 29.06%.
legumes is summarized in Table 1. Vigna racemosa (E), Canavalia ensiformis (C), and
Table 1. Proximate composition (%, dry basis) of the Sphenostylis sterocarpa (H) had the highest starch
underutilized legumesa contents of all the nine legumes studied (around
29%) reflecting no significant difference (p<0.05)
among the samples. The two varieties of the Vignea
subterranean (D, G) had the least starch content of
around 13 % which were not different statistically.
All others were above 23% except for Mallotus
subulatus (red variety, F). Total starch has been
reported to be 31.8% in chickpeas and 39.9% in
green gram (Bravo et al. 1999). A range of 24 to 37%
starch was reported for wrinkled pea and 32 to 48%
in cowpea indicating these underexploited legumes
as promising commodities in the human diet (Zhou
et al., 2013). Siddhuraju and Becker (2005) reported
a
Each value is an average of two replications
Means with the same letter along the same column are not 28% starch content in mucuna beans. Extremely
significantly different (p>0.05). low starch values in the range of 0.2 to 3.9% have
A=Mallotus subulatus (white variety); B= Cassia hirsutta; C= been reported for some legumes such as soybean and
Canavalia ensiformis; D= Vignea subterranean (checkered lupine seed.
variety); E= Vigna racemosa; F= Mallotus subulatus (red
variety); G= Vignea subterranean (cream variety); H= The non-starch polysaccharides (NSP)
Sphenostylis sterocarpa; I= Cajanus cajan constituents of the legume seeds varied significantly
(p<0.05) from 12.8 to 32.7%. Canavalia ensiformis
Crude protein content in the underutilized was the richest source of NSP, followed by
legumes ranged between 18.3 and 24% in sample D, Mallotus subulatus (red variety, F), Cassia hirsutta,
Vignea subterranean (checkered variety) and sample Mallotus subulatus (white variety) and Sphenostylis
F, Mallotus subulatus (red variety) respectively. sterocarpa. Vignea subterranean (checkered variety),
The lowest protein contents corresponded to the Vignea subterranean (cream variety) and Canavalia
two varieties of Vignea subterranean (D, G) whilst ensiformis were significant sources of NSP as they
Mallotus subulatus (red variety) had the highest contained more than 12 %. Fibre contents of 10.4 to
protein value, close to 24% of dry matter which 17.2 % has been reported for different varieties of
was significantly different (p<0.05) from other cowpeas (Mamiro et al., 2011), while total dietary
samples. Significant differences were not observed fibre in some legumes in India ranged between 18.5
among samples A, B and C. In the same vein, the and 30.9% and a range of 1.2 to 25.6% was reported
difference in the protein values between samples E elsewhere for various legumes (Bravo et al. 1999;
and H was not significant. Legumes are known to Zhou et al., 2013). Growing evidence indicates the
be good sources of protein which this study has also potential health benefits of legume bean fiber and
801 Ade-Omowaye et al./IFRJ 22(2): 798-806

Table 2. Fatty acids compositions (g/kg) of the nine underutilized legumes in Nigeria

Means with the same letter along the same row are not significantly different (p>0.05). A=Mallotus subulatus (white variety);
B= Cassia hirsutta; C= Canavalia ensiformis; D= Vignea subterranean (checkered variety); E= Vigna racemosa; F= Mallotus
subulatus (red variety); G= Vignea subterranean (cream variety); H= Sphenostylis sterocarpa; I= Cajanus cajan.

other dietary fibers. These advantageous effects C, E, H and I) and low fat/low starch (F).
may include, but are not limited to, an increase in
fecal bulk and fecal moisture, reduction of plasma Fatty acid composition of the legumes
cholesterol level, improved GI, and reduced risk of There were significant (p<0.05) variations in the
colon cancer (Nwokolo, 1996). This observation fatty acid profile of all the legumes studied (Table 2).
further suggests the potential food value of these It was evident that the total saturated fatty acids were
lesser known legumes which if included in the diet lower than the total unsaturated fatty acids in all the
could lower the risk of certain diseases and minimize legumes. The total saturated fatty acids were observed
food insecurity rampart in developing nations as to range from 28.24 to 39.87% in Canavalia ensiformis
Nigeria. and Mallotus subulatus (red variety), respectively.
There were significant (p<0.05) variations in Mallotus subulatus (red variety), Mallotus subulatus
the fat contents of the legume samples. Generally (white variety), Vignea subterranean (checkered
the samples had very low fat, less than 2% of the variety) and Vignea subterranean (cream variety)
dry matter, except for the two varieties of Vignea were found to have the greatest total saturated fatty
subterranean that were comparatively rich in fat acids (39.87, 37.40, 36.75 and 36.06%, respectively).
(6 - 7% d.m.). Samples B, E, H and I were not The levels of total unsaturated fatty acids ranged
significantly different (p<0.05) in their fat contents. from 60.13% in Mallotus subulatus (red variety)
This agrees with previous reports that legumes are to 71.76% in Canavalia ensiformis. The major
not good sources of fat except the oilseeds such as monounsaturated fatty acid (MUFA) present in
groundnut and soybean (Iqbal et al., 2006; Bravo et all the legumes was oleic acid (C18:1) which was
al., 1999). particularly high in Canavalia ensiformis, Vigna
The moisture contents were in the range of 11.3 racemosa and Sphenostylis sterocarpa. The most
to 12.7%, typical of dry seeds. No much difference abundant polyunsaturated fatty acid (PUFA) identified
(p<0.05) was observed in the moisture contents of in all the legumes studied was linoleic acid (C18:2).
the legumes. For instance, samples B, C, E, F, H and It was noticeably higher in Cassia hirsutta, Cajanus
I were not significantly different from one another. cajan and the two varieties of Vignea subterranean,
The generally low moisture content of the legumes cream and checkered, (50.11, 49.69, 43.06, 40.34 g/
suggests relatively long shelf life of the commodities. kg, respectively). The differences (p<0.05) between
Based on the components of the legumes the following samples I and B, A and F, C and E, D and G were
classifications could be deduced: high protein/high not significant. Interestingly, all the legumes had
fibre (samples A, B, E, F and I); high protein/low varying levels of linolenic acid (C18:3). The two
fibre (samples C, D, G and H); high fat/low starch varieties of Mallotus subulatus were exceptionally
(samples D and F); low fat/high starch (samples A, B, rich in this fatty acid with the red variety having
 Ade-Omowaye et al./IFRJ 22(2): 798-806 802

15.70 while the white variety had 13.26 g/kg. All Table 3. Total polyphenolics and antioxidant activities of
other legumes had concentrations between 2.61 in the nine underutilized legumes
Vignea subterranean (cream variety) and 5.04 g/kg
in Canavalia ensiformis. The information contained
in Table 2 shows that Sphenostylis sterocarpa had the
least total essential fatty acids (PUFA) at 32.73% and
the highest was 57.25% found in Cassia hirsutta. All
other legumes studied had their PUFA above 40%
except Canavalia ensiformis and Vigna racemosa
with around 35%. The results are similar to those
observed in some legumes by Ryan et al. (2007).
The literature provides compelling evidence for
the health benefit of n-3 PUFA consumption not only Means with the same letter along the same column are not
significantly different (p>0.05).
on the metabolic syndrome, cardiovascular risks, and
A=Mallotus subulatus (white variety); B= Cassia hirsutta;
associated comorbidities but also on other conditions C= Canavalia ensiformis; D= Vignea subterranean (checkered
such as neuroinflammatory and neurodegenerative variety); E= Vigna racemosa; F= Mallotus subulatus (red
diseases (Molendi-Coste et al., 2011). PUFA (n- variety); G= Vignea subterranean (cream variety);
3) has been reported to be the most potent anti- H= Sphenostylis sterocarpa; I= Cajanus cajan
inflammatory effector and inflammation is at the under medium antioxidant activity commodities
base of many chronic diseases, including coronary (Kaur and Kapoor, 2002). Oboh (2006) reported a
heart disease, diabetes, arthritis, cancer and mental similar observation for Cajanus cajan (brown) with
health, indicating that dietary intake of omega-3 a high total phenol content of 120 mg/100g and
fatty acids may prevent the development of many 70 mg/100g for Sphenostylis sterocarpa. Various
diseases (Hussein, 2013). Linoleic and α–linolenic reports have shown that the quantity of phenolic
acids are the most important essential fatty acids compounds in seed samples is influenced by soil,
needed for physiological functions, growth, and body environmental conditions, genotype (cultivar/
maintenance (Singh, 2005). These underutilized variety), agronomic practices (irrigation, fertilization
legumes if consumed in substantial quantity will and pest management), maturity level at harvest
participate well in these functions. The considerably and post-harvest storage, which might explain the
lower total saturated fatty acids than PUFA in all the differences in the values obtained for similar legumes
lesser known legumes studied in this work points to studied elsewhere (Vadivel et al., 2011). Evidence
the health significance of these legumes in the human abounds that plant phenolics are highly effective free
diet. radical scavengers and antioxidants signifying the
potential of these underutilized legumes as promising
Total phenolic content and the antioxidant activities food commodities in human diet. Epidemiological
of the legumes studies revealed a strong correlation between the
Variations in the levels of the total phenolics and consumption of natural food products high in phenols
the antioxidant activities in all the nine underutilized with low incidence of cancer, coronary heart disease
legumes studied (Table 3). The result revealed that and atherosclerosis (Randhir et al. 2004; Alothman
Cajanus cajan had the highest total phenolic content et al. 2009).
(293.23 mg/100g), while the lowest content was The antioxidant activity ranged between 0.39
exhibited by Vignea subterranean (cream variety) (68 and 1.00 mmolTE/100g in Cassia hirsutta and
mg/100g). Other legume samples with relatively high Cajanus cajan, respectively. Interestingly the sample
contents were Sphenostylis sterocarpa, Canavalia with the highest total phenolic content had the
ensiformis, Mallotus subulatus (red variety) and highest antioxidant power but the sample with the
Vignea subterranean (checkered variety) with 288.68, lowest phenolic content had 0.45 mmolTE/100g.
281.64, 255.27 and 170.95 mg/100g, respectively. All the legumes generally exhibited relatively high
These values are lower than those reported (3.12–6.69 antioxidant power as reflected in the values of their
g/100 g DM) for some wild Indian legumes (Vadivel antioxidant activities. However, it was observed
and Biesalski, 2012). The values are however that Vignea subterranean (checkered variety),
higher than those reported (9.7 to 12.6 mg/100g) Canavalia ensiformis, Sphenostylis sterocarpa and
by Gharachorloo et al. (2013) for four pulses. The Mallotus subulatus (red variety) had relatively higher
values are also higher than total phenolics (100-200 activities (0.88, 0.70, 0.67 and 0.66 mmolTE/100g,
mg/100 g) reported for some vegetables grouped respectively) than the remaining evaluated legume
803 Ade-Omowaye et al./IFRJ 22(2): 798-806

Table 4. Amino acid composition (g/kg) of the nine underutilized legumes

a
Essential Amino Acids; Means with the same letter along the same row are not significantly different (p>0.05). A=Mallotus
subulatus (white variety); B= Cassia hirsutta; C= Canavalia ensiformis; D= Vignea subterranean (checkered variety); E= Vigna
racemosa; F= Mallotus subulatus (red variety); G= Vignea subterranean (cream variety); H= Sphenostylis sterocarpa;
I= Cajanus cajan

samples. The result corresponds with previous studies red variety (sample F), respectively. Vadivel and
that legumes are good sources of total phenolics Janardhanan (2005) reported similar observation for
and possess considerable antioxidant activity (Xu the amino acids of seven south Indian wild legumes.
and Chang, 2008; Oboh, 2006). The result shows The most concentrated essential amino acid in all
low correlation (r = 0.690) between total phenolics the legumes studied was leucine with values ranging
and antioxidant activity which agrees with previous from 14.96 to 17.90 g/kg (Vignea subterranean,
observations by different researchers. No correlation checkered variety, sample D and Mallotus subulatus,
was found between scavenging activity and total white variety, sample A, respectively). Ogunbusola
phenolic content in lupin genotypes and cocoa beans et al. (2010) noted similar observation for Lagenaria
(Oomah et al., 2006; Othman et al., 2007). Maheshu siceraria seed flour and its protein fractions. All
et al. (2013) also noted low correlation between total the legumes are rich in lysine, phenylalanine and
phenols and the antioxidative activity in seeds of field arginine but deficient in sulphur containing amino
bean stating that the major antioxidant compounds acids (methionine and cystine). Canavalia ensiformis
may be tannins. The trends of relationships between (C) however rated best in terms of the cystine and
the antioxidant activity and the total phenolics may methionine contents among all the legumes evaluated.
be explained as the total phenolics content does Generally, sulphur-rich amino acids (methionine
not incorporate all the antioxidants. In addition, the and cystine) are limiting in legumes. Commonly
synergism between the antioxidants in the mixture consumed food pulses such as chickpea, field pea,
makes the antioxidant activity not only dependent green pea, lentils and common beans have about 11
on the concentration, but also on the structure and g/kg protein of methionine and cysteine (Wang and
the interaction between the antioxidants (Djeridane Daun, 2004), the exceptions being cowpea, which has
et al., 2006). about 22 g/kg protein of methionine, and green pea,
which has about 18 g/kg protein of cysteine (Iqbal et
Amino acid composition of the legumes al., 2006). Amino acid deficiencies in the little known
There were significant (p<0.05) variations in the legumes could be complemented by eating cereals,
amino acid composition of the nine legumes (Table which are rich in amino acids containing sulphur
4). Glutamic acid was the most abundant amino (Jukanti et al., 2012). Legumes are usually consumed
acid in all the legumes evaluated. The values were along with cereals, especially in Nigeria, thereby
between 27.32 and 43.31 g/kg with the lowest value allowing the daily dietary amino acid requirements
in Mallotus subulatus, white variety (sample A) to be met. Tryptophan was not determined.
and highest value in Cajanus cajan (sample I). The The total amino acid contents (Table 5) were
second most abundant amino acid in all the legumes between 180 in Vignea subterranean (D) and 213
was aspartic acid ranging from 20.85 to 27.78 g/ g/kg in Mallotus subulatus (F). The total essential
kg in Cassia hirsutta (B) and Mallotus subulatus, amino acids of the legumes ranged between 84 and
 Ade-Omowaye et al./IFRJ 22(2): 798-806 804

Table 5. Summary of amino acid composition (g/kg protein) of the nine underutilized legumes

A=Mallotus subulatus (white variety); B= Cassia hirsutta; C= Canavalia ensiformis; D= Vignea subterranean (checkered variety);
E= Vigna racemosa; F= Mallotus subulatus (red variety); G= Vignea subterranean (cream variety); H= Sphenostylis sterocarpa;
I= Cajanus cajan

102 g/kg in Vignea subterranean (D) and Mallotus total fat. All the legumes have relatively high contents
subulatus (F), respectively. This is within the range of total phenolics and antioxidant activity pointing
of total essential amino acids without tryptophan, to the potentials of these legumes as promising food
89 to 236 g/kg edible portion reported for seven crops for the tropics. The fatty acid profile, dietary
important food legumes (Zhou et al., 2013). The fibre, total phenolic content and antioxidant capacity
range of percentage total essential amino acid (45.53- of these legumes may contribute to reducing the risk
48.44) obtained for the nine little known legumes is of cardiovascular disease and other degenerative
well above 36%, which is considered adequate for an diseases associated with free radical damage. The
ideal protein (FAO/WHO, 1973). This indicates the proportions of the total essential amino acids in the
potentials of these legumes in contributing to solving legumes are considered adequate for ideal protein
the food and nutrition insecurity in the country and foods. With their protein, fiber and antioxidant
beyond. Mallotus subulatus (white variety, A) had capacity, these underutilized legumes would offer
the highest percentage of total essential amino acid good nutrition to a wider community if promoted and
and the lowest was found in Vignea subterranean adopted.
(cream variety, G). The values of total amino acids
containing sulphur ranged from 6.80 to 9.51 g/kg Acknowledgement
with cystine ranging from 62.65 to 72.35%. The
range of total neutral, acidic and basic amino acids The author, B.I.O. Ade-Omowaye, is grateful to
were 53.11–57.18%, 25.30–30.02% and 16.29- Commonwealth and DAAD (Deutcher Akademischer
18.05%, respectively, which suggests that the protein Austausch Dienst) for financial support.
in the legumes may be acidic in nature. Ogunbusola
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