Research Journal of Medicinal Plant 9 (5): 227-233, 2015

ISSN 1819-3455 / DOI: 10.3923/rjmp.2015.227.233

© 2015 Academic Journals Inc.

Anti-Diabetic Activity of Ipomoea batatas Leaves Extract: Effects on

Hepatic Enzymes in Alloxan-Induced Diabetic Rats

O.O. Ogunrinola, O.O. Fajana, S.N. Olaitan, O.B. Adu and M.O. Akinola
Cell and Tissue Culture/Drug Discovery Laboratory, Department of Biochemistry, Faculty of Science,
Lagos State University, Ojo Lagos, Nigeria

Corresponding Author: Olabisi O. Ogunrinola, Cell and Tissue Culture/Drug Discovery Laboratory, Department of
Biochemistry, Faculty of Science, Lagos State University, Ojo Lagos, Nigeria Tel: +2348033204476

ABSTRACT
Diabetes mellitus is the most common endocrine disorder of man, whose devastating effect is
increasing by the day and severity almost at epidemic level. This study was carried out to
investigate the anti-diabetic activity of Ipomoea batatas (sweet potato) leaves extract and its effect
on hepatic enzymes, total protein and albumin in alloxan induced diabetic rats. A total of
twenty animals was divided into four experimental groups consisting of five animals each. The
groups included a positive control, negative control, diabetic-treated Ipomoea batatas and
Diabetic-treated tolbutamide for 14 days. All were fed normal diet ad libitum. After the treatment
a significant reduction was observed in fasting serum glucose levels in the treated diabetics’ rats.
There was a significant (p<0.05) reduction of feed and water intakes by the animals after the
treatment with Ipomoea batatas and tolbutamide. Treatment also improved the weight gain
compared to untreated diabetic rats. Alkaline phosphatase activity in the diabetes untreated is
significantly higher compared to that normal and treated animal and others treated with extract
and tolbutamide. A Similar trend was observed in the Aspartate transaminase and Alanine
transaminase activity, respectively, the reversed was observed in the albumin and total protein
level, respectively. Hence, the result shows that the extract is not toxic and possesses anti-diabetic
properties.

Key words: Ipomoea batatas, anti-diabetic, hepatic enzymes, alloxan, albumin

INTRODUCTION
Diabetes Mellitus (DM), a common endocrine disorder of man, is considered one of the major
health concerns all over the world today (Rohilla and Ali, 2012). It is a disease of disordered
metabolism of carbohydrate, protein and fat, caused by the complete or relative insufficiency of
insulin secretion and/or insulin action (Ivorra et al., 1989). The number of people suffering from the
disease worldwide is increasing at an alarming rate, according to the World Health Organization
(WHO), more than 180 million people worldwide have diabetes and that this number is likely to
double by 2030 (Wild et al., 2004). This increase in incidence follows the trends of urbanization and
lifestyle changes, perhaps most importantly a Western-style diet. The greatest increase in
prevalence is however expected to occur in Asia and Africa, where most patients will probably be
found by 2030 (Wild et al., 2004).
One of the most potent methods to induce experimental diabetes mellitus is chemical induction
by alloxan, a well-know diabetogenic agent. Alloxan is a urea derivative, which causes selective

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necrosis of the β-cells of pancreatic islets. Its toxic action on pancreatic β-cells involve oxidation of
essential sulfhydryl (-SH) groups, inhibition of glucokinase enzyme, generation of free radicals and
disturbances in intracellular calcium homeostasis resulting in diabetic mellitus disease
(Rohilla and Ali, 2012). Diabetes can be managed by exercise, diet and pharmaceutical drugs like
tolbutamide, which are either too expensive or have undesirable sides effects or contraindications
(Serrano, 1990). Thus, the search for new drugs with low cost, more potential and without adverse
effects becomes inevitable.
A great number of medicinal plants have been used in the treatment of diabetes in different
parts of the world, some of which are without scientific scrutiny. The World Health Organization
has also encouraged and recommended the use of plants as an alternative therapy for diabetes
especially in countries where access to the conventional treatment of diabetes is not adequate
(WHO., 1980). Sweet potatoes (Ipomoea batatas) are excellent sources of plant proteins with very
low calories. Unlike other starchy root vegetables, it is used in folk medicine for the treatments of
metabolic diseases (Niwa et al., 2011). Its leaves, the by-products, possess activities of accelerating
metabolism, preventing atherosclerosis, protecting eyesight, hypoglycemia and anti-oxidant
(Islam, 2006). Ipomoea batatas is used for the treatments of diabetes, although its mechanism of
action is enigmatic. The present study was therefore intended to investigate the anti-diabetic
activity of Ipomoea batatas leaves extract and its effect on hepatic enzymes in alloxan induced
diabetic rats.

MATERIALS AND METHODS

Collection of plant materials and preparation of extract: Ipomoea batatas were collected
between May and June in Yaba area of Lagos State, Nigeria and identified and authenticated in
the Department of Botany, Lagos State University, Ojo-Lagos, Nigeria. The fresh plant material
was air-dried for 4 weeks at room temperature and ground into a powder. The plant powder
(500 g) was decocted in 4 L of distilled water for 15 min. This was repeated four times, until the
resulting extract gave no further colouration. The aqueous extract was then filtered and evaporated
to dryness in an oven at 40°C to obtain 100 g of crude residue (yield: 20%).

Experimental animals: Three month old male Wistar Albino rats weighing between 160-200 g
were obtained from the animal house of the laboratory of Biochemistry, Department of
Biochemistry, Lagos State University, Ojo-Lagos, Nigeria. They were acclimatized for two weeks,
fed with standard rat feed supplied by Animal Care Ltd., Nigeria.

Experimental induction of diabetes: Diabetes was induced in the animals 14 days before
commencement of treatment. The animals were fasted overnight and then injected with alloxan
monohydrate dissolved in sterile normal saline at a dose of 150 mg kgG1 body weight,
intraperitoneally. Since, alloxan is capable of producing fatal hypoglycaemia as a result of the
massive pancreatic insulin release, rats were treated with 20% glucose solution intraperitoneally
after 6 h. The animals were then allowed to drink 5% glucose solution for the next 24 h to prevent
hypoglycaemia (Dhandapani et al., 2002). After a fortnight, rats with marked hyperglycaemia were
selected and used for the study.

Experimental design: In the experiment, a total of 20 rats were divided into 4 groups with five
animals in each group:

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C Group A: Positive Control-normal rats

C Group B: Negative Control-Diabetic untreated rats
C Group C: Diabetic rats treated with Ipomoea batatas leaves extract (150 mg kgG1 body weight)
for 14 days (Li et al., 2009)
C Group D: Diabetic rats treated with tolbutamide (80 mg kgG1 body weight) for 14 days

All the rats had access to water. Every 7 days (1, 7, 14) the water, feed, body weight and blood
glucose of the animals were carefully monitored and after 14 days of treatment, the rats were
sacrificed by cervical dislocation under ether anaesthesia after an overnight fasting. Blood samples
were drawn at weekly intervals till the end of the study and processed for the estimation of serum
glucose, total protein, Alkaline phosphate (ALP), Aspartate Aminotransferase (AST), Alanine
Aminotransferase (ALT) and albumin. All the experimental animals were conducted according
to the ethical norms approved by the Guide for the Care and Use of Laboratory Animals
(NIH., 1985) and was approved by the Animal Ethical Committee of the Department of
Biochemistry, Lagos State University, Ojo-Lagos, Nigeria.

Biochemical assay: The blood glucose levels was determined for all the samples by the
glucose-oxidase method (Varley et al., 1976). Aspartate aminotransferase (AST) and Alanine
aminotransferase (ALT) activities were assayed at 546 nm (Schmidt and Schmidt, 1963). The
activity of alkaline phosphatase (ALP) was determined using phenolphthalein mono-phosphate
method (Wright et al., 1972). Serum total protein concentration was determined at 540 nm using
the Biuret method (Plummer, 1978). Serum albumin determination was done using the method of
Doumas et al. (1971).

Statistical analysis: The data were analyzed using one-way ANOVA followed by Turkey Honest
Significant Difference (THSD). The differences were considered statistical significant at p<0.05.

RESULTS
Water, feed intakes and body weight: Table 1 shows a significant (p<0.001) increase in
the index of water intakes of negative diabetic rats compared to positive control-control rats,

Table 1: Effect of tolbutamide and Ipomoea balatas leaves extract on the intakes (mL ratG1 dayG1) and feed intake (g ratG1 dayG1) of
alloxan-induces diabetic animals
Days
----------------------------------------------------------------------------------------
Treatment groups 0 7 14
Water intakes (mL ratG1 dayG1)
Positive control-normal rate 16.20±0.42 18.00±0.79 15.00±0.36
Negative control-diabetic untreated rats 77.80±4.16# 87.60±0.76# 79.40±2.28#
Diabetic rats treated with Ipomoea batatas leaves extract 80.80±3.93 74.80±0.42*** 48.80±0.65***
Diabetic rats treated with tolbutamide 81.80±0.89 53.20±0.96*** 41.20±3.15***
Feed intake (g ratG1 dayG1)
Positive control-normal rate 14.00±0.36 15.60±0.45 15.20±0.23
Negative control-diabetic untreated rats 20.40±1.04# 28.20±0.42# 32.80±0.42#
Diabetic rats treated with Ipomoea batatas leaves extract 27.20±0.42 31.60±0.57 25.20±0.42*
Diabetic rats treated with tolbutamide 28.20±0.74 24.40±0.28 20.90±0.98*
Values are Mean±SD for 5 rats in each group. Values having different superscript differ significantly when compared with position
control-normal (#p<0.001) and negative control-diabetic untreated rats (***p<0.001 and *p<0.001)

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which was decreased with the administration of Ipomoea balatas but further reduction by
tolbutamide. This same pattern was observed in the feed intakes.
The effect of tolbutamide and Ipomoea batatas leaf extract on body weights (g) in
alloxan-induced diabetic animals is depicted in Table 2. Significant (p<0.001) weight loss was
observed in negative control-diabetic untreated rats compared to positive control-normal rats.
Treatment with aqueous extract of Ipomoea batatas and tolbutamide improved the weight gain
throughout the 14 days but the highest improvement in the weight gain was by Ipomoea batatas
aqueous leaf extract.

Blood glucose and hepatic enzymes: The change in blood glucose on treatment of diabetic rats
with Ipomoea batatas and tolbutamide is shown in Table 3. The blood glucose concentration was
increased significantly in negative control-diabetics untreated rats compared to positive
control-normal rats (p<0.05). Administration of Ipomoea batatas and tolbutamide led to significant
decrease in blood glucose levels in diabetics treated groups (p<0.001). In Table 4, the ALP activity
in the negative control-diabetic untreated rats was significantly (p<0.001) higher compared to that
of positive control-normal animal but treatment with Ipomoea batatas extract and tolbutamide
reduced its activity, although, Ipomoea batatas was more potent. This trend was observed in the
AST and ALT activities, albumin and total protein levels, respectively.

Table 2: Effect of tolbutamide and Ipomoea balatas leaves extract on b.wt. (g) of alloxan-induces diabetic animals
Days
------------------------------------------------------------------------------------------
Treatment groups 0 7 14
Body weights (g)
Positive control-normal rate 168.20±3.33 180.00±0.00 186.80±0.36***
Negative control-diabetic untreated rats 176.80±4.29 156.20±0.00 144.40±0.28#
Diabetic rats treated with Ipomoea batatas leaves extract 171.60±4.19 197.00±0.00* 200.40±0.65***
Diabetic rats treated with Tolbutamide 169.00±4.47 175.60±0.00 190.80±3.15***
Values are Mean±SD for 5 rats in each group. Values having different superscript differ significantly when compared with position
control-normal (#p<0.001) and negative control-diabetic untreated rats (***p<0.001 and *p<0.001)

Table 3: Effect of tolbutamide and Ipomoea balatas leaves extract on the serum glucose concentration (mg dLG1) of alloxan-induces diabetic
animals
Days
-------------------------------------------------------------------------------------------
Glucose concentrations (mg dLG1) 1 7 14
Positive control-normal rate 84.20±02.66 64.60±2.75 59.00±3.47
Negative control-diabetic untreated rats 244.20±09.66# 257.00±8.35# 268.00±5.23#
Diabetic rats treated with Ipomoea batatas leaves extract 247.00±10.40 183.80±3.53*** 268.00±5.23#
Diabetic rats treated with tolbutamide 245.00±11.18 162.00±2.75*** 114.60±7.83***
Values are Mean±SD for 5 rats in each group. Values having different superscript differ significantly when compared with position
control-normal (#p<0.001) and negative control-diabetic untreated rats (***p<0.001 and *p<0.001)

Table 4: Effect of tolbutamide and Ipomoea balatas extract on the serum biochemical indices of alloxan-induces diabetic animals
Biochemical indices
---------------------------------------------------------------------------------------------------------------------
ALP AST ALT Albumin Total protein
Treatment groups (U LG1) (U LG1) (U LG1) (mg d LG1) (mg d LG1)
Positive control-normal rate 24.840±09.00 8.80±00.82 3.600±0.45 3.72±0.40 7.11±0.42
Negative control-diabetic untreated rats 104.880±20.00# 74.80±10.00# 10.400±1.10# 4.30±0.43# 5.55±0.22#
Diabetic rats treated with Ipomoea batatas 33.120±06.17** 8.20±01.34*** 4.800±0.90*** 4.81±0.66 5.86±0.19**
leaves extract
Diabetic rats treated with tolbutamide 44.160±07.56** 7.00±01.54*** 5.600±0.45*** 4.36±0.19 6.84±0.42**
Values are Mean±SD for 5 rats in each group. Values having different superscript differ significantly when compared with position
control-normal (#p<0.001) and negative control-diabetic untreated rats (***p<0.001 and *p<0.001), ALT: Alanine aminotransferase,
AST: Aspartate aminotransferase, ALT: Alkaline phosphate

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DISCUSSION
Available evidence shows that alloxan causes diabetes through its ability to destroy the
insulin-producing beta cells of the pancreas, inducing hyperglycaemia and other diseases in
animals (Lenzen and Panten, 1998; Ijaola et al., 2014). Tolbutamide and some plant drugs were
known to influence the effect of diabetes mellitus, however, their anti-diabetic efficacy and
hypoglycemic mechanisms are unknown. In the present study, we revealed that while the
treatments of Ipomoea batatas leaf extract significantly reduced the increased feed and water
intakes, there was increase in body weight of the animals which may be due to the regeneration
of the adipocytes and muscle tissues to make up for energy in the body. This agrees with the
findings of previous workers (Ijaola et al., 2014; Niwa et al., 2011; Pant et al., 1968).
Our finding showed a significant decrease in serum glucose concentration of diabetic animals
treated with Ipomoea batatas extract compared to treatment with tolbutamide. This observation
supports the report of Nishikant et al. (2014) and Ijaola et al. (2014). The possible mechanism by
which aqueous extract of Ipomoea batatas brings about its hypoglycaemic action may be, by
potentiating the insulin effect, either by increasing the pancreatic secretion of insulin from the cells
of islets of Langerhan’s or its release from bound insulin, thereby, decreasing the postprandial
glucose in animals. This may be the cause of the increased body weight in Ipomoea batatas extract
treated rats (Oliveira et al., 2008; Pandikumar et al., 2009).
Some enzymes act as markers and indicators of disease states, thus, their increased activities
in serum are indicative of cell damage (Udobre et al., 2009). The reduction in ALP activity following
Ipomoea batatas treatment shows its stability of biliary function against the damage caused by
alloxan. The result is similar to what was reported on treatment with Caralluma fimbriata
(Latha et al., 2013). AST and ALT activities act as an indicators of liver function, hence the
restoration of these enzymes after administration of Ipomoea batatas, indicates that the normal
functioning of the liver and the bile duct was restored. This is in consistent with reports of
Udayakumar et al. (2009) on the Withania somnifera extracts.
Albumin constitutes the major component of the Total Protein (TP) and therefore a diagnostic
tool for the determination of liver function (Spencer et al., 2011). In this present study, while there
was an increased in the levels of both albumin and total protein by the administration of
Ipomoea batatas extract, tolbutamide significantly increased total protein. This observation agreed
with the findings of Omoniwa and Luka (2012). The result implied that the liver’s synthetic activity
and ability to maintain nutrient homeostasis was enhanced as a result of administration of the
Ipomoea batatas extract.
From the above results, it may be concluded that the Ipomoea batatas leaf extracts show no
sign of toxicity and possess anti-diabetic activities in alloxan-induced diabetic rats compared to
tolbutamide.

ACKNOWLEDGMENTS
The authors acknowledged the assistance of the technical staff of Cell and Tissue Culture/Drug
Discovery Lab, Department of Biochemistry, Faculty of Science, Lagos State University, Ojo Lagos,
Nigeria during the course of this study.

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