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International Journal of Applied Research in Natural Products
Vol. 1(2), pp. 32-36, June/July 2008
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Original Article
Hypoglycemic Activity of Methanolic Stem Bark of
Adansonnia digitata Extract on Blood Glucose Levels of
Streptozocin-Induced Diabetic Wistar Rats
Tanko Y1*, Yerima M2, Mahdi MA2, Yaro AH3, Musa KY4, Mohammed A1
1
Department of Human Physiology, Ahmadu Bello, University, Zaria, Nigeria. 2Department of Pharmacology
and Clinical Pharmacy Ahmadu Bello, University, Zaria. Nigeria. 3Department of Pharmacology, Bayero
University, Kano, Nigeria. 4Department of Pharmacognosy and Drug Development Ahmadu Bello,
University, Zaria. Nigeria.
Summary: Evaluation of hypoglycemic activity of methanolic stem bark extract of Adansonnia digitata in Wistar rats has been
investigated. Antidiabetic potentials of the plant extract at the doses of 100,200 and 400 mg/kg intraperitoneally administered on
Streptozocin diabetes Wistar rats. Treatment of streptozocin diabetic Wistar rats with the extract caused a significant (P<0.05)
reduction in the blood glucose levels when compared with control. The dose of 100mg/kg shown a significant decreased (p<0.05)
after 1, 3 5 and 7 hours of extract administration when compared to control normal saline. Also the dose of 200 mg/kg shown a
significant decreased (p<0.05) after 3, 5 and 7 hours of extract administration. The dose of 400 mg/kg also shown a significant
decreased( p<0.05) after 5 and 7 hours of extract administration when compared to control normal saline. The highest activity resides
at the dose of 100 mg/kg with percentage glycemic change of 51 % after 7 hours of extract administration while the other two doses
200 and 400 mg/kg have glycemic change of 39% and 31% respectively after 7 hours of extract administration. The phytochemical
screening revealed the presences of tannins, carbohydrate, terpenes, saponins, flavonoids and alkaloids. The median lethal dose (
LD50) in mice was calculated to be 1264.9 mg/kg bodyweight. This result suggests that the methanolic stem bark of Adansonnia
digitata possess antidiabetic effect on streptozocin induced diabetic Wistar rats.
Industrial relevance: The herbal medicines are getting more importance in the treatment of diabetes and others ailments because of
the hazardous adverse effect of the current therapy used to treat those ailments using synthetic drugs. Herbal medicine is free from
side effects and less costly when compared to the synthetic hypoglycemic agents. The present study will help the industry to produce
herbal drug with less side effect, less costly affordable and more effective in the treatment of diabetes mellitus. In vivo models were
utilized to test the antidiabetes activity and important to optimized the dose in the herbal formulation. Finally the phytochemical
screening or elucidation of the bioactive compounds from the plant would be effective drug against diabetes mellitus.
Keywords: Hypoglycemic activity, streptozocin Phytochemical Adansonnia digitata,
Introduction
Diabetes mellitus is a group of metabolic disorders characterized by hyperglycemia and defective metabolism of
glucose and lipids. Diabetes was estimated to affect 177 million people world wide in 2000 and this figure is projected to
increase to 300 million by 2025 (Porter and Barret, 2005). Diabetes is not a single disease rather it is a heterogeneous
group of syndromes characterized by an elevation of blood glucose caused by relative or absolute deficiency of insulin.
Diabetes can be divided into two main groups based on their requirements of insulin: insulin dependent diabetes mellitus
(Type 1), and non-insulin dependent diabetes mellitus (Type 2). However, other types of diabetes have also been
identified. Maturity Onset Diabetes of the Young (MODY) is now classified as Type 3 and gestational diabetes classified
as Type 4.
NIDDM type 2 diabetes account for about 90 percent of diabetic cases (WHO, 2002). Insulin resistance and β-Cell
dysfunction are the metabolic abnormalities in the type 2 diabetes (Sa’ad et al., 1991). Glycemic control is one of the
targets for managing diabetes mellitus. Studies have confirmed that for the type 2 diabetes, effective control of blood
glucose substantially decrease the risk of developing diabetic complications (Ohkubo et al., 1995; UKPDS, 1997).
Orthodox treatment of diabetes mellitus includes a modification of life style, such as diet and exercise and the use of
insulin and/or oral hypoglycaemic drugs. These pharmacologic agents target increased insulin secretion, decreased
hepatic glucose production and increased sensitivity to insulin (Kelly and Mandarino, 2000). Management of this disease
with insulin and/or oral hypoglycaemic agents have certain drawbacks (University Group Diabetes Program, 1974;
*Corresponding Author:
Tel: +1-234-8037054274
Fax: +1-234-62248314
E-mail: [email protected]
Accepted 27 March 2008
32
Hypoglycemic activity and Adansonia digitata
Knatterud et al., 1978). For insulin such drawbacks include ineffectiveness on oral administration, short shelf life,
requirement of constant refrigeration and in the event of excess dosage-fatal hypoglycaemia. The use of oral
hypoglycaemic drugs like sulfonylureas and biguanides is also associated with side effects such as propensity to gain
weight (Rang and Dale, 1991).
Adansonnia digitata. L. ( Bombacaceae). An African plant known as baobab tree. Leaves, bark and fruits of this plant
are traditionally employed in several African regions as food stuffs and for medicinal purposes, and for that reason
baobab is also named “the small pharmacy or chemist tree” (Etkin and Ross 1982; Kerharo and Adam,1974).The native
African population commonly used, baobab fruit as famine food to prepared, decoctions, sauces and natural refreshing
drink due to it nutritional properties ( Obizoba and Anyika 1994; Lunven and Adrian, 1960). The pulp is therapeutically
employed as analgesic anti-diarrhea and for treatment of smallpox and measles (Kerharo and Adam, 1974).
The present study was designed to test the hypoglycemic effect of methanolic extract of Adansonnia digitata stem
bark on streptozocin- induced diabetes.
Materials and Methods
Plant material: The stem bark of Adansonnia digitata was collected around area of Basawa, Sabongari L.G.A. Zaria of
Kaduna State Nigeria in the Month of August 2007. The plant specimen was identified by Mal A.U Gallah of the
Herbaruim Unit, Department of Biological Sciences, Ahmadu Bello University, Zaria- Nigeria, where a voucher
specimen has been deposited.
Extract preparation: The stem bark of Adansonnia digitata was dried under shade for one week and the pulverized
into fine powder in a pestle and mortar and passed through a mesh sieve. The powdered was macerated with 70%
methanol for 72 hours. Later the extract was filtered then concentrated using rotary evaporator and was kept in dessicator
until use.
Chemicals used: All chemicals and drugs were obtained commercially and were of analytical grade. Streptozocin
(Sigma).The Biphasic Isophane insulin AS Mixtard 30 HM Pen fill (Novo Nordisk AIS 2880 Bagsvaerd, Denmark.
NAFDAC Reg.no 04-1601).
Acute toxicity study: The lethal dose (LD50) of the plant extract was determined by method of Lorke (1983) using 13
mice. The animals were handled in accordance with international principles guiding the use and handling of
experimental animals (United State National Institute for Health, 1985). In the first phase mice were divided into 3
groups of 3 mice each and were treated with the extract at doses of 10, 100 and 1000mg/kg body weight intraperitoneal.
They were observed for 24 hours for signs of toxicity. In the second phase 4 mice were divided into 4 groups of 1 rat in
each group and were also treated with the extract at doses of 600, 1000, 1600 and 2900 mg/kg bodyweight (i.p).The
median lethal dose ( LD50 ) was calculated using the second phase.
Phytochemical screening: The preliminary phytochemical screening of the crude extract of Adansonnia digitata was
carried out in order to ascertain the presence of its constituents utilizing standard conventional protocols (Trease and
Evans, 1983).
Induction of Diabetes Mellitus: Twenty five Wistar rats of both sexes weighing 150-180 grams were used for the
study of the effects of Adansonnia digitata extract on the blood glucose levels of the animals. They were kept in standard
cages at 250C and 12 hour light/dark condition in the animal room of the Department of Human Physiology, AB.U,
Zaria. The animals were fed on commercial feeds and were given water ad libitum. The animals were fasted from feeds
for 12 hours before the commencement of each experiment, but were allowed water ad libitum. The rats were injected
with streptozocin dissolved in citrate buffer pH 4.5 in a dose of 60mg/kg body weight intraperitoneal. Since Streptozocin
is capable of producing fatal hypoglycemia as a result of massive pancreatic release of insulin, the rats were treated with
20% glucose solution intraperitoneally after 6 hours (Stanley et al., 2001).The were kept for the next 24 hours on 5%
glucose solution bottles in their cages to prevent hypoglycemia. After a period of three days the rats with a blood glucose
levels greater than 180mg/dL were considered diabetic and used for this research work
Experimental Design
The Streptozocin-induced diabetic Wistar rats were randomly assigned into five groups (1-5) of five rats (n=5) each as
follows, namely
Group 1- Received normal saline i.p
Group2- Received Biphasic Isophane Insulin 6 i.u/kg i.p(Stanley et al.,2001)
Group3- Received 100 mg/kg body weight of the Adansonnia digitata extract i.p
Group4- Received 200 mg/kg body weight of the Adansonnia digitata extract i.p
Group5- Received 400 mg/kg body weight of the Adansonnia digitata extract i.p
Determination of blood glucose levels
Blood samples were collected by cutting the tail-tip of the rats, for blood glucose determination at intervals of 0, 1, 3, 5
and 7 hours. Determination of the blood glucose level was done by the glucose-oxidase principle (Beach and Turner
1958) using the ONE TOUCH Basic (Lifescan, Milpitas, CA) instrument and results were reported as mg/dl (Rheney
and Kirk, 2000).
Statistical analysis: Blood glucose levels were expressed in mg/dl as mean ± SEM. The data were statistically
analyzed using ANOVA with multiple comparisons versus control group. The values of p<0.05 were considered as
significant (Duncan et al., 1977).
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Tanko et al
Results
Phytochemical analysis
Freshly prepared extracts were subjected to preliminary phytochemical screening test for various constituents. This
revealed the presence of tannins, carbohydrate, terpenes, saponins, flavonoids and alkaloids.
Acute toxicity study (LD50)
The sign of toxicity were first noticed after 10-12 hours of extract administration. There was decreased locomotor
activity and decreased in sensitivity to touch. Also there was decreased feed intake, and prostration after 18 hours of
extract administration. The median lethal dose (LD50) in rats was calculated to be 1264.9 mg/kg body weight.
Anti diabetic study
Table 1 showed the results of the effects of three doses (100mg/Kg, 200mg/Kg and 400 mg/Kg) of Adansonnia
digitata extract, Insulin and control groups in streptozocin-induced diabetic Wistar rats. A drop of blood samples was
collected by cutting the tail-tip of the rats, for the blood glucose determination at intervals of 0, 1, 3, 5 and 7 hours. The
dose of Insulin and the dose of the extract 100mg/kg there was a significant decreased the blood glucose levels when
compared to control after 1 hour of extract administration while the other two doses of the extract 200 and 400 mg/kg
did not show any significantly change in the blood glucose levels after 1 hour of extract administration when compared
to control group with percentage glycemic change of 19 and 4 % After 3 hours of extract administration there was a
significant decrease in the blood glucose level in 100 and 200 mg/kg when compared to control group with percentage
glycemic change of 38 and 29% while the dose of 400 mg/kg there was no any significant change in the blood glucose
levels with percentage of glycemic change of 9% . However, after 5 and 7 hours of treatment there was a significant
decrease (p<0.05) in the blood glucose levels when compared to control in all the three doses given with percentage
glycemic change of 43, 29 and 20 respectively. And after 7 hours of extract administration the glycemic change of 51, 39
and 31 % respectively.
Table 1. Effect of stem bark of aqueous methanolic Adansonnia digitata on streptozocin-induced diabetic Wistar rats
Treatment
0 hour
BLOOD GLUCOSE LEVELS(Mg/dl)
1 hours
3 hours
5 hours
7 hours
Group 1
Control
(N/Saline)
189±7.6
226±18.2
231±17.1
232±13.8
239±16.2
Group 2
(Insulin 6.i.u/kg)
193±11.9
170±10.2 a
(25%)
143±8.66 a
(38%)
115±6.42 a
(50%)
103±4.27 a
(56%)
Group 3
(100 mg/kg)
192±9.13 ns
165±14.4 a
( 27%)
143±10.7 a
(38%)
131± 11.8 a
(43%)
115±3.31 a
(51%)
Group 4
(200 mg/kg)
189±14.0 ns
182±12.9 ns
(19%)
162±10.8 a
(29%)
165±12.1a
(29%)
146±12.1 a
(39%)
Group 5
(400 mg/kg)
192±57.37 ns
216.±19.2ns
(4%)
209±18.3 ns
(9%)
185±14.9 a
(20%)
166±13.9a
(31%)
Vales are given as mean ± SD for 5 rats in each group; experimental groups are compared with diabetic control. Values
are statistically significant at a=P<0.05 ns=not significant
% Glycemic change= Glucose concentration (2, 4, 8 or 24) – fasting blood glucose x 100
Fasting blood glucose
Figure in parenthesis represent percentage glycemic change
Discussion
Medicinal plants are widely used by the populations of underdeveloped countries as alternative therapy. In Africa,
hundreds of plants are used traditionally for the management and/or control of diabetes mellitus. Unfortunately only a
few of such African medicinal plants have received scientific scrutiny. The present work was therefore designed to study
the anti-diabetic property of Adansonnia digitata stem bark Streptozocin-diabetic rats.
Streptozocin-induced hyperglycaemia has been described as a useful experimental model to study the activity of
hypoglycemic agents ( Szkudelski, 2001). Streptozocin selectively destroyed the pancreatic insulin secreting β –cells,
leaving less active cell resulting in a diabetic state (Kamtchouing et al., 1998; Szkudelski, 2001).
34
Hypoglycemic activity and Adansonia digitata
Many secondary metabolites participate in a variety of anti-diabetic functions in vivo (Kako et al., 1997). The glycemic
change in blood glucose levels of diabetic rat at different time intervals after intraperitoneal administration Adansonnia
digitata extract of at the doses of 100, 200, and 400mg/kg as showed in Table 1.
In relation to the diabetes rats that received 100, 200 and 400 mg/kg bodyweight of Adansonnia digitata extract there
was a significant (p<0.05)reduction in the blood glucose levels when compared to the control group after 2 hours of
extract administration as regard to the dose of 100 mg/kg and the reference drug . In relation to the dose of 200 and 400
mg/kg of the Adansonnia digitata there was no any significant change in the blood glucose levels after 1 hour of extract
administration. Also after 3 hours of extract administration as regard to the doses of 100 and 200 mg/kg there was
significant reduction in the blood glucose levels extract administration when compared to control group. After 5 and 7
hours of extract administration there was a significant change in the blood glucose level in all the three doses of the
extract given when compared to control group. In relation to the reference drug biphasic insulin 6.i.u/kg there was a
significant decrease in the blood glucose level when compared to control group. The dose of 100 mg/kg was found to
be more effective in the glycaemic change after 7 hours of extract administration than the other two doses of the extract
20 and 400 mg/kg body weight. The extract might possess Insulin like effect on peripheral tissues either by promoting
glucose uptake and metabolism or inhibiting hepatic Gluconeogenesis. The phytochemical studies of Adansonnia
digitata extract of revealed the presence of tannins, carbohydrate, terpenes, saponins, flavonoids and alkaloids.
flavonoids . Flavonoid and terpenes isolated from the other antidiabetic medicinal plants has been found to stimulate
secretion or possess an insulin like-effect (Marles and Farnsworth 1995). Effect of the flavonoids quercetin and ferulic
acid on pancreatic β-cells leading to their proliferation and secretion of more insulin have been proposed by Mahesh and
Menon (2004) and Sri-Balasubashini, et al., (2004) as the mechanism by which they reduced hyperglycaemia caused by
streptozocin in diabetic rats. The flavonoids present in Adansonnia digitata may also be acting similarly thereby
decreasing the high blood glucose levels of streptozocin-diabetic rats.
In conclusion, the experiment evidence obtained in the present laboratory animal study indicate that methanolic extract
Adansonnia digitata stem bark possess anti-diabetic properties which suggest the presence of biologically active
components which may be worth further investigation and elucidation.
Acknowledgements
The authors wish to thank Mallam Bala Mohammed, a technical staff of the Department of Human Physiology, ABU,
Zaria for taking care of the experimental animals throughout the period of this research work.
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