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African Journal. Traditional, Complementary and Alternative Medicines Vol. 3, Num. 1, 2006, pp.129-136 HYPOGLYCAEMIC AND ANTIDIABETIC EFFECT OF ROOT EXTRACTS OF CEIBA PENTANDRA IN NORMAL AND DIABETIC RATS Paul Désiré Dzeufiet Djomeni a *; Léonard Tédong a; Emmanuel Acha Asongalemb; Théophile Dimo a; Selestin Dongmo Sokengc; Pierre Kamtchouing a aDepartment of Animal Physiology,
Faculty of Science , University of Yaounde I P.O Box 812 Yaounde Cameroon, bDepartment
of Physiological Sciences, Faculty of Medicine and Biomedical Sciences,
Pharmacology and Toxicology Unit, University of Yaounde I P.O Box 812 Yaoundé
Cameroon, cDepartment of Biological Sciences, Faculty of
Sciences, University of Ngaoundere, P.O Box 454 Ngaoundere Cameroon Code Number: tc06014 Abstract The effect of the root bark extract of Ceiba pentandra (Linn) in normal and streptozotocin-induced diabetic rats was studied. Blood glucose levels were determined after oral administration of graded doses of C. pentandra (40, 75,150 and 300 mg/kg) in fasted normal and diabetic groups. In both groups, 40 and 75 mg/kg of the extract, significantly reduced blood glucose levels 8 h after administration, which was consistent and time-dependent. C. pentandra at the lower dose of 40mg/kg produced blood -glucose-lowering effect of 40.0% and 48.9%, in normal and diabetic rats respectively when compared with control rats. The higher doses of 150 and 300 mg/kg did not affect significantly the blood glucose levels. In multiple dose studies, the diabetic rats were treated orally by gavages, twice a day for 3 days. On day 3, C. pentandra (40 and 75mg/kg) significantly decreased blood and urine glucose levels as compared to initial values. The 14 h fasting blood glucose concentration was lowered by 59.8 % and 42.8% at the doses of 40 and 75 mg/kg and the corresponding urine glucose levels reductions were 95.7% and 63.6%, respectively. The results indicated that C. pentandra possessed hypoglycaemic effect. The plant extract was capable of ameliorating at lower doses, hyperglycaemia in streptozotocin-induced diabetic rats and could be a potential source for isolation of new orally active agent(s) for anti-diabetic therapy. Key words: Ceiba pentandra, Plant extract, Diabetes mellitus, Hypoglycaemic. Introduction Diabetes mellitus is a group of disorders with different aetiologies. It is characterized by derangements in carbohydrate, protein and fat metabolism caused by the complete or relative insufficiency of insulin secretion and / or insulin action (Balkau et al., 2000) Approximately 140 million people worldwide suffer from diabetes (WHO, 1999). The disease becomes a real problem of public health in developing countries, where its prevalence is increasing steadily and adequate treatment is often expensive or unavailable (Djrolo et al., 1998). Alternative strategies to the current modern pharmacotherapy of diabetes mellitus are urgently needed (WHO, 2002), because of the inability of existing modern therapies to control all the pathological aspects of the disorder, as well as the enormous cost and poor availability of the modern therapies for many rural populations in developing countries. Plants used in traditional medicine to treat diabetes mellitus represent a valuable alternative for the control of this disease. Ceiba pentandra (L) Gaertner (Bombacaceae) known as silk cotton tree and locally as “ dum “is widely reputed in the African traditional medicine (Ueda et al., 2002). Various morphological parts of this plant have been reported to be useful as effective remedies against diabetes, hypertension, headache, dizziness, constipation, mental trouble, fever, peptic ulcer, rheumatism and leprosy. It is also used as a diuretic and to expel evil spirits (Noumi et al., 1999; Ngounou et al., 2000; Noumi and Dibako, 2000; Noumi and Tchakonang, 2001; Ueda et al., 2002). The hypoglycaemic activity of the aqueous extract of the plant’s stem barkat high doses has been reported (Olusola et al., 2003). In the present study, the hypoglycaemic effect of the root bark methylene chloride / methanolic extract in normal and steptozotocin - induced diabetic rats was evaluated. Materials and Methods Animals Male albino Wistar rat (175 - 225 g) raised in the Animal House of the Faculty of Science, University of Yaounde I were used. They were fed with standard chow and watered ad libitum. Before testing for blood glucose level or injection of streptozotocin to induce diabetes, the rats were fasted overnight (at least 12 h) but had free access to water. The study was approved by institutional animal ethical committee. Preparation of the plant extract Roots of C. pentandra were collected in Yaounde (Centre Province, Cameroon). Botanical identification was performed at the National Herbarium, Yaounde, voucher specimens HNC 43623. The barks were removed from roots, sliced into small pieces, air dried at ambient temperature and ground into powder form. A kilogram of the powdered of the plant was macerated in a 1:1 (volume /volume) mixture of methylene chloride / methanol for 2 days (with occasional stirring) at room temperature. The filtrate obtained after filtration were concentrated using a rotavapor at a temperature of 80°C to obtain 106g to yield an equivalent of 10.6% yield of the starting material. Induction of diabetes Streptozotocin (STZ), purchased from Sigma Chemical Co., (Saint Louis, MO), was dissolved in ice-cold 0.9% NaCl saline solutions immediately before use. The overnight fasted rats were anaesthetised with diethyl ether and received STZ (55mg/kg) through the dorsal vein of the penis. Fasted blood glucose levels were assessed 48 hours after STZ injection as well as glycosuria to confirm the diabetic states. The rats were kept for 15 days to stabilise the diabetic condition (Jyoty et al., 2002). Only rats with a fasting blood glucose level of at least 200 mg/dl and positive urine glucose were used in the experiment. Treatment of animals Two set of experiments were carried out: single and multiple dose studies. Single dose studies This experiment involved testing for hypoglycaemic effect of the plant in normal and diabetic rats after single oral administration. Six groups of normal and diabetic rats of 5 rats/group were used. The control and diabetic groups received 1.5% dimethyl sulphoxide in distilled water. Four groups each of normal and diabetic rats were given p.o. 40, 75, 150 and 300 mg/kg of the plant extracts respectively. Their positive control groups had 5 mg/kg glibenclamide (DaonilR), a standard oral hypoglycaemic agent for comparison. Blood glucose levels were determined at time zero and subsequentlyat time 0.5, 1, 2, 3, 5 and 8 h. Multiple dose studies The experiment consisted of two groups of 5 diabetic rats given orally, 40 and 75mg/kg the extract twice daily for 3 consecutive days. Normal and diabetic control groups received 1.5% DMSO/H2O twice daily whereas the positive control rats took 2 IU of insulin once daily. Following 14 hours of fasting, blood and urine glucose levels were assessed before and at the end of the 3 day treatment period. Body weight, food and water intakes were also monitored. Blood sampling and measurement of blood and urine glucose Blood samples (20 µl) were obtained from the tail tip of fasted rats, and the blood glucose level was determined using a glucometer ACCUTREND GC (Boerhinger, Mannheim, Germany) while the glucose in fresh urine was assessed using glucose indicator sticks (Boerhinger Mannheim Germany) before and after treatment. Statistical analysis All the values in the test are presented as mean ± SEM (Standard Error of the Mean). Statistical differences between the means of the various groups were evaluated by one-way analysis of variance (ANOVA) using the SPSS program followed by Students’t-test. P values of 0.05 or less were considered to be significant. Results The effect of single dose administration of the exract on blood glucose level in fasting normal and diabetic rats are as shown in Figure 1a. The hypoglycaemic effects of the extract were significant (P < 0.05) one h. after dosing at 40, 75, and 150 mg/kg in the normal rats and only significant at 40 and 75 mg/kg in the diabetic rats (Figure 1b. At the highest dose tested (300 mg/kg), these effects were observed in normal rats 5 h post dosing. Glibenclamide had its significant effect 3 h post dosing. Twice daily administration for 3 days of the extract decreased the blood and urine glucose levels in diabetic rats diabetic rats (Table 1). The extract at40 and 75 mg/kg significantly P 0.001), reduced blood glucose levels by 60.0 p 0.001) and 42.8%, compared to 27% produced by insulin (P < 0.05). These results confirmed the corresponding reduction (P < 0.001) of urine glucose levels by 91.0%, 64.0% at 40 and 75 mg/kg of the extract and 46.0% for insulin. There was no significant change in body weights, food and water intakes of the rats. Discussion Streptozotocin - induced hyperglycaemic has been described as a useful experimental model to study the activity of hypoglycaemic agents (Szkudelski, 2001). Streptozotocin selectively destroys the pancreatic insulin secreting β-cells, leaving less active cells and resulting in a diabetic state (Kamtchouing et al., 1998; Szkudelski, 2001). At a single dose of 40mg/kg, the root bark extract produced significant reduction (P < 0.01) in the blood glucose concentration of fasted normal and diabetic rats after 8 h. These results were similar to those of Olusola et al.,(2003) who reported highest doses of the aqueous extract of the stem bark of C. pentandra. These observations may suggest that active principle (s) may be more liposoluble than hydrosoluble. A similar observation was reported by Kameswara et al. (2001) on the effect of bark extract of Pterocarpus santalinus on blood glucose in experimental animals. Glibenclamide treatment (5 mg/kg) was not as effective in reducing blood glucose in STZ-diabetic rats as in normoglycaemic rats. It has been reported that glibenclamide was not effective when destruction of β-cells has occurred and hence more effective in moderate diabetic rats than in severe diabetic animals (Sharma et al., 1997; Cetto et al., 2000; Hosseinzadeh et al., 2002). The acute hypoglycaemic effect of glibenclamide results has been shown from the stimulation of insulin release from the residual β-cells and inhibition of glucagon secretion (Moller, 2001). 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 C. pentandra revealed the presence of epicatechin isolated from other plants has been found to stimulate insulin secretion or possess an insulin-like effect (Marles and Farnsworth, 1995;Noreen et al., 1998; Kameswara et al., 2001). In this study, it was observed that administration of C. pentandra extract to diabetic rats reversed at lower doses their blood glucose which was also reflected in their urine sugar levels. Conclusion These results indicated that the root bark of C. pentandra was effective in decreasing the blood glucose level in normal and induced diabetic animals. However the nature of the molecule(s) responsible for such an effect requires further investigation. The possible mode of action of the plant extract might be by potentiation of the insulin effect by increasing the pancreatic secretion of insulin from -cells of islet of Langerhans or its release from the bound form Acknowledgements Authors are thankful to International Foundation of Science (IFS) for the grant nº F3341-1 to Dr Sokeng and to Pr Lontsi and Dr Meli for providing plant materialfor the preliminary experiments. References
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