Anti-diabetic Activity of Aqueous Extracts of Vitex doniana Leaves and Cinchona calisaya Bark in Alloxan–Induced Diabetic Rats

Vitex doniana Sweet and Cinchona calisaya WEED are tropical medicinal plants endued with important pharmacological properties. The effects of aqueous extracts of V. doniana leaves and C. calisaya bark on alloxan-induced diabetes mellitus in Wistar albino rats were evaluated. Diabetes mellitus was induced by a single intraperitoneal ( i.p) injection of 150 mg/kg body wt of alloxan monohydrate. The aqueous extracts of V. doniana leaves and C. calisaya bark were administered intraperitoneally to four diabetic groups at same doses of 50 and 100 mg/kg body wt. The actions of the extracts were compared with that of the standard oral hypoglycaemic agent, glibenclamide. Both extracts caused significant (p < 0.001) decreases in blood sugar levels of the rats at both doses tested. At 50 mg/kg body wt. V. doniana leaf extract produced 82.9% reduction in blood sugar level (i.e from 492.8 to 84.5 mg/dl) after four days whereas, C. calisaya caused 64.4% decrease. Unlike C. calisaya bark, V. doniana at both doses tested, was more potent than the reference drug, glibenclamide (0.3 mg/ kg body wt.). The antidiabetic activity of V. doniana did not vary with the dose, whereas the observed effect of C. calisaya decreased with increase in dose. C. calisaya exhibited higher antidiabetic activity at a lower dose of 50 mg/kg body wt. Both medicinal plants therefore possess valuable antidiabetic property. Their effects on the antioxidant status were also investigated. V. doniana and C. calisaya extracts caused increases in the activity of SOD and lipid peroxidation when compared with control, but the increases were lower than that produced by alloxan, indicating attenuation of free radical generation. Quantitative phytochemical analyses of both extracts showed the presence of saponins(0.92%), flavonoids(7.05%), alkaloids(1.8%), and cardiac glycosides(2.8%) in V. doniana, whereas saponins(2.0%), flavonoids(5.0%), alkaloids(6.0%), and cardiac glycosides(3.54%) were detected in C. calisaya.