Anti-diabetic activity of methanol/methylene chloride stem bark extracts of Terminalia superba and Canarium schweinfurthii on streptozotocin-induced diabetic rats

Stem bark extracts of Terminalia superba Engl. and Diels and Canarium schweinfurthii Engl. are used in Africa for the treatment of various ailments, including diabetes mellitus. The anti-diabetic effects of the methanol/methylene chloride extracts of the stem barks on streptozotocin (STZ)-induced diabetes were evaluated on male rats. Through the subcutaneous route, diabetes was induced using 60 mg/mL of streptozotocin. After 2 days, the rats received, by gavage, 150 mg/kg and 300 mg/kg of extract daily for 14 days. At 300 mg/kg, the two extracts (Terminalia superba and Canarium schweinfurthii), significantly showed at least 67.1% and 69.9% reduction in blood glucose level, respectively, while insulin (three units) given subcutaneously and once daily, had 76.8% reduction compared to diabetic untreated control rats. Similarly, the weight gains were 6.6% and 4.9%, respectively, and were comparable to the normal rats, whereas, diabetic untreated rats lost 14.1% body weight. Still with the same dose, there was 68.5% and 58.5% (p < 0.001) significant decrease in food consumption and 79.7% and 64.0% (p < 0.001) in fluid intake by diabetic rats treated with the respective plant extracts. The insulin-treated rats showed 56.4% and 75.8% decrease in food and fluid intake compared to an augmentation for diabetic control rats, 43.0% and 383.8%, respectively, at the end of the second week of experimentation. These results showed that the plant extracts can reverse hyperglycemia, polyphagia and polydipsia provoked by streptozotocin, and thus, they have anti-diabetic properties.