Evaluation of the Antidiabetic and Associated Effect of Methanol Root Extract of Strophanthushispidus DC (Apocynaceae) on Alloxan-Induced Diabetic Rats

Abstract

The antidiabetic properties of the methanol root extract of Strophanthus hispidus DC (Apocynaceae) was evaluated on normoglycaemic and hyperglycaemic rats. Diabetes was induced in rats using alloxan (150mg/kg body weight intraperitoneally). Normoglycaemic and hyperglycaemic rats were administered orally with single doses of (200, 400 and 800 mg/kg) the root extract of Strophanthus hispidus, 5mg/kg of Glibenclamide (positive control) and distilled water (negative) control for 14 days. The blood sugar level was determined using Glucometer. The acute toxicity (LD₅₀) test of methanol root extract was determined. The effect of the extract on some pathological parameters and the phytochemical constituents were also investigated.  The root extract produced a dose reduction (P < 0.05) in blood sugar levels of both normoglycaemic and hyperglycaemic rats. When doses of 200, 400 and 800mg/kg of the extract were administered orally to alloxan induced diabetic rats, significant reduction in blood sugar level occurred (64.72, 67.69 and 69.43 % respectively) while Glibenclamide caused a 67.74% reduction. In normal rats, the extract (200, 400 and 800 mg/kg) exhibited a significant reduction of the blood sugar level of 27.59, 34.28 and 41.92% respectively, while Glibenclamide caused a 39.78% reduction. Phytochemical analysis on Strophanthus hispidus showed the presence of alkaloids, flavonoids, carbohydrates, tannins, terpenoids, reducing sugars, steroids, proteins, glycosides and saponins. Acute toxicity test carried out in mice using Lorke's method showed that the root extract was relatively safe, since no death was recorded at the dose 5000mg/kg. There was significant (p< 0.05) increase in the liver enzymes level in the diabetic rats on day 0 before the administration of the extract.  At day 14 in the alloxan-induced diabetic rats, there was a significant (p< 0.05) decrease in the liver enzymes at studied doses (200, 400 and 800 mg/kg) when compared to the normal. There was significant (p< 0.05) difference in the AST level at day 14 when compared to day 0 in alloxan-induced diabetic rats.  At the doses extract, there was a significant decrease in the ALP level when compared to the normal at day 0. Also, the extract has the effect of decreasing the urea level at a dose of 200, 400 and 800 mg/kg from 36.35, 40.95 and 41.00 mg/dl at day 0 to 17.60, 16.31 and 14.60 mg/dl at day 14. The level was similarly reduced for the positive group (Glibenclamide). At day 14 there was a decrease in the urea level in the diabetic rats when compared to day 0. The methanol root extract has no significant effect in the creatinine level. The study shows that the root extract of Strophanthus hispidus has a significant hypoglycaemic activity in normoglycaemic and alloxan-induced diabetic rats. Similarly, the extract does possess hepatoprotective effect in alloxan-induced diabetic rats.