Antidiabetic Activity of the Leaf Extracts of Pentas schimperiana Subsp. schimperiana (A. Rich) Vatke on Alloxan-Induced Diabetic Mice

Pentas schimperiana (A. Rich) Vatke (Rubiaceae) is widely used for the treatment of diabetes mellitus and various other ailments in the traditional medical practices of Ethiopia. This study reports the antidiabetic and free radical scavenging activities of extracts and solvent fractions prepared from the leaves of P. schimperiana grown in Ethiopia on alloxan-induced diabetic mice and 2,2-diphenyl-1-picrylhydrazil (DPPH) assay, respectively. A single dose of 500 mg/kg of each of the aqueous dried leaf, hydroalcoholic fresh and dried leaf extracts of P. schimperiana did not show significant antidiabetic effect. However, at a dose of 1000 mg/kg, the extracts lowered blood glucose level by 26.97%, 21.90% and 26.70%, respectively. At a dose of 500 mg/kg, the aqueous and methanol fractions prepared from the dried plant material lowered blood glucose level by 23% and 27.2%, respectively, as compared with diabetic untreated mice. Treatment with a known antidiabetic drug glibenclamide (5 mg/kg of body weight) lowered blood glucose by 38%. The antidiabetic activity of the dried plant material was shown to be better than that of the fresh plant material. Both the hydroalcoholic extracts and the methanol fraction of the dried leaves of P. schimperiana displayed a very good DPPH scavenging activity with IC50 values of 7.83 and 8.84 μg/ml, respectively. In this study ascorbic acid showed an IC50 value of 4.42 μg/ml. Acute toxicity study of the aqueous and the hydroalcholic extracts of P. schimperiana performed on Swiss albino mice indicated that the median lethal dose (LD50) of the extract is above 4000 mg/kg. Phytochemical screening carried out on the total leaf extracts of the plant confirmed the presence of flavonoids, saponinns, steroids and tannins. The results of the current study support the traditional use of the plant in the management of diabetes.Key words: Pentas schimperiana, antidiabetic activity, alloxan, 2,2-diphenyl-1-picrylhydrazil, free radical scavenging activit