Abstract
Durio zibethinus Murr., commonly called Durian, though well known for its rich medicinal uses, only fewer studies are available on the leaves of this plant. In this study, we investigated the antioxidant and antidiabetic potential of ethanol extract of D. zibethinus leaves (DZL) from Malaysian geographical origin. DZL was subjected to the preliminary phyto chemical screening along with the quantitative analysis of phenols and flavonoids. The in vitro antioxidant properties were evaluated by DPPH and ABTS methods and in vitro antidiabetic properties were evaluated by alpha-amylase and alpha-glucosidase enzyme inhibition studies. The results of the above biological activities were expressed as inhibitory concentration 50% for DZL and standard drugs (acarbose and ascorbic acid). Based on the acute oral toxicity test, two test doses (100 and 200 mg/kg) of DZL were compared with glibenclamide (5 mg/kg) for their effect on fasting blood glucose at various time intervals (0 to12 h) in glucose-loaded normoglycemic rats. DZL (200 mg/kg) showed a better response in streptozotocin (STZ) induced diabetic rats. The antioxidant assay of DZL showed an appreciable extract inhibitory concentration 50% against the free radicals generated by DPPH (1.61 +/- 0.07 mu g/ mL) and ABTS (1.47 +/- 0.07 mu g/mL) assays. Similarly, the in vitro antidiabetic assay results demonstrated a dose-dependent inhibition of alpha-amylase (2.58 +/- 0.08 mu g/mL) and alpha-glucosidase enzymes (2.41 +/- 0.08 mu g/ mL) by DZL. Both glucose-loaded normoglycemic rats and STZ-induced diabetic rats treated with DZL (200 mg/kg) exhibited a significant post-dose reduction in blood glucose levels (P <0.01, 8 h and P <0.001, 12 h) when compared to normal and diabetic control rats, respectively. These findings suggest that the presence of polyphenols in DZL might be responsible for antioxidant and antidiabetic properties and DZL could be a natural source as an herbal remedy for diabetes.