To investigate the therapeutic effects of methanol extract of Citrus macroptera Montr.fruit in α-amylase inhibitory activity (in vitro) and hypoglycemic activity in normal and glucose induced hyperglycemic rats (in vivo). Fruits of Citrus macroptera without rind was extracted with pure methanol following cold extraction and tested for presence of phytochemical constituents, α-amylase inhibitory activity, and hypoglycemic effect in normal rats and glucose induced hyperglycemic rats. Presence of saponin, steroid and terpenoid were identified in the extract. The results showed that fruit extract had moderate α-amylase inhibitory activity [IC50 value=(3.638±0.190) mg/mL] as compared to acarbose. Moreover at 500 mg/kg and 1 000 mg/kg doses fruit extract significantly (P<0.05 and P<0.01 respectively) reduced fasting blood glucose level in normal rats as compared to glibenclamide (5 mg/kg). In oral glucose tolerance test, 500 mg/kg dose significantly reduced blood glucose level (P<0.05) at 2 h but 1 000 mg/kg dose significantly reduced blood glucose level at 2 h and 3 h (P<0.05 and P<0.01 respectively) whereas glibenclamide (5 mg/kg) significantly reduced glucose level at every hour after administration. Overall time effect is also considered extremely significant with F value=23.83 and P value=0.0001 in oral glucose tolerance test. These findings suggest that the plant may be a potential source for the development of new oral hypoglycemic agent.
