The present study was undertaken to evaluate the antihyperglycemic and antioxidant activity of methanolic extract of stem bark of Polyalthia longifolia var. angustifolia (PL). The plant extract was found with low toxicity (LD50 >3 g/kg). The methanolic extract of PL at the dose levels of 200 and 300 mg/kg b. wt. produced a significant decrease in fasting blood glucose (FBG) level by 48.83 and 53.68 % respectively with respect to initial FBG level after 21 days treatment. In the Oral Glucose Tolerance Test (OGTT), this extract at the dose levels of 100, 200, and 300 mg/kg decreased glycemia at 60 min and the effect persisted until 120 min (p < 0.05) after glucose loading, which showed impaired glucose tolerance. The elevated level of SGPT, SGOT and ALP in the diabetic control group reflected the significant alteration of liver function by STZ induction and was found to be equipotent to Glibenclamide in restoration of the elevated enzyme levels to normal. The elevated lipid levels (Triglyceride and total cholesterol) were restored to near normal in this extract. The extract at 100 μg/ml concentration showed maximum scavenging of the radical cation in ABTS observed up to 54.79 % followed by scavenging of stable radical DPPH (75.36 %), Nitric oxide (57.25 %) and Super oxide dismutase (78.40 %) at the same concentration. The IC50 values of this extract in these models were calculated as 77.07, 46.84, 88.54 and 40.91 respectively at 1 mg/ml concentration. For all the estimated parameters, the results of the extract treated groups were restored to the near normal level, thereby indicating good antihyperglycemic and antioxidant activity of the methanolic extract of Polyalthia longifolia var. angustifolia.
