In vitro and in vivo antidiabetic activity of Polyalthia longifolia (Sonner.) Thw. leaves

To study the α-amylase and α-glucosidase enzymes inhibitory activity in vitro of ethanol (PLEE) and chloroform (PLCE) extracts of Polyalthia longifolia (Sonner.) Thw. leaves and in vivo antidiabetic activity against streptozotocin-induced type 1 diabetes mellitus in rats. In vitro studies were performed using α-amylase and α-glucosidase enzymes followed by enzyme kinetics using Lineweaver-Burk plot analysis. Acute toxicity studies were performed as per OECD guidelines 423. Streptozotocin (60 mg/kg b.w., i.p .) was used to induce type 1 diabetes mellitus in rats. Changes in body weight changes, blood glucose levels, serum marker enzymes, serum lipid profile, enzymatic and non-enzymatic antioxidants in liver homogenates were measured and histopathology of pancreatic tissues were done. The IC 50 of PLEE for α-amylase was found to be 154.3 ± 2.42 μg/ml whereas PLCE was 180.3 ± 1.35 μg/ml. The IC 50 values of the PLEE for α-glucosidase inhibition was found to be 208.7 ± 2.54 μg/ml and PLCE showed at 271.6 ± 0.85 μg/ml. Acute toxicity studies showed that the extracts were safe at 2000 mg/kg b.w. Both the extracts dose dependently reversed the abnormal changes observed in untreated diabetic rats. The effect produced by the ethanol extract was slightly higher than the chloroform extract. The results of this present study suggest that the ethanol and chloroform extracts of leaves of Polyalthia longifolia showed α-amylase and α-glucosidase enzymes inhibitory activity. The effect was further highlighted by the protection of the extracts against streptozotocin-induced type 1 diabetes mellitus in rats.