Bioassay guided isolation of alpha-glucosidase inhibitory compound, in vivo postprandial anti hyperglycemia and docking study of the isolated compound from the leaves of the methanolic extract of Quercus serrata

Diabetes mellitus is rapidly emerging creating major health problem worldwide. Though synthetic drugs are available, due to their association with side effect, there is always interest for search of herbal formulation. Quercus serrata is a plant used by traditional healers of Manipur, India as a folk remedy to treat diabetes mellitus. The objective of this study is bioassay guided isolation of alpha-glucosidase inhibitory compound from the leaves of Quercus serrata and to check the postprandial antihyperglycaemic effect of the isolated compound in STZ-induced diabetic albino mice. And to perform molecular docking studies to predict the binding interaction of the isolated compounds with alpha-glucosidase.The methanolic extract of Quercus serrata leaves was screened for alpha-glucosidase inhibitory activity and fractionated into n-butanol, ethyl acetate and water fraction to isolate the active compound. Quantification of isolated compound was done by HPLC-PDA. Postprandial antihyperglycaemia effect was check in normal and STZ (100mg/kg) + nicotinaniide (120mg/kg) induced diabetic mice after sucrose load (2g/kg). Molecular docking study was done using AutoDock 4.2.6. Rosmarinic acid was identified as the active compound present in Quercus serrata leaves responsible for the inhibition of alpha-glucosidase with IC50 0.23 +/- 0.02 mu gmL-1 (0.636 mu molmL-1). Postprandial blood sugar and Area tinder Curve were significantly (p<0.05) reduced by treatment with rosmarinic acid in normal and diabetic mice. Additionally, in silica docking study elaborated the possible binding between rosmarinic acid and alpha-glucosidase. Above finding confirmed the and-diabetic potential of traditionally used Quercus serrata leaves and the isolated compound, rosmarinic acid.