Liquid chromatography-mass spectroscopy and molecular docking analysis of Gymnema sylvestre methanol leaf extract revealed antioxidant potential of quercetin

Gymnema sylvestre, commonly known as periploca of the woods, belongs to the family Asclepiadaceae. Several studies have reported that the plant possesses some medicinal properties. A wide variety of diseases such as cancer, diabetes, and cardiovascular disease in human are directly associated with oxidative stress. This study was aimed to examine the possible antioxidant activity of ethyl acetate and aqueous fractions of G. sylvestre. The antioxidant property of the extract fractions was determined using in vitro assays, 2,2 - diphenyl-2-picrylhydrazyl (DPPH) and ferric reducing antioxidant potential (FRAP) methods. To identify compounds in the fractions with the antioxidant property, liquid chromatography-mass Spectroscopy (LC-MS) was carried out. Ethyl acetate fraction showed the highest DPPH scavenging activity (significantly higher than the standard) [(88.98±2.69)% with lowest IC50 at 1.01±0.04 mg/cm3] compared to aqueous fraction [(83.86±0.64)% with highest IC50 at 1.04±0.01 mg/cm3] and standard ascorbic acid [(84.71±0.60)% and IC50 1.03±0.01 mg/cm3]. However the aqueous fraction was significantly weaker than the standard for DPPH scavenging activity. The FRAP assay yielded similar result to those of DPPH assay [(0.452±0.002)%, (0.426±0.000)%, and (0.425±0.001)% for ethyl acetate extract, aqueous extract and the standard (ascorbic acid), respectively]. LC-MS of the fractions revealed different compounds including C17H15O7, C27H20O18, C28H24O16 (in ethyl acetate extract) and C15H10O9S, C15H16O12, C27H26O16 (in aqueous extract). Molecular docking analysis of the identified compounds against some useful enzymes (alpha glucosidase and alpha amylase) suggested that these compounds could be a potential inhibitors of the enzymes. Therefore, G. sylvestre leaf extract could be recommended as a potential natural antioxidant source that could be used in preventing oxidative stress-associated diseases and in drug management.