Inhibition of Alpha-Amylase Activity by Gymnocarpos decandrus Forssk. Constituents

Abstract

The methanolic extract of the aerial parts of Gymnocarpos decandrus, the plant growing wildly in the middle east area and north Africa, showed a promising -amylase inhibitory activity. The ethyl acetate fraction of the plant showed the highest inhibitory activity followed by the methylene chloride fraction. Phytochemical investigation of both fractions led to the isolation of 10 compounds; oleanolic acid (1), maslinic acid (2), apigenin (3), β-sitosterol glucoside (4), luteolin (5), afzelechin (6), epiafzelechin (7), catechin (8), epicatechin (9) and gallocatechin (10). The structures of compounds 1-10 were established on the basis of extensive 1D- and 2D-NMR spectroscopic techniques. This is the first report for the isolation of these compounds from G. decandrus. The phenolic compounds (6-10) isolated from the ethyl acetate fraction showed the highest -amylase inhibitory activity. The more the hydroxylation pattern of the isolated phenolic compounds (6, 8, 9 and 10), the higher the ability to inhibit the -amylase activity. This was confirmed through the molecular docking experiment. The wild plant G. decandrus is a promising -amylase inhibitor that can be used in the management of obesity and diabetes mellitus.