Identification and theoretical explanation of chemical composition against α-amylase in the n-hexane extract from Sargassum fusiforme

Sargassum fusiforme is an edible alga that possesses a number of bioactivities, such as antidiabetic effects. In the present study, the n-hexane extract of S. fusiforme showed inhibitory activity against alpha-amylase. To interpret the alpha-amylase inhibitory activity of this extract, a method based on GC-MS and molecular docking was established. A total of 25 compounds were identified using GC-MS and then individually docked with alpha-amylase to simulate interactions between the latter and the ligands. Among the compounds determined, phenol, 2,2'-methylenebis [6-(1,1-dimethylethyl)-4-methyl- (PMDM) was completely enfolded in the active site of alpha-amylase via hydrophilic and electrostatic interactions, van der Waals forces, hydrogen bonds and pi-pi stacking interactions and showed the lowest binding energy (-6.25 kcal/mol). The activity of PMDM against alpha-amylase was further tested and verified in vitro, and its IC50 was found to be 79.96 +/- 0.34 mu M. Thus, this compound is responsible for the alpha-amylase inhibitory activity of the n-hexane extract of S. fusiforme.