Phytonutrients for controlling starch digestion: Evaluation of grape skin extract

The objective of this work was to evaluate the structure–function relationship between grape skin extract and human α-amylase. The grape skin extract was characterised as resveratrol-3-O-glucoside by RP-HPLC–ESI-MS, which showed strong inhibition towards α-amylase and the IC50 value was 1.35 mg/ml. The kinetic results demonstrated grape skin extract obeyed the non-competitive mode against amylase. Fluorescence data revealed the ability of grape skin binding to amylase belonged to static quenching mechanism with a complex formation and there was only one binding site in α-amylase for grape skin extract. Docking study showed a best pose with total energy value of −118.3 kJ/mol and grape skin extract interacted with side chain of Asp300 with hydrogen bonds and Van der Waals forces. This preliminary observation provides the basis for further evaluation of the suitability of grape skin extract as natural inhibitor with potential health benefits.