Synthesis of ECG ((-)-epicatechin gallate) acylated derivatives as new inhibitors of α-amylase and their mechanism on delaying starch digestion

(-)-Epicatechin gallate (ECG), as a natural alpha-amylase inhibitor, has received extensive attention. However, poor liposolubility of ECG limits its application. In this study, lipophilic derivatives of ECG (1A-ECG, 2A-ECG, 1B-ECG, and 2B-ECG) were synthesized by Lipozyme TLIM (Thennomyces lanuginosus) and their mechanism on delaying starch digestion was investigated. The results showed that the conversion of ECG exceeded 70% under optimal conditions. Interestingly, compared with ECG, the inhibitory activities of ECG derivatives on alpha-amylase decreased, while the inhibitory activity of 1A-ECG on alpha-amylase increased. Though the main force between ECG and 1A-ECG with alpha-amylase was induced by hydrogen bond, hydrophobic interaction was the main force be-tween other derivatives with alpha-amylase. However, the addition of four ECG derivatives can effectively reduce the proportion of rapidly digestible starch, and delay the digestion of starch. This study may expand the applications of ECG and provide a theoretical basis for 1A-ECG to delay the digestion of starch.