The structural characteristics of hydroxyl and galloyl groups determine the inhibitory activity of α-amylase in four catechin monomers

In this study, the effect of hydroxyl and galloyl groups structure of catechin monomers on the inhibitory activity of α-amylase were studied by substrate depletion, inhibition kinetics, fluorescence quenching, circular dichroism analysis, molecular docking, and molecular dynamics methods. The catechin monomers of EGCG and ECG with more phenolic hydroxyl groups and specific gallate esters showed the stronger inhibitor effect, higher fluorescence quenching effects and more intense structural disruption on α-amylase than EGC and EC. Molecular simulation further elucidated that EGCG and ECG, due to their specific gallate esters and more phenolic hydroxyl groups, interact more favorably with amino acid residues in the α-amylase active site compared to EGC and EC. These findings reveal the mechanism of α-amylase inhibition by catechin monomers with different structures and provide the theoretical basis for the role of catechins as anti-glycemic components in the dietary management of diabetes. • EGCG and ECG showed stronger inhibition against α-amylase than EGC and EC. • Catechin monomers inhibited α-amylase by hydrogen bond and hydrophobized force. • The gallate and phenolic OH group promoted the inhibition of α-amylase activity. • EGCG and ECG bound more stably to α-amylase and required less energy than EGC and EC.