Inhibitory effect and mechanism of tannic acid against two starch digestive enzymes

Abstract Backgrounds Tannic acid (TA), as a plant-derived phenolic substance, is involved in regulating the activity of starch digestive enzymes, but its underlying mechanism remains unclear. Methods and Results In the present study, inhibition rate and inhibition kinetics assays were performed and confirmed that TA had a strong inhibitory effect on both α-amylase and α-glucosidase with IC50 values of 0.1585 mg/mL and 0.00542 mg/mL, respectively, through a mixed inhibition mode. The secondary structures of both enzymes were confirmed to be modified by TA through circular dichroism (CD) spectra. Fluorescence quenching analysis revealed that the interaction between TA and two enzymes was a static process of pontaneous complex formation. Finally, molecular docking revealed that non-covalent bonds were the main interaction forces between TA and both enzymes. Conclusions Thus, TA was a promising candidate for the inhibition of starch-digesting enzymes, and the present research provided insight into postprandial glucose regulation through polyphenols.