Inhibition of α-glucosidase activity and non-enzymatic glycation by tannic acid: Inhibitory activity and molecular mechanism

The inhibition of alpha-glucosidase and glycation is considered as an effective approach for the treatment of type 2 diabetes. In this study, multispectroscopic and molecular docking techniques were employed to investigate the inhibition of tannic acid on alpha-glucosidase and glycation. Kinetics analyses revealed that tannic acid had a significant inhibition on alpha-glucosidase (IC50 = 0.35 +/- 0.02 mu M) in a reversible and mixed competitive manner. The results acquired from fluorescence quenching and ANS-binding fluorescence methods revealed that tannic acid could bind to alpha-glucosidase and reduce the hydrophobic area on the surface of the enzyme. In addition, synchronous fluorescence analysis showed that tannic acid decreased the hydrophobicity of alpha-glucosidase and changed the conformation of the enzyme. In vitro glycation assays showed that tannic acid had strong inhibitory effects on the formation of fructosamine, dicarbonyl compounds, and fluorescent AGEs. ANS-binding fluorescence analysis showed that tannic acid could bind to BSA and reduce the hydrophobicity of BSA in glycation. Moreover, the results of molecular docking showed the interaction between tannic acid and alpha-glucosidase was mainly driven by hydrogen bond, electrostatic, and hydrophobic interaction. And the interaction between tannic acid and BSA was mainly driven by hydrogen bond and hydrophobic interaction. (C) 2019 Elsevier B.V. All rights reserved.