Binding of Specific Tea Polyphenols to Hydrolytic Enzymes and Their Inhibitory Effects on Oat Starch Digestion

The purpose of this study was to investigate the effects of tea polyphenols (TPs) on the activity of starch digestion enzymes, including α-amylase, pancreatin, and amyloglucosidase (AMG), which simulate the digestion process in the oral cavity, stomach, and small intestine, respectively. We determined the main polyphenol composition of green tea polyphenols using high-performance liquid chromatography (HPLC), with a focus on epicatechin (EC), epigallocatechin (EGC), epigallocatechin gallate (EGCG), and epicatechin gallate (ECG). When mixed with hydrolytic enzymes, the fluorescence emission spectra data revealed a significant decrease in the fluorescence intensity of TPs over time, indicating an increased interaction between TPs and the hydrolytic enzymes with increasing TPs concentration within the measured range. The inhibition percentage (%) and fluorescence emission spectral data demonstrated an initial increase in the inhibition of TPs with increasing concentration, followed by a plateau. Moreover, molecular docking studies revealed that EGC exhibited a higher affinity than did the other catechins, resulting in the formation of more hydrogen bonds between amino acid residues in the digestion enzymes and EGC. In vitro digestion experiments showed that TPs reduced the extent of starch hydrolysis. The findings of this study contribute to the theoretical understanding and provide a foundation for combating human health issues by elucidating the effects of TPs on the starch digestion process. The knowledge gained from this research has implications for developing strategies to enhance the health-promoting properties of tea and its potential application in preventing or managing metabolic disorders.