Acteoside and Acyl-Migrated Acteoside, Compounds in Chinese Kudingcha Tea, Inhibit α-Amylase In Vitro

Acteoside, the predominant polyphenol of small-leaved kudingcha, the Chinese tea, has various biological activities. In this study, we examined the acyl migration of acteoside to isoacteoside with high-temperature treatment of acteoside. The inhibitory effects of acyl-migrated acteoside and acteoside on α-amylase were investigated, as were their binding interaction with α-amylase. The binding of acteoside and isoacteoside to α-amylase was investigated by using the fluorescence spectra assay, circular dichroism, and protein–ligand docking studies. Acteoside was more effective than preheated acteoside and isoacteoside in inhibiting α-amylase activity. Acteoside and isoacteoside binding to α-amylase may induce conformational changes to α-amylase, and the binding site of acteoside and isoacteoside being near the active site pocket of α-amylase may explain the decreased activity of α-amylase. The different affinities and binding sites of acteoside and isoacteoside for α-amylase resulted in different inhibition rates, which may be due to structural differences between acteoside and isoacteoside.