Study on the effects of endogenous polyphenols on the structure, physicochemical properties and in vitro digestive characteristics of Euryales Semen starch based on multi-spectroscopies, enzyme kinetics, molecular docking and molecular dynamics simulation

Abstract

Euryales Semen (ES) is a highly nutritious food with low digestibility, which is closely associated with its endogenous phenolic compounds. In this study, five phenolic compounds (naringenin, isoquercitrin, gallic acid, epicatechin and quercetin) with high concentrations in ES were selected to prepare starch-polyphenol complexes. Subsequently, the effects of endogenous polyphenols on the structure, physicochemical properties and digestion characteristics of ES starch were studied using multiple techniques. The addition of phenolic compounds markedly reduced the in vitro digestibility, swelling power, gelatinization enthalpy, while increased the solubility of ES starch. Fourier-transform infrared spectroscopy and X-ray diffraction analysis showed that phenolic compounds interacted with the starch through non-covalent bonds. Five phenolic compounds inhibited α-amylase activity through a mixed competitive inhibition mechanism, with the inhibition potency ranked as follows: quercetin > epicatechin > gallic acid > isoquercitrin > naringenin. The spectroscopic analysis and molecular dynamics simulations confirmed that five phenolic compounds interacted with the amino acid residues of α-amylase through hydrogen bonding and hydrophobic interactions, caused α-amylase static fluorescence quenching, and altered its conformation and microenvironment. This study provides a better understanding of the interaction mechanisms between ES starch and polyphenols, and supports the development of ES as a food that lowers sugar levels.