Combined Inhibition of Polyphenol Oxidase by Oxyresveratrol and Epigallocatechin Gallate: A Natural Anti-Browning Strategy for Fresh-Cut Pears

Abstract

Polyphenol oxidase (PPO) is a key enzyme responsible for enzymatic browning in fresh-cut fruits and vegetables, severely compromising their quality and shelf life. This study aimed to investigate the combined inhibitory mechanism of oxyresveratrol (OXY) and epigallocatechin gallate (EGCG) on PPO through multi-spectroscopic analyses, molecular docking, TEM, and XRD, with the goal of developing a natural and effective anti-browning strategy for fresh-cut fruits. The results showed that the optimal combined effect was achieved at an OXY:EGCG ratio of 1:2, where the inhibition rate was significantly enhanced by 43.72% and 14.36% compared to using OXY or EGCG single treatment, respectively. The combined treatment exhibited enhanced chelation capacity of copper ion and DPPH radical scavenging activity, and enhanced hydrogen-bonding interactions while lowering binding energy, exhibiting characteristics of mixed inhibition kinetics. Structural characterization showed that the combined treatment drastically reduced the enzyme’s fluorescence intensity to 39.81% of that of the native enzyme, induced rearrangements in α-helix and random coil structures, triggered obvious protein aggregation, and weakened the intensity of crystal diffraction peaks. Importantly, the combined treatment effectively delayed browning in fresh-cut pear slices, demonstrating its practical application potential. These findings provide a promising natural combined approach for controlling enzymatic browning and extending the shelf life of fresh-cut produce.