Delay of pericarp browning by chondroitin sulfate attributes of enhancing antioxidant activity and membrane integrity in litchi fruit after harvest

Litchi fruit is prone to rapid pericarp browning, which impacts its marketability. Herein, the application of a natural glycosaminoglycan polysaccharide, chondroitin sulfate to inhibit the development of pericarp browning in litchi fruit was investigated. The results revealed that chondroitin sulfate suppressed browning progression and changes in color indicated by chromaticity values. It markedly reduced the production rates of superoxide anion (O₂^.-) radical and hydrogen peroxide (H₂O₂), retarded the increase in malondialdehyde (MDA) content and relative electrolyte leakage rate, thereby preserving membrane integrity. Chondroitin sulfate also prevented the decline in total phenols, flavonoids, anthocyanins, and antioxidant activity, as evidenced by maintained scavenging capacity of 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and reducing power. It enhanced the enzymatic activities of superoxide dismutase (SOD), catalase (CAT), and phenylalanine ammonia lyase (PAL), which are critical for antioxidant defense, while suppressing the activities of oxidative enzymes such as polyphenol oxidase (PPO), peroxidase (POD), and laccase (LAC). Furthermore, chondroitin sulfate modulated the expression levels of key genes such as LcPAL1, LcANS1, LcANS2 associated with phenol synthesis, and LcPPO1/2, LcPOD1/12, LcLAC2/14 for the oxidative enzymes involved in phenol synthesis. These findings demonstrate that chondroitin sulfate effectively regulates reactive oxygen species (ROS) status and enhances antioxidant activity, underscoring its potential as a natural preservative for extending shelf life of litchi fruit during storage.