2,4-Epibrassinolide as a postharvest preservative for leaf-vegetable sweetpotato: alleviating water loss through antioxidant-mediated membrane integrity

Abstract Leaf-vegetable sweetpotato, with rich nutritious and antioxidant compounds, is favored by consumers; however, it is highly prone to postharvest water loss. This study investigated the effect of 2,4-epibrassinolide (EBR) on the water status and storage quality of leaf-vegetable sweetpotato. The findings showed that treatment with 2 µmol/L EBR effectively preserved visual quality, minimized weight loss, increased the proportion of free water, and maintained cellular ultrastructure. Furthermore, EBR reduced membrane damage, as demonstrated by decreased relative conductivity and malondialdehyde levels. It also enhanced antioxidant capacity by raising polyphenol and flavonoid contents and improving ·OH and DPPH radical scavenging capacity by 3%-6%. The key antioxidant enzyme activities of superoxide dismutase, catalase, ascorbate peroxidase, peroxidase, and phenylalanine ammonia-lyase were increased. EBR further strengthened oxidative homeostasis and upregulated the expression of genes related to aquaporins and autophagy. Molecular docking revealed the potential interaction between EBR and respiratory burst oxidase homologue (RBOH) A protein to suppress excessive reactive oxygen species (ROS) generation. A mechanistic pathway was elucidated in which EBR mitigated wilting by modulating RBOH-mediated signaling, which coordinately regulated ROS metabolism, water transport, and autophagy to preserve cellular integrity and enhance water retention. This study provides a practical strategy and mechanistic understanding for enhancing the postharvest quality of leafy vegetables.