Carvacrol treatment enhances the quality of peach fruit by regulating the metabolism of reactive oxygen species and the phenylpropanoid pathway

This study treated peaches with carvacrol, focusing on the effects of carvacrol treatment on peach reactive oxygen species (ROS) metabolism, ascorbic acid-glutathione (AsA-GSH) cycle, and phenylalanine metabolism. The results indicated that carvacrol treatment reduced the fruit rot incidence and weight loss rate, effectively maintaining fruit hardness, TSS, TA and reducing sugar content. In addition, carvacrol reduced the accumulation of oxidized glutathione (GSSG), dehydroascorbic acid (DHA), malondialdehyde (MDA), superoxide anions (O . 2 - ), and hydrogen peroxide (H 2 O 2 ). It also enhanced the activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and peroxidase (POD), as well as those involved in the AsA-GSH cycle, namely glutathione reductase (GR), monodehydroascorbate reductase (MDHAR), and dehydroascorbate reductase (DHAR). This resulted in elevated levels of reduced ascorbic acid (AsA) and reduced glutathione (GSH). Meanwhile, carvacrol improved DPPH, ABTS, and FRAP radical scavenging capacities, while also increasing lignin, total phenolic, and flavonoid contents. These enhancements were closely linked to the activation of key enzymes in the phenylpropanoid metabolic pathway. The activities of phenylalanine ammonia-lyase (PAL), cinnamic acid 4-hydroxylase (C4H), 4-coumarate:CoA ligase (4CL), and cinnamyl alcohol dehydrogenase (CAD) were markedly increased, polyphenol oxidase (PPO) activity was effectively suppressed. In summary, 0.03 mg mL − 1 carvacrol treatment effectively preserves the postharvest quality of peach fruit by modulating ROS metabolism, enhancing the AsA-GSH cycle, and activating phenylpropanoid metabolism, thereby demonstrating its potential as a promising strategy for extending storage life.