Yun Ze's research while affiliated with Chinese Academy of Sciences and other places

Background Most of postharvest fruits are highly perishable, which limits greatly marketability and potential expansion. In recent years, significant progresses on understanding the role of melatonin in delaying senescence have been achieved while the melatonin as a postharvest alternative in maintaining quality and extending shelf life of postharvest fruit has been developed. Scope and approach This paper reviews the recent progresses in the multiple functions of melatonin, summaries the detection, content and synthesis of endogenous melatonin in postharvest fruit, discusses the possible mechanisms of melatonin in maintaining quality and extending shelf life of postharvest fruit, emphasizes the beneficial effects of the melatonin-related handling and provides the future research direction for postharvest alternative. Key findings and conclusions The amount of melatonin in postharvest fruit is relatively low and affected greatly by many factors. The major precursors and genes of melatonin biosynthetic pathway have been identified in various fruits. Exogenous melatonin treatment not only delayed ripening, senescence and quality deterioration, but also enhanced disease resistance and chilling tolerance of postharvest fruit. The multiple biological functions of melatonin in postharvest fruit were attributed to the induction and interaction with reactive oxygen species and nitric oxide and coordination with plant hormones and other signaling molecules, which enhanced antioxidant and defense systems, reduced oxidative damage, and maintained energy of postharvest fruit.

This study investigated the effect of synephrine hydrochloride (Syn-HCl) on litchi pericarp browning and the potential regulating mechanism. Results showed that 0.5 g L⁻¹ Syn-HCl significantly inhibited the development of pericarp browning. Compared to control, Syn-HCl treatment reduced malondialdehyde and H2O2 content and inhibited activities of polyphenol oxidase (PPO) and peroxidase (POD). Meanwhile, Syn-HCl-treated litchi fruit exhibited higher amounts of USFA (unsaturated fatty acids) as well as lower amounts of SFA (saturated fatty acids) through regulating activities of membrane lipids-degrading enzymes: lipase and lipoxygenase. Additionally, higher ratio of USFA to SFA and double bond index were shown in Syn-HCl-treated fruit. Further analysis showed that key genes involved in fatty acid synthesis were also regulated by Syn-HCl treatment. Taken together, these findings indicated that Syn-HCl alleviated litchi pericarp browning resulting from regulation of fatty acid metabolism and maintenance of membrane integrity, which inhibited the enzymatic browning caused by PPO and POD.