Melatonin-Induced Modulation of Polyphenols and Glycolytic Pathways in Relation to Postharvest Quality of Blue...

The impact of exogenous melatonin treatment on the postharvest quality and storability of blue honeysuckle fruit was investigated. Fruits were immersed in melatonin solutions at concentrations of 0 (control), 0.01, 0.05, and 0.25 mM for 5 min and subsequently stored at -1 °C for 63 d. Among all treatments, the combination of two-week storage without fruit puncturing and 0.05 mM melatonin application significantly delayed fruit softening and decay even at the initial stage of storage, while also increasing the concentration of phenolic compounds and enhancing antioxidant activity. During the later storage period (28-63 d), melatonin-treated fruits maintained higher levels of maltose, fructose, and sucrose, contributing to improved flavor retention. In contrast, both lower (0.01 mM) and higher (0.25 mM) concentrations were less effective or even detrimental to fruit quality. HPLC-ESI-QTOF-MS² analysis revealed that 0.05 mM melatonin effectively preserved several functional phenolics, including p-coumaroylquinic acid, caffeoyl glucose, 5-O-caffeoylquinic acid, 3-O-caffeoylquinic acid, luteolin-7-O-glucoside, and hydroxytyrosol. Thus, 0.05 mM melatonin is effective in delaying senescence and maintaining the postharvest quality of blue honeysuckle fruit.