Wei Dongling, Yang Jiali, Xiang Yue, Meng Lanhuan, Pan Yonggui, Zhang Zhengke
School of Food Science and Engineering, Hainan University, Haikou, China.
Key Laboratory of Food Nutrition and Functional Food of Hainan Province, Haikou, China.
Front Nutr. 2022 Jun 20;9:905006. doi: 10.3389/fnut.2022.905006. eCollection 2022.
Rambutan is a famous tropical fruit with a unique flavor and considerable economic value. However, the high vulnerability to postharvest browning leads to a short shelf life of rambutan fruit. Melatonin (MT) is an excellent bioactive molecule that possesses the potential to improve the storability of the harvested crops. In this study, the physiological mechanism of exogenous MT in affecting pericarp browning and senescence of postharvest rambutan fruit was investigated. Experimental results showed that the application of MT at 0.125 mmol L appreciably retarded the advancement of pericarp browning and color parameters (*, *, and *). MT treatment inhibited the increase in membrane relative electrolytes leakage (REL) while lowering the accumulation of reactive oxygen species (ROS) (O and HO) and malonaldehyde (MDA). Reduced phenolics oxidation, as indicated by higher contents of total phenolics, flavonoids, and anthocyanins along with fewer activities of peroxidase (POD) and polyphenol oxidase (PPO), was detected in MT fruit compared with control fruit. MT treatment maintained the cellular redox state by inducing antioxidant enzyme activity and reinforcing the ascorbate-glutathione (AsA-GSH) cycle. Furthermore, the ultrastructural observation revealed that the spoilage of cellular and subcellular structures was milder in MT fruit than that in control fruit. The results suggest that MT could ameliorate the browning and senescence of rambutan fruit by inhibiting phenolic oxidation and enhancing the antioxidative process.
红毛丹是一种著名的热带水果，具有独特的风味和可观的经济价值。然而，红毛丹果实采后极易褐变，导致其货架期较短。褪黑素（MT）是一种出色的生物活性分子，具有提高收获作物耐贮性的潜力。本研究探讨了外源MT影响红毛丹采后果实果皮褐变和衰老的生理机制。实验结果表明，0.125 mmol/L的MT处理显著延缓了果皮褐变的进程和颜色参数（*、和）。MT处理抑制了膜相对电解质渗漏（REL）的增加，同时降低了活性氧（ROS）（O和HO）和丙二醛（MDA）的积累。与对照果实相比，MT处理的果实中总酚、类黄酮和花青素含量较高，而过氧化物酶（POD）和多酚氧化酶（PPO）活性较低，表明酚类氧化减少。MT处理通过诱导抗氧化酶活性和加强抗坏血酸-谷胱甘肽（AsA-GSH）循环来维持细胞氧化还原状态。此外，超微结构观察表明，MT处理果实的细胞和亚细胞结构损伤比对照果实轻。结果表明，MT可以通过抑制酚类氧化和增强抗氧化过程来改善红毛丹果实的褐变和衰老。
