Abstract 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.

中文翻译：

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盐酸辛弗林缓解荔枝果皮褐变与膜脂代谢的关系

摘要 本研究考察了盐酸辛弗林(Syn-HCl)对荔枝果皮褐变的影响及其潜在调控机制。结果表明，0.5 g L-1 Syn-HCl 显着抑制果皮褐变的发展。与对照相比，Syn-HCl 处理降低了丙二醛和 H2O2 的含量，并抑制了多酚氧化酶 (PPO) 和过氧化物酶 (POD) 的活性。同时，经 Syn-HCl 处理的荔枝果实通过调节膜脂降解酶：脂肪酶和脂肪氧化酶的活性，表现出较高的 USFA（不饱和脂肪酸）含量和较低的 SFA（饱和脂肪酸）含量。此外，在 Syn-HCl 处理的果实中显示出更高的 USFA 与 SFA 比率和双键指数。进一步的分析表明，参与脂肪酸合成的关键基因也受到 Syn-HCl 处理的调节。总之，这些发现表明 Syn-HCl 减轻了由于调节脂肪酸代谢和维持膜完整性而导致的荔枝果皮褐变，从而抑制了 PPO 和 POD 引起的酶促褐变。