Abstract To investigate the underlying mechanism of melatonin (MT) involvement in the browning of lotus pods and seeds, the samples were immersed in 100 μmol L−1 MT and 10 μmol L−1 luzindole, a nonselective MT1/MT2 receptor antagonist. The energy and membrane lipid metabolisms of lotus seeds during 8 d at 25 ± 1 °C were evaluated. The results indicated that MT treatment suppressed the browning of lotus seeds through enhancing the endogenous MT content, while luzindole demonstrated an opposite effect. Compared with the control, the MT treatment ensured the energy status of lotus seeds, as the ATP content and energy charge were promoted. The activities of cytochrome C oxidase (CCO), succinate dehydrogenase (SDH), and ATPases were enhanced by the treatment, which might contributued to the ATP production. Additionally, the cell membrane integrity of lotus seeds was maintained by MT treatment through reducing the cell membrane permeability, O2 ¯ production rate, and malondialdehyde and H2O2 contents, as well as enhancing the unsaturated-to-saturated fatty acids ratio, which could be explained by inhibited lipoxygenase (LOX), lipase (LPS) and phospholipase D (PLD) activities. Thus, the sufficient energy supply and normal cell membrane function may be responsible for the attenuated browning of lotus pods and seeds by MT treatment.

中文翻译：

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褪黑激素通过能量代谢和膜脂代谢缓解莲子采后褐变的作用

摘要 为了研究褪黑激素 (MT) 参与莲荚和种子褐变的潜在机制，将样品浸泡在 100 μmol L-1 MT 和 10 μmol L-1 luzindole（一种非选择性 MT1/MT2 受体拮抗剂）中。评估了莲子在 25±1°C 下 8 d 的能量和膜脂代谢。结果表明，MT处理通过提高内源MT含量来抑制莲子褐变，而luzindole则表现出相反的效果。与对照相比，MT处理保证了莲子的能量状态，促进了ATP含量和能量电荷。细胞色素 C 氧化酶 (CCO)、琥珀酸脱氢酶 (SDH) 和 ATP 酶的活性通过处理增强，这可能有助于 ATP 的产生。此外，MT 处理通过降低细胞膜通透性、O2 产生率、丙二醛和 H2O2 含量以及提高不饱和脂肪酸与饱和脂肪酸的比例来维持莲子的细胞膜完整性，这可以通过抑制脂氧合酶 (LOX)、脂肪酶 (LPS) 和磷脂酶 D (PLD) 活性。因此，充足的能量供应和正常的细胞膜功能可能是 MT 处理莲荚和种子褐变减弱的原因。