Huang Lei, Zhu Yu, Peng Tong, Qiu Jianfei, Rao Qing, Song Jingrui, Xiao Shiji, Li Yanmei, Tang Lin
State Key Laboratory of Functions & Applications of Medicinal Plants, Guizhou Medical University, Guiyang 550014, China.
Key Laboratory of Bio-resources and Eco-environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu 610065, China.
Food Funct. 2021 Mar 1;12(4):1651-1661. doi: 10.1039/d0fo01813a.
Idesia polycarpa Maxim. leaves are an excellent source of hydroxycinnamic acid derivatives and have drawn special attention due to their various biological activities. However, the effects of post-harvest treatment on the structure-activity relationships of hydroxycinnamic acid derivatives in leaves of I. polycarpa are still unknown. In the current study, we compared the contents of unstable compounds in leaves with four drying methods, namely sun-drying, freeze-drying, shade-drying, and oven-drying. We found that the four hydroxycinnamic acid derivative isomers of leaves were significantly affected after drying processing with four different drying methods. Consequently, the underlying mechanisms responsible for the variation of these compounds during the drying processes have been well elucidated: UV lighting induced the isomerization of 1-[(6'-O-(E)-p-coumaroyl)-β-d-glucopyranosyl]-oxy-2-phenol (1) and 1-[(4'-O-(E)-p-coumaroyl)-β-d-glucopyranosyl]-oxy-2-phenol (3) into 1-[(6'-O-(Z)-p-coumaroyl)-β-d-glucopyranosyl]-oxy-2-phenol (2) and 1-[(4'-O-(Z)-p-coumaroyl)-β-d-glucopyranosyl]-oxy-2-phenol (4). Also, heat (exceeding 20 °C) led to the rearrangement of the (E/Z)-p-coumaric acid moiety of compounds 3 and 4, of which the 4-O-acylglucoses changed into the 6-O-acylglucoses to generate compounds 1 and 2, respectively. Interestingly, the hepatocyte-free fatty acid accumulation in OA-induced steatosis-conditioned HepG2 cells decreased by 65.00%, 10.69%, and 47.00%, respectively, following treatment with compounds 2, 3 and 4, and compound 1 presented no lipid-lowering activity. In addition, the bioactivities of compounds 2 and 4 were substantially enhanced by 58.42% and 25.33% with the sun-drying method compared to the freeze-dying methods. Our study suggests that sun-drying processing is the best method among the four drying processing methods of I. polycarpa Maxim. leaves.
山桐子叶是羟基肉桂酸衍生物的优质来源，因其具有多种生物活性而备受关注。然而，采后处理对山桐子叶中羟基肉桂酸衍生物构效关系的影响尚不清楚。在本研究中，我们比较了采用晒干、冻干、阴干和烘干四种干燥方法处理后山桐子叶中不稳定化合物的含量。我们发现，采用四种不同干燥方法处理后，山桐子叶中的四种羟基肉桂酸衍生物异构体受到了显著影响。因此，已充分阐明了干燥过程中这些化合物发生变化的潜在机制：紫外线照射导致1-[(6'-O-(E)-对香豆酰基)-β-D-吡喃葡萄糖基]-氧基-2-苯酚（1）和1-[(4'-O-(E)-对香豆酰基)-β-D-吡喃葡萄糖基]-氧基-2-苯酚（3）异构化为1-[(6'-O-(Z)-对香豆酰基)-β-D-吡喃葡萄糖基]-氧基-2-苯酚（2）和1-[(4'-O-(Z)-对香豆酰基)-β-D-吡喃葡萄糖基]-氧基-2-苯酚（4）。此外，加热（超过20℃）导致化合物3和4的（E/Z）-对香豆酸部分发生重排，其中4-O-酰基葡萄糖分别转变为6-O-酰基葡萄糖，生成化合物1和2。有趣的是，在用化合物2、3和4处理后，OA诱导的脂肪变性条件下的HepG2细胞中肝细胞游离脂肪酸积累分别减少了65.00%、10.69%和47.00%，而化合物1没有降脂活性。此外，与冻干方法相比，采用晒干方法时化合物2和4的生物活性分别显著提高了58.42%和25.33%。我们的研究表明，晒干处理是山桐子叶四种干燥处理方法中的最佳方法。
