Xie Yulu, Li Xican, Xu Jieying, Jiang Qian, Xie Hong, He Jianfeng, Chen Dongfeng
School of Chinese Herbal Medicine, Guangzhou University of Chinese Medicine, Waihuan East Road No. 232, Guangzhou Higher Education Mega Center, Guangzhou, 510006, China.
Innovative Research & Development Laboratory of TCM, Guangzhou University of Chinese Medicine, Guangzhou, 510006, China.
Chem Cent J. 2017 Aug 25;11(1):84. doi: 10.1186/s13065-017-0313-1.
Suoyang originates from a psammophyte named Cynomorium songaricum Rupr and has been known as a phenolic-antioxidant-enriched traditional Chinese herbal medicine. The present study attempted to investigate the protective effect of phenolic antioxidants in Suoyang towards •OH-mediated MSCs and then further discusses the chemical mechanisms.
The lyophilized aqueous extract of Suoyang (LAS) was prepared and characterized using HPLC. Then, two phenolic antioxidant references, epicatechin and luteolin-7-O-β-D-glucoside, along with LAS, were investigated for their effects on the viability of •OH-treated MSCs using the 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyl (MTT) assay. The comparison and mechanistic chemistry of epicatechin and luteolin-7-O-β-D-glucoside were further explored using various antioxidant assays, including PTIO•-scavenging, FRAP (ferric ion reducing antioxidant power), ABTS•-scavenging, and DPPH•-scavenging. Their Fe-binding capacities were also compared using ultraviolet (UV) spectra.
The HPLC analysis indicated that there are 8 phenolic antioxidants in LAS, including epicatechin, luteolin-7-O-β-D-glucoside, gallic acid, protocatechuic acid, catechin, isoquercitrin, phlorizin, and naringenin. The MTT assay revealed that epicatechin could more effectively increase the survival of •OH-treated MSCs than luteolin-7-O-β-D-glucoside. Similarly, epicatechin exhibited higher antioxidant abilities than luteolin-7-O-β-D-glucoside in the DPPH•-scavenging, ABTS•-scavenging, FRAP, and PTIO•-scavenging assays. In the Fe-binding assay, luteolin-7-O-β-D-glucoside gave a stronger UV peak at 600 nm, with ε = 2.62 × 10 M cm, while epicatechin produced two peaks at 450 nm (ε = 8.47 × 10 M cm) and 750 nm (ε = 9.68 × 10 M cm).
As two reference antioxidants in Suoyang, epicatechin and luteolin-7-O-β-D-glucoside can enhance the viability of •OH-damaged MSCs. Such a beneficial effect may be from their antioxidant effects, including direct-antioxidant and indirect-antioxidant (i.e., Fe-binding) processes. In the direct-antioxidant process, proton (H), one electron (e), or even hydrogen-atom (•H) transfer may occur to fulfill radical-scavenging (especially •OH-scavenging); in this aspect, epicatechin is superior to luteolin-7-O-β-D-glucoside due to the presence of more phenolic -OHs. The additional -OHs can also be responsible for the better cytoprotective effect. In terms of indirect-antioxidant potential, however, epicatechin is inferior to luteolin-7-O-β-D-glucoside due to the absence of a hydroxyl-keto moiety. These findings will provide new information about medicinal psammophytes for MSC transplantation.
锁阳来源于一种名为锁阳的沙生植物，一直被认为是一种富含酚类抗氧化剂的传统中草药。本研究试图研究锁阳中酚类抗氧化剂对•OH介导的间充质干细胞的保护作用，并进一步探讨其化学机制。
制备锁阳冻干水提取物（LAS）并采用高效液相色谱法进行表征。然后，使用3-(4,5-二甲基噻唑-2-基)-2,5-二苯基四氮唑溴盐（MTT）法研究两种酚类抗氧化剂对照品表儿茶素和木犀草素-7-O-β-D-葡萄糖苷以及LAS对•OH处理的间充质干细胞活力的影响。使用各种抗氧化测定法，包括PTIO•-清除、铁离子还原抗氧化能力（FRAP）、ABTS•-清除和DPPH•-清除，进一步探索表儿茶素和木犀草素-7-O-β-D-葡萄糖苷的比较和机理化学。还使用紫外（UV）光谱比较它们的铁结合能力。
高效液相色谱分析表明，LAS中含有8种酚类抗氧化剂，包括表儿茶素、木犀草素-7-O-β-D-葡萄糖苷、没食子酸、原儿茶酸、儿茶素、异槲皮苷、根皮苷和柚皮素。MTT分析表明，表儿茶素比木犀草素-7-O-β-D-葡萄糖苷更有效地提高•OH处理的间充质干细胞的存活率。同样，在DPPH•-清除、ABTS•-清除、FRAP和PTIO•-清除测定中，表儿茶素表现出比木犀草素-7-O-β-D-葡萄糖苷更高的抗氧化能力。在铁结合测定中，木犀草素-7-O-β-D-葡萄糖苷在600nm处给出更强的紫外峰，ε = 2.62×10 M cm，而表儿茶素在450nm（ε = 8.47×10 M cm）和750nm（ε = 9.68×10 M cm）处产生两个峰。
作为锁阳中的两种对照抗氧化剂，表儿茶素和木犀草素-7-O-β-D-葡萄糖苷可以提高•OH损伤的间充质干细胞的活力。这种有益作用可能来自它们的抗氧化作用，包括直接抗氧化和间接抗氧化（即铁结合）过程。在直接抗氧化过程中，可能发生质子（H）、一个电子（e）甚至氢原子（•H）转移以实现自由基清除（尤其是•OH清除）；在这方面，由于存在更多的酚羟基，表儿茶素优于木犀草素-7-O-β-D-葡萄糖苷。额外的羟基也可导致更好的细胞保护作用。然而，就间接抗氧化潜力而言，则由于缺乏羟基-酮部分，表儿茶素不如木犀草素-7-O-β-D-葡萄糖苷。这些发现将为间充质干细胞移植的药用沙生植物提供新的信息。
