Two phenolic antioxidants in Suoyang enhance viability of ?OH-damaged mesenchymal stem cells: comparison and mechanistic chemistry

摘要

Background 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. MethodsThe 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 Fe2+-binding capacities were also compared using ultraviolet (UV) spectra. ResultsThe 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 Fe2+-binding assay, luteolin-7- O - β -D-glucoside gave a stronger UV peak at 600?nm, with ε =?2.62?×?106 M?1?cm?1, while epicatechin produced two peaks at 450?nm ( ε =?8.47?×?105?M?1?cm?1) and 750?nm ( ε =?9.68?×?105?M?1?cm?1). ConclusionAs 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., Fe2+-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.