Protective Effect of Sinapine against Hydroxyl Radical-Induced Damage to Mesenchymal Stem Cells and Possible Mechanisms.

As a phenolic alkaloid occurring in Cruciferous plants, sinapine was observed to protect mesenchymal stem cells (MSCs) against ·OH-induced damage in this study. It was also found to prevent DNA from damage, to scavenge various free radicals (·OH, ·O2(-), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid diammonium salt) (ABTS)(+·), and 1,1-diphenyl-2-picrylhydrazyl radical (DPPH·)), and to reduce Cu(2+) to Cu(+). To further explore the mechanism, the end-product of sinapine reaction with DPPH· was determined using HPLC-electrospray ionization (ESI)-MS/MS and HPLC-diode array detector (DAD). Four molecular ion peaks (m/z 701, 702, 703, and 351) in HPLC-ESI-MS/MS analysis indicated a radical adduct formation (RAF) pathway; while a bathochromic shift (λ(max) 334→475 nm) in HPLC-DAD indicated the formation of quinone as the oxidized product of the phenolic -OH group. Based on these results, it may be concluded that, (i) sinapine can effectively protect against ·OH-induced damage to DNA and MSCs; such protective effect may provide evidence for a potential role for sinapine in MSC transplantation therapy, and be responsible for the beneficial effects of Cruciferous plants. (ii) The possible mechanism for sinapine to protect against ·OH-induced oxidative damage is radical-scavenging, which is thought to be via hydrogen atom (H·) transfer (HAT) (or sequential electron (e) proton transfer (SEPT))→RAF pathways.