Maclurin protects against hydroxyl radical-induced damages to mesenchymal stem cells: antioxidant evaluation and mechanistic insight

Abstract

Maclurin, an exceptional member of phytophenol family, was found to effectively protect against mesenchymal stem cells (MSCs) oxidative damage induced by hydroxyl radical (OH) at 62.1-310.5 μM. Antioxidant assays indicated that maclurin could efficiently protect DNA from OH-induced damage at 114.6-382.2 μM, and scavenge OH, DPPH (1,1-diphenyl-2-picrylhydrazyl radical), ABTS(+) (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid radical), and bind Cu(2+) (IC50 values were respectively 122.87 ± 10.14, 10.15 ± 0.85, 0.97 ± 0.07, and 133.95 ± 11.92 μM). HPLC-DAD and HPLC-ESI-MS/MS analyses of the end-product of maclurin reaction with DPPH clearly suggested that maclurin (m/z = 261.12 [M-H](-)) donated two hydrogen atoms to DPPH (m/z = 394.06 [M](+)) to form ortho-benzoquinone moiety (λmax = 364 nm; m/z = 259.06 [M-H](-), loss of m/z = 28) and DPPH2 molecule (m/z = 395.03, 396.01), via hydrogen atom transfer (HAT) or sequential electron (e) proton transfer (SEPT), not radical adduct formation (RAF) mechanisms. Therefore, we concluded that: (i) maclurin can effectively protect against OH-induced damages to DNA and MSCs, thereby it may have a therapeutic potential in prevention of many diseases or MSCs transplantation; (ii) a possible mechanism for maclurin to protect against oxidative damages is OH radical-scavenging; (iii) maclurin scavenges OH possibly through metal-chelating, and direct radical-scavenging which is mainly via HAT or SEPT mechanisms; and (iv) the protective and antioxidant effects of maclurin can be primarily attributed to ortho-dihydroxyl groups, and ultimately to the relative stability of the ortho-benzoquinone form.

Keywords: Antioxidant mechanism; Hydrogen atom transfer HAT; Hydroxyl radical; Maclurin; Ortho-benzoquinone; Sequential electron proton transfer SEPT.