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

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.

A hydroxyl-scavenging assay based on DNA damage in vitro.

Previous deoxyribose degradation method lacks biological relevance, specificity, and even reliability. In this study, a new hydroxyl radical-scavenging assay based on DNA damage is described. 2-Thiobarbituric acid-reactive substance (TBARS, λmax = 530 nm) was chosen as the biomarker of hydroxyl-mediated DNA damage. On the basis of systematic investigations into various factors affecting A530 nm and solvent interference, the experimental procedure was developed. The successful measurement of 30 selected antioxidants demonstrated that the proposed DNA damage method is reliable, simple, specific, and biologically relevant. It is suitable for all types of antioxidants in vitro.

Antioxidant ability and mechanism of rhizoma Atractylodes macrocephala.

Rhizoma Atractylodes macrocephala (AM) has been used in Traditional Chinese Medicine (TCM) for about 2,000 years. In the study, we firstly determined the antioxidant levels of five AM extracts by •OH-scavenging, •O2−-scavenging, Fe2+-chelating, Cu2+-chelating, DPPH·-scavenging, and ABTS+·-scavenging assays. After measurement of the chemical contents in five AM extracts, we quantitatively analyzed the correlations between antioxidant levels and chemical contents. It was observed that total phenolics and total flavonoids had significant positive correlations with antioxidant levels (R = 0.685 and 0.479, respectively). In contrast, total sugars and total saponins presented lower correlations with antioxidant levels (R=−0.272 and 0.244, respectively). It means that antioxidant activity of AM should be attributed to total phenolics (including phenolic acids and flavonoids), and not total sugars and total saponins. Further analysis indicated that phenolic acids exhibited higher R values with radical-scavenging assays (R=0.32­1.00), while flavonoids showed higher R values with metal-chelating assays (R=0.86 and 0.90). In conclusion, AM exerts its antioxidant effect through metal-chelating, and radical-scavenging which is via donating hydrogen atom and donating electron. Its metal-chelating may result from flavonoids, while its radical-scavenging can be attributed to phenolic acids, especially caffeic acid, ferulic acid, and protocatechuic acid.

Antioxidant Activity of Rhizoma Cibotii in vitro.

PURPOSE: The paper tried to systematically investigate the in vitro antioxidant activity of Rhizoma Cibotii (RC) for the first time. METHOD: The methanol extract from RC (MERC) was prepared then systematically investigated by various antioxidant assays, including: DPPH• (1, 1-diphenyl-2-picrylhydrazyl radical), ABTS•(+) (3-ethylbenzthiazoline-6- sulfonic acid diammonium salt radical), •O2- (superoxide anion radical), •OH (hydroxyl radical) scavenging assays, Fe(3+) reducing power, Cu(2+) reducing power assays, compared with positive controls Trolox (± -6 -hydroxyl -2,5, 7, 8-tetramethlychromane-2-carboxylic acid) and BHA (butylated hydroxyanisole). Its total phenolics and caffeic acid content were also measured by Folin-Ciocalteu method and HPLC, respectively. RESULT: MERC exhibited effective antioxidant activity in dose-dependent manners and its IC50 values were calculated as 44.2 ± 0.62, 19.84 ± 0.31, 137.66 ± 2.90, 22.94 ± 0.90, 289.73 ± 46.17, 53.52 ± 1.51 µg /mL，for DPPH•, ABTS•(+), •O2 (-), •OH scavenging assays, Fe(3+) reducing power, Cu(2+) reducing power assays, respectively. Its total phenolics content was 50.88 ± 1.24 mg CAE /g and the caffeic acid content was 1.82 ± 0.19 mg/g. CONCLUSION: Rhizoma Cibotii has effective in vitro antioxidant activity which may attribute to its total phenolics, among which caffeic acid can be considered as one of the active components. The pharmacological effects or healthcare functions of whole RC may result from the synergistic effects caused by the combination of its components and its antioxidant effect plays an important role in the synergistic effects.