Antioxidant effects of phenothiazine, phenoxazine, and iminostilbene on free-radical-induced oxidation of linoleic acid and DNA

Antioxidant effects of phenothiazine (PtzNH), phenoxazine (PozNH), and iminostilbene (IsbNH) on the oxidation of linoleic acid (LH) and DNA induced by 2,2′-azobis(2-amidinopropane) dihydrochloride (AAPH) were investigated in this work. LH was suspended in the liposome of dipalmitoyl phosphatidylcholine (DPPC) to mimic a biomembrane. In the course of AAPH-induced oxidation of LH, the inhibition period (tinh) generated by PtzNH, PozNH, and IsbNH was proportional to the concentrations of PtzNH, PozNH, and IsbNH employed. The abilities of PtzNH, PozNH, and IsbNH to protect LH were similar to that of trolox (6-hydroxyl-2,5,7,8-tetramethylchroman-2-carboxylic acid). Quantum chemical calculations elucidated that the nonplanar configurations of PtzNH, PozNH, and IsbNH transformed to planar ones when they were converted into radicals. In addition, spin-densities (SDs) on the N atom in the radicals derived from PtzNH, PozNH, and IsbNH were calculated. The N atom in the radical of PtzNH possessed the lowest SD, indicating that the radical of PtzNH was the most stable one. Moreover, PtzNH, PozNH, and IsbNH were applied to protect the DNA against AAPH-induced oxidation, in which PozNH and IsbNH were able to generate tinh. The tinh generated from PozNH and IsbNH was also proportional to their concentrations. The antioxidant effect of PozNH on the oxidation of DNA was higher than that of IsbNH. Copyright © 2009 John Wiley & Sons, Ltd.