Ubiquinone-Dependent Recycling of Vitamin E Radicals by Superoxide

• Published in: Archives of biochemistry and biophysics Vol. 323; no. 2; pp. 343 - 351
• Main Authors: Stoyanovsky, Detcho A., Osipov, Anatoly N., Quinn, Peter J., Kagan, Valerian E.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 10.11.1995
• Subjects: antioxidants; Dimethyl Sulfoxide; Electron Spin Resonance Spectroscopy; Free Radicals; ion; iones; ions; Luminescent Measurements; oxidacion; oxidation; Oxidation-Reduction; oxydation; quinonas; quinone; quinones; radical libre; radicales libres; Spectrum Analysis; superoxide; Superoxides - chemistry; tocoferoles; tocopherol; tocopherols; ubiquinone; Ubiquinone - chemistry; Vitamin E - chemistry; α-tocopherol; ubiquinone; superoxide; antioxidants; α-tocopherol
• ISSN: 0003-9861; 1096-0384
• DOI: 10.1006/abbi.1995.9955

Superoxide-driven reduction of α-tocopheroxyl radical in the presence of ubiquinone-10 has been demonstrated in dimethylsulfoxide. Our HPLC measurements showed that ubiquinone-10 protected α-tocopherol against oxidation by KO2in a concentration-dependent manner. α-Tocopherol was oxidized by KO2to form ESR-detectable radicals of tocopherol ubisemiquinone. In the presence of ubiquinone-10, neither these radicals nor α-tocopheroxyl radicals (generated by uv light or PbO2) could be detected in ESR spectra. Instead, ESR signals of ubisemiquinone-10 radicals were observed. Formation of ubisemiquinone-10 radicals from ubiquinone-10 upon addition of KO2was ascertained by their characteristic ESR and uv–vis spectra. α-Tocopherol caused a concentration-dependent decrease of the ubisemiquinone-10 radical steady-state concentration. We conclude that one-electron reduction of ubiquinone-10 by superoxide ion resulting in the formation of ubiquinone-10 radicals caused redox-cycling of α-tocopherol from its phenoxyl radical, thus preventing loss of α-tocopherol. This suggests that coenzyme Q may have another physiological function, i.e., protection of α-tocopherol against superoxide-driven oxidation.