Formation of TEMPOL-hydroxylamine during reaction between TEMPOL and hydroxyl radical: HPLC/ECD study.
Nitroxyl radicals are important antioxidants that have been used to protect animal tissues from oxidative damage. Their reaction with hydroxyl radical ((*)OH) is generally accepted to be the mechanism of antioxidant function. However, the direct interaction of nitroxyl radicals with (*)OH does not always provide a satisfactory explanation in various pH, because the concentration of hydrogen ion may affect the generation of secondary (*)OH-derived radicals. In the present study, it was confirmed that the reaction between 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPOL) and (*)OH generated TEMPOL-hydroxylamine, 4-oxo-2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPON) and TEMPON-hydroxylamine using HPLC coupled with electrochemical detection. In the absence of NADH, TEMPOL-H may be generated by the reaction with secondary (*)OH-derived radicals in acidic condition. In the presence of NADH, a large proportion of the non-paramagnetic products was TEMPOL-H. Finally, it was clarified that TEMPOL-H was generated during dopamine metabolism, which is believed to be one of the (*)OH sources in pathological processes such as Parkinson's disease.
Kudo
Wataru
W
Department REDOX Medicinal Science, Faculty of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan.
Yamato
Mayumi
M
Yamada
Ken-Ichi
K
Kinoshita
Yuichi
Y
Shiba
Takeshi
T
Watanabe
Toshiaki
T
Utsumi
Hideo
H
D000975:Antioxidants / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D003497:Cyclic N-Oxides / Q000494:pharmacology*; D004298:Dopamine / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals; D006801:Humans; D006859:Hydrogen / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D017665:Hydroxyl Radical; D006898:Hydroxylamines / Q000737:chemistry*; D009569:Nitric Oxide / Q000737:chemistry; D010880:Piperidines / Q000737:chemistry; D013113:Spin Labels; D014216:Triacetoneamine-N-Oxyl / Q000494:pharmacology*
D000975:Antioxidants; D003497:Cyclic N-Oxides; D005609:Free Radicals; D006898:Hydroxylamines; D010880:Piperidines; D013113:Spin Labels; D014216:Triacetoneamine-N-Oxyl; D009569:Nitric Oxide; D017665:Hydroxyl Radical; C103674:1-hydroxy-2,2,6,6-tetramethyl-4-oxopiperidine; D006859:Hydrogen; C001803:tempol; D004298:Dopamine