Nonradical mechanism of (bi)sulfite reaction with DEPMPO: cautionary note for SO₃^−• radical spin trapping

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• 作者：Potapenko ; Dmitrii I. ; Clanton ; Thomas L. ; Bagryanskaya ; Elena G. ; Gritsan ; Nina P. ; Reznikov ; Vladimir A. ; et. al.
• 关键词：Free radicals ; Spin trapping ; NMR spin trapping ; Sulfite-derived radicals ; Sulfite toxicity ; Nitrones
• 刊名：Free Radical Biology and Medicine
• 出版年：2003
• 期刊代码：105_08915849
• 类别：med
• 出版时间：January 15, 2003
• 卷：34
• 期：2
• 页码：196-206
• 文件大小：251 K

摘要

Knowledge of the formation of radicals from sulfites, in vivo, is of interest in understanding the allergic and inflammatory responses to environmental sulfur dioxide exposure. Sulfite anion trioxide (SO₃^−•) radical formation was measured in mice, preloaded with the spin trap, 5-(diethoxy-phosphoryl)-5-methyl-pyrrolidine-N-oxide, (DEPMPO). Based on spin trapping NMR, a surprising quantity of reduced SO₃^−•-adduct was observed that did not depend on co-administration of oxidizing agents, suggesting a possible nonradical reaction between (bi)sulfite and DEPMPO. The products of the reversible nucleophylic addition of (bi)sulfite to the nitrone functional group were identified using ³¹P-NMR, ¹H-NMR, and ¹³C-NMR spectroscopy as cis- and trans- stereoisomers of hydroxylamine and confirmed by quantum chemical calculations. Oxidation of the hydroxylamines results in the formation of two corresponding cis- and trans-isomeric nitroxides, only one of which has been earlier described as the paramagnetic adduct of genuinely trapped SO₃^−• radical. The results demonstrate that SO₃^−• detection using nitrone spin traps such as DEPMPO and DMPO may involve nonradical addition reactions except in cases when the required controls unambiguously prove a radical mechanism.