期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 104, 期 10, 页码 3698-3702出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0605527104
关键词
electron spin resonance spin-trapping; 2,5-dichloro-1,4-benzoquinone; 2,5-dichlorosemiquinone anion radical; reactive intermediate; metal chelators
资金
- NCCIH NIH HHS [P01 AT002034, AT 002034] Funding Source: Medline
- NCRR NIH HHS [RR 01008] Funding Source: Medline
- NIEHS NIH HHS [ES 00210, P30 ES000210, ES 11497] Funding Source: Medline
The metal-independent decomposition of organic hydroperoxides and the formation of organic alkoxyl radicals in the absence or presence of halogenated quinones were studied with electron spin resonance (ESR) and the spin-trapping agent 5,5-dimethyl-1-pyrroline N-oxide (DMPO). We found that 2,5-dichloro-1,4-benzoquinone (DCBQ) markedly enhanced the decomposition of tert-butylhydroperoxide (t-BuOOH), leading to the formation of the DMPO adducts with t-butoxyl radicals (t-BuO center dot) and methyl radicals ((CH3)-C-center dot)The formation of DMPO/t-BuO center dot and DMPO/(CH3)-C-center dot was dose-dependent with respect to both DCBQ and t-BuOOH and was not affected by iron- or copper-specific metal chelators. Comparison of the data obtained with DCBQ and t-BuOOH with those obtained in a parallel study with ferrous iron and t-BuOOH strongly suggested that t-BuO center dot was produced by DCBQ and t-BuOOH through a metal-independent mechanism. Other halogenated quinones were also found to enhance the decomposition of t-BuOOH and other organic hydroperoxides such as cumene hydroperoxide, leading to the formation of the respective organic alkoxyl radicals in a metal-independent manner. Based on these data, we propose a mechanism for DCBQ-mediated t-BuOOH decomposition and formation of t-BuO center dot: a nucleophilic attack of t-BuOOH on DCBQ, forming a chloro-t-butylperoxyl-1,4-benzoquinone intermediate, which decomposes homolytically to produce t-BuO center dot. This represents a mechanism of organic alkoxyl radical formation not requiring the involvement of redox-active transition metal ions.
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