A Novel Mechanism for Metal-independent Hydroxyl Radical Production by Hydrogen Peroxide and Halogenated Quinones

Author(s): Ben-Zhan Zhu, Rui-Mei Fan, Na Qu.

Journal Name: Mini-Reviews in Organic Chemistry

Volume 8 , Issue 4 , 2011

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Abstract:

The hydroxyl radical (˙OH) has been considered to be one of the most reactive oxygen species that are produced in biological systems. Frequently, ˙OH formation is ascribed to the transition metal-catalyzed Fenton reaction. During the study of the molecular mechanism for the genotoxicity of the wood preservative pentachlorophenol (PCP), we found that ˙OH could be produced by H2O2 and PCP metabolite tetrachloro-1,4-benzoquinone (TCBQ) independent of transition metal ions. Further studies showed that TCBQ, but not its corresponding semiquinone radical, is essential for ˙OH production. Metal-independent production of ˙OH could also be observed with other halogenated quinones and H2O2. Based on these data, we propose that ˙OH production by TCBQ and H2O2 is not through a semiquinone-dependent organic Fenton reaction, but rather through a novel nucleophilic substitution and homolytical decomposition mechanism. This represents a novel mechanism for ˙OH production not requiring the catalysis of redox-active transition metal ions, and may partly explain the potential carcinogenicity of the widely used biocides such as PCP and other polyhalogenated aromatic compounds.

Keywords: Hydroxyl radical, Tetrachloro-1,4-benzoquinone, Electron spin resonance (ESR) spin-trapping, Hydrogen peroxide, Carcinogenicity, polyhalogenated aromatic compounds

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Article Details

VOLUME: 8
ISSUE: 4
Year: 2011
Page: [434 - 437]
Pages: 4
DOI: 10.2174/157019311797440290
Price: $58

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