A Novel Mechanism for Metal-Independent Production of Hydroxyl Radicals and Carbon-Centered Quinone Ketoxy Radicals

Abstract

Abstract:

The hydroxyl radical (·OH) has been considered to be one of the most reactive oxygen species produced in biological systems. It has been shown that ·OH can cause oxidative damage to DNA and other macromolecules. One of the most widely accepted mechanisms for ·OH production is through the transition metal-catalyzed Fenton reaction. Pentachlorophenol (PCP) has been widely used as a wood preservative. Using electron spin resonance (ESR) secondary spin-trapping methods, we found that ·OH can be produced by H₂O₂ and tetrachloro-1,4-benzoquinone (TCBQ) (one of the major carcinogenic metabolites of PCP) independent of transition metal ions. Further studies showed that TCBQ, but not its corresponding semiquinone radical, the tetrachlorosemiquinone radical, is essential for ·OH production. Based on these data, we propose that ·OH production by H₂O₂ and TCBQ is through the following novel mechanism: a nucleophilic attack of H₂O₂ to TCBQ, forming a trichloro-hydroperoxyl-1,4-benzoquinone intermediate, which decomposes homolytically to produce ·OH. Through complementary application of ESR spin-trapping and other methods, we also detected and identified, for the first time, a novel carbon-centered quinone ketoxy radical.

Key words: electron spin resonance spin-trapping method, hydroxyl radical, pentachlorophenol, tetrachloro-1,4-benzoquinone, hydrogen peroxide, carbon-centered quinone ketoxy radical

CLC Number:

O482.53

ZHU Ben-Zhan, QIN Hao, HUANG Chun-Hua. A Novel Mechanism for Metal-Independent Production of Hydroxyl Radicals and Carbon-Centered Quinone Ketoxy Radicals[J]. Chinese Journal of Magnetic Resonance, 2011, 28(4): 479-489.

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