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一种新型羟基自由基产生分子机理的研究

ISSN号：0023-074X
期刊名称：科学通报
时间：0
页码：1673-1680
分类：O621.146[理学—有机化学;理学—化学] X703[环境科学与工程—环境工程]
作者机构：[1]中国科学院生态环境研究中心,环境化学与生态毒理学国家重点实验室,北京100085
相关基金：国家重点基础研究发展计划（编号：2008CB418106）、国家自然科学基金（批准号：20777080,20877081,20747001,20890112,20621703）和中国科学院“百人计划”资助项目
相关项目：典型持久性有机污染物的环境过程与毒理效应

作者：朱本占|ZHU Ben-Zhan State Key Laboratory of Environmental|

关键词：羟基自由基, 五氯酚, 电子自旋共振自旋捕获, 四氯苯醌, 过氧化氢, hydroxyl radical, pentachlorophenol, electron spin resonance （ESR） spin-trapping method, tetrachloro-1, 4-benzoquinone hydrogen peroxide

中文摘要：

羟基自由基（·OH）被公认是生物系统中最具活性的活性氧物种,能导致生物体内DNA,蛋白质和脂质氧化损伤.目前,关于·OH的产生机理,最被广泛接受的是过渡金属离子催化的Fenton反应.五氯酚（PCP）是一种重要的工农业生物杀灭剂,主要用作木材保护.采用水杨酸羟基化法和电子自旋共振自旋捕获等作为分析手段,发现H2O2和五氯酚的代谢产物之一四氯-1,4-苯醌（TCBQ）能通过不依赖于金属离子的途径产生·OH;进一步的研究发现,TCBQ而非其相应的半醌自由基对·OH的产生极其重要.TCBQ和H2O2反应的主要产物被鉴定为三氯羟基-1,4-苯醌（TrCBQ-OH）,其中的氧原子被证明来源于H2O2.基于这些数据和分析,提出以下假设：TCBQ和H2O2反应产生·OH不是通过依赖于半醌自由基的有机Fenton反应进行,而是H2O2对TCBQ进行亲核攻击,形成不稳定的三氯氢过氧基-1,4-苯醌（TrCBQ-OOH）中间产物,其可均裂产生·OH和三氯羟基-1,4-苯醌自由基（TrCBQ-O·）.上述反应途径展示了一类新型的·OH产生机理,即·OH的形成不需要具有氧化还原活性的过渡金属离子参与.该机理可部分解释五氯酚等其他多卤芳香类杀虫剂的致癌性.

英文摘要：

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 DNA, protein, and lipid oxidation. One of the most widely accepted mechanisms for ^＊OH production is the transition metalcatalyzed Fenton reaction. Pentachlorophenol （PCP） has been widely used as a wood preservative. Using the salicylate hydroxylation assay and electron spin resonance （ESR） 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 （TCSQ^＊）, is essential for ^＊OH production. The major reaction product between TCBQ and H2O2 was identified to be the ionic form of trichloro-hydroxy-1, 4-benzoquinone （TrCBQ-OH）, and H2O2 was found to be the source and origin of the oxygen atom inserted into the reaction product TrCBQ-OH. Based on these data, we propose that ^＊OH production by H2O2 and TCBQ is not through a semiquinone-dependent organic Fenton reaction, but rather through the following novel mechanism： a nucleophilic attack of H2O2 on TCBQ, forming a trichloro- hydroperoxyl-1, 4-benzoquinone （TrCBQ-OOH） intermediate, which decomposes homolytically to produce ^＊OH. These findings represent a novel mechanism of ^＊OH formation not requiring the involvement of redox-active transition metal ions, and may partly explain the potential carcinogenicity of widely used biocides such as PCP and other polyhalogenated aromatic environmental pollutants.