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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.
Hydroxyl radicals (· OH) are recognized as the most active reactive oxygen species in the biological system and lead to the oxidative DNA, protein and lipid damage in vivo. At present, the most widely accepted mechanism for the generation of · OH is transition Metal ion-catalyzed Fenton reaction PCP is an important industrial and agricultural biocide and is mainly used for wood protection. Hydroxylation of salicylic acid and spin resonance of electron spin resonance (TCBQ), one of the metabolites of H2O2 and pentachlorophenol, was found to produce · OH through a metal ion-independent pathway. Further studies showed that TCBQ, rather than its corresponding half-quinone Radicals are extremely important for the production of · OH. The main product of the reaction between TCBQ and H2O2 has been identified as TrCBQ-OH, of which oxygen atoms have been proven to originate from H2O2. Based on these data and The following assumptions were proposed: the reaction of TCBQ and H2O2 to generate · OH is not carried out by organic Fenton reaction which depends on semiquinone free radicals, but nucleophilic attack of TCBQ by H2O2 to form unstable trichlorohydroperoxy-1, The 4-benzoquinone (TrCBQ-OOH) intermediate, which can be cleaved to produce · OH and tris Hydroxy-1,4-benzoquinone free radical (TrCBQ-O ·). The above reaction pathway shows a new class of · OH production mechanism that · OH formation does not require the participation of transition metal ions with redox activity. It may partly explain the carcinogenicity of other polyhaloaromatic pesticides such as PCP.