Zhu Ben-Zhan, Zhao Hong-Tao, Kalyanaraman Balaraman, Frei Balz
Linus Pauling Institute, Oregon State University, Corvallis, OR 97331, USA.
Free Radic Biol Med. 2002 Mar 1;32(5):465-73. doi: 10.1016/s0891-5849(01)00824-3.
The metal-independent production of hydroxyl radicals (*OH) from H(2)O(2) and tetrachloro-1,4-benzoquinone (TCBQ), a carcinogenic metabolite of the widely used wood-preservative pentachlorophenol, was studied by electron spin resonance methods. When incubated with the spin trapping agent 5,5-dimethyl-1-pyrroline N-oxide (DMPO), TCBQ and H(2)O(2) produced the DMPO/*OH adduct. The formation of DMPO/*OH was markedly inhibited by the *OH scavenging agents dimethyl sulfoxide (DMSO), ethanol, formate, and azide, with the concomitant formation of the characteristic DMPO spin trapping adducts with *CH(3), *CH(CH(3))OH, *COO(-), and *N(3), respectively. The formation of DMPO/*OH and DMPO/*CH(3) from TCBQ and H(2)O(2) in the absence and presence, respectively, of DMSO was inhibited by the trihydroxamate compound desferrioxamine, accompanied by the formation of the desferrioxamine-nitroxide radical. In contrast, DMPO/*OH and DMPO/*CH(3) formation from TCBQ and H(2)O(2) was not affected by the nonhydroxamate iron chelators bathophenanthroline disulfonate, ferrozine, and ferene, as well as the copper-specific chelator bathocuproine disulfonate. A comparative study with ferrous iron and H(2)O(2), the classic Fenton system, strongly supports our conclusion that *OH is produced by TCBQ and H(2)O(2) through a metal-independent mechanism. Metal-independent production of *OH from H(2)O(2) was also observed with several other halogenated quinones.
通过电子自旋共振方法研究了过氧化氢（H₂O₂）与四氯-1,4-苯醌（TCBQ，广泛使用的木材防腐剂五氯苯酚的致癌代谢物）在无金属情况下产生羟基自由基（·OH）的过程。当与自旋捕获剂5,5-二甲基-1-吡咯啉N-氧化物（DMPO）一起孵育时，TCBQ和H₂O₂产生了DMPO/·OH加合物。·OH清除剂二甲基亚砜（DMSO）、乙醇、甲酸盐和叠氮化物显著抑制了DMPO/·OH的形成，同时分别形成了与·CH₃、·CH(CH₃)OH、·COO⁻和·N₃的特征性DMPO自旋捕获加合物。在分别不存在和存在DMSO的情况下，三羟基肟酸化合物去铁胺抑制了TCBQ和H₂O₂形成DMPO/·OH和DMPO/·CH₃，同时形成了去铁胺-氮氧化物自由基。相比之下，非羟基肟酸铁螯合剂4,7-二苯基-1,10-菲啰啉二磺酸、亚铁嗪和菲咯嗪，以及铜特异性螯合剂4,4'-双(2-磺酸基苯)-2,2'-联喹啉，均不影响TCBQ和H₂O₂形成DMPO/·OH和DMPO/·CH₃。与经典的芬顿体系亚铁离子和H₂O₂的对比研究有力地支持了我们的结论，即TCBQ和H₂O₂通过无金属机制产生·OH。还观察到其他几种卤代醌在无金属情况下由H₂O₂产生·OH。
