TitleMetal-independent production of hydroxyl radicals by halogenated quinones and hydrogen peroxide: an ESR spin trapping study.
Publication TypeJournal Article
Year of Publication2002
AuthorsZhu B-Z, Zhao H-T, Kalyanaraman B, Frei B
JournalFree Radic Biol Med
Date Published2002 Mar 01
KeywordsChelating Agents, Chloranil, Copper, Cyclic N-Oxides, Electron Spin Resonance Spectroscopy, Hydrogen Peroxide, Hydroxyl Radical, Iron, Molecular Structure, Spin Labels

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.

Alternate JournalFree Radic. Biol. Med.
PubMed ID11864786
Grant ListAT00066 / AT / NCCIH NIH HHS / United States
ES00210 / ES / NIEHS NIH HHS / United States
ES11497 / ES / NIEHS NIH HHS / United States
HL60886 / HL / NHLBI NIH HHS / United States
RR01008 / RR / NCRR NIH HHS / United States