Chlorination Increases the Persistence of Semiquinone Free Radicals Derived from Polychlorinated Biphenyl Hydroquinones and Quinones
- 8 October 2008
- journal article
- research article
- Published by American Chemical Society (ACS) in The Journal of Organic Chemistry
- Vol. 73 (21), 8296-8304
- https://doi.org/10.1021/jo801397g
Abstract
Polychlorinated biphenyls (PCBs) comprise a group of persistent organic pollutants that differ significantly in their physicochemical properties, their persistence, and their biological activities. They can be metabolized via hydroxylated and dihydroxylated metabolites to PCB quinone intermediates. We have recently demonstrated that both dihydroxy PCBs and PCB quinones can form semiquinone radicals (SQ•−) in vitro. These semiquinone radicals are reactive intermediates that have been implicated in the toxicity of lower chlorinated PCB congeners. Here we describe the synthesis of selected PCB metabolites with differing degrees of chlorination on the oxygenated phenyl ring, e.g., 4,4′-dichloro-biphenyl-2,5-diol, 3,6,4′-trichloro-biphenyl-2,5-diol, 3,4,6,-trichloro-biphenyl-2,5-diol, and their corresponding quinones. In addition, two chlorinated o-hydroquinones were prepared, 6-chloro-biphenyl-3,4-diol and 6,4′-dichloro-biphenyl-3,4-diol. These PCB (hydro-)quinones readily react with oxygen or via comproportionation to yield the corresponding semiquinone free radicals, as detected by electron paramagnetic resonance spectroscopy (EPR alias ESR). The greater the number of chlorines on the (hydro-)quinone (oxygenated) ring, the higher the steady-state level of the resulting semiquinone radical at near neutral pH.Keywords
This publication has 44 references indexed in Scilit:
- Semiquinone Radicals from Oxygenated Polychlorinated Biphenyls: Electron Paramagnetic Resonance StudiesChemical Research in Toxicology, 2008
- Molecular cytotoxic mechanisms of catecholic polychlorinated biphenyl metabolites in isolated rat hepatocytesChemico-Biological Interactions, 2007
- Cerium(IV) Ammonium NitrateA Versatile Single-Electron OxidantChemical Reviews, 2007
- The Synthesis and Biological Activity of Pyranonaphthoquione Derivatives from Streptomyces sp. and Their Related SubstancesBulletin of the Chemical Society of Japan, 2004
- Intracellular Signaling and Developmental NeurotoxicityPublished by Informa UK Limited ,2004
- Characterization and Quantitative Analysis of DNA Adducts Formed from Lower Chlorinated PCB-Derived QuinonesChemical Research in Toxicology, 2004
- Initiating Activity of 4-Chlorobiphenyl Metabolites in the Resistant Hepatocyte ModelToxicological Sciences, 2004
- Polychlorinated Biphenyls. VI. 2,3,7,8-Tetrachlorodibenzofuran, a Critical Byproduct in the Synthesis of 2,2',4,4',5,5'-Hexachlorobiphenyl by the Ullmann Reaction.Acta Chemica Scandinavica, 1973
- Electron spin resonance spectra of radicals derived from arylhydroquinonesJournal of the Chemical Society, Perkin Transactions 2, 1972
- Electron Paramagnetic Resonance of Undissociated p-BenzosemiquinonesJournal of the American Chemical Society, 1965