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Title: Gas chromatographic analysis with chiral cyclodextrin phases reveals the enantioselective formation of hydroxylated polychlorinated biphenyls by rat liver microsomes.

Authors: Kania-Korwel, Izabela; Duffel, Michael W; Lehmler, Hans-Joachim

Published In Environ Sci Technol, (2011 Nov 15)

Abstract: Chiral PCB congeners are major components of PCB mixtures and undergo enantioselective biotransformation to hydroxylated (OH-)PCBs by cytochrome P450 enzymes. While it is known that biotransformation results in an enantiomeric enrichment of the parent PCB, it is currently unknown if OH-PCBs are formed enantioselectively. The present study screened seven commercial capillary gas chromatography columns containing modified ýý- or ýý-cyclodextrins for their potential to separate the atropisomers of methylated derivatives of OH-PCB. The atropisomers of 3-, 4- and 5-methoxy derivatives were at least partially separated on one or more columns. A subsequent biotransformation study was performed with rat liver microsomes to assess if hydroxylated metabolites are formed enantioselectively from PCBs 91, 95, 132, and 149. The OH-PCBs were extracted from the microsomal incubations, derivatized with diazomethane and analyzed as the respective methoxylated (MeO-)PCB derivatives using selected columns. The 5-hydroxylated metabolites of PCBs 91, 95, 132, and 149 were the major metabolites, which is consistent with PCB's biotransformation by cytochrome P450 2B enzymes. All 5-hydroxylated metabolites displayed a clear, congener-specific enantiomeric enrichment. Overall, this study demonstrates for the first time that chiral PCBs, such as PCB 91, 95, 132, and 149, are enantioselectively metabolized to OH-PCBs by cytochrome P450 enzymes.

PubMed ID: 21966948 Exiting the NIEHS site

MeSH Terms: Animals; Chromatography, Gas/methods; Cyclodextrins/chemistry; Hydroxylation; Isomerism; Microsomes, Liver/metabolism*; Polychlorinated Biphenyls/chemistry; Polychlorinated Biphenyls/isolation & purification; Polychlorinated Biphenyls/metabolism*; Rats

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