Alpha and Beta Isomers of Tetrabromoethylcyclohexane (TBECH) Flame Retardant: Depletion and Metabolite Formation In Vitro Using a Model Rat Microsomal Assay
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- 作者：Shaogang Chu ; Lewis T. Gauthier ; Robert J. Letcher
- 刊名：Environmental Science & Technology (ES&T)
- 出版年：2012
- 出版时间：September 18, 2012
- 年：2012
- 卷：46
- 期：18
- 页码：10263-10270
- 全文大小：305K
- 年卷期：v.46,no.18(September 18, 2012)
- ISSN：1520-5851
文摘
The metabolism of 伪- and 尾-isomers of the flame retardant chemical tetrabromoethylcyclohexane (TBECH) was investigated using a model in vitro enzyme-mediated biotransformation assay based on rat liver microsomes. In enzymatically active assays, concentrations of both 伪- and 尾-TBECH isomers were equally depleted by about 40% and in a time-dependent fashion over a 60-min assay incubation period, and determined by GC-MS(ECNI) analysis. No such depletion was observed in nonenzymatically active control assays. After the full 60-min assay incubation period, debrominated TBECH metabolites were not detected by GC-MS(ECNI), and suggested that enzyme-mediated debromination of TBECH did not occur via cyctochrome P450 enzyme-mediated catalysis or that the rate of TBECH metabolism in vitro was too slow. In the enzymatically active assays, but not in the nonezymatically active control assays, 伪- and 尾-monohydroxy-TBECH (OH-TBECH), dihydroxy-TBECH ((OH)2-TBECH), and some additional compounds with molecular formulas of C8H13Br3O2 and C8H11Br3O2 were identified by LC-Q-ToF-MS. Two unique sets of OH-TBECH and (OH)2-TBECH metabolites were derived from both 伪- and 尾-TBECH isomers. The LC-ESI(鈭?-MS/MS peak areas of all four OH-TBECH and (OH)2-TBECH metabolites increased at a comparable rate in a time-dependent manner over a 60-min assay incubation period. This study demonstrated that metabolism via hydroxylation can occur in vitro for 伪- and 尾-TBECH. These results underscore the importance of understanding the biological fate of TBECH and the possible implications on the health and TBECH levels in exposed wildlife and in the environment.