In vitro metabolism of BDE-47, BDE-99, and α-, β-, γ-HBCD isomers by chicken liver microsomes.
The in vitro oxidative metabolism of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47), 2,2',4,4',5-pentabromodiphenyl ether (BDE-99), and the individual α-, β- and γ-hexabromocyclododecane (HBCD) isomers catalyzed by cytochrome P450 (CYP) enzymes was studied using chicken liver microsomes (CLMs). Metabolites were identified using a liquid chromatography-tandem mass spectrometry method and authentic standards for the oxidative metabolites of BDE-47 and BDE-99. Six hydroxylated tetra-BDEs, namely 4-hydroxy-2,2',3,4'-tetrabromodiphenyl ether (4-OH-BDE-42), 3-hydroxy-2,2',4,4'-tetrabromodiphenyl ether (3-OH-BDE-47), 5-hydroxy-2,2',4,4'-tetrabromodiphenyl ether (5-OH-BDE-47), 6-hydroxy-2,2',4,4'-tetrabromodiphenyl ether (6-OH-BDE-47), 4'-hydroxy-2,2',4,5'- tetrabromodiphenyl ether (4'-OH-BDE-49), and 2'-hydroxy-2,3',4,4'-tetrabromodiphenyl ether (2'-OH-BDE-66), were identified and quantified after incubation of BDE-47 with CLMs. 4'-OH-BDE-49 was the major metabolite formed. Three hydroxylated penta-BDEs (5'-hydroxy-2,2',4,4',5-pentabromodiphenyl ether (5'-OH-BDE-99), 6'-hydroxy-2,2',4,4',5- pentabromodiphenyl ether (6'-OH-BDE-99), and 4'-hydroxy-2,2',4,5,5'-pentabromodiphenyl ether, 4'-OH-BDE-101, were formed incubating BDE-99 with CLMs. Concentrations of BDE-99 metabolites were lower than those of BDE-47. More than four mono-hydroxylated HBCD (OH-HBCD), more than four di-hydroxylated HBCD (di-OH-HBCD), more than five mono-hydroxylated pentabromocyclododecenes (OH-PBCD), and more than five di-hydroxylated pentabromocyclododecenes (di-OH-PBCD) were detected when α-, β-, or γ-HBCD were individually incubated with CLMs. Response values (the ratio between the peak areas of the target compound and its internal standard) for OH-HBCD were 1-3 orders of magnitude higher than those for OH-PBCD, di-OH-HBCD, and di-OH-PBCD, suggesting that OH-HBCD might be the major metabolites of α-, β- and γ-HBCD produced by CLMs. No diastereoisomeric or enantiomeric bioisomerisation was observed incubating α-, β- or γ-HBCD with CLMs. Collectively, our data suggest that (i) BDE-47 is metabolized at a faster rate than BDE-99 by CLMs, (ii) OH-HBCD are the major hydroxylated metabolites of α-, β- and γ-HBCD produced by CLMs and (iii) the diastereoisomeric or enantiomeric bioisomerisation of α-, β- and γ-HBCD is not mediated by chicken CYP enzymes.
College of Natural Resources and Environment, South China Agricultural University, Guangzhou 510642, People's Republic of China; Toxicological Centre, University of Antwerp, Universiteitsplein 1, 2610 Wilrijk, Belgium; State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry and Guangdong Key Laboratory of Environmental Protection and Resources Utilization, Chinese Academy of Sciences, Guangzhou 510640, People's Republic of China.
Xiaobo
X
Zheng
Toxicological Centre, University of Antwerp, Universiteitsplein 1, 2610 Wilrijk, Belgium.
Claudio
C
Erratico
Division of Environmental Health and Risk Management, College of Life and Environmental Sciences, University of Birmingham, Birmingham B15 2TT, United Kingdom; Department of Analytical Chemistry, Faculty of Pharmacy, Assiut University, 71526 Assiut, Egypt.
Mohamed Abou-Elwafa
MA
Abdallah
Toxicological Centre, University of Antwerp, Universiteitsplein 1, 2610 Wilrijk, Belgium.
Noelia
N
Negreira
State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry and Guangdong Key Laboratory of Environmental Protection and Resources Utilization, Chinese Academy of Sciences, Guangzhou 510640, People's Republic of China.
Xiaojun
X
Luo
State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry and Guangdong Key Laboratory of Environmental Protection and Resources Utilization, Chinese Academy of Sciences, Guangzhou 510640, People's Republic of China.
Bixian
B
Mai
Toxicological Centre, University of Antwerp, Universiteitsplein 1, 2610 Wilrijk, Belgium. Electronic address: adrian.covaci@uantwerpen.be.
Adrian
A
Covaci
D000818:Animals; D002645:Chickens / Q000378:metabolism*; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D055768:Halogenated Diphenyl Ethers / Q000737:chemistry / Q000378:metabolism*; D006842:Hydrocarbons, Brominated / Q000737:chemistry / Q000378:metabolism*; D066298:In Vitro Techniques; D007536:Isomerism; D057230:Limit of Detection; D008862:Microsomes, Liver / Q000201:enzymology / Q000378:metabolism*; D015203:Reproducibility of Results; D021241:Spectrometry, Mass, Electrospray Ionization
C477694:2,2',4,4',5-brominated diphenyl ether; D055768:Halogenated Diphenyl Ethers; D006842:Hydrocarbons, Brominated; C511295:2,2',4,4'-tetrabromodiphenyl ether; C089796:hexabromocyclododecane; D003577:Cytochrome P-450 Enzyme System
Biotransformation; Chicken liver microsomes; Cytochrome P450; Hexabromocyclododecane; Polybrominated diphenyl ethers