title: The effect of the structure of polychlorinated biphenyls on their hydroxylation, oxidation, and glutathionyl conjugation reactions.
abstract: OBJECTIVE
  To compare the nature of the metabolites formed from the phase I metabolism (hydroxylation and oxidation) and phase II metabolism (glutathionyl conjugation) of PCBs that have different chlorine substitution patterns. To discuss the structure-activity relationships and metabolic mechanisms of PCBs.
  
  
  METHODS
  4-Cl-biphenyl (PCB3), 4,4'-Cl-biphenyl (PCB15), 3,4,3',4'-Cl-biphenyl (PCB77) were used for in vitro metabolic study. LC/MS and UV-Vis studies were performed for metabolites identification.
  
  
  RESULTS
  The cytochrome P-450 catalyzed hydroxylation rate decreased as the number of chlorine substitutions increased. In this reaction, PCB3 was fully metabolized, approximately half of the PCB15 was metabolized and PCB77 was not metabolized at all. The oxidation rate of PCB15-HQ was higher than that of PCB3-HQ under various oxidation conditions. The LC/MS and UV-Vis data suggest that in the conjugation reaction of PCB15-Q and GSH, the Michael addition reaction occurs preferentially over the displacement reaction.
  
  
  CONCLUSIONS
  The metabolic profiles of polychlorinated biphenyls (PCBs) are dramatically affected by chlorine substitution patterns. It is suggested that the metabolic profiles of PCBs are related to their chlorine substitution patterns, which may have implications for the toxicity of PCB exposure.
authors: Key Laboratory of Luminescence and Real-Time Analysis, Ministry of Education, College of Pharmaceutical Sciences, Southwest University, Chongqing 400715, China. eqsong@swu.edu.cn
authors: Er Qun
authors: EQ
authors: Song
authors: Xiao Yan
authors: XY
authors: Ma
authors: Xing Guo
authors: XG
authors: Tian
authors: Jing
authors: J
authors: Liu
authors: Li Chao
authors: LC
authors: Liu
authors: Hui
authors: H
authors: Dong
authors: Yang
authors: Y
authors: Song
mesh_terms: D006900:Hydroxylation; D015394:Molecular Structure; D010084:Oxidation-Reduction; D011078:Polychlorinated Biphenyls / Q000737:chemistry*
chemical_list: D011078:Polychlorinated Biphenyls
keywords: Cytochrome P450; Glutathione; Hydroquinone; PCB; Quinone; metabolism