METABOLISM OF 2,4,5,2',4',5'-HEXACHLOROBIPHENYL WITH LIVER-MICROSOMES OF PHENOBARBITAL-TREATED DOG - THE POSSIBLE FORMATION OF PCB 2,3-ARENE OXIDE INTERMEDIATE

1. Metabolism of 2,4,5,2',4',5'-hexachlorobiphenyl (HCB) was investigated in vitro using liver microsomes of one male beagle dog after phenobarbital treatment. 2. Three major metabolites were isolated and identified as 3-hydroxy-2,4,5,2',4',5'-HCB, 2-hydroxy-4,5,2',4',5'-pentachlorobiphenyl (PenCB), and 2-hydroxy-3,4,5,2',4',5'-HCB, by comparison of g.l.c.-mass spectrometry and H-1-n.m.r. data with those of authentic samples. 3. 2-Hydroxy-3,4,5,2',4',5'-HCB was found as a metabolite of 2,4,5,2',4',5'-HCB for the first time using dog liver microsomes. Present results indicate that this metabolite and the dechlorinated PenCB are derived from a metabolic intermediate, namely, 2,3-epoxy-2,4,5,2',4',5'-HCB. 2,3-Epoxide formation is a new metabolic pathway of PCB.