RT Journal Article SR Electronic T1 Metabolism of Dimethyl-4,4′-dimethoxy-5,6,5′,6′-dimethylene dioxybiphenyl-2,2′-dicarboxylate (DDB) by Human Liver Microsomes: Characterization of Metabolic Pathways and of Cytochrome P450 Isoforms Involved JF Drug Metabolism and Disposition JO Drug Metab Dispos FD American Society for Pharmacology and Experimental Therapeutics SP 381 OP 388 VO 29 IS 4 A1 Min-Sun Baek A1 Ji-Yeon Kim A1 Seung-Woon Myung A1 Yong Hyeon Yim A1 Jin-Hyun Jeong A1 Dong-Hyun Kim YR 2001 UL http://dmd.aspetjournals.org/content/29/4/381.abstract AB Metabolic fate of DDB and identification of P450 isozymes involved in the metabolism of DDB were investigated in human liver microsomes. DDB was rapidly metabolized to five different metabolites, and the structures of each metabolite were characterized based on UV, mass, and NMR spectral analyses. The major metabolic pathways of DDB in human liver microsomes were identified as O-demethylation of the carboxymethyl moiety (M4) and demethylenation of the methylenedioxyphenyl group (M2). The intramolecular lactonization between the hydroxyl group at the C6 and carboxymethyl group at the C2′ of M2 resulted in the generation of M5, which was either hydrolyzed to its hydrolyzed derivative (M1) or further metabolized to the O-demethylated derivative (M3). The interconversion of M1, M2, and M5 took place nonenzymatically depending on the solvent condition. M5 was predominantly detected at the acidic condition, whereas M1 was preferentially detected at the basic environment. Cytochrome P450 (P450) isoform(s) involved in the metabolism of DDB was identified using several in vitro approaches. Chemical inhibition using isoform-selective P450 inhibitors, correlation of DDB metabolites formation with several isoform-specific P450 activities in a panel of liver microsomes, metabolism by microsomes derived from P450 cDNA-expressed B-lymphoblastoid cells, and immunoinhibition by isoform-specific anti-P450 antibodies collectively indicated that CYP1A2, CYP2C9, and CYP3A4 are responsible for the metabolism of DDB.O-Dealkylation of the carboxymethyl group was preferentially catalyzed by CYP1A2, whereas demethylenation of the methylenedioxyphenyl moiety was catalyzed by CYP3A4 and CYP2C9. The American Society for Pharmacology and Experimental Therapeutics