title: Cytochrome p450-mediated metabolic activation of diosbulbin B.
abstract: Diosbulbin B (DIOB), a furan-containing diterpenoid lactone, is the most abundant component of Dioscorea bulbifera L. (DB), a traditional Chinese medicine herb. Administration of purified DIOB or DB extracts has been reported to cause liver injury in animals. The mechanisms of DIOB-induced hepatotoxicity remain unknown. The major objective of this study was to identify reactive metabolites of DIOB. A DIOB-derived cis-enedial was trapped by N-acetyl lysine (NAL) and glutathione (GSH) or N-acetyl cysteine (NAC) in rat and human liver microsomal incubation systems after exposure to DIOB. Four metabolites (M1-M4) associated with GSH were detected by liquid chromatography coupled to tandem mass spectrometry. Apparently, M1 was derived from both NAL and GSH. M2 and M3 resulted from the reaction of GSH without the involvement of NAL. Two molecules of GSH participated in the formation of M4. M2 and M3 were also detected in bile and urine of rats given DIOB. M5, a DIOB-derived NAC/NAL conjugate, was detected in microsomal incubations with DIOB fortified with NAC and NAL as trapping agents. Biomimetic M1-M5 were prepared by oxidation of DIOB with Oxone for metabolite identification. Microsomal incubation study demonstrated that ketoconazole inhibited the production of the enedial in a concentration-dependent manner, and CYP3A4 was found to be the enzyme responsible for the metabolic activation of DIOB. The metabolism study facilitates the understanding of the role of bioactivation of DIOB in its hepatotoxicity.
authors.affiliation: School of Pharmacy (D.L., Y.P.), School of Traditional Chinese Medicine (C.L.), and Key Laboratory of Structure-Based Drug Design and Discovery of Ministry of Education (H.G., J.Z.), Shenyang Pharmaceutical University, Shenyang, Liaoning, People's Republic of China; and Division of Gastroenterology and Hepatology, Department of Pediatrics, Center for Developmental Therapeutics, Seattle Children's Research Institute, University of Washington School of Medicine, Seattle, Washington (J.Z.).
authors.forename: Dongju
authors.initials: D
authors.lastname: Lin
authors.affiliation: School of Pharmacy (D.L., Y.P.), School of Traditional Chinese Medicine (C.L.), and Key Laboratory of Structure-Based Drug Design and Discovery of Ministry of Education (H.G., J.Z.), Shenyang Pharmaceutical University, Shenyang, Liaoning, People's Republic of China; and Division of Gastroenterology and Hepatology, Department of Pediatrics, Center for Developmental Therapeutics, Seattle Children's Research Institute, University of Washington School of Medicine, Seattle, Washington (J.Z.).
authors.forename: Chunyan
authors.initials: C
authors.lastname: Li
authors.affiliation: School of Pharmacy (D.L., Y.P.), School of Traditional Chinese Medicine (C.L.), and Key Laboratory of Structure-Based Drug Design and Discovery of Ministry of Education (H.G., J.Z.), Shenyang Pharmaceutical University, Shenyang, Liaoning, People's Republic of China; and Division of Gastroenterology and Hepatology, Department of Pediatrics, Center for Developmental Therapeutics, Seattle Children's Research Institute, University of Washington School of Medicine, Seattle, Washington (J.Z.).
authors.forename: Ying
authors.initials: Y
authors.lastname: Peng
authors.affiliation: School of Pharmacy (D.L., Y.P.), School of Traditional Chinese Medicine (C.L.), and Key Laboratory of Structure-Based Drug Design and Discovery of Ministry of Education (H.G., J.Z.), Shenyang Pharmaceutical University, Shenyang, Liaoning, People's Republic of China; and Division of Gastroenterology and Hepatology, Department of Pediatrics, Center for Developmental Therapeutics, Seattle Children's Research Institute, University of Washington School of Medicine, Seattle, Washington (J.Z.).
authors.forename: Huiyuan
authors.initials: H
authors.lastname: Gao
authors.affiliation: School of Pharmacy (D.L., Y.P.), School of Traditional Chinese Medicine (C.L.), and Key Laboratory of Structure-Based Drug Design and Discovery of Ministry of Education (H.G., J.Z.), Shenyang Pharmaceutical University, Shenyang, Liaoning, People's Republic of China; and Division of Gastroenterology and Hepatology, Department of Pediatrics, Center for Developmental Therapeutics, Seattle Children's Research Institute, University of Washington School of Medicine, Seattle, Washington (J.Z.) jiang.zheng@seattlechildrens.org.
authors.forename: Jiang
authors.initials: J
authors.lastname: Zheng
mesh_terms: D000111:Acetylcysteine / Q000378:metabolism; D065767:Activation, Metabolic / Q000187:drug effects; D000818:Animals; D001646:Bile / Q000378:metabolism; D051544:Cytochrome P-450 CYP3A / Q000378:metabolism*; D005978:Glutathione / Q000378:metabolism; D006576:Heterocyclic Compounds, 4 or More Rings / Q000378:metabolism* / Q000652:urine; D006801:Humans; D007654:Ketoconazole / Q000494:pharmacology; D008239:Lysine / Q000378:metabolism; D008297:Male; D008862:Microsomes, Liver / Q000378:metabolism; D051381:Rats; D014556:Urine
chemical_list: D006576:Heterocyclic Compounds, 4 or More Rings; C569454:diosbulbin B; C465260:Cyp3a2 protein, rat; D051544:Cytochrome P-450 CYP3A; D005978:Glutathione; D008239:Lysine; D007654:Ketoconazole; D000111:Acetylcysteine