Metabolic activation of the antibacterial agent triclocarban by cytochrome P450 1A1 yielding glutathione adducts

Nils Helge Schebb, Jaya B. Muvvala, Dexter Morin, Alan R Buckpitt, Bruce D. Hammock, Robert H. Rice

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


Triclocarban (3,4,4′-trichlorocarbanilide; TCC) is an antibacterial agent used in personal care products such as bar soaps. Small amounts of chemical are absorbed through the epidermis. Recent studies show that residues of reactive TCC metabolites are bound covalently to proteins in incubations with keratinocytes, raising concerns about the potential toxicity of this antimicrobial agent. To obtain additional information on metabolic activation of TCC, this study characterized the reactive metabolites trapped as glutathione conjugates. Incubations were carried out with 14C-labeled TCC, recombinant CYP1A1 or CYP1B1, coexpressed with cytochrome P450 reductase, glutathione-S-transferases (GSH), and an NADPH-generating system. Incubations containing CYP1A1, but not 1B1, led to formation of a single TCC-GSH adduct with a conversion rate of 1% of parent compound in 2 hours. Using high-resolution mass spectrometry and diagnostic fragmentation, the adduct was tentatively identified as 3,4-dichloro-3′-glutathionyl-4′-hydroxycarbanilide. These findings support the hypothesis that TCC is activated by oxidative dehalogenation and oxidation to a quinone imine. Incubations of TCDD-induced keratinocytes with 14C-TCC yielded a minor radioactive peak coeluting with TCC-GSH. Thus, we conclude that covalent protein modification by TCC in TCDD-induced human keratinocyte incubations is mainly caused by activation of TCC by CYP1A1 via a dehalogenated TCC derivative as reactive species.

Original languageEnglish (US)
Pages (from-to)1098-1102
Number of pages5
JournalDrug Metabolism and Disposition
Issue number7
StatePublished - 2014

ASJC Scopus subject areas

  • Pharmacology
  • Pharmaceutical Science
  • Medicine(all)


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