The mechanism for the hepatotoxicity of trovafloxacin remains unresolved. Trovafloxacin contains a cyclopropylamine moiety which has a potential to be oxidized to reactive intermediate(s) although other putative elements may exist. In this study, a drug model of trovafloxacin containing the cyclopropylamine substructure was synthesized. Chemical oxidation of the drug model by K(3)Fe(CN)(6) and NaClO revealed that both oxidants oxidize this drug model to a reactive alpha,beta-unsaturated aldehyde, 11. The structure of 11 was fully elucidated by LC/MS/MS and NMR analysis. These results suggested that P450s with heme-iron center and myeloperoxidase generating hypochlorous acid in the presence of chloride ion are capable of bioactivating the cyclopropylamine moiety of trovafloxacin. This deleterious metabolism may lead to eventual hepatotoxicity.