Toxic metabolite formation from Troglitazone (TGZ): new insights from a DFT study.

The hepatotoxicity of Troglitazone (TGZ) has been ascribed to the formation of reactive metabolites, and the primary reactive metabolite of TGZ has been confirmed to be an o-quinone methide. Oxidation of the chromane moiety is also known to produce quinone containing metabolites. Quantum chemical studies have been performed to analyze the possible reaction pathways for the metabolism of the TGZ side chain, 6-hydroxy-2,2,5,7,8-pentamethylchromane (HPMC). From this analysis, a new pathway including oxidation at the C13 and C14 atoms of HPMC has been proposed for the formation of o-quinone methide (M2), while oxidation at the hydroxyl group leads to the formation of the quinone metabolite (M7). o-Quinone methide reactive metabolites have been shown to be more electrophilic at the reactive methylene center using quantum chemically estimated parameters.