A one-electron oxidation of carcinogenic nonaminoazo dye Sudan I by horseradish peroxidase.

OBJECTIVES: The aim of the study was to examine oxidation of carcinogenic Sudan I by peroxidase and characterize the structure of its two major peroxidase-mediated metabolites. Another target of the study was to evaluate a mechanism of this oxidation. METHODS: Thin layer chromatography (TLC) and high performance liquid chromatography (HPLC) with ultraviolet (UV) and visible (VIS) detection was employed for the separation of Sudan I metabolites formed by peroxidase. UV/ VIS-, and mass- spectroscopy as well as nuclear magnetic resonance (NMR) were used to characterize structures of two major Sudan I metabolites. RESULTS: Peroxidase oxidizes Sudan I by a one electron oxidation to eight products. Two major Sudan I metabolites were isolated by TLC on silica gel and HPLC and structurally characterized. The major product formed during the Sudan I oxidation by peroxidase is Sudan I metabolite M 2 , which corresponds to a Sudan I dimer molecule. The second major metabolite (M 1 ) is the product of secondary, enzyme independent reactions, being formed from the Sudan I dimer that lost the benzenediazonium moiety. CONCLUSIONS: The data are the first report on structural characterization of Sudan I metabolites formed by its oxidation with peroxidase.