Quantification of Urinary Aflatoxin B1 Dialdehyde Metabolites Formed by Aflatoxin Aldehyde Reductase Using Isotope Dilution Tandem Mass Spectrometry

The aflatoxin B1 aldehyde reductases (AFARs), inducible members of the aldo-keto reductase superfamily, convert aflatoxin B1 dialdehyde derived from the exo- and endo-8,9-epoxides into a number of reduced alcohol products that might be less capable of forming covalent adducts with proteins. An isotope dilution tandem mass spectrometry method for quantification of the metabolites, C-8 monoalcohol, dialcohol, and C-6a monoalcohol, was developed to ascertain their possible role as urinary biomarkers for application to chemoprevention investigations. This method uses a novel 13C17-aflatoxin B1 dialcohol internal standard, synthesized from 13C17-aflatoxin B1 biologically produced by Aspergillus flavus. Chromatographic standards of the alcohols were generated through sodium borohydride reduction of the aflatoxin B1 dialdehyde. This method was then explored for sensitivity and specificity in urine samples of aflatoxin B1-dosed rats that were pretreated with 3H-1,2-dithiole-3-thione to induce the expression of AK...