HT-2 Toxin 4-Glucuronide as New T-2 Toxin Metabolite: Enzymatic Synthesis, Analysis, and Species Specific Formation of T-2 and HT-2 Toxin Glucuronides by Rat, Mouse, Pig, and Human Liver Microsomes

Abstract

Glucuronides of the mycotoxin T-2 toxin and its phase I metabolite HT-2 toxin are important phase II metabolites under in vivo and in vitro conditions. Since standard substances are essential for the direct quantitation of these glucuronides, a method for the enzymatic synthesis of T-2 and HT-2 toxin glucuronides employing liver microsomes was optimized. Structure elucidation by nuclear magnetic resonance spectroscopy (NMR) and mass spectrometry revealed that besides T-2 toxin glucuronide and HT-2 toxin 3-glucuronide also the newly identified isomer HT-2 toxin 4-glucuronide was formed. Glucuronidation of T-2 and HT-2 toxin in liver microsomes of rat, mouse, pig, and human was compared and metabolites were analyzed directly by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). A distinct, species specific pattern of glucuronidation of T-2 and HT-2 toxin was observed with interesting interindividual differences. Until recently, glucuronides have frequently been analyzed indirectly by quantitation of the aglycone after enzymatic cleavage of the glucuronides by β-glucuronidase. Therefore, the hydrolysis efficiencies of T-2 and HT-2 toxin glucuronides using β-glucuronidases from Helix pomatia, bovine liver, and Escherichia coli were compared.