Biotransformation and Fate of Mycotoxins

Abstract

Mycotoxins are well known lo undergo biotransformations in humans and animal species. These bioconversions generally take place in liver or the gastrointestinal tract and are a consequence of the action of tissue enzymes or microflora. Metabolites can correspond to oxidative derivatives which are produced in liver, such as hydroxymetabolites of aflatoxin B₁ or ochratoxin A. In some cases highly reactive epoxides represent the first step in the formation of carcinogenic intermediates like exo epoxides of aflatoxins. Hepatic and intestinal phase II enzymes, includmg transferases, are involved in the conjugation of the above-mentioned oxidative metabolites. In this respect, they are generally considered as detoxifying enzymes: glucuronidation of deacetylated trichothecenes or hydroxy-aflatoxins, or glutathione conjugation of epoxides. Microbial flora participate generally in toxicological deactivation pathways such as hydrolysis of ochratoxin A or deepoxidation of trichothecenes. In the case of other mycotoxins. there is of lack of information regarding the fate of patulin, fumonisins or rubratoxin B. The major metabolism of zearalenone consists of reduction leading to estrogenic zearalenols which is characterized by large interspecies differences. Consequences of biotransformations are reviewed in term of residues of metabolites occurring in animal-derived food products such as milk or eggs.