An assessment of the biotransformation and bioavailability of zearalenone and its modified forms using the Caco-2 cell line

Zearalenone (ZEN) is a common Fusarium mycotoxin that is found in cereal products and has xenoestrogenic properties. ZEN's toxicity and interaction with the environment in vivo have been widely studied, but fewer data are available on its metabolites. This study aimed to evaluate the intestinal permeability of ZEN, its hydrogenated metabolites, and its glucosidic conjugates and qualitatively assess the metabolism of these compounds in the epithelium. A monolayer of Caco-2 cells was used as the bioavailability prediction model. The MTT cytotoxicity assay (metabolic activity assessment) was used to determine the concentrations of the test compound that do not reduce cell viability. Permeability coefficients were determined based on the compounds' concentrations in the acceptor compartment. Cell lysates were analysed to obtain a qualitative assessment of the potential of ZEN metabolisation in epithelial cells. Quantitative and qualitative analyses were performed using LC-HRMS. The results indicate the efficient and variable intestinal permeability of ZEN and its hydrogenated metabolites. A lower permeability of the glucoside metabolites compared with the native forms was observed. Glucosidic conjugates were characterised by higher efflux ratios, suggesting more efficient intestinal reflux. Concerning the metabolism occurring in the intestinal epithelium model, the hydrolysis of ZEN derivatives and the release of native toxins, the bilateral conversion between ZEN and α-zearalenol (α-ZOL) / β-zearalenol (β-ZOL), and the presence of glucuronide metabolites were observed. Sulphated metabolites of α-ZOL and β-ZOL were also detected.