Comparative metabolism of the Alternaria toxins altenuene and tentoxin in rat and human primary hepatocytes

The ubiquitously occurring food contaminants altenuene (ALT) and tentoxin (TEN) are recognized as emerging Alternaria mycotoxins, yet substantial data gaps remain when it comes to their toxicological behavior and toxicokinetic characteristics. This study aimed to compare and generate quantitative data on their hepatic metabolism and to obtain semi-quantitative insights into their metabolite profiles. To this end, primary rat and human hepatocytes were incubated with 10 {micro}M ALT or TEN over multiple time points up to 4 h. Both substrate depletion and metabolite identification revealed pronounced interspecies differences. The extent of ALT metabolism was significant, with an 88% and 57% decrease in rat and human hepatocytes after 4 h, respectively. In contrast, TEN showed extensive biotransformation in rats (67%) but only modest turnover in humans (27%) over the same period. Hepatocellular clearances were consistently higher for ALT than TEN, with hepatic extraction ratios indicating intermediate extraction for ALT and low extraction for TEN. High-resolution mass spectrometry combined with targeted analysis of selected metabolites annotated phase II conjugation as the predominant metabolic pathway for ALT and phase I oxidative metabolism for TEN, including mono- and double-metabolized species for the latter. Overall, these results provide a comprehensive characterization of ALT- and TEN-metabolism in hepatocytes, offering a foundation for future studies on their toxicological relevance and impact on human health.