TY - JOUR A1 - Drzymala, Sarah A1 - Herrmann, Antje A1 - Maul, Ronald A1 - Pfeifer, Dietmar A1 - Garbe, L.-A. A1 - Koch, Matthias T1 - In vitro phase I metabolism of cis-zearalenone N2 - The present study investigates the in vitro phase I metabolism of cis-zearalenone (cis-ZEN) in rat liver microsomes and human liver microsomes. cis-ZEN is an often ignored isomer of the trans-configured Fusarium mycotoxin zearalenone (trans-ZEN). Upon the influence of (UV-) light, trans-ZEN isomerizes to cis-ZEN. Therefore, cis-ZEN is also present in food and feed. The aim of our study was to evaluate the in vitro phase I metabolism of cis-ZEN in comparison to that of trans-ZEN. As a result, an extensive metabolization of cis-ZEN is observed for rat and human liver microsomes as analyzed by HPLC-MS/MS and high-resolution MS. Kinetic investigations based on the substrate depletion approach showed no significant difference in rate constants and half-lives for cis- and trans-ZEN in rat microsomes. In contrast, cis-ZEN was depleted about 1.4-fold faster than trans-ZEN in human microsomes. The metabolite pattern of cis-ZEN revealed a total of 10 phase I metabolites. Its reduction products, α- and β-cis-zearalenol (α- and β-cis-ZEL), were found as metabolites in both species, with α-cis-ZEL being a major metabolite in rat liver microsomes. Both compounds were identified by co-chromatography with synthesized authentic standards. A further major metabolite in rat microsomes was monohydroxylated cis-ZEN. In human microsomes, monohydroxylated cis-ZEN is the single dominant peak of the metabolite profile. Our study discloses three metabolic pathways for cis-ZEN: reduction of the keto-group, monohydroxylation, and a combination of both. Because these routes have been reported for trans-ZEN, we conclude that the phase I metabolism of cis-ZEN is essentially similar to that of its trans isomer. As trans-ZEN is prone to metabolic activation, leading to the formation of more estrogenic metabolites, the novel metabolites of cis-ZEN reported in this study, in particular α-cis-ZEL, might also show higher estrogenicity. KW - Cis-ZEN KW - Phase I metabolism KW - LC-MS/MS KW - HRMS KW - Depletion kinetics PY - 2014 U6 - https://doi.org/10.1021/tx500312g SN - 0893-228X SN - 1520-5010 VL - 27 IS - 11 SP - 1972 EP - 1978 PB - Soc. CY - Washington, DC, USA AN - OPUS4-32071 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -