Zearalenone (ZON) is a potent estrogenic mycotoxin produced by several Fusarium species most frequently
on maize and therefore can be found in food and animal feed. Since animal production performance is
negatively affected by the presence of ZON, its detoxification in contaminated plant material or by-products of
bioethanol production would be advantageous. Microbial biotransformation into nontoxic metabolites is one
promising approach. In this study the main transformation product of ZON formed by the yeast Trichosporon
mycotoxinivorans was identified and characterized by liquid chromatography-tandem mass spectrometry (LCMS/MS)
and LC-diode array detector (DAD) analysis. The metabolite, named ZOM-1, was purified, and its
molecular formula, C18H24O7, was established by time of flight MS (TOF MS) from the ions observed at m/z
351.1445 [M-H] and at m/z 375.1416 [MNa]. Employing nuclear magnetic resonance (NMR) spectroscopy,
the novel ZON metabolite was finally identified as (5S)-5-({2,4-dihydroxy-6-[(1E)-5-hydroxypent-1-en-
1-yl]benzoyl}oxy)hexanoic acid. The structure of ZOM-1 is characterized by an opening of the macrocyclic ring
of ZON at the ketone group at C6. ZOM-1 did not show estrogenic activity in a sensitive yeast bioassay, even
at a concentration 1,000-fold higher than that of ZON and did not interact with the human estrogen receptor
in an in vitro competitive binding assay.