Transformations of zearalenone and alpha-zearalanol by homogenates of human prostate glands.

The present study applied high-pressure liquid chromatography, gas chromatography/mass spectrometry and crystallizations to constant specific activity for identification of the radiometabolites of tritiated zearalenone and alpha-zearalanol in homogenates of human prostate glands. Radiolabelled zearalenone or alpha-zearalanol (6.3 microM) was incubated for 30 min at 37 degrees C with prostatic homogenate in 5 ml 0.067 M phosphate buffer (pH 7.4) containing 0.5 mM oxidized or reduced NAD or NADP. Reduction of zearalenone occurred only with NADPH while oxidation of alpha-zearalanol was favoured both by NADP+ and NAD+. Separation of the substrates from their metabolites by high-pressure liquid chromatography showed the radioactivity of the metabolite of zearalenone to be associated with the alpha-zearalenol carrier while that of the alpha-zearalanol metabolite was found with the zearalanone carrier. Crystallizations to constant specific activity after isotopic dilution and gas chromatography/mass spectrometry confirmed the identity and the radiochemical purity of the alpha-zearalanol substrate and of its zearalanone metabolite. In contrast, the poor radiochemical purity of the zearalenone substrate and of its alpha-zearalenol metabolite was explained by the presence of large quantities of cis-isomer contaminants which were identified by gas chromatography/mass spectrometry. Formation of the cis-isomer of zearalenone was shown to occur spontaneously in incubations with boiled homogenates. The other stereospecific reductions or oxidations of the substrates were due to the prostatic enzymes which could be those involved in the C19-steroid hormone metabolism.