Mercapturic acid occurrence in fish bile. A terminal product of metabolism of the herbicide molinate.

1. Molinate sulphoxide, an oxidation metabolite of molinate, is cleaved in vitro by Japanese carp liver cytosol fraction, indicating the presence of GSH-S-transferase activity, since cleavage of the sulphoxide is dependent on the amount of supernatant protein and GSH in the assay medium. 2. Molinate mercapturate was identified as a major metabolite recovered from bile of carp treated with molinate. 3. The structure of the mercapturate was established by co-chromatography with an authentic standard in three t.l.c. systems and by mass spectrometry.