Thioethers as urinary metabolites of thiophene and monobromothiophenes

1. Thiophene and its two monobromo derivatives were administered to rats and the amounts of thioether excreted in urine were measured by an assay based on Ellman's reagent. This assay, which involves extraction and hydrolysis, was validated by determining extraction and hydrolysis efficiencies for several authentic thioethers including N-acetyl-S-(2-thienyl)-L-cysteine, a previously reported metabolite of thiophene and 2-bromothiophene. 2. The thioethers present in urine of animals dosed with thiophenes have been examined chromatographically. Contrary to previous reports, the present work indicates that S-substituted, N-acetyl-L-cysteines (mercapturic acids) are not important thioether metabolites of thiophene in rats, and the small quantity of such compounds formed does not include either of the two simple S-thienyl derivatives. 3. The two monobromo thiophenes form higher proportions of thioethers than does thiophene, and one of these thioethers, arising from 3-bromothiophene, was identified, chromatographically, as N-acetyl-S-(3-thienyl)-L-cysteine.