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A coumarin mercapturic acid, N-acetyl-S-(3-coumarinyl)cysteine, has been identified in the urine of coumarin-treated rats. [14C]Coumarin was applied by gavage as a single dose to male Wistar rats (10-150 mg/kg body weight). Twenty-four-hour urine was collected, and the deproteinized concentrate was analyzed for radiolabeled metabolites by HPLC. The new mercapturic acid metabolite is supposed to result from oxidative biotransformation of coumarin to its 3,4-epoxide and subsequent coupling with glutathione.

The excretion and tissue distribution of 14C-labelled chloroethanol were studied in rats following single oral administration of 5 and 50 mg/kg body weight. At both dose levels, the radioactivity was rapidly eliminated, mainly in the urine. On the first day after application of 5 mg/kg body weight, 77.2% of the dose were found in the urine, 1.7% in the faeces, and 1.0% as carbon dioxide in the expired air. Only 2.8% were excreted by these routes during the following 3 days. The residual radioactivity remaining in the tissues after 4 days was almost equally distributed and amounted to about 0.4% of the dose in the liver and 3% in the whole organism. At the higher dose level, excretion rates and tissue concentrations were similar. Examination of the urine by anion exchange chromatography on DEAE-Sephadex revealed two metabolites which were identified by GC/MS analysis as thiodiacetic acid and thionyldiacetic acid. These metabolites represented almost the whole urinary radioactivity. They were excreted in approximately equal amounts at the low dose whereas the thiodiacetic acid predominated with about 70% of the urinary radioactivity at the high dose. Unchanged chloroethanol, chloroacetic acid, S-carboxymethylcysteine and sulphonyldiacetic acid were not found in the urine.