Metabolism of the thiocarbamate herbicide SUTAN® in rats

Abstract

1. The metabolism of the thiocarbamate herbicide SUTAN° (butylate) was studied after administration of single oral doses of [isobutyl-1-¹⁴C]SUTAN to male and female rats.

2. The radiolabelled dose was rapidly absorbed and excreted, with 79% of the dose excreted in the urine in 72 h. The small percentages of radioactivity excreted in the faeces and as ¹⁴CO₂ were significantly higher (P≤0.05) in males than in females.

3. SUTAN was extensively metabolized, and no unmetabolized SUTAN was found in the urine. A total of 18 of the 29 urinary metabolites were identified, and identified metabolites represented 83–88% of the urinary radioactivity.

4. Diisobutylamine was the major urinary metabolite in both males and females, averaging 51% of the urinary radioactivity.

5. Other significant urinary metabolites included primary hydroxylated and tertiary hydroxylated diisobutylamines and a series of mercapturic acid pathway metabolites, including an S-glucuronide and several hydroxylated and unhydroxylated mercapturates.

6. Oxidations at the three alkyl groups produced a variety of minor urinary metabolites, and hydroxylation of the primary or tertiary carbon on the isobutyl groups, followed by an intramolecular reaction, generated a series of minor cyclized metabolites.