Biotransformation, excretion kinetics, and tissue distribution of an N-pyrrolo[1,2-c]imidazolylphenyl sulfonamide herbicide in rats.

TY029, an N-pyrrolo[1,2-c]imidazolylphenyl sulfonamide herbicide, controls economically important weeds through inhibition of protoporphyrinogen oxygenase. Due to the potential for exposure to this compound in food and animal feed items, a rat metabolism study was required to define the biotransformation of this compound. Animals were exposed to single 50- and 2-mg/kg doses of TY029 [hydantoin-5-(14)C] by oral gavage. About 90% of the administered dose was excreted within 96 h after oral administration. Excretion plateaued after 48 h, and the cumulative sum of urinary or fecal excretion after 48 h was less than 5% of the orally administered dose. TY029 yielded seven major metabolites. While some metabolites were formed by epimerization around chiral centers, others were generated through hydrolytic bond cleavage and hydroxylations and subsequent oxidation of hydroxyl groups to carboxylic acids. One metabolite, about 6.1% of the dose, was observed only in the urine from low-dose female rats. This metabolite was characterized as a glutamate conjugate of an extensively oxidized analog of TY029. With the exception of the glutamate conjugate, the same metabolites were observed in the excreta of all dose groups. However, the relative ratios of the metabolites were different between various dose groups.