Identification of metabolites of propyrisulfuron in rats

• The structures of 17 metabolites of propyrisulfuron were determined by HPLC with UV and RI detectors, tandem MS and NMR.
• Propyrisulfuron is different from other sulfonylurea herbicides regarding low water solubility.
• The metabolic patterns found are similar among sulfonylurea herbicides.

The metabolites found in the urine, feces and bile of male and female rats administered with 14C-labeled herbicide, propyrisulfuron [1-(2-chloro-6-propylimidazo[1,2-b]pyridazin-3-ylsulfonyl)-3- (4,6-dimethoxypyrimidin-2-yl)urea] were identified by high-performance liquid chromatography (HPLC) with the ultraviolet (UV) and radioisotope (RI) detectors, tandem mass spectrometry and nuclear magnetic resonance (NMR). Administered 14C was excreted into the urine (5.7–29.8%) and feces (64.6–97.4%). Urine and bile samples were concentrated and purified using a solid-phase extraction cartridge, and fecal homogenates were extracted using acetonitrile. Conjugates were hydrolyzed with enzyme or hydrochloric acid solution for identification. The proposed major metabolic reactions of propyrisulfuron are as follows: (1) hydroxylation of the pyrimidine ring, propyl group, and imidazopyridazine ring, (2) O-demethylation, (3) cleavage of the pyrimidine ring, and (4) glucuronic acid and sulfate conjugation. The metabolic patterns found are not different among sulfonylurea herbicides.