In vitro metabolism of flucetosulfuron by artificial gastrointestinal juices

To investigate the metabolism of pesticides by gastrointestinal (GI) juices, artificial GI juices were incubated with threo- and erythro-isomers of flucetosulfuron. The metabolites produced in each reaction mixture of artificial GI juices were unambiguously identified using liquid chromatography-tandem mass spectrometry. Flucetosulfuron was observed to be stable in saliva. However, in the intestinal juices, approximately 18% of flucetosulfuron was degraded, producing N-(4,6-dimethoxypyrimidin-2-ylcarbomoyl)-2-(2-fluoro-1-hydroxypropyl)pyrimidine-3-sulfonamid (M1). In artificial gastric juices, about 85% of flucetosulfuron was rapidly degraded, producing the metabolites 2-(2-fluoro-1-hydroxypropyl) pyridine-3-sulfonamide (M2), 4,6-dimethoxypyrimidin-2-amine (M3), and 2-fluoro-1-(3-sulfamoylpyridin-2-yl)propyl 2-methoxyacetate (M4). These results indicate that the sulfonylurea bridge and ester bond of flucetosulfuron are hydrolyzed in artificial GI juices. No significant differences were noted in the degradation patterns between the two isomers of flucetosulfuron in the artificial GI juices that were tested. Considering the rapid degradation of flucetosulfuron in vitro by artificial GI juices, it is likely that there would be no significant absorption of flucetosulfuron from the GI tract into the blood stream after oral administration.