Animal metabolism of propham (isopropyl carbanilate): The fate of residues in alfalfa when consumed by the rat and sheep

Abstract

Alfalfa was root-treated with [ 14C]propham (isopropyl carbanilate[ 14C-phenyl(U)]) for 7 days and then harvested and freeze-dried. Rats and sheep were orally given either 14C-labeled alfalfa roots ([ 14C]root) or 14C-labeled alfalfa shoots ([ 14C]shoot). When the [ 14C]root was given, 6.5–11.0% of the 14C was excreted in the urine and 84.6–89.4% was excreted in the feces within 96 h after treatment. Less than 3% of the 14C remained in the carcass (total body—gastrointestinal tract and contents) 96 h after treatment. When [ 14C]shoot was given, 53.2–55.2% of the 14C was excreted in the urine, 32.1–43.4% was excreted in the feces, and the carcass contained 0.2–1.1% of the 14C 96 h after treatment. When the insoluble fraction (not extracted by a mixture of CHCl 3, CH 3OH, and H 2O) of both alfalfa roots and shoots was fed to rats, more than 86% of the 14C was excreted in the feces and less than 3% remained in the carcass 96 h after treatment. The major radiolabeled metabolites in the urine of the sheep fed 14C shoot were purified by chromatography and identified as the sulfate ester and the glucuronic acid conjugates of isopropyl 4-hydroxycarbanilate. Metabolites in the urine of the sheep treated with [ 14C]root were tentatively identified as conjugated forms of isopropyl 4-hydroxycarbanilate, isopropyl 2-hydroxycarbanilate, and 4-hydroxyaniline. The combined urine of rats dosed with [ 14C]shoot and [ 14C]root contained metabolites tentatively identified as conjugated forms of isopropyl 4-hydroxycarbanilate, isopropyl 2-hydroxycarbanilate, and 4-hydroxyaniline.