IDENTIFICATION OF [C-14] QUIZALOFOP-P-TEFURYL METABOLITES IN GOAT URINE BY NUCLEAR-MAGNETIC-RESONANCE AND MASS-SPECTROMETRY

The urinary metabolites of [C-14]quizalofop-P-tefuryl, (R,S)-tetrahydrofurfuryl (R)-2-[4-[(6-chloro-2-quinoxalinyl)oxy]phenoxy]propanoate, were identified. A lactating goat received three consecutive daily oral doses of quizalofop-P-tefuryl, equivalent to 330 ppm in the daily diet. The animal was sacrificed 24 h after the last administration. A major route of elimination was found to be via the urine, where two metabolites were observed by HPLC. The major metabolite was identified by mass and NMR spectrometry as quizalofop, a compound resulting from hydrolysis of the tetrahydrofurfuryl alcohol moiety of quizalofop-P-tefuryl. The minor metabolite was more polar than quizalofop, and its molecular weight was 16 amu higher than that of quizalofop. This metabolite was identified as a hydroxy derivative of quizalofop. Cochromatographic comparison of the minor metabolite with synthetic (R)-2-[4-[(6-chloro-3-hydroxy-2-quinoxalinyl)oxy]phenoxy]propanoic acid, prepared in three steps, revealed that hydroxylation had occurred at the 3-position of the quinoxaline ring.