Identification of [14C]quizalofop-P-tefuryl metabolites in goat urine by nuclear magnetic resonance and mass spectrometry

Abstract

The urinary metabolites of [14C]quizalofop-P-tefuryl, (JZ,S)-tetrahydrofurfuryl (R)-2-[4- [(6-chloro-2quinoxalinyl)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.

Enantioselectivity in degradation and transformation of quizalofop‐ethyl in soils

“…Quizalofop‐ethyl (ethyl ( R,S )‐2‐[4‐(6‐chloroquinoxalin‐2‐yloxy)phenoxy]propionate) is a widely used selective, postemergence aryloxyphenoxypropionate herbicide and is generally used to control annual and perennial grass weeds in potatoes, soybeans, sugar beets, peanuts vegetables, cotton, and flax. Quizalofop‐ethyl is easily hydrolyzed to quizalofop‐acid in soils, plants, and animals, which was documented to be the main herbicidal form . As seen in Figure , quizalofop‐ethyl and quizalofop‐acid has one chiral center each and thus consists of two enantiomers, where the herbicidal activity is mainly originated from the R ‐enantiomer .…”

Enantioselective Metabolism of Quizalofop-Ethyl in Rat

“…The half-life (T 1/2 ) of quizalofop ethyl on onion was about 0.8 day [12] . QE could be rapidly metabolized to its primary metabolite quizalofop-acid (QA) in soybean, cotton foliage and goat [11] , [13] . The study of potential effects of QE on the development of rats has been conducted, and the results showed a significant decrease in the number of fetuses alive and a significant increase in the number of rats with retained placenta [14] .…”

Differential enantioselectivity of quizalofop ethyl and its acidic metabolite: Direct enantiomeric separation and assessment of multiple toxicological endpoints

“…The (R) enantiomer is a more potent inhibitor against acetyl-CoA carboxylase (ACCase) in chloroplasts of target weeds thus exhibiting higher herbicidal activities [13]. Chiral free acids of AOPP herbicides [e.g., quizalofop acid (QA)] are actually active form [14], and can rapidly occur via hydrolysis of the esters in plants [13,15], animals [16] and environment media [17][18][19].…”