Acifluorfen metabolism in soybean: Diphenylether bond cleavage and the formation of homoglutathione, cysteine, and glucose conjugates

Abstract

Metabolism of the substituted diphenylether herbicide, acifluorfen [sodium 5-(2-chloro-4-trifluoromethylphenoxy)-2-nitrobenzoate], was studied in excised leaf tissues of soybean [ Glycine max (L.) Merr. ‘Evans’]. Studies with [ chlorophenyl- 14C]- and [ nitrophenyl- 14C]acifluorfen showed that the diphenylether bond was rapidly cleaved. From 85 to 95% of the absorbed [ 14C]acifluorfen was metabolized in less than 24 hr. Major polar metabolites were isolated and purified by solvent partitioning, adsorption, thin layer, and high-performance liquid chromatography. The major [ chlorophenyl- 14C]-labeled metabolite was identified as a malonyl-β- d-glucoside (I) of 2-chloro-4-trifluoromethylphenol. Major [ nitrophenyl- 14C]-labeled metabolites were identified as a homoglutathione conjugate [ S-(3-carboxy-4-nitrophenyl) γ-glutamyl-cysteinyl-β-alanine] (II), and a cysteine conjugate [ S-(3-carboxy-4-nitrophenyl)cysteine] (III).