Metabolism of Metolachlor by the Fungus Cunninghamella elegans

Abstract.

The metabolism of metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] by the fungus Cunninghamella elegans ATCC 36112 was determined. The six metabolites identified comprised 81% of the total [¹⁴C]-metolachlor metabolized by C. elegans. These metabolites were separated by reversed-phase high-performance liquid chromatography and identified by ¹H nuclear magnetic resonance, UV, and atmospheric pressure chemical ionization (APCI) mass spectral techniques. Metabolites I and II were identified as stereoismers of 2-chloro-N-[2-ethyl-6-hydroxymethylphenyl)]-N-(2-hydroxy-1-methylethyl)acetamide. Metabolites III and IV have been tentatively identified as stereoismers of 2-chloro-N-[2-(1-hydroxyethyl)-6-methylphenyl]-N-(2-methoxy-1-methylethyl)acetamide. Metabolites V and VI were identified as stereoismers of 2-chloro-N-(2-ethyl-6-hydroxy-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide and 2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-hydroxy- 1-methylethyl)acetamide, respectively. The fungus Cunninghamella elegans was able to biotransform metolachlor. Multiple site oxidation of metolachlor by C. elegans occurred predominantly by O-demethylation of the N-alkyl side chain and benzylic hydroxylation of the arylalkyl side chain.