Identification of [¹⁴c]fonofos metabolites isolated from insecticide-treated culture media of the soil fungus rhizopus japonicus

The degradation of the insecticide [ring-¹⁴C]fonofos (Dyfonate) and [ethoxy-¹⁴C]fonofos into water-soluble substances was studied with the soil fungus Rhizopus japonicus. After 4 days of incubation of fungal cultures treated with the insecticide, 83% of the applied radioactivity partitioned into the water extraction phase of the culture media, while no radiocarbon could be detected in their hexane extraction phases. In noninoculated controls, however, only 6% of the applied radiocarbon was water-soluble, while 75% still appeared in the hexane extraction phase. After analysis by chromatographic and GC-mass spectrometric methods of water extraction phases of media from [¹⁴C]fonofos-treated fungal cultures, the presence of eight compounds was determined of which four were actual metabolites. Their structure, molecular weight, R_f values, and retention times relative to fonofos are shown.