Oxidative Desulfuration and Dearylation of Selected Organophosphate Insecticides

Abstract

Desulfuration enzymes create powerful anticholinesterase metabolites of phosphorothionate $\begin{array}{*{20}{c}} {\,\,\,\,\,\,S}\\ {\,\,\,\,\,\,\,||}\\ {\left[ {{{\left( {RO} \right)}_2}POX} \right]\,} \end{array}$, phosphonothionate $\begin{array}{*{20}{c}} {\,\,\,\,\,\,\,\,\,\,\,S}\\ {\,\,\,\,\,\,\,\,\,\,\,\,||}\\ {\left[ {\left( {RO} \right)\left( Y \right)POX} \right]} \end{array}$, and phosphorodithioate $\begin{array}{*{20}{c}} {\,\,\,\,\,\,S}\\ {\,\,\,\,\,\,\,||}\\ {\left[ {{{\left( {RO} \right)}_2}PSX} \right]\,} \end{array}$ insecticides (Heath, 1961; O’Brien, 1960). In these formulae, “R” stands for an alkyl group such as methyl or ethyl, “X” stands for an alkyl or aryl group, and “Y” stands for a phenyl group (specifically for EPN, O-ethyl O-p-nitrophenyl phenylthiophosphonate). These three groups of organophosphorus compounds include several dozen compounds either being used for the management of insect-pest populations or in some stage of development for this purpose. The most comprehensive references to organophosphorus insecticides are those by Heath (1961) and O’Brien (1960). Proceedings of a conference on enzymatic oxidations of toxicants, which includes much information on drug and insecticide metabolism, was edited by Hodgson (1968). O’Brien (1962) has specifically discussed desulfuration reactions, with emphasis on the conversion of phosphorothionates to phosphates.

Journal Paper No. J-6584 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa 50010, USA. Projects No. 1351, 1435, and 1686. Preparation of this manuscript was supported by Public Health Service Research Grant ES-00205 from the Division of Environmental Health Sciences and North Central Regional Project NC-85.