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S-methylation of O,O-dialkyl Phosphorodithioic Acids: O,O,S-trimethyl Phosphorodithioate and Phosphorothiolate as Metabolites of Dimethoate in Mice

S-methylation of O,O-dialkyl Phosphorodithioic Acids: O,O,S-trimethyl Phosphorodithioate and Phosphorothiolate as Metabolites of Dimethoate in Mice

M Mahajna, G B Quistad, J E Casida

Chem Res Toxicol. Oct-Nov 1996;9(7):1202-6.

PMID: 8902277

Abstract:

O,O,S-Trimethyl phosphorodithioate and phosphorothiolate [(MeO)2P(S)SMe and (MeO)2P-(O)SMe, respectively are known from earlier studies to be impurities, delayed toxicants, and detoxication inhibitors in several major O,O-dimethyl phosphorodithioate insecticides. Our recent studies show extensive S-methylation of mono- and dithiocarbamic acids in mice, suggesting the possibility that phosphorodithioic acids such as (MeO)2P(S)SH might also undergo S-methylation. This possibility was examined in ip-treated mice with emphasis on the metabolites of dimethoate [(MeO)2P(S)SCH2C(O)NHMe], one of the most important organophosphorus insecticides. The urinary metabolites of dimethoate, which contains no P-SMe substituent, were found to include four compounds with P-SMe moieties identified by 31P NMR spectroscopy as MeO(HS)P(O)SMe, MeO(HO)P(O)SMe, (MeO)2P(S)SMe, and (MeO)2P-(O)SMe; the latter two compounds are also established by GC-MS as dimethoate metabolites in mouse urine, liver, kidney, and lung. Several approaches verified unequivocally that the previously unknown P-SMe metabolites in urine and tissues are due to in vivo S-methylation rather than to impurities. Studies with other O,O-dimethyl and O,O-diethyl phosphorodithioate insecticides established the analogous S-methylation pathway for ethion, malathion, phenthoate, phosalone, and phosmet in mice. Thus, metabolism of O,O-dialkyl phosphorodithioate insecticides in mammals is shown here for the first time to yield S-methyl phosphorodithioates and phosphorothiolates from in vivo S-methylation of the intermediate O,O-dialkyl phosphorodithioic acids.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP1219794816	Dimethoate-(O,O-dimethyl-d6)		1219794-81-6	Price

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