抄録
The racemic, (+)- and (-)-forms of cyanofenphos (O-p-cyanophenyl O-ethyl phenyl-phosphonothioate) were rapidly metabolized in the rat by cleavage of P-O-aryl linkage, cleavage of P-O-alkyl linkage and conjugation of p-cyanophenol with sulfuric acid. There was a marked difference in the proportion of the major urinary metabolites, p-cyanophenol and p-cyanophenyl sulfate, with three forms of cyanofenphos.
The three forms of cyanofenphos were metabolized at almost equal rates in rat liver microsomes-NADPH system. (+)-Cyanofenphos underwent oxidation of P=S to P=O and cleavage of P-O-aryl linkage predominantly. In contrast, the (-)-isomer was converted to the corresponding oxon analog by mixed function oxidase, and then the oxon analog was rapidly hydrolyzed to p-cyanophenol by microsomal arylesterase-type enzyme, This microsomal enzyme had a remarkable selectivity in hydrolyzing (-)-cyanofenphos axon versus the (+)-isomer. Stereoselectivity in the metabolism of the cyanofenphos isomers in the rat appears likely to be mainly due to selective hydrolysis of the (-)-oxon analog by the arylesterase-type enzyme.
