17.
The
in vitro metabolism of the chiral isomers of fonofos and fonofos oxon in the presence of mouse liver mixed-function oxidase and serum esterase was investigated. The metabolism of
35S-labeled phenyl-(
S)
P-fonofos mediated by mixed-function oxidase took place stereoselectively, resulting predominantly in (
R)
P-fonofos oxon. Similarly, (
R)
P-fonofos was converted to (
S)
P-oxon. In each case, however, a significant amount of racemization occurred. Other products were diphenyl disulfide and diphenyl disulfide oxide. In addition to stereospecificity, the oxidative metabolism of (
R)
P-fonofos proceeded at a rate faster than that of (
S)
P-fonofos. Stereoselective rate differences also were observed in mouse or rat serum-catalzyed degradation of the fonofos oxon enantiomers, the (
S)
P isomer being degraded about twofold faster than its enantiomer. The differences in toxicities of the isomers of fonofos and fonofos oxon were consistent with the
in vitro metabolism data.
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