Cyanox and Surecide are 4-cyanophenol esters of 0, 0-dimethyl phosphorothioic acid and 0-ethyl phenylphosphonothioic acid, respectively. Metabolism of these compounds in bean plants follows the typical pathway for organophosphorus compounds and in neither case does the nitrile group seem to be involved. There is, however, a remarkable quantitative difference in the rate of metabolism between the two compounds.Cyanox is lost rapidly from treated leaves by volatilization and metabolism, and the half-life is one day or less. In contrast, Surecide is much more persistent; the half-life is estimated to be about two weeks. Moreover, cyanoxon, the toxic metabolite of Cyanox, was detected as a transient intermediate to further degradation products, whereas surecide-oxon was not detected.Perhaps the bean plant has the capacity to degrade surecide-oxon as soon as it is produced or perhaps there is no pathway from Surecide to the oxon in bean plants. Desalkyl compounds and 4-cyanophenol are the major metabolites of both compounds.In neither case does photodegradation seem to play a significant role. Intact Cyanox is absorbed from water culture by bean plants, whereas there is practically no uptake of Surecide under the same conditions. Cyanox also dissipates from soil at a much faster rate than does Surecide, giving 4-cyanophenol and desalkyl compounds, whereas Surecide persists longer and gives practically only 4-cyanophenol as degradation products.
Twelve transformation products from phenthoate (PAP)[(CH30)2P(S)SCH(Ph)000C2H5]were identified by using intact mice, rat lliver subcellular fractions and peracid. Other than those previously reported, five products were newly found: (CH30)2P(0)SCH(Ph)000H by mice and microsome-NADPH system (mfo), CH3S(0)CH(Ph)000H by mice, HOCH(Ph)-000C2H5 by mice, mfo and cytosol, (CH3S)(CH30)P(0)SCH(Ph)000C2H5(PAP S-isomer) by mfo and (CH30)2P(0)SSCH(Ph)000C2H5 (phosphinyl disulfide) by peracid oxidation. Based on the identification of the products, the initial modifications seem to occur in five ways on PAP: i) hydrolysis of carboxy ethyl ester; ii) demethylation; iii) formation of phosphorus oxythionate; iv) cleavage of C-S bond; and v) isomerization. Further modifications result in various products. Twenty-three unidentified metabolites were found. PAP S-isomer by mfo and phosphinyl disulfide by peracid oxidation are considered to be produced in mice, but their instability does not allow their finding.
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