Fenthion (Bayer 29493, Mercaptophos, Baytex, Lebaycid) (0,0-Dimethyl 
O-[{ 3-methyl-4-methyl-mercaptophenyl] phosphorothioate) 
Sulfoxide appeared as the chief metabolite of fenthion when the latter 
was applied to bean plants. In addition to the sulfoxide, the sulfone, and 
the sulfoxide and sulfone of the phosphate, and the S-methyl isomeride were 
also found. The latter was also oxidized to the corresponding sulfone and 
sulfoxide (Francis and Barnes, 1963; Niessen et al., 1962). When applied 
to cabbage and tea plants, metabolism was rapid. The sulfoxide and sulfone 
were the main metabolites although some oxidation of thiophosphate to phos- 
phate also occurred (Tomizawa, 1962). On rice plants, only about 10% of 
the applied material remained after six hours. The major part of the meta- 
bolites in both rice leaf and ear was the sulfoxide and sulfone. The S- 
methyl isomer was also found in ears. Using labeled material, almost half 
of the activity was found in bran; 6.5% in the husk, and 14.7% in polished 
rice. Fourteen days after application, water soluble metabolites were 
found in the rice grains: phosphate and thiophosphate, dimethyl phosphate 
and thiophosphate, demethyl fenthion, and an unknown compound (Fikudo et 
al., 1965). 
When rats, houseflies, the German cockroach, boll weevil, and cotton 
plant were exposed to p32-1abeled fenthion, five compounds were found in 
different proportions (Brady and Arthur, 1961). 
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