Transformation of herbicide pentoxazone by soil microorganisms

The metabolism of herbicide pentoxazone, 3-(4-chloro-5-cyclopentyloxy-2-flu orophenyl)-5-isopropylidene-1,3-oxazolidine-2,4-dione, was investigated by soil microorganisms with a liquid medium applied with radiolabeled pentoxaz one. Four different types of Japanese agricultural soils were inoculated as the sources of microorganisms. There was no marked difference in the degra dation profiles among the four soils. Pentoxazone decreased rapidly, and N- (4-chloro-5-cyclopentyloxy-2-fluorophenyl)-3-methyl-2-oxobutanamide (A-0505 , a hydrolysate at the carbonyl group of C2 in 1,3-oxazolidine-2,4-dione ri ng followed by decarboxylation) increased up to about 57% of applied dosage . After transient accumulation of A-0505, N-(4-chloro-5-cyclopentyloxy-2-fl uorophenyl)-2-hydroxy-3-methylbutanamide (A-1374, a reduction product of A- 0505) increased up to about 71%. The other metabolites, 4-chloro-5-(cyclope ntyloxy)-2-fluoroaniline aniline (A-0480, an aniline derivative), hydrated- pentoxazone (another hydrolysate at the carbonyl group of C4 in 1,3-oxazoli dine-2,4-dione ring) and one unidentified compound were detected over 10% o f applied dosage. Pentoxazone is likely to be readily transformed by ubiqui tous soil microorganisms. These microbes which can proliferate in soil/wate r environment would play an important role in the progress of the degradati on of pentoxazone.