Transformation of herbicide pentoxazone by soil microorganisms

The metabolism of herbicide pentoxazone, 3-(4-chloro-5-cyclopentyloxy-2-fluorophenyl)-5-isopropylidene-1, 3-oxazolidine-2, 4-dione, was investigated by soil microorganisms with a liquid medium applied with radiolabeled pentoxazone. Four different types of Japanese agricultural soils were inoculated as the sources of microorganisms. There was no marked difference in the degradation 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 ring followed by decarboxylation) increased up to about 57% of applied dosage. After transient accumulation of A-0505, N-(4-chloro-5-cyclopentyloxy-2-fluorophenyl)-2-hydroxy-3-methylbutanamide (A-1374, a reduction product of A-0505) increased up to about 71%. The other metabolites, 4-chloro-5-(cyclopentyloxy)-2-fluoroaniline (A-0480, an aniline derivative), hydrated-pentoxazone (another hydrolysate at the carbonyl group of C4 in 1, 3-oxazolidine-2, 4-dione ring) and one unidentified compound were detected over 10% of applied dosage. Pentoxazone is likely to be readily transformed by ubiquitous soil microorganisms. These microbes which can proliferate in soil/water environment would play an important role in the progress of the degradation of pentoxazone.