Cleavage of the Diketonitrile Derivative of the Herbicide Isoxaflutole by

J. Agric. Food Chem. 2000, 48, 4529−4534

4529

Cleavage of the Diketonitrile Derivative of the Herbicide Isoxaflutole by Extracellular Fungal Oxidases Christian Mougin,* Franc¸ ois-Didier Boyer, Eliane Caminade, and Rachel Rama† INRA, Unite´ de Phytopharmacie et Me´diateurs Chimiques, Route de saint-Cyr, 78026 Versailles Cedex, France

Isoxaflutole is a herbicide activated in soils and plants to its diketonitrile derivative, the active herbicide principle. The diketonitrile derivative undergoes cleavage to the inactive benzoic acid analogue. In this paper, it is established that an oxidative mechanism implicating two successive reactions in the presence of dimethyldioxirane can chemically initiate the cleavage of the diketonitrile. It is also shown that two white rot strains, Phanerochaete chrysosporium and Trametes versicolor, are able to convert the diketonitrile to the acid when cultured in liquid media. This main metabolite amounts to 24.6 and 15.1% of initial herbicide content after 12-15 days of culture. Another polar metabolite represents