ISOXAFLUTOLE

Description

Isoxaflutole is a 4-benzoyl isoxazole molecule and is used as a pre- and early post-emergence herbicide for the control of a wide range of important broadleaf and grass weeds in maize (Zea mays), both in Europe and in North America. It is also registered for use in sugarcane in Central and South America (2–4). It causes characteristic bleaching of newly developed tissues of susceptible species followed by growth cessation and necrosis. Marketed as Balance for corn (maize) in the United States, and Merlin for corn in Europe; and in sugarcane, it mixes well with metolachlor, acetochlor, dimethenamid, and atrazine to complete the weed spectrum and to reduce the application rates of the latter compounds (2). Isoxaflutole also controls triazineresistant weeds in the field (4).

Uses

Isoxaflutole is an pesticide used to selectively control both grass and broad-leaved weeds in maize and sugar cane. Isoxaflutole is known to work by inhibiting the enzyme 4-Hydroxyphenylpyruvate dioxygenase (HPPD) which results in the disruption of pigment biosynthesis.

Uses

Herbicide.

Definition

ChEBI: Isoxaflutole is a member of the class of isoxazoles that is 1,2-oxazole substituted by a 2-(methanesulfonyl)-4-(trifluoromethyl)benzoyl group and a cyclopropyl group at positions 4 and 5, respectively. It is a 4-hydroxyphenylpyruvate dioxygenase inhibitor which is used as a herbicide for weed control in maize and sugarcane. It has a role as an EC 1.13.11.27 (4-hydroxyphenylpyruvate dioxygenase) inhibitor, a proherbicide and an agrochemical. It is a member of cyclopropanes, a member of isoxazoles, an aromatic ketone, a member of (trifluoromethyl)benzenes and a sulfone.

Pharmacology

Isoxaflutole is readily taken up by roots and foliar tissues and then rapidly degraded to a diketonitrile derivative (2-cyclopropyl-3-(2-mesyl-4-trifluoromethylphenyl)- 3-oxo propanenitrile) , which is translocated throughout the plant via xylem and phloem (2,3,6,8). It is this metabolite that inhibits HPPD (7), thereby depleting the plastoquinone pools in developing leaves. Plastoquinone is a cofactor in the desaturation of phytoene, levels of which increase in bleached leaves, concomitant with decreases in colored carotenoids (6). Although bleaching is the primary symptom associated with HPPD inhibition, subsequent growth suppression and necrosis are also believed to be a consequence (8).
Isoxaflutole also degrades to the diketonitrile derivative in the soil (3,8). The half-life of isoxaflutole in soil is dependent on soil type, pH, and moisture, ranging from 12 hours to 3 days under laboratory conditions (8). The physicochemical properties of isoxaflutole and of diketonitrile play an important role in both soil and herbicidal activity and selectivity (8).