Toxicities of 4,5-Dihydroisoxazoles Against Root-Knot Nematodes and in Silico Studies of Their Modes of Action.

The present work sought to contribute to the development of new nematicides. Benzaldehydes were initially converted to nitrile oxides that underwent 1,3-dipolar cycloaddition reactions with methyl acrylate to generate 4,5-dihydroisoxazoles. In in vitro tests, methyl 3-phenyl-4,5-dihydroisoxazole-5-carboxylate () and methyl 3-(4-chlorophenyl)-4,5-dihydroisoxazole-5-carboxylate () increased the mortality of and second-stage juveniles (J2). Compounds and presented necessary concentrations of 398 and 501 μg mL, respectively, to kill 50% of J2 (LC values), while the value for carbofuran (positive control) was 168 μg mL. In in vivo tests, compounds and reduced the number of galls in tomato roots by 70 and 40%, respectively, and the number of eggs by 89 and 44%. Using an in silico approach, we showed that compounds and were toxic to the nematodes by binding to the allosteric binding sites of the agonist-binding domains of the nematode nicotinic acetylcholine receptors. These results opened up possibilities for further investigations aimed at developing novel commercial nematicides.