Design, Synthesis, and Mechanism of Action Study of Novel Tioxazafen-Derived Nematicides Bearing Benzoxazine Moiety

Global agriculture faces severe threats from plant-parasitic nematodes. However, the limited structural diversity of commercial nematicides and rising nematode resistance highlight an urgent need for novel compounds with innovative modes of action. To identify potent alternatives, 30 tioxazafen-derived were synthesized with tioxazafen as the lead scaffold. Among these derivatives, Pot experiments verified that compound A18 exhibited prominent nematicidal activity against Meloidogyne incognita, with control efficacies reaching 66.95% and 83.33% at concentrations of 50 mg/L and 100 mg/L, respectively. The activity was comparable to that of the positive control tioxazafen (67.30% and 88.89%) and superior to that of cyclobutrifluram (61.11% and 73.68%). Preliminary mechanistic investigations demonstrated that these compounds significantly impaired the locomotor activity of Caenorhabditis elegans. Furthermore, alterations in oxidative stress-associated biochemical markers demonstrated that several active compounds elicited nematode toxicity via potentiated oxidative damage.