Synthesis of Potential Inhibitors Targeting Dihydroorotate Dehydrogenase as Herbicide Candidates

The ongoing discovery of effective agrochemicals remains one of the key activities to meet crop protection needs. Computer-aided molecular design, combined with systematic bioassay screening, was employed to identify novel herbicides targeting dihydroorotate dehydrogenase (DHODH). The hydroxypyrazole scaffold previously reported was also recognized by our virtual screening system, based on which its newly designed analogues, with access selectivity affinity for <i>Setaria viridis</i> DHODH over human DHODH, were chosen and synthesized. In vitro enzymatic assays revealed that <b>WF-8</b> and <b>WF-19</b> displayed relatively high potency against <i>Sv</i>DHODH, with IC₅₀ values of 64.97 and 91.52 μM, respectively. Preemergence herbicidal activity assessed using the Murashige and Skoog plant growth medium revealed that <b>WF-8</b>, <b>WF-30</b>, and <b>WF-32</b> had remarkable inhibitory effects (>66% at 100 μg/mL) against <i>Echinochloa crus-galli</i> and <i>S. viridis</i>, comparable to niazsulfuron and atrazine controls. Postemergence foliar application tests demonstrated that <b>WF-8</b> and <b>WF-19</b> had more than 65% fresh weight growth inhibition activity against <i>E. crus-galli</i> and <i>S. viridis</i> at 135 g ai/ha, with performance similar to that of mesotrione and nicosulfuron. Notably, <b>WF-8</b> displayed favorable crop safety toward the four tested dryland species, and molecular dynamics simulations further confirmed its binding interactions with <i>Sv</i>DHODH. These data support the claim that <b>WF-8</b> acts as a potential herbicide against DHODH.