Novel Design of Pyrazolyl-Containing Monoterpene Compounds to Enhance Antifungal Efficacy Against <i>Rhizoctonia solani</i>

In the fields of agriculture and forestry, there are major unknown risks associated with the toxicity of chemical pesticide residues and pathogen resistance. To address this issue, in this study, 52 novel pyrazole monoterpene compounds were obtained by organic synthesis of highly active monoterpene natural products and evaluated for their in vitro and in vivo antifungal activities and crystal structure analysis of compound <b>5b</b>. The results showed that compounds <b>4g</b> and <b>8f</b> exhibited remarkable antifungal activities against <i>Rhizoctonia solani</i>, with the corresponding EC₅₀ values reaching 4.27 and 4.81 mg/L. At the same time, the results of in vivo and in vitro experiments showed that both compounds <b>4g</b> and <b>8f</b> had good control effects against rice sheath blight. The antifungal activity of these compounds was preliminarily explored by scanning electron microscopy, molecular docking, enzyme activity determination, and cytotoxicity, indicating that these compounds have the potential for development into low-toxic antifungal drugs.