Design, Synthesis, Antifungal Activity, and Action Mechanism of Novel <scp>l</scp> -Perillyl Alcohol Derivatives Containing a Piperazine Moiety

Natural products serve as a vital source of compounds for the development of novel agricultural antifungal agents. In this study, a series of novel l -perillyl alcohol amide/hydrazide derivatives containing a piperazine moiety were designed and synthesized using l -perillyl alcohol as the structural scaffold. In vitro bioactivity assays demonstrated that most of the target compounds exhibited significant antifungal activity. Notably, compound F2 displayed broad-spectrum antifungal potency, with EC 50 values of 0.212, 2.35, 4.76, 2.31, and 1.90 μg/mL against Rhizoctonia solani, Valsa mali, Botrytis cinerea, Alternaria solani, and Sclerotinia sclerotiorum, respectively. Further in vivo evaluations confirmed that compound F2 exhibited favorable protective efficacy against R. solani, A. solani, and S. sclerotiorum, highlighting its potential as a novel agricultural antifungal agent. Mechanistic studies demonstrated that the antifungal activity of compound F2 against R. solani is achieved by disrupting the normal morphology and cellular structure of hyphae, increasing cell membrane permeability, inducing the generation and accumulation of reactive oxygen species, and impairing mitochondrial function, which ultimately inhibits the growth and proliferation of hyphae. Moreover, succinate dehydrogenase (SDH) enzymatic activity assays and molecular dynamic simulations further confirmed that compound F2 shares a highly analogous action mechanism and binding mode to SDH with boscalid. These findings offer valuable insights for developing novel SDH-inhibiting fungicides.