Multi-bioactivity of sesquiterpenes from Zanthoxylum piasezkii: contact toxicity, repellent and antifeedant effects against Tribolium castaneum via odorant receptor modulation

Plant-derived secondary metabolites, particularly monoterpenes and sesquiterpenes, have been proven effective for controlling stored-product pests. However, their application has been limited because their mechanisms of action remain unclear. In this work, three sesquiterpenes were isolated from Zanthoxylum piasezkii Maxim. oils and identified as α-cadinol, τ-cadinol and α-cadinol methyl ether by nuclear magnetic resonance (NMR). Thereafter, the contact toxicity, repellent and antifeedant activities of the three sesquiterpenes were evaluated against the red flour beetle, Tribolium castaneum , and their underlying mechanisms were investigated using molecular dynamics simulations (MDs). Insecticidal assay showed that α-cadinol exhibited the strongest contact toxicity against Tribolium castaneum adults with an LD 50 value of 10.53 μg/adult. In addition, τ-cadinol showed significant repellent activity, with efficacy during the 4-h exposure comparable to that of the positive control and, at 3.15 nL/cm 2 , significantly higher than that of the positive control. In addition, α-Cadinol methyl ether demonstrated the most potent antifeedant activity, with an EC 50 value of 115.39 μg/mL. Notably, α-cadinol, τ-cadinol and α-cadinol methyl ether exhibited strong binding free energies with the odorant receptor of T. castaneum (TcasOR, D6X4X7), measuring −23.21 ± 3.53, −28.40 ± 2.68, and −30.37 ± 4.05 kcal/mol, respectively, indicating that all three compounds could bind to the protein. Moreover, to explore the anti-insect mechanism, functional verification of ion channels revealed that the three sesquiterpenes mediate channel opening, leading to Na + influx and the generation of olfactory electrical signals. Na + selectivity was primarily determined at the channel entrance, whereas the channel exit exhibited no selectivity between Na + and K + . The findings suggest that α-cadinol, τ-cadinol, and α-cadinol methyl ether hold promise as lead compounds for environmentally benign botanical insecticides or pest behavior modulators, providing a theoretical basis for developing novel strategies against stored-product pests.