Discovery and exploration of lignans from Dendrobiun chrysotoxum as new botanical insecticides against Acyrthosiphon pisum and Bursaphelenchus xylophilus.

Twenty-three lignans, including three new compounds (1-3), were isolated from Dendrobium chrysotoxum. Compound 1 exhibited significant contact and oral toxicities against Acyrthosiphon pisum, with LC50 values of 88.7 and 43.1 μg/mL, respectively, along with favorable repellent activity. Its aphicidal mechanism was associated with shrunken and wrinkled aphid cuticles, as well as altered activities of chitinase and digestive and detoxification enzymes. Meanwhile, compound 1 showed optimal nematicidal activity against Bursaphelenchus xylophilus, with an LC50 of 32.9 μg/mL. SEM, TEM and physiological assays revealed that compound 1 mainly killed nematodes mainly by destroying body structures, interfering with detoxification and antioxidant systems, and disrupting material and energy metabolism, thus inducing severe tissue damage and nematode death. Molecular dynamics simulations have revealed the potential mechanism of action of compound 1 with OfChtI. Meanwhile, 1 was highly safe for pea crops. Collectively, these findings may inform future development of environmentally friendly biopesticides for controlling aphids and nematodes.