Identification of aphicidal sesquiterpenoids from Dendrobium nobile: Novel botanical insecticidal candidates against Acyrthosiphon pisum

Natural products serve as prime sources for discovering novel biopesticides to manage globally devastating agricultural pests. Given the growing prevalence of Acyrthosiphon pisum resistance to chemical insecticides, exploring eco-friendly botanical insecticides with unique modes of action has emerged as a pressing research priority. In this study, fifteen sesquiterpenoids ( 1 − 15 ) with insecticidal potential were characterized from D. nobile , including ten novel compounds ( 1 − 10 ) and five known ones ( 11 − 15 ). Structural determination of these compounds was accomplished using a combination of extensive spectroscopic techniques, quantum chemical calculations, and X-ray crystallographic analysis. Against A. pisum , compound 1 exerted favorable oral toxicity at 72 h (LC 50 = 22.24 μ g/mL), its efficacy being slightly higher than that of the commercial botanical insecticide Rote (LC 50 = 24.39 μ g/mL). Compounds 1 and 6 also demonstrated notable repellent activity toward A. pisum , attaining a RI of 1.00 at 100–400 μ g/mL. Treatment with compound 1 , shriveling of mouthparts and structural disruption of cuticles were observed in A. pisum . The inhibition of chitinase and α -AL, coupled with bidirectional regulation of GST may serve as potential mechanistic contributors to the appreciable insecticidal efficacy of compound 1 against A. pisum . In addition, the favorable safety profile of compound 1 toward pea crops provides support for its potential as a novel botanical pesticide candidate for the sustainable management of A. pisum . • Ten novel sesquiterpenoids ( 1 − 10 ) and five known metabolites ( 11 − 15 ) were identified from D. nobile . • Compound 6 is a highly aromatized cadinane-type sesquiterpenoid. • Compound 1 showed significant oral toxicity against A. pisum (LC 50 =22.24 μ g/mL) , comparable to Rotenone (LC 50 =24.39 μ g/mL). • Compounds 1 and 6 displayed potent repellent activity against A. pisum with a RI of 1.00 under 100–400 μ g/mL at 24 h.