Diterpenoid alkaloids as potential insecticidal constituents from Aconitum carmichaelii lateral roots against Acyrthosiphon pisum and their neurotoxicity-associated responses.

Botanical pesticides are increasingly being explored for integrated pest management with environment friendly properties, which attracts our interests on the discovery of insecticidal candidates from Aconitum carmichaelii lateral-root for pest control. Herein, we evaluated the insecticidal activity of A. carmichaelii lateral-root extracts against the pea aphid, Acyrthosiphon pisum. The Total Alkaloids fraction, in which diterpenoid alkaloids represented the largest annotated category (35.07%), showed insecticidal activity after oral exposure (24-h LC₅₀ = 0.82 μg/mL) and contact exposure (24-h LC₅₀ = 16.47 μg/mL). Seven known diterpenoid alkaloids were isolated from this fraction; among them, neoline and isotalatizidine were potential insecticidal constituents, with mortality rates of 63.3% and 60.0%, respectively, against A. pisum at 100 μg/mL. Biochemical assays showed that Total Alkaloids exposure reduced acetylcholinesterase and glutamate decarboxylase activities, induced acetylcholine accumulation, and decreased Ca2+/Mg2+-ATPase activity. Transcriptomic and metabolomic analyses further indicated that the aphicidal action of the Total Alkaloids fraction was associated with neuroactive ligand-receptor interactions, ion homeostasis disturbance, detoxification responses, and metabolic stress. Molecular docking predicted that isotalatizidine and neoline may interact with neurotoxicity-related protein models, including GAD67, AChBP, AChE, and RDL. The results indicated that diterpenoid alkaloids were representative active constituents of the Total Alkaloids fraction from A. carmichaelii, supporting its potential development as a biopesticide for aphid control, and its potential neurotoxic mechanisms involved changes in cholinergic signaling, GABA metabolism, and calcium-mediated ion homeostasis.