Twenty-five diterpenoid alkaloids were isolated from the roots of two Aconitum species. The structures of seven new C 19 -diterpenoid alkaloids, apetaldines A-G (1-7), and 10 known alkaloids (8-17) from Aconitum apetalum and eight known alkaloids (18-25) from Aconitum franchetii var. villosulum were elucidated via HRESIMS, IR, and NMR data. Alkaloids 1-10, 15, 16, and 18-25 were screened for their antifeedant activity. Among the compounds tested, chasmanthinine (19) showed highly potent antifeedant activity with an effective concentration for 50% feeding reduction (EC 50 ) at 0.07 mg/cm 2 . The antifeedant structure-activity relationship of the diterpenoid alkaloids is also discussed. © 2017 The American Chemical Society and American Society of Pharmacognosy.