Diterpenoid alkaloids from Delphinium naviculare var. lasiocarpum with their antifeedant activity on Spodoptera exigua

A new lycoctonine diterpenoid alkaloid navicularine, along with eighteen known diterpenoid alkaloids, were isolated from the whole plant of Delphinium naviculare var. lasiocarpum. Their structures were elucidated on the base of extensive spectroscopic analysis (HR-ESI-MS and NMR) and comparison with data reported in the literature. Most of alkaloids were tested for their antifeedant activity against larvae of Spodoptera exigua (Hübner). The compound shawurensine showed considerably potent antifeedant activity (EC₅₀ = 0.42 and 0.81 mg/cm² in the choice test and no choice test, respectively).