Antifeedant Activity of Camptothecin and its Semisynthetic Derivatives Against Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae) Larvae

The antifeedant activities of camptothecin 1 and its semisynthetic derivatives 2-12 were evaluated against an economically important pest, Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae). Simple chemical conversions were carried out on the natural camptothecin obtained from a Chinese medicinal plant Camptotheca acuminate. These conversions focused on different functional modified sites in the camptothecin skeleton considered to be important for the biological activity. Among all the tested compounds, compounds 4, 5, 7 and 8 displayed more promising antifeedant activity than camptothecin 1. Especially compound 7 was found to exhibit exceptionally potent antifeedant activity with AFC50 values of 92.03μg/mL, compared to 1 and toosendanin, a commercial insecticide derived from Melia azedarach (IC50 528.40μg/mL and 91.68μg/mL, respectively). The different antifeedant activity range of compounds 1-12 indicated that variation of chemical structures in the camptothecin skeleton markedly affected the activity profiles of this compound class, and some preliminary SAR information has been observed from it.