ANTIFEEDANT DELPHINIUM DITERPENOID ALKALOIDS - STRUCTURE-ACTIVITY-RELATIONSHIPS

The insect antifeedant and toxic activity of the Delphinium diterpene alkaloids 15-acetylcardiopetamine, cardiopetamine along with its amino alcohol, the beta,gamma unsaturated ketone, and the acetylated ketone derivatives were studied in Spodoptera littoralis and Leptinotarsa de cemlineata. Cardiopetamine and 15-acetylcardiopetamine strongly inhibi ted the feeding activity of S. littoralis and L. decemlineata, respect ively. Structure-activity studies with S. littoralis showed that the C 13 and C15 hydroxy substituents are essential features of the active m olecule, while a C13 hydroxy and/or a C15 acetate determined their eff ect on L. decemlineata. The C11 benzoate group enhanced the biological effect on both insect species. These alkaloids were not toxic to S. l ittoralis, while their toxicity on L. decemlineata was inversely corre lated with their antifeedant effects, the beta,gamma unsaturated keton e derivative being the most toxic. Cardiopetamine showed little antifu ngal action against several species of plant pathogens and did not hav e any mutagenic effects on Salmonella typhimurium by means of the Ames test.