Antifeedant C20 diterpene alkaloids

We have tested the insect antifeedant and toxic activity of 21 C, diterpenoid alkaloids on Spodoptera littoralis and Leptinotarsa decemlineata. The antifeedant effects of the test compounds were structure- and species-dependent. The most active antifeedants to L. decemlineata and S. littoralis were the rearranged form of hetisine (20; EC50 = 1.7 mug/cm(2)) and 19-oxodihydroatisine (9; EC50 = 0.1 mug/cm(2)), resp. Glandulosine (8) moderately affected orally injected S. littoralis larvae. A few compounds (13-oxocardiopetamine (4), 9, and atisinium chloride (13)) had cytotoxic effects to insect-derived Sf 9 cells with varying degrees of selectivity with respect to mammalian CHO cells. Compounds 4 and 15,22-O-diacetyl-19-oxodihydroatisine (10) increased Trypanosoma cruzi mortality. Our results support the plant protective role of C-20 diterpenoid alkaloids and open a new field for parasite control strategies.