Pyrrolizidine alkaloids from Canarian endemic plants and their biological effects

Pyrrolizidine alkaloid (PA) producing plants belonging to the Boraginaceae (Echium wildpretti) and Asteraceae (Canariothamnus palmensis, Kleinia neriifolia, Pericallis appendiculata, Pericallis echinata, Pericallis hansenii, Pericallis multiflora, Pericallis steetzii and Senecio bollei) were selected to study their alkaloidal composition and the defensive properties (antifeedant and phytotoxic effects) of their ethanolic and alkaloidal extracts plus their isolated PAs against insects (Spodoptera littoralis, Leptinotarsa decemlineata, the aphids Myzus persicae and Rhopalosiphum padi) and Lactuca sativa seeds. We also tested the selective cytotoxic effects of these PAs on insect-derived Sf9 and mammalian CHO cells. Most of the insect antifeedant effects were found in the ethanolic extracts. The isolated PAs had species- and structure-dependent antifeedant effects and all of them decreased L. sativa radicle growth, suggesting a specific mode of action against insects and a generalized one against plants. Given the relatively low alkaloid content of these species, we assume that their herbivore defenses are not only alkaloid-based.