The objectives of this work are to isolate and determine the structures of pyrrolizidine alkaloids of various Heliotropium, Crotalaria, Cynoglossum, Trichodesma, Senecio and other plant genera indigenous to Israel and to screen these compounds for anti-tumor activity. Ultimately, it is hoped that a structure-activity relationship may be developed for pyrrolizidine alkaloids. The following alkaloids have thus far been characterized: eropine, heliosupine, echinatine, monocrotaline, crosemperene and lasiocarpine. In addition, several eremophilane sesquiterpenes have been isolated from a specie of Senecio: trans-9-oxo-furanoeremophilane, 8 alpha-ethoxy-10 alpha H-eremophilenolide and 3 alpha-angeloyloxy-9-oxo-10 alpha H-furanoeremophilane. Other plants presently under investigation in this project are: Artemisia herba abla, Varthemica montana, thymus decussatus and Inula viscosa.