The basic properties of many pyrrolizidine alkaloids are well known l.5, A lthough they have been isolated from representatives of about 13 plant fami lies, they occur most abundantly in the large genera sen~cio (Asteraceae), Crola/aria (Papilionaceae) and in many members of Boraginaceae including Heliotropium and CynoglossUlI1. More recently they have been detected in LepidopheraJ,4 Over 75 sp...