Four pyrrolizidine alkaloids have been isolated from Senecio cacaliaster and their structures analysed by spectroscopic methods (IR, mass, 1H, 13CNMR). One of them is new and the name sencalenine (3) is proposed. Alkaloids O7-senecioylretronecine (1) and 7-senecioyl-9-sarracinylretronecine (2) have recently been identified elsewhere. The fourth is bulgarsenine (4) which was isolated from a Senecio species before. © 1984.