Pyrrolizidine alkaloids from Neurolaena lobata

Neurolaena lobata was investigated for the occurrence of pyrrolizidine alkaloids. The untypical methyl ester alkaloids tussilagine, isotussilagine and their possible biosynthetic precursor 2-pyrrolidineacetic acid were found in the methanolic leaf extract. As previously found for Arnica species and Tussilago farfara, all methyl esters are artifacts derived from the corresponding acids during Soxhlet extraction. The occurrence of toxic necines, often found in the Senecioneae, could be ruled out.