2-Pyrrolidineacetic Acid and Pyrrolizidine Alkaloids from Melampodium divaricatum.

The atypical, non-toxic pyrrolizidine alkaloid tussilagin and its isomers have been found in only a few plants of the Asteraceae (Roeder et al., 1981,1984; Passreiter et al., 1992; Roeder et al., 1993; Sener and Etgun, 1996; Wernery et al., 1997; Passreiter, 1998). Their possible biosynthetic precursor pyrrolidine-2-acetic acid and its methylester were isolated and identi"ed together with the pyrrolizidine alkaloids tussilagin, isotussilagin and their C-1 epimers neo-tussilagin and neo-isotussilagin from Arnica species and Tussilago farfara (Passreiter, 1992). Later on both types of compounds were also found in Neurolaena lobata (Passreiter, 1998).