The taxonomic significance of alkaloids in the South American genus Anarthrophyllum

The major alkaloids of the genus Anarthrophyllum have been identified for the first time. More than 28 alkaloids were detected in nine extracts from six different species. All the extracts showed a typical α-pyridone pattern, with sparteine, β-isosparteine, N-methylcytisine, cytisine, 5,6-dehydrolupamine, lupanine, N-formylcytisine, N-acetylcystisine and anagyrine as major alkaloids. Lupinine, epilupinine, ammodendrine and lamprolobine were also present as major compounds in some of the extracts. Tetrahydrocytisine and structurally related alkaloids occur in most of the species, but rarely in more than trace amounts. The discovery of α-pyridone alkaloids in Anarthrophyllum has important taxonomic implications. It provides evidence that the true affinities of the genus are with the Argyrolobium group (presently in the tribe Crotalarieae) and Lupinus (tribe Genisteae) with which it shares, in addition to the alkaloid pattern, circumcauline stipules, a trifid lower lip of the calyx and a similar chromosome number. The alkaloid data agree with morphological evidence that Anathrophyllum and Sellocharis will be better placed near Lupinus in the tribe Genisteae.