Observations on the occurrence and distribution of alkaloids in some genera and species of the tribe Crotalarieae (Fabaceae)

A general survey of alkaloids in the tribe Crotalarieae showed that useful chemotaxonomic data may be obtained. Although the pyrrolizidine alkaloids of Crotalaria L. have been studied in considerable detail, virtually nothing is known for the other, predominantly southern African genera. The genera Dichilus DC., Lebeckia Thunb., Melolobium Eckl. & Zeyh. and Polhillia Stirton were found to contain several alkaloids in sufficient quantities to warrant further investigation. The major alkaloids (presumably all of the quinolizidine type) seem to be characteristic for each of these genera. Aspalathus L., Buchenroedera Eckl. & Zeyh., Lotononis (DC.) Eckl. & Zeyh., Pearsonia Duemmer, Rafnia Thunb. and Wiborgia Thunb. appear to produce much smaller amounts. The possibility of obtaining useful information from these genera seems limited in view of the large quantities of plant material required to enable proper identification of the compounds. Methods of extraction and detection are described. The Rf values of the major alkaloids are given for the different thin-layer chromatographic systems used. Some preliminary identifications were confirmed by mass spectrometry