SEED FLAVONOIDS OF THE PODALYRIEAE AND LIPARIEAE (FABACEAE)

A study of the phenolic compounds of the closely related papilionoid t ribes, Podalyrieae and Liparieae, proved that the flavonoid patterns o f hydrolysed seed extracts are remarkably conservative. Butin (7, 3', 4'-trihydroxyflavanone), 3'-hydroxydaidzein (7, 3', 4'-trihydroxyisofl avone), vicenin-2 (6, 8-di-beta-D-glucopyranosyl-5, 7, 4'-trihydroxyfl avone) and orobol (5, 7, 3', 4'-tetrahydroxyisoflavone) were isolated and identified as the major flavonoids. The seeds of Amphithalea, Coel idium, Liparia, Xiphotheca, Calpurnia, Stirtonanthus and Podalyria acc umulated three isoflavone O-glycosides that yielded 3'-hydroxydaidzein on hydrolysis. In contrast, Virgilia contained a unique combination o f vicenin-2 and orobol. Vicenin-2 was also present in Calpurnia as a m ajor compound, but Stirtonanthus insignis was the only other species s tudied that contained orobol (in trace amounts only). Butein, a chalco ne, was reported by HARBORNE from the seed of Cyclopia subternata. Thi s compound's flavanone analog, butin, was the principal component in C yclopia. A cladistic analysis, using flavonoid, alkaloid and morpholog ical data, showed that the seed flavonoids of the Podalyrieae and Lipa rieae behave rather poorly as cladistic characters. They are, however, of considerable taxonomic value at the tribal level favouring the opi nion that the two tribes should, be combined. The apparent absence of flavonoids in the seed of Hypocalyptus supports the suggestion that it should be excluded from the Liparieae. Flavonoids also show that the Argyrolobium-group is very different from the tribe Crotalarieae and s upport the recent transfer of this group to the tribe Genisteae.