THE UTILITY OF LEAF FLAVONOIDS AS TAXONOMIC MARKERS IN THE SUBFAMILY AND GENERIC CLASSIFICATION OF THE VELLOZIACEAE

As a result of surveying 99 species of the Velloziaceae, it was found that the major leaf flavonoids are flavonol glycosides (in 68%) and flavone C-glycosides (in 48% of taxa). In the subfamily Vellozioideae, flavones such as luteolin occur in the free state together with flavone C-glycosides and this combination of characters distinguishes this subfamily from the Barbacenioideae. The genus Pleurostima is unique in producing two new 6-hydroxyflavone glycosides identified as the 7-apiosides of 6-hydroxyluteolin and 6-hydroxy-8-methoxyluteolin. The genus Barbacenia is distinguished by the regular presence of isorhamnetin and occasional presence of quercetin 3-methyl ether. The only other plants where isorhamnetin is frequent are the Madagascan Xerophyta species, which also produce quercetin 3-methyl ether, luteolin and some unidentified constituents, but lack flavone C-glycosides. Otherwise Vellozia and Xerophyta species have similar flavonoid patterns, including the presence of 5-deoxykaempferol and the anthocyanin; petunidin 3,5-diglucoside. Nanuza plicata is distinguished from all other genera by the presence of the biflavonoid, amentoflavone.