DIFFERENCES IN FLAVONOID PATTERNS BETWEEN GENERA WITHIN THE VELLOZIACEAE

Detailed flavonoid analysis of seven representative species of Aylthonia, Barbacenia, Burlemarxia and African and Madagascan Xerophyta have confirmed the paucity of surface flavonoids in these genera compared with Vellozia, where complex mixtures of lipophilic flavonoids are common. However, some simple flavonol O-methyl ethers including 6-methoxykaempferol 3-O-methyl ether were found in small amounts on the leaf surface of two Barbacenia species. In the subfamily Barbacenioideae, Aylthonia was distinguished from both Barbacenia and Burlemarxia in its vacuolar flavonoids by the presence of flavone mono-C-glycosides rather than flavone di-C-glycosides and Pleurostima is unique in lacking glycoflavones but possessing 6-hydroxyflavones. Complex mixtures of flavonol mono-O- and di-O-glycosides were found within the leaves of Barbacenia and Burlemarxia species, while only quercetin monoglycosides were detected in Aylthonia riedeliana. In Balbacenia conicostigma, the 3-apiosylgalactosides and 3-apiosylglucosides of quercetin and isorhamnetin were characterized; the former two compounds were present also in Burlemarxia spiralis. In Xerophyta eglandulosa var. eglandulosa from Madagascar an isomeric quercetin 3-apiosylglucoside occurred. The Madagascan Xerophyta species were distinguished from the African Xerophyta species by the absence of glycoflavones and presence of isorhamnetin glycosides, while in X. dasylirioides quercetin 3-methyl ether and quercetin di- and trimethyl ethers were identified free within the leaf. Similarly, in Barbacenia conicostigma four flavonol methyl ethers, as well as kaempferol and chrysoeriol occurred in the free state. However, X. retinervis from South Africa was exceptional in producing 6-C-methyl quercetin 3-methyl ether, chrysoeriol 7-glucoside and both flavone mono- and di-C-glycosides within the leaf. The present results confirm that flavonoid patterns are useful in determining generic limits within the family.