DISTRIBUTION AND CHEMOTAXONOMIC SIGNIFICANCE OF FLAVONOIDS IN ALOE (ASPHODELACEAE)

A chemotaxonomic study of practically all the species of the genus Alo e showed that flavonoids occur as major compounds in 31 out of a total of 380 species investigated. Flavanones and dihydroflavonols are pres ent in the exudate of species in Aloe ser. Rhodacanthae and Superposit ae and also in a number of the endemic species from Madagascar. Flavon es occur as the only major compound in the leaf extracts of the sects. Leptoaloe and Graminialoe. In ser. Macrifoliae and in Lomatophyllum, the sister genus of Aloe, isovitexin co-occurred with the C-glucosylan throne aloin. The chemotaxonomic implication of these results are disc ussed together with the significance of the taxonomic and chemogeograp hical distribution of flavonoids in Aloe. With a few rare exceptions, the leaf compounds from two different biogenetic pathways (polyketide pathway and flavonoid pathway) are mutually exclusive. Since flavonoid s are restricted to the basal groups in Aloe, we conclude that flavono ids are plesiomorphic characters in Aloe reflecting ancient phylogenet ic and biogeographic links.