GOSSYPETIN AND HERBACETIN AS TAXONOMIC MARKERS IN HIGHER PLANTS

Four yellow flavonol pigments earlier reported in the Leguminosae, Ericaceae and Papaveraceae as quercetagetin glycosides have now been found to be the isomeric gossypetin derivatives. Reliable methods are outlined for distinguishing between these isomeric 6- and 8-hydroxyquercetin derivatives on a microscale, including a simple colour test which can be carried out on chromatograms. The yellow flavonol monomethyl ether reported in Lotus corniculatus flower is now shown to be gossypetin 7-methyl ether. Gossypetin, besides occurring in Rhododendron petals, is also widespread in the leaves of this (in 76 of 103 species examined) and nine related genera of the Ericaceae. It also occurs as a leaf constituent in the related Empetrum (Empetraceae). In a survey of legume leaves, gossypetin was only detected once, in Acacia constricta. Surveys indicate that herbacetin, the kaempferol analogue of gossypetin, is much less common, but it has been detected as principal flower pigment in Meconopsis paniculata (Papaveraceae). Consideration of the known natural distribution of the two yellow flavonols indicates that they are of most interest as taxonomic markers at the generic and subfamilial levels. © 1970.