OCCURRENCE OF FLAVONOL 5-METHYL ETHERS IN HIGHER PLANTS AND THEIR SYSTEMATIC SIGNIFICANCE

Kaempferol 5-methyl ether has been identified for the first time in plants. It was found in leaves or flowers of Rhododendron spp., of Erica, Kalmiopsis and Rhodothamnus (all Ericaceae) and in Tetracera (Dilleniaceae). Surveys of the Ericaceae have also revealed that quercetin 5-methyl ether (azaleatin) is common as a leaf as well as a flower constituent; it is widespread in Rhododendron and also occurs in seven other genera. It is accompanied by the 3,5-dimethyl ether, caryatin, in leaves of some of these plants; in Rhododendron, caryatin is confined to species of the subgenus Eurhododendron. The presence of azaleatin in Tetracera (Dilleniaceae) has been confirmed. Together with earlier results, these findings show that flavonol 5-methyl ethers occur in fifteen genera from six plant families. Their systematic value is mainly confined to their distribution within these families but their presence in only woody families may have phyletic significance. © 1969.