Occurrence of Azaleatin and Caryatin in Eucryphia

Abstract

ALTHOUGH quercetin ((Fig. 1), R = R′ = H) itself frequently occurs in the leaves and flowers of higher plants, its simple mono and dimethyl ethers (apart from isorhamnetin, the 3′-methyl ether) have very rarely been reported. Azaleatin, the 5-methyl ether ((Fig. 1), R′ = Me, R = H), for example, was first isolated from the flowers of Rhododendron mucronatum in 1956 (ref. 1) and has since been recorded in forty-four other Rhododendron species, in Plumbago capensis, in Ceratostigma willmottiana² and in Carya pecan³. Caryatin, the 3,5-dimethyl ether ((Fig. l),R = R′ = Me), has only been found once⁴ in the bark of the latter plant, together with azaleatin. We now wish to record the occurrence and distribution of both these rare quercetin methyl ethers in the leaves of species of Eucryphia (Eucryphiaceae).