A chemotaxonomic survey of flavonoids and simple phenols in leaves of the Ericaceae

Leaves of 344 species of the Ericaceae and of 37 species in three related families have been surveyed for flavonoids and simple phenols. The yellow flavonol gossypetin was found in 158 ericaceous species and is of chemotaxonomic interest within the Rhododendroideae (where it occurs in 11 of 19 genera) and in the Vaccinioideae (in 3 of 22 genera). 5-0-methylflavonols appear in 81 species, again mainly in the Rhododendroideae (eight genera); whereas 3,5-di-O-methylquercetin, caryatin, is present only in Bejaria, Phyllodoce and Rhododendron. Dihydroflavonols. common in Rhododendron, show a sporadic distribution elsewhere in the family. Of the simpler phenols surveyed, gentisic acid is common but methyl salicylate is present mainly in Gaultheria. Hydroquinone appears in ten related genera, methylhydroquinone in three and orcinol in seven. The chemical evidence generally supports Stevens' recent classification of the family, particularly his inclusion of Epigaea in the Rhododendroideae and his transfer of Diplarche from the Diapensiaceae to the Ericaceae. There is also chemical evidence to support the separation of Calluna and Cassiope, the inclusion of the Aibutoideae within the Vaccinioideae and the retention of the Pyroloideae and Monotropoideae within the Ericaceae. In addition, chemistry indicates that Phyllodoce should be placed nearer to the Rhodoreae than in Stevens' system and that Cassiope and Harrimanella, placed together in the Cassiopeae by Stevens, are distinctly different.