Distribution of 6-hydroxy-, 6-methoxy- and 8-hydroxyflavone glycosides in the labiatae, the scrophulariaceae and related families

A leaf survey of 308 species belonging to the Labiatae, Scrophulariaceae and to five related families has shown that the common flavones, apigenin, luteolin and chrysoeriol are widely present, occurring especially as the 7-glucuronides. In addition 48 species (16% of sample) contain 8-hydroxyflavones and 131 species (43%) 6-hydroxy- or 6-methoxyflavones in glycosidic combination. The frequencies recorded are slightly higher than those found (35% for both groups) in earlier surveys. 8-Hydroxyflavones based on apigenin and luteolin are restricted to the Labiatae (5 genera), Scrophulariaceae (Gratiola and Veronica) and Lentibulariaceae (Pinguicula). In Labiatae, they only occur in the subfamily Lamoideae and not in the Nepetoideae. In Veronica, they are restricted to species in the sections Alsinebe and Chamaedrys. 6-Oxygenated flavones have a more sporadic distribution, but are consistently present in genera such as Scutellaria, Phlomis, Micromeria, Origanum and Thymus (Labiatae), in Parahebe (Scrophulariaceae) and Globularia (Globulariaceae). Although uncommon, flavonol glycosides were detected in a few species of the Labiatae, Scrophulariaceae and Globulariaceae, and C-glycosylflavones were detected in a few species of the former two families. The chemosystematic significance of these findings is discussed.