FLAVONOID AGLYCONES FROM THE LEAF SURFACES OF SOME LABIATAE SPECIES

The distribution of excreted flavonoid aglycones within the family Labiatae was studied and differences were found, especially in the A-ring substitution patterns. Thus, 5,7-dihydroxy-6-methoxyflavones with substituted B-rings are characteristic of species of Salvia (sect. Salvia), Rosmarinus and Ocimum; 5,7-dihydroxy-6,8-dimethoxyflavones occur only in Ocimum and 5,6-dihydroxy-7,8-dimethoxyflavones in Thymus and related species. Members of the two subfamilies Lamioideae and Nepetoideae produce exudate flavonoids, but some genera are devoid of these compounds. There is a correlation between the habitat where the plant grows and production of these compounds, the species from (semi-)arid habitats being those which generally accumulate external flavonoids. © 1990 Springer-Verlag.