The occurrence of iridoid glycosides in the Labiatae

Iridoid glycosides were found in many species of the following taxa of the Labiatae: Prostantheroideae, Ajugoideae, Prasioideae, Scutellarioideae, Stachydoideae-Marrubieae and St.- Stachydeae. Iridoid glycosides were not found in any species of the following subfamilies: Rosmarinoideae, Ocimoideae, Lavanduloideae, and Stachydoideae (except the two tribes mentioned). The former group of taxa coincides with the taxa having binucleate, tricolpate pollen grains, while the latter group has trinucleate, hexacolpate pollen grains, the binucleate, tricolpate Pogostemoneae being exceptional. Of the many iridoid glycosides present in the binucleate, tricolpate part of the Labiatae, a considerable proportion is still unidentified and the chemical structures of several of them are as yet unknown. Some of the latter were isolated and characterized by their specific optical rotations and RF-vaIues on paper chromatograms.