Chemotaxonomic Markers in Digitalideae (Plantaginaceae)

In a chemosystematic investigation of Digitalideae (Plantaginaceae), the water-soluble part of extracts of two species of Digitalis, two species of Isoplexis, as well as Erinus alpinus and Lafuentea rotundifolia were studied with regard to their content of iridoids, caffeoyl phenylethanoid glycosides (CPGs) and main sugars. Digitalis and Isoplexis were found to lack iridoid glucosides but contained sorbitol, cornoside and a number of other phenylethanoid glycosides including the new tyrosol b-D-mannopyranoside, sceptroside. Erinus contained mainly glucose, the new 8,9-double bond iridoid, erinoside and a number of known iridoid glucosides including two esters of 6-rhamnopyranosylcatalpol as well as the CPG poliumoside. Finally, Lafuentea was characterized by the presence of glucose, aucubin and cryptamygin B but apparently lacked CPGs. The chemosystematic significance of the isolated compounds is discussed.