Chemotaxonomic interest of iridoids isolated from a Malagasy species: Perichlaena richardii

Three known iridoid glycosides, verminoside (1), 6-O-trans-caffeoyl-ajugol (2), and 10-O-trans-caffeoyl-catalpol (3), together with 1-β-O-caffeoyl-d-glucose (4), caffeic acid (5), and a flavonol glycoside, rutin (6), were isolated from the leaves of Perichlaena richardii Baill. (Bignoniaceae), an endemic species to Madagascar. This is the first report of these compounds from this species. The structures of the isolated compounds were established using different spectroscopic methods including extensive 1D and 2D-NMR and mass spectrometry. The activity of verminoside, rutin and caffeic acid on enzymes involved in inflammation, cyclooxygenases and lipoxygenases, was determined on human peripheral venous blood samples. Moreover, the distribution of iridoids among the clades of Bignoniaceae, according to Von Poser et al. in 2000, was revisited on the basis of the new classification of Bignoniaceae described in 2009 by Olmstead et al. The chemotaxonomy of iridoids isolated from P. richardii, in addition to the Bignoniaceae family as a whole, is also discussed.