Polar constituents composition of endemic Sideritis italica (MILL.) GREUTER et BURTER from Central Italy.

Endemic Sideritis italica (MILL.) GREUTER et BURTER (Lamiaceae) occurs mainly in Southern Italy and Sicily and has previously only been studied for the essential oil composition. In this paper, we complete the phytochemical study of a sample of S. italica, previously analysed for its volatile constituents, occurring in the Appennino Umbro-Marchigiano (Central Italy), which is the northern border of the areal distribution of the species. The analysis of medium polarity constituents led to the isolation of several glycosides, such as flavonoids, i.e. scutellarein derivatives; phenylethanoids, i.e. verbascoside; and iridoids, i.e. melittoside and 5-allosyloxy-aucubin, besides the diterpene siderol. The data reported have chemotaxonomic relevance, since they are in contrast with the hypothesis that in Lamiaceae the species producing iridoids do not usually have relevant essential oil production and vice versa.