Sesquiterpene compounds from Inula Viscosa

Two new compounds, 2,5-dihydroxyisocostic acid and 2,3-dihydroxycostic acid together with three known sesquiterpene compounds, Isocostic acid, Carabrone and Tomentosine, have been isolated from the acetone extract of Inula viscosa (L.) Aiton. The structures of all new compounds were determined by spectroscopic methods, in particular 1D and 2D 1H- and 13C-NMR. The 13C NMR spectra of Isocostic acid and of Tomentosine are reported here for the first time