Rhaposerine and rhaserolide, new sesquiterpene lactones from Rhaponticum serratuloides

Two new crystalline guaianolides, viz., rhaposerine and rhaserolide, were i solated from an ethanolic extract of the above-ground part of the plant Rha ponticum serratuloides by column chromatography along with sesquiterpene la ctones, viz., centaurepensin and acroptilin, which have been found in other plants. The chemical structures of the title lactones were established by H-1 and C-13 NMR spectroscopy and 2D H-1-H-1 (COSY) and C-13-H-1 (COSY and COLOC) NMR spectroscopy.