LAUSR

Abstract Within the large Compositae family, Phitosia is considered a monotypic genus of the Greek flora, with its only species P. crocifolia (Boiss. & Heldr.) Kamari & Greuter growing wild with limited distribution, exclusively on the mountains Taigetos and Parnonas in Peloponnese. P. crocifoliaʼs chemical profile was obtained, herein, for the first time and led to the isolation of 20 compounds, thirteen of which were characterized as sesquiterpene lactones and the rest mainly as phenolic derivatives. The isolates 1 – 3, 5  –  7 and 11  –  13 represent new chemical structures. Compounds 2 and 3 especially are substituted with a pentose moiety, a rare phenomenon in sesquiterpene lactone backbones. A series of spectrometric and spectroscopic techniques were used to elucidate their structures. The relative configurations of the unreported compounds were established via extensive analysis of NMR spectroscopic and HRESIMS data, assisted by CD spectroscopic measurements. Throughout the entire isolation procedure, selected fractions rich in sesquiterpene lactones were tested against HeLa cancerous cell line for their cytotoxic effects with the lowest IC 50 values being 18.84 µg/mL. Accordingly, among the tested isolates, compounds 5 and 9 exerted IC 50 values of 13.5 µM and 11.4 µM, respectively.