Bioactivity-guided isolation of anti-proliferative compounds from endemic Centaurea kilaea

Context: The genus Centaurea L. (Asteraceae) is one of the largest genera in Turkey. Compounds and extracts obtained from different Centaurea species have significant anti-cancer activity against various cancer cell lines. Objective: To determine the anti-proliferative activity of isolates from the chloroform extract of C. kilaea Boiss. Materials and methods: Eleven compounds were isolated using column chromatography and preparative TLC from the chloroform extract of aerial parts of endemic C. kilaea. The structures of the isolated compounds were elucidated by various spectroscopic methods, including UV, (l)H-NMR and (13)C-NMR. Anti-proliferative activity of compounds (0.5–50 μg/mL) were measured against one normal cell line (L-929, mouse fibroblast) and three human cancer cell lines (Hela, cervix carcinoma; MCF-7, breast carcinoma; PC-3, prostate carcinoma) using MTT assay. Results were expressed as IC(50) values. Results: None of the 11 compounds displayed activity against L-929 and HeLa. Two of these compounds, cnicin and cirsimaritin, showed fairly strong activity against MCF-7 and PC-3 with IC(50) values of 3.25 and 4.3 μg/mL, respectively. Discussion and conclusion: This is the first report on cirsimaritin. Cirsimaritin and cnicin could serve as potential anti-cancer drug candidates against breast and prostate cancer, respectively.