Bioactivity-guided isolation of antiproliferative compounds from Centaurea jacea L

Bioassay-guided fractionation of the chloroform extract of Centaurea jacea L. afforded the isolation of cirsiliol, apigenin, hispidulin, eupatorin, isokaempferide, axillarin, centaureidin, 6-methoxykaempferol 3-methyl ether, trachelogenin, cnicin, 4'-acetylcnicin and three aliphatic glucose diesters, including the new natural product 1β-isobutanoyl-2-angeloyl-glucose. The structures of the compounds were established on the basis of spectroscopic analyses (UV, MS and NMR). All compounds were isolated for the first time from this species. The compounds were evaluated for their tumour cell growth inhibitory activities on HeLa, MCF-7 and A431 cells. Different types of secondary metabolites (flavonoids, sesquiterpenes) were found to be responsible for the antitumour effects of the extracts; the highest activity was exerted by centaureidin, in addition to moderately active compounds (cirsiliol, isokaempferide, apigenin, hispidulin, cnicin and 4'-acetylcnicin).