Secondary metabolites of Centaurea calolepis and evaluation of cnicin for anti-inflammatory, antioxidant, and cytotoxic activities

Objective: Secondary metabolite determination, isolation and structure elucidation of pure compounds were performed on C. calolepis. Cnicin, which is the main component of several Centaurea species, was tested for its in vitro anti-inflammatory, antioxidant and cytotoxic activities. Materials and methods: Chloroform and methanol extracts of the aerial parts of C. calolepis were subjected to isolation process using column chromatography. The structures of the compounds were characterized by 1D- and 2D-NMR experiments. Thin--layer chromatography and high performance liquid chromatography were used in determination of phenolics. Cnicin was subjected to a panel of cellular assays to test for inhibition of nuclear factor kappa kappa B (NF-kappa kappa B), inducible nitric oxide synthase (iNOS), reactive oxygen species and cytotoxicity. Results: Cnicin, lucenin-2, schaftoside and 3-O-feruloylquinic acid were isolated from C. calolepis extracts. Vicenin-2, vitexin, isovitexin, homoorientin, rutin, orientin, luteolin-7-O-glycoside and chlorogenic acid were determined in fractions. Cnicin showed inhibition of NF-kappa kappa B and inhibition of iNOS activity with IC(50) Values of 1.8 and 6.5 mu A mu M, respectively. Cytotoxic activity of cnicin was observed toward pig kidney epithelial (LLC-PK(11)), human malignant melanoma (SK-MEL) and human ductal carcinoma (BT-549) cells with IC(50) values of 23.3, 14.0 and 18.3 mu A mu M, respectively. Discussion and conclusion: This is the first detailed report of secondary metabolites of C. calolepis. Evaluation of biological activity of cnicin establishes the potential of this compound as an anti-inflammatory and cytotoxic agent.