Chemical Constituents and Biological Activities of Cirsium leucopsis, C. sipyleum, and C. eriophorum

Two endemic Cirsium species, C. leucopsis DC. and C. sipyleum O. Schwarz, and C. eriophorum (L.) Scop. growing in Turkey were investigated to establish their secondary metabolites, fatty acid compositions, and antioxidant and anticholinesterase potentials. Spectroscopic methods were used to elucidate the structures of thirteen known compounds (p-hydroxy-benzoic acid, vanillic acid, cis-epoxyconiferyl alcohol, syringin, balanophonin, 1′-O-methyl-balanophonin, apigenin, kaempferol-3-O-β-d-glucopyranoside, kaempferol-3-O-α-l-rhamnopyranoside, taraxasterol, taraxasterol acetate, β-sitosterol, β-sitosterol-3-O-β-d-glucopyranoside). cis-Epoxyconiferyl alcohol and 1′-O-methyl-balanophonin were isolated for the first time from Cirsium species. Palmitic acid (47.1 %) was found to be the main fatty acid of C. leucopsis, linoleic acid in both C. sipyleum (42.1 %) and C. eriophorum (37.8 %). Assays of β-carotene bleaching, scavenging of 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radicals, 2,2-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium (ABTS) cation radicals, and superoxide anion radicals, as well as cupric reducing antioxidant capacity (CUPRAC) were used to determine the antioxidant activities of the extracts and isolated compounds. Vanillic acid, balanophonin, and kaempferol-3-O-α-l-rhamnopyranoside exhibited strong antioxidant activity. Taraxasterol was a potent inhibitor of acetyl- and butyrylcholinesterase activity, respectively.