New pentacyclic triterpene ester and flavone glycoside from the biologically active extract of Carduus pycnocephalus L.

Abstract

Bioassay guided phytochemical investigation of petroleum ether, chloroform and butanol fractions obtained from biologically active total alcoholic extract of Carduus pycnocephalus led to isolation of two new compounds, 3-O-acetyl-ursolic acid-28-ethyl ester (compound 1) and diosmetin-7-O-α-L-arabinopyransyl (1```→4``)-β-D- glucopyranoside (compound 5) along with three known compounds, bis (2-ethylhexyl) benzene-1,2-dicarboxylate) (compound 2), 3α, 24 dihydroxyolean-12-en-28, 30-dioic acid dimethyl ester (compound 3) and kaempferol (compound 4). Their structures were established on the basis of spectroscopic methods (UV, MS, 1H NMR, 13C NMR, COSY, HSQC and HMBC) and by comparison with published data. Compounds 2 and 3 were isolated for the first time from genus Carduus. The cytotoxic, antioxidant, and antimicrobial activities of the ethanolic extract were evaluated and the extract showed variable degrees of activities. It showed significant cytotoxic activity against MCF-7, A-549 and HepG-2 cell lines with IC50, 17.9, 17.5 and 21.8 µg, respectively. The extract displayed weak antioxidant activity by scavenging of DPPH with SC50 554.2 µg. In agar diffusion assay, the extract exhibited strong antibacterial activities against Gram negative bacteria Pseudomonas aeruginosa and Escherichia coli and strong antifungal activity against Syncephalastrum racemosum. Key words: Carduus pycnocephalus L.; new triterpene ester, flavonoidal glycoside, antioxidant, cytotoxic, antimicrobial activity.