Anti-inflammatory activity of Onopordum acanthium extracts and isolated compounds

Onopordum acanthium L. (Scotch thistle, Asteraceae) is a biennial plant, widely distributed in Europe and Asia. This plant has been used traditionally in the treatment of different cancers and inflammatory disorders. The aim of the present study was the investigation of anti-inflammatory effect of O. acanthium, and identification of its active compounds. The chloroform-soluble fraction of the MeOH extract of the aerial parts was subjected to multiple chromatographic purification (CC, VLC, RPC, TLC and gel filtration), and lignans (pinoresinol, medioresinol, syringaresinol) and flavonoids (hispidulin, nepetin, apigenin and luteolin) were isolated. The compounds were identified by means of MS and 1D- and 2D-NMR spectroscopy. Our earlier phytochemical work on the chloroform extract of the roots resulted in the isolation of sesquiterpene lactones (4β,15-dihydro-3-dehydrozaluzanin C, zaluzanin C and 4β,15,11β,13-tetrahydrozaluzanin C), and the neolignan nitidanin-diisovalerianate, besides of 13-oxo-9Z,11E-octadecadienoic acid and 24-methylenecholesterol [1]. Extracts of different polarity and compounds obtained from the aerial parts and roots were evaluated for their inhibitory effects on COX-2 and NF-κB1 gene expression, iNOS, 5-LOX, COX-1 and COX-2 enzymes in in vitro assays. It was found that O. acanthium extracts exert strong anti-inflammatory effect in vitro and some compounds play substantial role in the activity. 4β,15-Dihydro-3-dehydro-zaluzanin C and zaluzanin C were the most active against LPS/IFN-γ-induced NO production and in the inhibition of COX-2 and NF-κB1 gene expression. In order to verify whether the gene expression inhibitory effect of the active sesquiterpene lactones were due to cytotoxicity, these compounds were investigated by the XTT-assay at different time points (4h, 24h, 48h, 72h) in various concentrations. It was concluded that these anti-inflammatory effects are not due to cytotoxicity.

Keywords: Onopordum acanthium, Asteraceae, anti-inflammatory activity, sesquiterpenes lactones, flavonoids, lignans, neolignan

References:

[1] Csupor-Löffler B, Zupkó I, Molnár J, Forgo P, Hohmann J. Bioactivity-guided isolation of antiproliferative compounds from the roots of Onopordum acanthium. Nat Prod Commun 2014; 9: 337 – 340.