In order to identify the active anti-inflammatory ingredient(s) in Cirsium chanroenicum (Compositae), its methanol extract and several solvent fractions were prepared; the methanol extract and the ethylacetate fraction inhibited cyclooxygenase-2 (COX-2)-mediated prostaglandin E2 (PGE2) and 5-lipoxygenase (5-LOX)-mediated leukotriene (LT) production in lipopolysaccharide-treated RAW 264.7 cells and A23187-treated rat basophilic leukemia (RBL-1) cells, respectively. Further bioactivity-guided fractionation of the ethylacetate fraction using column chromatography led to the isolation of pectolinarigenin (5,7-dihydroxy-4′,6-dimethoxyflavone), along with pectolinarin [pectolinarigenin 7-rhamnosyl-(1→6)-glucoside]. Pectolinarigenin strongly inhibited COX-2-mediated PGE2 and 5-LOX-mediated LT production at >1 μM, indicating that it is a dual inhibitor of COX-2/5-LOX. However, pectolinarigenin did not affect COX-2 expression or nuclear transcription factor (NF-κB) activation. In addition, in vivo studies demonstrated that oral administration of these two compounds at 20—100 mg/kg resulted in similar inhibitory activities against several animal models of inflammation/allergy: arachidonic acid-induced mouse ear edema, carrageenan-induced mouse paw edema and passive cutaneous anaphylaxis. All of these results suggest that pectolinarigenin and pectolinarin possess anti-inflammatory activity and that they may inhibit eicosanoid formation in inflammatory lesions. These activities certainly contribute to the anti-inflammatory mechanism of C. chanroenicum.
2008 The Pharmaceutical Society of Japan