Pectolinarigenin is a Cirsium isolate with anti-inflammatory activity and belongs to the flavones. Pectolinarigenin strongly inhibited COX-2-mediated PGE2 and 5-LOX-mediated LT production at >1 microM, 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-kappaB) 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.