To assess the anti-inflammatory activity of the constituents of the roots of Aralia continentalis, ent-pimara-8(14),15-diene-19-oic acid (continentalic acid, pimaradienoic acid, compound I), 7beta-hydroxy-ent-pimara-8(14),15-diene-19-oic acid (compound II), 7-oxo-ent-pimara-8(14),15-diene-19-oic acid (compound III), 15alpha,16alpha-epoxy-17-hydroxy-ent-kauran-19-oic acid (compound IV) and ent-kaura-16-en-19-oic acid (kaurenoic acid, compound V), their inhibitory effects against cyclooxygenase-2 (COX-2)-catalyzed PGE(2) and inducible nitric oxide synthase (iNOS)-catalyzed NO production by lipopolysaccharide-treated RAW 264.7 cells were examined. Among the compounds tested, compound III and V moderately inhibited NO production. In addition, compound III weakly inhibited PGE2 production, while treatment with compounds II and IV at concentrations of up to 100 microM had no significant effects. Conversely, compound I only weakly inhibited PGE2 and NO production. To elucidate the mechanism by which these changes occurred, the iNOS down-regulating capacity of compound III was investigated. Western blot analysis and an electrophoretic mobility shift assay demonstrated that compound III weakly inhibited COX-2 and iNOS expression at 50-100 microM, and inhibited NF-kappaB activation. When in vivo anti-inflammatory activities of compounds I, III and V were examined, intraperitoneal injection of 4-100 mg/kg of compound I and V significantly inhibited carrageenan-induced paw edema in mice, whereas compound III did not. Taken together, the results of this study suggest that some constituents of A. continentalis, especially compounds I, III and V, exert significant anti-inflammatory activity, which suggests that these constituents contribute, at least in part, to the anti-inflammatory action of the roots of A. continentalis.