Several sesquiterpene lactones that have been isolated from medicinal plants are known to have many pharmacological activities. In this study, we investigated the anti-inflammatory effects of zedoarondiol, a sesquiterpene lactone isolated from the rhizoma of Curcuma heyneana, in lipopolysaccharide (LPS)-stimulated macrophage cells. Zedoarondiol dose-dependently inhibited LPS-stimulated nitric oxide (NO), prostaglandin E(2) (PGE(2)), tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), and interleukin-1beta (IL-1beta) productions in RAW 264.7 macrophage and in mouse peritoneal macrophage cells. Consistent with these findings, in RAW 264.7 cells, zedoarondiol suppressed the LPS-stimulated protein levels of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) and the mRNA expressions of iNOS, COX-2, TNF-alpha, IL-6, and IL-1beta in a concentration-dependent manner. Moreover, molecular data revealed that zedoarondiol inhibited LPS-stimulated DNA binding activity and the transcription activity of nuclear factor-kappa B (NF-kappaB), and this effect was accompanied by decreases in the degradation and phosphorylation of inhibitory kappaB (IkappaB)-alpha, and in the subsequent blocking of NF-kappaB translocations to the nucleus. Furthermore, zedoarondiol attenuated the phosphorylations of IkappaB kinase (IKK), extracellular signal-regulated kinase (ERK), p38 mitogen-activated protein kinase (p38), and c-Jun N-terminal kinase (JNK) in LPS-stimulated RAW 264.7 cells. Taken together, the findings of the present study indicate that zedoarondiol inhibits iNOS, COX-2, and pro-inflammatory cytokine expressions by suppressing the phosphorylations of IKK and MAPKs, and by subsequently inactivating the NF-kappaB pathway. These relations reveal, in part, the mechanism underlying the anti-inflammatory properties of zedoarondiol.