Coronarin D, a labdane diterpene, inhibits both constitutive and inducible nuclear factor-κB pathway activation, leading to potentiation of apoptosis, inhibition of invasion, and suppression of osteoclastogenesis

Compounds isolated from members of the Zingiberaceae family are traditionally used as a medicine against inflammatory diseases, but little is known about the mechanism. Here, we report the isolation and structural identification of coronarin D [E-labda-8(17),12-diene-15-ol], a labdane-type diterpene, from Hedychium coronarium and delineate its mechanism of action. Because the transcription factor nuclear factor-κB (NF-κB) is a key mediator of inflammation, apoptosis, invasion, and osteoclastogenesis, we investigated the effect of coronarin D on NF-κB activation pathway, NF-κB-regulated gene products, and NF-κB-regulated cellular responses. The coronarin D inhibited NF-κB activation induced by different inflammatory stimuli and carcinogens. This labdane also suppressed constitutive NF-κB activity in different cell lines and inhibited IκBα kinase activation, thus leading to the suppression of IκBα phosphorylation, degradation, p65 nuclear translocation, and reporter gene transcription. Coronarin D also inhibited the NF-κB-regulated gene products involved in cell survival (inhibitor of apoptosis protein 1, Bcl-2, survivin, and tumor necrosis factor receptor-associated factor-2), proliferation (c-myc, cyclin D1, and cyclooxygenase-2), invasion (matrix metalloproteinase-9), and angiogenesis (vascular endothelial growth factor). Suppression of these gene products by the diterpene enhanced apoptosis induced by TNF and chemotherapeutic agents, suppressed TNF-induced cellular invasion, and abrogated receptor activator of NF-κB ligand-induced osteoclastogenesis. Coronarin D was found to be more potent than its analogue coronarin D acid. Overall, our results show that coronarin D inhibited NF-κB activation pathway, which leads to inhibition of inflammation, invasion, and osteoclastogenesis, as well as potentiation of apoptosis. [Mol Cancer Ther 2008;7(10):3306–17]