Diterpenoids from the Soft Coral Sinularia maxima and Their Inhibitory Effects on Lipopolysaccharide-Stimulated Production of Pro-inflammatory Cytokines in Bone Marrow-Derived Dendritic Cells

Nine new diterpenoids, termed sinumaximols A-I (1-3, 5-9, 12), together with three known compounds (4, 10, 11), were isolated from the methanol extract of the soft coral Sinularia maxima. Their structures were elucidated on the basis of extensive spectroscopic methods, including one-dimensional (1D) and two-dimensional (2D) nuclear magnetic resonance (NMR) and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). The isolated compounds were evaluated for their inhibitory effects on the lipopolysaccharide (LPS)-stimulated production of pro-inflammatory cytokines in bone marrow-derived dendritic cells (BMDCs). Among them, compounds 2, 3, and 11 were potent inhibitors of LPS-stimulated interleukin-12 (IL-12) p40 with half-maximal inhibitory concentration (IC50) values ranging from 4.35 +/- 0.12 to 18.04 +/- 0.21 mu M. Compounds 2, 3, and 11 showed moderate inhibitory activity on IL-6 production with IC50 values ranging from 17.72 +/- 0.31 to 59.77 +/- 2.34 mu M.