Diterpenoids from the soft coral Pachyclavularia violacea and their anti-inflammatory activities

The detailed chemical investigation of the South China Sea soft coral Pachyclavularia violacea, led to the isolation and characterization of a new casbane-type diterpenoid, 7,8-epoxy-casbene (1), along with seven known compounds (2-8). Their structures were determined by extensive spectroscopic analysis, quantum mechanical nuclear magnetic resonance (QM-NMR) method, time-dependent density functional theory electronic circular dichroism (TDDFT-ECD) calculation, and comparison with the spectral data previously reported in the literature. In in vitro bioassays, the anti-inflammatory activities of the isolated compounds were evaluated in the lipopolysaccharide (LPS)-induced RAW 264.7 cells, and compounds 6-8 displayed interesting inhibitory effects on LPS-induced tumor necrosis factor (TNF)-α protein release with half-maximal inhibitory concentration (IC₅₀) values of 201.1, 231.7, and 66.21 µM, respectively.