Terpenoids from the Soft Coral Sinularia densa Collected in the South China Sea

The chemical investigation of the South China Sea soft coral <i>Sinularia densa</i> has resulted in the isolation of seven new terpenoids, including two new meroterpenoids, namely sinudenoids F-G (<b>1</b>-<b>2</b>), and five new cembranes, namely sinudenoids H-L (<b>3</b>-<b>7</b>). Their structures and absolute configurations were elucidated based on extensive analyses of spectroscopic data, single-crystal X-ray diffraction, comparison with the literature data, and quantum chemical calculations. Among them, sinudenoid F (<b>1</b>) and sinudenoid G (<b>2</b>) are rare meroterpenoids featuring a methyl benzoate core. Sinudenoid H (<b>3</b>) possesses a rare carbon skeleton of 8, 19-bisnorfuranocembrenolide, which is the second reported compound with this skeleton. In a bioassay, sinudenoid H (<b>3</b>) exhibited better anti-inflammatory activity compared to the positive control indomethacin at 20 µM in CuSO₄-treated transgenic fluorescent zebrafish. Moreover, sinudenoid J (<b>5</b>) and sinudenoid L (<b>7</b>) exhibited moderate anti-thrombotic activity in arachidonic acid (AA)-induced thrombotic zebrafish at 20 µM.