Discovery of uncommon terpenoids from the South China Sea soft coral Sinularia scabra

Sinulatones A and B, presented as the unusual carbon skeleton with bicyclo[4.5.0] system, two undescribed sesquiterpenoids, namely sinulalides A and B, along with eight known terpenoids, were isolated from the South China Sea soft coral Sinularia scabra. The structures and stereochemistry of these compounds were determined based on extensive spectroscopic data analyses, and computer-assisted methods, including the quantum mechanical-nuclear magnetic resonance (QM-NMR) and TDDFT-ECD calculations. In bioassay, sinulatones A and B showed inhibitory activity against osteoclast precursor cells, with IC50 values of 16.8 and 5.8 μM, respectively. [Display omitted] •Sinulatones A and B, with unusual carbon skeletons, were isolated.•Two undescribed sesquiterpenoids, sinulalides A and B, were isolated.•Some compounds showed an inhibitory effect on osteoclast precursor cells.