Placotylene A, an Inhibitor of the Receptor Activator of Nuclear Factor-.B Ligand-Induced Osteoclast Differentiation, from a Korean Sponge Placospongia sp.

A new inhibitor, placotylene A (1), of the receptor activator of nuclear factor-B ligand (RANKL)-induced osteoclast differentiation, and a regioisomer of placotylene A, placotylene B (2), were isolated from a Korean marine sponge Placospongia sp. The chemical structures of placotylenes A and B were elucidated on the basis of 1D and 2D NMR, along with MS spectral analysis and revealed as an iodinated polyacetylene class of natural products. Placotylene A (1) displayed inhibitory activity against RANKL-induced osteoclast differentiation at 10 M while placotylene B (2) did not show any significant activity up to 100 M, respectively.