Amakusamine from a Psammocinia sp. Sponge: Isolation, Synthesis, and SAR Study on the Inhibition of RANKL-Induced Formation of Multinuclear Osteoclasts.

A simple methylenedioxy dibromoindole alkaloid, amakusamine ( 1 ), was isolated from a marine sponge of the genus Psammocinia , and its structure was determined from spectroscopic data, time-dependent density-functional theory calculations, and synthesis. Compound 1 inhibited the receptor activator of nuclear factor-κB ligand (RANKL)-induced formation of multinuclear osteoclasts with an IC ₅₀ value of 10.5 μM in RAW264 cells. The structure - activity relationship of 1 was also investigated with synthetic derivatives.