Densanins A and B, New Macrocyclic Pyrrole Alkaloids Isolated from the Marine Sponge Haliclona densaspicula

Densanins A (1) and B (2) were isolated from the sponge Haliclona densaspicula. On the basis of spectral data and the Mosher ester method, the complete structures were characterized as hexacyclic diamine alkaloids, which were probably derived from 3-alkylpyridine. Compounds 1 and 2 showed relatively potent inhibitory effects on lipopolysaccharide-induced nitric oxide production in BV2 microglial cells with IC50 values of 1.05 and 2.14 mu M, respectively.