A further chemical investigation of the Caribbean marine sponge Aplysina archeri led to the isolation of a novel bromo compound, archerine (1). Its structure was established through extensive NMR spectroscopy, including 1H-13C HSQC, 1H-13C HMBC and 1H-15N HMBC experiments, as well as positive FAB MS/MS spectra. The capability of archerine to chelate zinc ions was investigated. Archerine exhibited antihistamine activity on the isolated guinea pig ileum at concentrations as low as 1 µM.