As part of our studies to discover P2X7 receptor antagonists, the sponge Callyspongia sp. was investigated. A new tripyridine alkaloid niphatoxin C (1) was isolated and had P2X7 receptor antagonism; however, cytotoxicity of THP-1 cells was the predominant biological effect at higher concentrations. Its structure was determined by 1- and 2-D NMR spectroscopy.
