Antiviral sulfated polysaccharide from Navicula directa, a diatom collected from deep-sea water in Toyama Bay

A sulfated polysaccharide named naviculan was isolated from a diatom, Navicula directa (W. SMITH) RALFS, collected in deep sea water from Toyama Bay. The polysaccharide consisted of fucose, xylose, galactose, mannose, rhamnose and sulfate with an apparent molecular weight of 220000. It showed antiviral activities against herpes simplex viruses type 1 and 2, and influenza A virus with selectivity indices (CC50/IC50) of 270, 510 and 32, respectively. Naviculan also showed an inhibitory effect on cell-cell fusion between CD4-expressing and human immunodeficiency virus (HIV) gp160-expressing cells that was used as a model system of infection with HIV.