Isolation and characterization of a sulfated polysaccharide from the brown alga Sargassum patens and determination of its anti-herpes activity.

Bioactivity-guided fractionation of the hot water extract from the brown alga Sargassun patens led to the isolation of a polysaccharide as an antiviral component against herpes simplex viruses which are the cause of cold sores (HSV-1) and genital herpes (HSV-2). The polysaccharide contained a sulfur group that could be present as a sulfate ester. It is thus a sulfated polysaccharide with a molecular mass of about 424 kDa, and is designated SP-2a. Gas chromatographic assay showed that the polysaccharide consisted of fucose, galactose, mannose, xylose, glucose, and galactosamine. The fucose is the major constituent sugar (35.3%), followed by galactose (18.4%). The 50% effective concentration (EC50) against HSV-2, HSV-1, and HSV-1 acyclovir resistant strain was 1.3, 5.5, and 4.1 microg/mL, respectively. The 50% cytotoxic concentration (CC50) of SP-2a on the growth of normal Vero cell line was more than 4000 microg/mL. Therefore SP-2a of S. patens may be a potent agent for treating HSV infections.