Structure of rhamnan sulfate from the green alga Monostroma nitidum and its anti-herpetic effect

"A sulfated polysaccharide from Monostroma nitidum Wittrock (Ulvophyceae)" was purified by anion-exchange and gel filtration column chromatographies. The isolated polysaccharide consisted of large amount of l-rhamnose with small amount of d-glucose, and it was regarded to be a rhamnan sulfate (RS). Methylation analysis of the native and desulfated polysaccharide suggested that this polymer was mainly composed of 1,2- and 1,3-linked rhamnose residues with a ratio of ca 1:2. In addition, it was found the presence of 1,2,3-linked rhamnose and 1,4-linked glucose residues. Sulfate groups were suggested to be mainly located at C-2 and C-3 of 1,3- and 1,2-linked rhamnose residues, respectively. NMR analyses including 1D and 2D experiments indicated that RS consisted of sugar linkage units as follows:. 1: →3)-α-l-Rha-(1 → 3)-α-l-Rha-(1→. 2: →3)-α-l-Rha-(1 → 2)-α-l-Rha-(1→. 3: →3)-α-l-Rha-(1 → 3)-α-l-Rha-(1→(2; β - D -Glc- (1 - ↑). Moreover, RS showed potent antiviral activity against herpes simplex virus type 2 virus, whereas it has no effect on the replication of influenza A virus. Anti-HSV-2 target(s) of RS was suggested to be virus adsorption and penetration steps onto host cell surface.