Structural characterization and antiviral effect of a novel polysaccharide PSP-2B from Prunellae Spica

•A novel polysaccharide, PSP-2B, was isolated from aqueous extracts of Prunellae Spica.•PSP-2B was a sulfated polysaccharide with molecular weight approximately 32 kDa.•The framework of PSP-2B was speculated to be a branched arabinogalactomannan.•PSP-2B exhibited interesting activity against herpes simplex virus.

In the present study, a novel polysaccharide, PSP-2B, was isolated from aqueous extracts of Prunellae Spica by direct ultrafiltration membrane separation and gel chromatography purification. PSP-2B is a partially sulphated polysaccharide with a molecular weight of approximately 32 kDa. Its sulfate content is 10.59% by elemental analysis. The major sugars comprising PSP-2B are arabinose, galactose and mannose, in addition to small amounts of glucose and uronic acids. The framework of PSP-2B is speculated to be a branched arabinogalactomannan, and the side chains are terminated primarily by the Araf residues. PSP-2B also contains 2.98% protein. PSP-2B exhibits activity against herpes simplex virus (HSV), with a half maximal inhibitory concentration (IC50) of approximately 69 μg/mL for HSV-1 and 49 μg/mL for HSV-2. However, PSP-2B demonstrated no cytotoxicity even when its concentration was increased to 1600 μg/mL, suggesting that it has potential as an anti-HSV drug candidate.