Characterization of structures and antiviral effects of polysaccharides from Portulaca oleracea L.

Three polysaccharides including a neutral polysaccharide (RN), an acidic polysaccharide (RA) and a pectic polysaccharide (RP) were isolated from aerial part of Portulaca oleracea L. and evaluated for their anti-herpes simplex virus type 2 (HSV-2) and anti-influenza A virus (IFV-A). RN was found to consist of glucose (Glc), mannose (Man) and arabinose (Ara) with small amounts of galactose (Gal), and identified to be an arabinoglucomannan. RA was mainly composed of Gal and Ara with a small proportion of glucuronic acid (GlcA). It was characterized as a type II arabinogalactan (AGII), which consisted of a 1,3-, 1,6- and 1,3,6-linked galactopyranosyl (Galp) and non-reducing terminal and 1,5-linked arabinofuranosyl (Araf ) residues. RP was deduced to be a pectin, which consisted of a predominant amount of galacturonic acid (GalA) with small amounts of Gal, rhamnose (Rha) and Ara. The GalA residues were found to be highly methyl-esterified and partially acetylated. Results of antiviral tests showed that only RP had anti-HSV-2 activity. Furthermore, its anti-HSV-2 target was elucidated to be the step of virus penetration into host cells. No marked virucidal activity of RP was observed.