Structures and anti-HSV-2 activities of neutral polysaccharides from an edible plant, Basella rubra L.

Four neutral polysaccharides (BRN-1, BRN-2, BRN-3 and BRN-4) were isolated from the hot water extract of the aerial part of Basella rubra L. They were found to consist of a large amount of D-galactose (81.0-92.4%) and small amounts of L-arabinose (5.4-7.8%), D-glucose (2.2-11.0%) and mannose (~2.9%). Linkage analysis revealed that all these neutral polysaccharides might be arabinogalactan type I polysaccharides in different molecular weight and chain length. Among them, only BRN-3 showed antiviral activity against herpes simplex virus type 2 (HSV-2) with 50% inhibitory concentration of 55 μg/mL without showing the cytotoxicity up to 2300 μg/mL. Furthermore, the main antiviral target of BRN-3 was shown to be the inhibition of virus adsorption to host cells. This is the first report on the neutral polysaccharide with anti-HSV-2 activity obtained from B. rubra L.