Characterization of a heteropolysaccharide isolated from diploid Gynostemma pentaphyllum Makino

A novel water-soluble polysaccharide (GPP), with a molecular mass of 7.1 × 103 Da, was isolated from the defatted whole-plant of diploid Gynostemma pentaphyllum Makino. Monosaccharide composition analysis indicated that GPP was a heteropolysaccharide mainly containing mannose, glucose, galactose and arabinose, at a molar ratio of 1.00:77.33:4.81:1.83. The detailed structure analysis revealed that GPP consisted of a (1→4)-α-d-glucoside backbone with a 1→)-α-d-glucopyranosyl branch at the C-6 position of (1→4,6)-linked-α-d-glucopyranosyl on every 5 monosaccharide residues, with a few mannose, galactose and arabinose terminal residues. GPP exhibited scavenging capacities against hydroxyl, peroxyl and DPPH radicals in vitro, and had a greater bile acid-binding ability than psyllium on a per weight basis. These results suggested a potential application of GPP in functional foods and dietary supplements.