Characterization of an Acidic Polysaccharide Having Immunological Activities from the Tuber of Alisma orientale

An acidic polysaccharide, called alisman PII, was isolated from the tuber of Alisma orientale Juzepcz. It was homogeneous on electrophoresis and gel chromatography, and its molecular mass was estimated to be 5.25 x 10⁴. It is composed of L-arabinose: D-galactose: D-glucuronic acid in the molar ratio of 4:9:2, in addition to some of O-acetyl groups. Reduction of carboxyl groups, methylation analysis, nuclear magnetic resonance and controlled Smith degradation indicated that the core structural features include a backbone chain composed of β-1,3-linked D-galactose units. Some of the galactose units in the backbone carry β-D-galactosyl side chains at position 6. Both α-1,5-linked L-arabinosyl side chains and terminal β-D-glucuronic acid residues are linked to the core galactan units. Alisman PII showed significant potentiation of the reticuloendothelial system using a carbon clearance test and also potent anti-complementary activity.