Characterization of a neutral polysaccharide having activity on the reticuloendothelial system from the rhizome of Curcuma longa.

A neutral polysaccharide, named ukonan D, was isolated from the rhizome of Curcuma longa L. It produced a single band on electrophoresis and a single peak on gel chromatography, and its molecular mass was estimated to be 28,000. It showed remarkable reticuloendothelial system-potentiating activity in a carbon clearance test. Ukonan D is composed of L-arabinose: D-galactose: D-glucose: D-mannose in the molar ratio of 1:1:12:0.2, in addition to small amounts of peptide moiety. Methylation analysis, carbon-13 nuclear magnetic resonance and enzymic degradation studies indicated that its structural features include mainly both alpha-1,5-linked L-arabino-beta-3,6-branched D-galactan type and alpha-4,6-branched D-glucan type structural units. The influence of degradation with alpha-amylase followed by the elimination of glucan side chains on its immunological activity was discussed.