Structural characterization of the water-extractable polysaccharides from Sophora subprostrata roots

The crude polysaccharide SSa, obtained from the roots of Sophora subprostrata by boiling-water extraction and ethanol precipitation, was fractionated by anion-exchange and gel permeation chromatography, giving four polysaccharide fractions termed SSa1, SSa2, SSa3, and SSa4. Their structural features were investigated by sugar analysis, methylation analysis, partial hydrolysis, and NMR spectroscopy. SSa1 and SSa2 were both characterized as highly branched amylopectins with small average unit chain length of 8–10 except that SSa2 was contaminated with small amount of arabinogalactan. SSa3 was mainly an arabinogalactan, attached to a rhamnogalacturonan core. SSa4 was a rhamnogalacturonan I (RG-I) pectic polysaccharide having a backbone consisting of 1,4-linked α-d-galacturonic acid and 1,2-linked α-l-rhamnose, with various branches attached to O-4 of l-rhamnose.