Structural investigation of two neutral polysaccharides isolated from rhizome of Polygonatum sibiricum

Two neutral polysaccharides, PSW-1a and PSW-1b-2, were isolated from the hot-water extract of Polygonatum sibiricum roots, using ethanol precipitation, anion-exchange chromatography, Fehling reagent complexing, and gel permeation chromatography. Their structures were investigated using composition and linkage analyses, periodate oxidation and Smith degradation, partial acid hydrolysis, and NMR spectroscopic methods. PSW-1b-2 was characterized as a branched homogalactan, containing a 1,4-linked β-d-galactopyranosyl backbone with one β-d-galactopyranosyl stub substituted at O-6 of every 7th backbone residue, whereas PSW-1a as a highly branched galactomannan, possessing a 1,4-linked β-d-mannopyranosyl backbone, with a β-d-galactopyranosyl stub attached to O-6 of every 9th mannosyl residue.