Water-soluble polysaccharides isolated from the rhizome of Polygonatum sibiricum and fractionated using ion-exchange chromatography were investigated to determine their structure and immunostimulating activity. Crude and fractions (F1 and F2) consisted of carbohydrates (85.1~88.3%) with proteins (4.51~11.9%) and uronic acid (1.79~7.47%), and included different levels of mannose (62.3~76.3%), glucose (15.2~20.3%), galactose (4.35~15.3%), and arabinose (4.00~7.65%). The crude contained two peaks with molecular weights (Mw) of 151×103 and 31.8×103, but F1 and F2 exhibited one major peak with Mw of 103×103 and 628×103, respectively. Little immunostimulatory activity was observed by the crude; however, F1 and F2 significantly activated RAW264.7 cells to release nitric oxide and various cytokines, suggesting they were potent immunostimulators. The backbone of the most immunostimulating fraction (F1) was (1→4)-manno- and (1→4)-gluco-pyranosyl residues with galactose and glucose attached to O-6 of manno-pyranoside.
Keywords: Polygonatum sibiricum; immunostimulation; molecular properties; water-soluble polysaccharides.