Water-soluble polysaccharide from Erythronium sibiricum bulb: Structural characterisation and immunomodulating activity

A water-soluble polysaccharide named ESBP2-1 was isolated from Erythronium sibiricum bulb through anion-exchange and size-exclusion chromatography. ESBP2-1 is a neutral polysaccharide fraction with an average molecular weight of 9.4 × 105 Da and is composed of glucose, galactose and arabinose in a ratio of 24.3:1.1:1. Methylation analysis, partial hydrolysis and NMR studies revealed that the backbone of ESBP2-1 primarily consists of repeating →1)-α-d-Glcp-(4→ units where the disaccharide side chains of Arap-(1 → 6)-α-d-Galp-(1→ residue are attached to the O-6 position of Glc. An in vitro assay showed that ESBP2-1 significantly promoted the proliferation and neutral red phagocytosis of RAW 264.7 macrophage cells. In addition, ESBP2-1 stimulated the production of secretory molecules (nitric oxide, TNF-α and IL-1β) of RAW264.7 cells in a dose-dependent manner. These results suggest that ESBP2-1 is a potential immunostimulator.