Structural analysis and immunological activity of a novel low molecular weight neutral polysaccharide isolated from Hemerocallis citrina Borani

A novel neutral water-soluble polysaccharide (HCBP1-1) was isolated and purified from Hemerocallis citrina Borani by column chromatography. The fine structure of HCBP1-1 was determined by a series of physical and chemical means. HCBP1-1 was a homogeneous low molecular weight polysaccharide of 7.25 kDa. Methylation and NMR analysis revealed that HCBP1-1 consisted of α-D-Glcp-(1→, →4)-α-D-Glcp-(1→, →4)-β-D-Galp-(1→, →4,6)-α-D-Glcp-(1→, →3,4)-α-D-Glcp-(1→. In particular, the main backbone of HCBP1-1 consisted of unsubstituted (4-α-D-Glcp and 4-β-D-Galp) and monosubstituted (4,6-α-D-Glcp and 3,4-α-D-Glcp) glucose and galactose units linked by α-(1 → 4) and β-(1 → 4) glycosidic linkages. The side chain consisted of α-D-Glcp-(1 → and →4)-α-D-Glcp-(1→. Furthermore, bioactivity assays show that HCBP1-1 significantly promoted the secretion of NO, TNF-α, IL-1β, and IL-6 and the expression of NF-κB p65 in RAW264.7 cells, which had good immune-enhancing activity. These results suggest that HCBP1-1 had beneficial immunomodulatory effects and could be developed into functional foods or nutraceuticals with immune-enhancing properties.