Purification, characterization and immunostimulatory effects of polysaccharides from Anemarrhena asphodeloides...

The crude polysaccharide was extracted from A. asphodeloides rhizomes and further purified to produce two fractions F₁ (50.0%) and F₂ (19.6%). The chemical constitutions of the polysaccharides were neutral sugars (51.4%-89.7%), uronic acids (1.0%-30.2%) and sulfate esters (3.4%-8.1%), with various ratios of monosaccharides including rhamnose (1.4%-6.1%), arabinose (7.1%-21.2%), xylose (0.2%-4.8%), mannose (39.9%-79.0%), glucose (6.0%-11.1%) and galactose (2.6%-22.0%). The molecular properties of the polysaccharides were investigated by the HPSEC-UV-MALLS-RI system, revealing the M_w 130.0 × 10³-576.5 × 10³ g/moL, R_g 87.6-382.6 nm and SV_g 0.3-54.3 cm³/g. The polysaccharides stimulated RAW264.7 cells to produce considerable amounts of NO and up-regulate the expression of TNF-α, IL-1 and COX-2 genes. Polysaccharides exhibited the growth inhibitory effects on cancer cells lines of AGS, MKN-28 and MKN-45, in which F₂ fraction exhibited prominent bioactivities. The AGS cells treated with F₂ experienced condensed cytoplasm, shrinkage of nucleus and chromatin marginalization with the highest number of cells at early-stage apoptosis reaching 54.6%. The inhibitory effect of F₂ polysaccharide on AGS cells was through MAPKs and STAT3 signaling pathways. The backbone of the F₂ was mainly linked by (1 → 4)-linked mannopyranosyl and (1 → 3)-linked galactopyranosyl. Taken together, the polysaccharide from A. asphodeloides rhizomes could be utilized as medicinal, pharmacological and functional food ingredients.