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

Abstract

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 Mw 130.0 × 103–576.5 × 103 g/moL, Rg 87.6–382.6 nm and SVg 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.