Isolation, structure elucidation, and biological activity of polysaccharides from Saussurea involucrata

The optimum extraction condition for the Saussurea involucrata polysaccharide (SIP) was determined to be a temperature of 80 °C, time 2 h, and a liquid-solid ratio of 30 mL/g with a yield of 11.37 %. An acidic homogenous polysaccharide, namely SIP-II was isolated from Saussurea involucrate through anion exchange and gel permeation column chromatography. The structure of the SIP-II was elucidated through the combination of HPLC, GC-MS, IC, peroxide oxidation, smith degradation, methylation, NMR analysis, it was mainly composed of arabinose, rhamnose, galactose, galacturonic acid, and glucose with the molar ratio of 19.85:20.30: 27.12:11.95:8.69 with a molecular weight of 237,570 Da. The glycosidic linkages of SIP-II mainly composed of →1)-α-L-Rhap-(2→, T-Araf, →1)-β-D-GalpA-(4→, →1)-β-D-Galp-(3,6→, →1)-β-D-Galp-(6→, →1)-α-L-Rhap-(2,4→, T-Galp, and →1)-α-L-Araf-(5→. Meanwhile, the structures were characterized through extensive analysis of UV, FT-IR, SEM-EDX, CD, XRD, and TG. SIP-II possessed a remarkable anti-inflammatory activity by effectively inhibiting the expression of pro-inflammatory cytokines and inflammation-related mediators in LPS-stimulated RAW264.7 macrophages, and the anti-inflammatory response of SIP-II might be attributed to the regulation of the NF-κB, MAPK and JAK/STAT pathways. The results showed that polysaccharides from Saussurea involucrate could be a potential ingredient in the functional food and pharmaceutical industry.