A novel polysaccharide from the roots of Millettia Speciosa Champ: preparation, structural characterization and immunomodulatory activity

A novel polysaccharide fraction (MSCP2) was extracted and isolated from the roots of Millettia Speciosa Champ. Structural characterization revealed that MSCP2 had an average molecular weight of 2.85 × 104 Da and was composed of fucose, arabinose, galactose, glucose and xylose with a ratio of 2.20: 2.52: 4.04: 87.29: 3.96. Methylation analysis and nuclear magnetic resonance (NMR) analysis showed that the main glycosidic linkage types of MSCP2 were proved to be α-D-Glcp-(1→, →4)-α-D-Glcp-(1→, →4)-α-D-Xylp-(1→, →6)-β-D-Galp-(1→, α-L-Araf-(1→, →3,4)-β-L-Fucp-(1→ and →4)-α-D-GalpA-(1→. The immunomodulatory assay suggested that MSCP2 could significantly improve the pinocytic capacity and increase the secretion of nitric oxide (NO) and cytokines by regulating the corresponding mRNA expression in RAW 264.7 cells. The data from the membrane receptor assay demonstrated that the potential mechanisms of MSCP2-induced macrophage activation were mainly through toll-like receptor 4 (TLR4), scavenger receptor type A (SRA) and glucan receptor (GR)-mediated signaling pathways. These results suggested that MSCP2 can be developed as a promising immunomodulatory agent in functional foods. •A novel polysaccharide (MSCP2) was isolated and purified from the roots of Millettia Speciosa Champ.•MSCP2 could significantly enhance the pinocytic capacity and promote the secretion of NO and cytokines in RAW 264.7 cells.•The pattern recognition receptors for MSCP2 binding to macrophages were elucidated.