Structural characterization and immunomodulatory activity of a polysaccharide from Salvia miltiorrhiza and its sulfated derivative

• A novel polysaccharide (PSMP2) was isolated from the root of Salvia miltiorrhiza. • The structural characterization of PSMP2 and its sulfated derivative were conducted for the first time. • Sulfation modification can improve the immunomodulatory activity of PSMP2 in vivo . • PSMP2 and its sulfated derivatives can regulate intestinal flora and short-chain fatty acids. A polysaccharide (PSMP2) was isolated from Salvia miltiorrhiza , and its sulfated derivative (PSMP2-S) was synthesized. The chemical structures of PSMP2 and PSMP2-S were analyzed by various chemical analysis methods and instrumental analysis methods. The ultrastructures and thermal stability were further investigated. In addition, PSMP2 and PSMP2-S had strong immunomodulatory activity and could regulate cytokines (interleukin-2, interleukin-6 and tumor necrosis factor-α), increased the content of short chain fatty acids and effectively reduced the relative abundance of Bacteroides and increased the relative abundance of Firmicutes , significantly increase Muribaculaceae and Lactobacillaceae , and inhibit Lachnospiraceae and Ruminococcaceae , improve the composition of gut microbiota. This study showed that PSMP2 and PSMP2-S might be used as potential natural immune regulators and gut microbiota regulators, and had great development value in the field of food and medicine.