Isolation, purification, characterization, and immunomodulatory effects of polysaccharide from Auricularia auricula on RAW264.7 macrophages

Auricularia auricula polysaccharide (AAP) was isolated by hot-water extraction and purified to evaluate its structural and immunomodulatory effects on RAW264.7 macrophages. The results show that three kinds of Auricularia auricula polysaccharides (c-AAP) were obtained and named as AAP-I, AAP-II, and AAP-III Their further purification found that AAP-I and AAP-II were glycoproteins, and only AAP-III was a pure polysaccharide, which we named AAP for further experiments. Structural characteristics revealed that AAP was a homogeneous galactan comprising mannose, rhamnose, gluconic acid, glucose, galactose, arabinose, and fucose in a molar ratio of 5.02:0.9:0.12:4.48:0.37:1.0:0.36, and the average molecular weight is approximately 23.51 kDa. Methylation analysis revealed that AAP mainly consisted of 1,4-linked-Glcp, 1,4,6-linked-Glcp, terminal Glcp, 1,4-linked-Manp, 1,2,6-linked-Manp, and terminal Arap. Furthermore, the in vitro immunomodulatory activities of AAP were evaluated by cell proliferation, NO production, and phagocytic ability using RAW264.7 macrophage cells. The results show that AAP not only promoted the activation of macrophages but also provided a scientific basis for the further use of AAP. Practical applications Three water-soluble polysaccharides were extracted from Auricularia auricula of Changbai Mountain, two of which contained binding proteins. Determination of molecular weight, structure, and immunoreactivity of pure polysaccharide components. The result clearly demonstrated the benefits of this plant as a healthy functional food.