Chemical characterization and immunomodulatory activity of acetylated polysaccharides from Dendrobium devonianum

The chain conformation, chemical characters and immunomodulatory activity of polysaccharide from Dendrobium devonianum (DDP) were investigated. Results showed that molecular weights, polydispersity index, radius of gyrations of DDP were 3.99×10⁵ Da1.27, 74.1nm, respectively. By applying the polymer solution theory, the exponent (v) values of 2>_z^1/2=kM_w^v was calculated as 0.38, which revealed that DDP existed as a globular shape in aqueous solution, and further confirmed by AFM analysis. Furthermore, the main monosaccharide compositions were Man and Glc with the ratio of 29.61:1.00. Indeed, the main glycosidic linkages were β-1,4-Manp, and substituted with acetyl groups at O-2 and O-3 position. Notably, DDP could promote the immune functions of macrophages including NO release and phagocytosis. Thus, DDP could be explored as a natural immune-stimulating agent in the health and functional food area as well as pharmaceutical industries.