Structural characterization and immunomodulatory activity of exopolysaccharides from submerged culture of Auricularia auricula-judae

Submerged culture of Auricularia auricula-judae has been documented, but there have been few studies on the structural characterization and medicinal properties of its exopolysaccharides. In present study, two exopolysaccharides, named CEPSN-1 and CEPSN-2, were isolated from submerged culture of A. auricula-judae, and their structural features as well as immunomodulatory activity were analyzed. The two exopolysaccharides both had a backbone chain composed of (1 → 4)-α-d-glucose residues in glucopyranose type. At the tested concentration range of 50-200 μg/mL, CEPSN-1 and CEPSN-2 not only showed non-toxicity to RAW 264.7 cells, but also could promote the release of NO and cytokines (IL-6, IL-10 and TNF-α) in the cells. The release of NO was significantly enhanced by the two exopolysaccharides at 100 μg/mL (p < 0.05). The IL-10 secretion was significantly increased by 1.80 and 1.61-fold, compared to the control after treatment with 50 μg/mL of CEPSN-1 and CEPSN-2, respectively (p < 0.05). These results demonstrated that, though their structural feature were different from that of polysaccharides from fruit body, exopolysaccharides of A. auricula-judae from submerged culture with the backbone of (1 → 4)-α-D-glucan could be explored as potential immunomodulatory agents for the application in complementary medicine or functional foods.