Antioxidant and immunostimulatory activities of polysaccharides extracted from Tremella aurantialba mycelia.

In the present study, the physiochemical and biological properties of crude mycelium polysaccharide (CMCP) and purified mycelium polysaccharide (MCP) extracted from the Tremella aurantialba mycelium were investigated. A series of physiochemical properties were determined, including the total sugar, uronic acid and protein content, monosaccharide composition and structure, and molecular weight. The reducing power and scavenging activity of 2,2-diphenyl-1-picrylhydrazyl (DPPH) and hydroxyl radicals were determined to investigate the antioxidant activity of CMCP and MCP. Furthermore, the immunostimulatory activity of the polysaccharides was evaluated by detecting the effects of CMCP and MCP on proliferation, nitric oxide (NO) production and cytokine secretion by RAW264.7 cells. The chemical analysis revealed that MCP had a molecular weight of 4.3x104 g/mol and was composed primarily of D‑glucose, D‑galactose and D‑mannose. The total carbohydrate contents of MCP and CMCP were 86.59 and 11.92%, respectively. Compared with CMCP, MCP demonstrated improved antioxidant properties. In addition, MCP induced RAW264.7 macrophage proliferation, NO production and secretion of tumor necrosis factor‑α, interleukin (IL)‑1 and IL‑6. These findings suggest that the total carbohydrate content may contribute to the improvement of antioxidant and immunostimulatory activities of MCP.