Characterization and Immunological Activities of Polysaccharides from Polygonatum sibiricum

In this study, we investigated the physicochemical properties and composition of monosaccharidex from Polygonatum sibiricum. Simultaneously, we explored the in vivo and in vitro immunomodulatory activity and mechanism of Polygonatum sibiricum polysaccharide (PSP) activity by monitoring changes in immune organs, immune cells, and cytokines. The average molecular weight (M_w) of PSP was 9.514 × 10⁴ Da. The monosaccharide components of PSP were galactose, rhamnose, arabinose, mannose, and glucose at a molar ratio of 11.72 : 1.78 : 4.15 : 1.00 : 2.48. PSP increased thymus and spleen indices, enhance the proliferative responses of splenocytes, and increased the phagocytosis of mononuclear macrophages. Simultaneously, PSP could recover the body mass of immunosuppressed mice, and increased blood erythrocyte counts in the sera of cyclophosphamide (Cy)-treated and normal mice, whilst blood leukocytes and platelet counts of Cy-treated mice recovered. PSP elevated the CD4⁺/CD8⁺ ratio is a dose-dependent manner and increased the levels of interleukin-2 (IL-2) and tumor necrosis factor-α (TNF-α) in the sera of Cy-treated mice. PSP further enhanced the expression of IL-2 and TNF-α in spleen lymphocytes. Additionally, PSP treatment accelerated the recovery of natural killer cell activity in a dose-dependent manner. Taken together, PSP not only regulated the immune function of normal mice, but participated in the protection against immunosuppression in Cy-treated mice, highlighting its potential as an immunostimulant.