Abstract: An exopolysaccharide from the fermentation supernatant of Cordyceps militaris strain 14014 from China Center of Industrial Culture Collection (CICC) was extracted and purified by sequential column chromatography on DEAE-Sephacel and Sephadex G-200. The molecular mass of the polysaccharide was determined by high performance liquid chromatography (HPLC) and it was structurally identified by Fourier transform infrared (FTIR) spectroscopy. Meanwhile, the immunostimulatory activity?of the polysaccharide in immunosuppressed BALB/c mice was evaluated by measuring the changes in body mass and immune organ indexes, observing spleen tissue sections, calculating the proliferation rate of spleen lymphocytes, and determining the contents of serum cytokines and immunoglobulins (Ig). The results showed that the polysaccharide content in the fermentation broth of Cordyceps militaris was 3.15 mg/mL, the molecular mass of the purified polysaccharide was 3.67 kDa, and its purity was 86.13%. The exopolysaccharide from Cordyceps militaris significantly improved immune organ indexes, promoted the proliferation of T (at low dose) and B cells, and stimulated the secretion of tumor necrosis factor (TNF)-α, interleukin (IL)-6, IL-2, interferon (IFN)-γ, IgG, IgA and IgM in mice, indicating a good immunoregulatory effect. The above results indicated that the exoposaccharide could repair cyclophosphamide-induced damage to immune functions in BALB/c mice. This finding may provide a theoretical basis for the development and utilization of Cordyceps militaris fermentation broth.

Key words: exopolysaccharide from Cordyceps militaris; polysaccharide structure; cyclophosphamide; spleen lymphocyte proliferation; immunoregulatory activity