Sulfated modification of the polysaccharides from Ganoderma atrum and their antioxidant and immunomodulating activities

In this study, three chemically sulfated polysaccharides (S-PSG) with different degree of sulfate substitution (DS) were derived from Ganoderma atrum. FT-IR and 13C NMR spectra indicated that the substitution was predominantly on C-6 position compared with the C-2 position. The antioxidant and immunomodulatory activities of S-PSG were further examined to determine the relationship between its structure and bioactivity. The results showed that compared with the native polysaccharide, the S-PSG-2 with moderate DS and molecular weight exhibited the highest immunomodulatory activity by increasing the macrophage phagocytosis capacity and TNF-α production. The DPPH radical scavenging activity was also greatly enhanced by S-PSG in all the groups compared with PSG. However, the reducing power and the antioxidant activities in β-carotene-linoleic acid assay were decreased. These results indicated that except for the DS, some other structural characteristics such as molecular weight, substitution position and chain conformation were also important factors affecting their bioactivities. And the S-PSG-2 we derived could be served as immunomodulator and free-radical inhibitors.