Effect of the degree of oxidation on the physicochemical and biological properties of Grifola frondosa polysaccharides

Polysaccharide extracted from Grifola frondosa was subjected to 2,2,6,6-tetramethyl-1-piperidine oxoammonium ion (TEMPO)-mediated oxidation of which effects on the structural and biological properties of the polysaccharide were investigated as a function of degree of oxidation. Successive oxidation of the polysaccharide was confirmed by 13C NMR spectroscopy and the molecular weight change of the oxidized polysaccharide was observed, decreasing from 10.6 × 105 Da to 7.5 × 105 Da by 100% oxidation. The oxidation also caused an increase in the water solubility of the polysaccharide while its viscosity was significantly reduced. In addition, when human fibrosarcoma HT1080 cells were treated with 100% oxidized polysaccharide, their in vitro growth was effectively inhibited. However, the oxidation reduced the activity of superoxide dismutase up to 82% at a concentration of 2.5 mg/mL. Thus, the chemical modification by TEMPO-mediated oxidation was shown to play a significant role in the biological properties of the polysaccharides derived from Grifola frondosa.