Four polysaccharides (GLP-I, GLP-II, GLP-III and GLP-IV) were obtained from fermented soybean curd residue by Ganoderma lucidum, and then purified using anion-exchange DEAE Sephadex A-50. Their structural characterization was conducted by Fourier transform infrared spectroscopy (FTIR), and their monosaccharide compositions were determined. The results demonstrated that the basic structural characterization of four polysaccharides were similar, however, monosaccharide compositions of four kinds of polysaccharides were significant difference. GLP-III and GLP-IV were composed of six kinds of monosaccharide. Nevertheless, GLP-II was composed of three kinds of monosaccharide. Moreover, their antioxidant activities were investigated on the basis of hydroxyl radical, reducing power, DPPH free radical, chelating activity, ABTS radical-scavenging and SOD-like activity. The results showed that four polysaccharides exhibited antioxidant activities in a concentration-dependent manner. Among four polysaccharides, GLP-III and GLP-IV exhibited the higher scavenging effects on hydroxyl radicals, ABTS radical, DPPH free radical, and stronger reducing power and SOD-like activity than GLP-I and GLP-II. In addition, treatment with 40 μg/mL of GLP showed significant stimulation to the macrophage proliferation and higher nitric oxide production. Overall, GLP from fermented SCR could have potential applications in the medical and food industries.
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