Purification, chemical characterization and antioxidant activities of a novel polysaccharide from Auricularia polytricha

A novel water-soluble polysaccharide coded APP3a was isolated and purified from Auricularia polytricha by DEAE-52 cellulose and Sephadex G-200 column chromatography. Chemical characterization of APP3a was investigated based on analysis of high performance liquid chromatography (HPLC), gas chromatography (GC), fourier transform infrared spectroscopy (FT-IR) and thermal gravimetric analysis (TGA). Antioxidant activities of APP3a were investigated on the basis of superoxide anion,1,1-diphenyl-2-picrylhydrazyl (DPPH), hydroxyl radical scavenging activity and reducing power. The results showed that APP3a consisted of arabinose, mannose, glucose and galactose in a molar ratio of 1:1.33:1.06:1.23 with an average molecular weight of 21,242 Da. Thermal gravimetric analysis showed that APP3a was relatively stable below 250 °C. APP3a showed the stronger reducing power and stronger scavenging activity against hydroxyl radicals, superoxide radicals and DPPH radicals in a concentration-dependent manner. These findings suggested that the polysaccharide APP3a could be served as a novel antioxidant in functional food.