Optimization of extraction process, characterization and antioxidant activities of polysaccharide from Leucopaxillus giganteus

Many literatures have been reported edible fungi with high protein, high carbohydrates, low fat and a variety of biological activities, while Leucopaxillus giganteus was rarely studied. In this study, in order to obtain high yield polysaccharides from L. giganteus, the best extraction process of polysaccharides was optimized by single factor and orthogonal experiments. The polysaccharide extracted by optimized method was characterized and its antioxidant activities were further investigated. The results showed that the optimum extraction conditions were as follows: ratio of material to water of 1:35, extraction temperature of 80 degrees C, extraction time of 4.5 h, ultrasound assisted and extraction times of 3. Under the optimal extraction conditions, the yield of polysaccharides from L. giganteus was 6.79 +/- 0.15% (n = 3). High Performance Gel Permeation Chromatography showed that molecular weight of partially purified polysaccharide was about 92.4 KDa. The results of TGA and Congo red test indicated that polysaccharides from L. giganteus had great thermal stability and contained triple-helix structure. The antioxidant results in vitro suggested that the polysaccharide from L. giganteus had excellent antioxidant activity on DPPH center dot (91.76%), OH center dot (67.22%) and ABTS + (81.03%) at the concentration of 2 mg/mL. This result provided a theoretical basis for the polysaccharide from L. giganteus as a potential natural antioxidant in the future.