Abstract

Three polysaccharides namely, exopolysaccharide (EPS), water-extracted mycelial polysaccharide (WPS) and sodium hydroxide-extracted mycelial polysaccharide (SPS), were prepared from the endophytic fungus Berkleasmium sp. Dzf12 isolated from the rhizomes of Dioscorea zingiberensis, and their in vitro antioxidant activities were investigated by using 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, Fe³⁺ reducing activity, Fe²⁺ chelating activity, and hydroxyl radical scavenging activity assays. Among these three polysaccharides, EPS and SPS exhibited more excellent antioxidant activities, with corresponding median effective concentration (EC₅₀) values as 61.60 µg/ml and 91.51 µg/ml by using DPPH scavenging assay, 47.82 and 63.91 µg/ml by using reducing Fe³⁺ assay, 53.37 and 51.27 µg/ml by using chelating Fe²⁺ assay, and 461.23 and 598.75 µg/ml by using hydroxyl radical scavenging assay, respectively. The results suggested that the polysaccharides, EPS and SPS from the endophytic fungusBerkleasmium sp. Dzf12 could be considered as a promising potential source for the development of natural antioxidants.

Key words: Polysaccharides, preparation, in vitro antioxidant activity, endophytic fungus,Berkleasmium sp. Dzf12, Dioscorea zingiberensis.