Purification, chemical characterization and antioxidant activities of polysaccharides isolated from Mycena dendrobii

•Two polysaccharides were isolated from the fermentation liquid of M. dendrobii.•MDP–1 mainly composed of mannose, xylose, and galactose with Mw of 6.02 × 105 Da.•MDP–2 mainly composed of galacturonic acid, galactose and rhamnose with Mw of 1.70 × 106 Da.•MDPs could effectively scavenge superoxide, hydroxyl and DPPH radicals.•MDP–2 performed noticeable antioxidant activities. Two polysaccharides, MDP-1 and MDP-2, were obtained from the fermentation liquid of M. dendrobii by anion exchange chromatography and gel filtration. Their chemical structures were measured by FT-IR, GC, 1H and 13C NMR spectra, indicating the mainly compositions of mannose, xylose, and galactose for MDP-1; galacturonic acid, galactose and rhamnose for MDP-2. Furthermore, the antioxidant activities of MDPs were investigated, showing different antioxidant activities, in which MDP–2 performed noticeable, with excellent superoxide radical activity better than BHT, high DPPH radical activity (IC50 at 227 μg/mL) comparable with BHT, moderate reducing power activity and hydroxyl radical scavenging activity. The results indicated that the fermentation liquid of M. dendrobii could be used as a potential natural source of antioxidant.