Rice bran polysaccharides and oligosaccharides modified by Grifola frondosa fermentation: Antioxidant activities and effects on the production of NO

Abstract Rice bran polysaccharides (RBPSs) are valuable compounds with many biological activities. In this work, a fungus called Grifola frondosa , was selected to ferment defatted rice bran water extracts and modify the RBPSs, which were then isolated by ethanol precipitation and deproteinization. GC analysis of fermented products suggested they are composed of glucose, arabinose, galactose, mannose, and xylose at a molar ratio of 9:5:8:2:5, which was 32:4:6:2:5 before fermentation. HPLC analysis revealed that the molecular weight of unfermented RBPS was distributed mainly from 10 3 to 10 4  Da, and it changed to 10 2 to 10 3  Da after fermentation. Antioxidant activities and effects on the production of NO were analyzed and it indicated that the scavenging ratios of hydroxyl and DPPH radicals by the fermented products were significantly enhanced compared to the unfermented ones, and also the products fermented for 9 days exhibited two-way adjusting effects on the production of NO in macrophages.