Extracellular polysaccharide with novel structure and antioxidant property produced by the deep-sea fungus Aspergillus versicolor N2bC

An extracellular polysaccharide, NI, was obtained from the culture medium of the deep-sea fungus Aspergillus versicolor N(2)bc by a combination of ethanol precipitation, ion-exchange and gel filtration chromatography. N1 was a mannoglucogalactan with molecular weight of about 20.5 kDa. Results of chemical and spectroscopic analyses, including Fourier-transform infrared, one- and two-dimensional nuclear magnetic resonance spectroscopy showed that the main chain of N1 consisted of -> 2)-alpha-D-Glcp-(1 ->, -> 2)-beta-D-Glcp-(1 -> and -> 6)-beta-D-Manp-(1 -> units, substituted at C-6 position of 2)-alpha-D-Glcp-(1 -> units. The branches were composed of galactofuranose-oligosaccharides built up of -> 5)-beta-D-Galf-(1 ->, -> 6)-beta-D-Galf-(1 -> and terminal beta-D-Galf units. At an average, there were two branching points for every five sugar residues in the backbone. N1 possessed a high in vitro antioxidant activity as evaluated by scavenging assays involving superoxide, 1,1-dipheny1-2-picrylhydrazyl, hydroxyl radicals and reducing power. The investigation revealed that N1 was a novel antioxidant polysaccharide differing from previously described extracellular polysaccharides and could be a potential antioxidant. (C) 2016 Elsevier Ltd. All rights reserved.