Structural characterization and antioxidant properties of an exopolysaccharide produced by the mangrove endophytic fungus Aspergillus sp. Y16

► Exopolysaccharide As1-1 was prepared from Aspergillus sp. Y16. ► The main chain of As1-1 consisted of mannopyranose units. ► The side chain contained specific galactofuranose units. ► As1-1 possessed a good antioxidant activity in vitro. ► As1-1 was a novel exopolysaccharide and potential source of antioxidant.