Structural elucidation and antioxidant activity of a water-soluble polysaccharide from the fruit bodies of Bulgaria inquinans (Fries)

The non-lichenized ascomycete Bulgaria inquinans (Fries), growing in the Changbai Mountain of China, has been used as medicinal diet for many years. In a previous study, we have reported that a heteropolysaccharide BIWS-4b from the fruit bodies of B. inquinans (Fries) exhibited markedly antimalarial and immunostimulating activities. In this paper, the structural features and antioxidant activity of BIWS-4b were investigated. The results showed that BIWS-4b contains an α-(1 → 2), (1 → 6)-mannan core to which the glucogalactan chains are attached. The glucogalactan chains were composed of (1 → 6)-, (1 → 5)- and (1 → 5,6)-linked β-Galf, (1 → 4)-linked and non-reducing terminal β-Glcp units, and might be attached to the mannan core at the O-2 positions of α-Manp units. The antioxidant assays showed that BIWS-4b exhibited good activities, including free radicals scavenging effects, ferrous ion-chelating ability and reducing power. Thus, BIWS-4b could be used as a natural antioxidant agent for food and pharmaceutical industries.