Isolation, characterization and antioxidant activity of polysaccharide from Schisandra sphenanthera

•Characterization of SSPP11 was firstly elucidated by GC–MS, NMR, IR, HPLC, etc.•Backbone consisted with 1,6, 1,2 and 1,3,6 Man, 1,4 and 1,6Glu, 1,4 and 1,4,6Gal.•Man, Glu, Gal of different linkage types distributing in branched chains.•SSPP11 had triple helix stereo-configuration.•Its activity was correlated with structure and conformation.

A water-soluble polysaccharide (SSPP11) from Schisandra sphenanthera was purified by DEAE-cellulose and Sephadex G-100 columns. Structure of SSPP11 and its antioxidant activity was evaluated. Results showed that SSPP11 has a molecular weight of 5.3 × 103 Da and is composed of Man, Glu and Gal. A linkage analysis and NMR study revealed that SSPP11 has a backbone of →1)-d-Man-(6→, →1)-d-Manp-(2→, →1)-d-Glup(4→, →1)-d-Glup-(6→, →1)-d-Galp-(4→, →1)-d-Galp-(4,6→ and →1)-d-Manp-(3,6→, with Man, Glu and Gal, which are distributed in branched chains. The Congo red absorption test revealed that SSPP11 has a triple helix stereo-configuration. Moreover, antioxidant activity of SSPP11 was stronger than the polysaccharide from Schisandra chinensis (Turcz.) Baill. In sum, this study demonstrates that a moderate molecular weight, triple helix stereo-configuration and higher degree of branching are beneficial for exerting antioxidant activity.