Structure elucidation of a non-branched and entangled heteropolysaccharide from Tremella sanguinea Peng and its antioxidant activity

• Structure of a polysaccharide was established by NMR and chemical approaches.
• The main-chain was mainly composed of (1 → 3)-linked-glycosidic linkages.
• TEM analysis revealed a primary entangled state in the microstructure.
• TSP-II was a non-branched polysaccharide.

A crude polysaccharide was extracted from the edible fungi Tremella sanguinea Peng, and a polysaccharide TSP-II (31.56%) was separated and purified from the crude polysaccharide. TSP-II was a homogeneous polysaccharide by the high-performance size-exclusion chromatography (HPSEC), had a molecular weight of 356 kD and consisted mainly of mannose, xylose, galactose and glucose at a molar ratio 5.9:2.4:1:1.1. The structural assignment of TSP-II was carried out using fourier transform infrared spectroscopy (FTIR) analysis, periodate oxidation-smith degradation, partial hydrolysis with acid, methylation analysis and nuclear magnetic resonance (NMR) studies, and the repeating unit of TSP-II was thus determined. The result indicated that →3)-α-d-Manp-(1→, →2)-α-d-Xylp-(1→, →6)-α-d-Glcp-(1→ and →3)-α-d-Galp-(1→ formed the major components of the main-chain structure, and TSP-II was a non-branched polysaccharide. Transmission electron microscopy (TEM) analysis revealed a primary non-branched and entangled state in its microstructure. TSP-II had higher scavenging activities on hydroxyl radical (EC50 = 0.088 mg/ml) and superoxide radical (EC50 = 0.127 mg/ml) than Vitamin C (Vc).