Structural elucidation and antioxidant activity of a novel polysaccharide (TAPB1) from Tremella aurantialba

A novel water-soluble acidic heteropolysaccharide (designated as TAPB1), with a mean molecular weight of 7.6 × 105 Da, was obtained from fruiting bodies of Tremella aurantialba. The heteropolysaccharide had a carbohydrate content of ∼97.6% and a negative response to the Bradford test. Monosaccharide composition analysis showed that TAPB1 comprised d-mannose, d-xylose, and d-glucuronic acid in the ratio 3.1:2.9:1.2, with trace amounts of d-galactose, d-glucose, and d-galacturonic acid. Methylation data and nuclear magnetic resonance spectral analysis indicated that TAPB1 contained an α-(1 → 3)-linked mannopyranosyl backbone, partially substituted at the O-4 positions with a side chain composed of two xyloses and at the O-2 position with a side chain comprising xylose and glucuronic acid. Antioxidant assays showed that TAPB1 exerted a significant scavenging effect on superoxide radicals and H2O2 in a dose-dependent manner.