Physicochemical characterization and antioxidant activity of a polysaccharide isolated from oolong tea

Oolong tea polysaccharide (OTPS) is a kind of water-soluble polysaccharide isolated from oolong tea. Its molecular weight, composition, and structure were analyzed by laser light scattering analysis, chemical methods, gas chromatography, and atomic force microscopy (AFM). Antioxidant potential was detected by hydroxyl radical scavenging, inhibition of lipid peroxidation, DPPH radical scavenging, and reducing power assays. Results showed that OTPS was a non-reductive acid heteropolysaccharide bound to protein. The amounts of uronic acid, protein and neutral sugar in OTPS were 40.65, 19.59, and 26.66%, respectively. The neutral sugar was composed of d-rhamnose, l-arabinose, d-galactose, and d-glucose with a molar ratio of 1.37:1.89:1.00:1.30. The molecular weight of OTPS was 1.28 × 106 Da and the second viral coefficient was 2.36 × 10−4 cm3 mol/g2. A globular image of OTPS was imaged by AFM. OTPS showed effective antioxidant activities on hydroxyl radical scavenging assay and inhibition assay of lipid peroxidation.