Structural Characterization and In Vitro Antioxidant Activity of a Novel Polysaccharide from Summer-Autumn Tea

To enhance the utilization of summer-autumn tea, a water-soluble polysaccharide (D1N1) was isolated through a series of techniques including hot water extraction, ethanol precipitation, and column chromatography. The structure of D1N1 was determined through the utilization of ultraviolet, Fourier-transform infrared, high-performance anion-exchange chromatography, gas chromatography-tandem mass spectrometry, and nuclear magnetic resonance. The results revealed that glucose was the predominant component of D1N1, accounting for 95% of its composition. Additionally, D1N1 also contained galactose, arabinose, and rhamnose. The molecular weight (Mw) of D1N1 was determined to be 224.71 kDa. The backbone of D1N1 consisted of -> 4)-alpha-D -Glcp (1 ->, -> 3,4)-alpha-D-Galp-(1 ->, -> 4,6)-alpha-D -Glcp (1 -> at a molar ratio of 35:1:1, and branching at the O-3 position of -> 3,4)-alpha-D-Galp-(1 -> and O-6 position of -> 4,6)-alpha-D-Glcp (1 -> with alpha-D -Glcp (1 ->. In addition, the antioxidant activity of D1N1 was also evaluated. D1N1 exhibited excellent antioxidant bioactivity against the DPPH, superoxide anion radical, and ABTS+ radical. These findings provide a theoretical basis for the application of summer-autumn tea polysaccharide as a potential functional food.