Extraction Process Optimization and Antioxidant Activity of Green Tea Polysaccharides

Objective: To optimize the extraction process of green tea polysaccharide (GTP), purify the polysaccharide and analyze the antioxidant activity in vitro. Methods: The single factor experiments combined with response surface analysis was used to optimize the extraction process of polysaccharides. High performance gel permeation chromatography (HPGPC), gas chromatography (GC) and Fourier transform infrared spectroscopy (FTIR) were used to analyze the preliminary structure of polysaccharides, and the antioxidant activity of polysaccharides was studied by in vitro antioxidant experiments. Results: The optimal extraction conditions for GTP were determined as follows: Liquid/solid ratio 30:1 mL/g, extraction temperature 60 ℃, extraction time 70 min. Under these conditions, the yield of GTP reached to 10.56%. Structural analysis results showed that the total sugar, protein and uronic acid contents in GTP were 90.75%±3.69%, 0.92%±0.09%, and 0.82%±0.07%, respectively, and the average molecular weight was about 7.3 kDa. In vitro antioxidant test results showed that GTP had scavenging rates of 39.8%, 72.2% and 32.5% on ABTS⁺ free radical, DPPH free radical and hydroxyl free radical (OH·) at 2 mg/mL, respectively. Conclusion: In this process, green tea polysaccharides had presented high yield, low molecular weight and high antioxidant activity.