Extraction,purification and antioxidant activity of total polyphenols from tea and grape skin

This study used oolong tea and grape skins as the research object. On the basic of single factor experiment,the extraction conditions of polyphenols from tea and grape skin were optimized by response surface methodology( RSM).Under the condition of liquid to solid ratio of 22∶1( m L / g),ethanol concentration of 48%( v / v)as solvent,at the temperature of 88℃,extraction time of 40 min,the average extraction yield of polyphenols was 4.76%,compared to the theoretical value,the relative error of 0.62%. Optimized by response surface regression equation had some practical significance.After purification by NKA9 type macroporous resin,polyphenol content increased from 25.54% to 82.19%. The antioxidant activities of the purified polyphenols and VCwere evaluated in vitro by hydroxyl free radical elimination ability and reducing power,respectively. The results showed that the hydroxyl free radical elimination ability and reducing power of the purify polyphenols are better than that of the same concentration of VC.The total polyphenols had ·OH elimination rate of 50%( IC50) when the concentration of total polyphenols 17.60μg / m L.The results showed that the total polyphenols can be used as a source of potential antioxidant.