Study On The Method Of Extraction And Isolation Of Polyphenols From Pu'er Tea

Pu'er tea is post fermented tea, a special tea with many bioactivities processed in China. The method of extraction and isolation of polyphenols from pu'er tea was studied in my project in order to find feasible way to further develop pu'er tea.1. Parameters for extraction of polyphenols from pu'er teaThe influence of temperature, heating time, ratio of tea to solvent, con centration and pH value of solvent on extraction rate of pu'er tea polyphenols were studied. The results showed that all parameters except pH value affected the extraction rate noticeably, and the optimized parameters were: using 30% ethanol water solution as extract solvent, the ratio of tea to solvent was 1:30, and extracting at 80°C for 50min.2. The method for isolation of polyphenols from Pu'er teaFour isolation methods of polyphenols including precipitating by metal ion, extracting by organic solvents, extracting by supercritical fluid CO₂ and isolating by macroporous adsorption resin were compared and the yield, purity and antioxidant activity of polyphenols get from the four methods were studied. The result showed that the yield change tendency of four methods was declined from organic solvents extraction to ion precipitation extraction to supercritical fluid CO2 extraction to macroporous adsorption resin extraction; and the purity change tendency was increasing from supercritical fluid CO₂ extraction to organic solvents extraction to ion precipitation extraction to macroporous adsorption resin extraction; the content of catechins in polyphenols isolated by four methods were greatly different, the content from macroporous adsorption resin extraction was largest, and the content from supercritical fluid CO₂ extraction was least. The results also indicated that the polyphenols isolated from Pu'er tea had great ability to scavenge superoxide anion radical. All results leaded to the conclusion that Pu'er tea polyphenols extracting by organic solvent had good quality, and the method was easy to operate and feasible for industry.Further study on the conditions of extracting by ethanol acetate indicated that the yield of polyphenols was greatly affected by the time and times. The optimize condition was extracting for 40min, 2 times.3. The method of purification of pu'er tea polyphenolsSeveral kinds of resins were compared on the capability of static adsorption , desorption to Pu'er tea polyphenols and the content of catechins in the products desorpted. Results showed that No.3 was more suitable than others.The resin column was eluted by ethanol water solution. The eluting ability increased with the ethanol concentration increasing below 80% while decreased with concentration increasing above 80%. Considering the eluting capability and the product quality, the concentration of crude polyphenol was 10mg/ml, the eluent was 80% ethanol water solution and the flow rate was 0.8ml/min.