Characterization of polyphenols from green tea leaves using a high hydrostatic pressure extraction

A new extraction technique, high hydrostatic pressure extraction (HHPE), was used to obtain polyphenols from green tea leaves. Various experimental conditions, such as different solvents (acetone, methanol, ethanol and water), pressure (100, 200, 300, 400, 500, 600 MPa), holding time (1, 4, 7, 10 min), ethanol concentration (0-100% mL/mL), and liquid/solid ratio (10:1 to 25:1 mL/g) for the HHPE procedure, were investigated to optimize the extraction. The optimal conditions were as follows: 50% (mL/mL) of ethanol concentration, 20:1 (mL/g) of liquid/solid ratio and 500 MPa of high hydrostatic pressure for 1 min. Under such conditions the extraction yield of polyphenols was up to 30+/-1.3%. The extraction yields of polyphenols with HHPE for only 1 min were the same as those of extraction at room temperature for 20 h, ultrasonic extraction for 90 min and heat reflux extraction for 45 min, respectively. On the basis of the extraction yields of polyphenols, extraction time and the percentages of polyphenols in extracts, the HHPE is more effective than the conventional extraction methods studied.