Extraction Of Tea Polyphenols From Green Tea And Preparation Of Tea Polyphenols Liposomes

Tea polyphenols are functional materials and abound in the tea, which is clean up of radical in human being, anti-caducity, anti-radialization, anti-cancer, lowering the blood-lipids, and so on. The traditional extraction of polyphenols was used in solvents, which caused many solvents left in the products and environment pollution, etc. This dissertation adopt microwave-assisted extraction method to extract tea polyphenols from green tea-leaf. The method is privileged in the low extraction temperature, high efficiency, no organic solvent left in the product with good quality. For the poor stability and vulnerable oxidation characteristics of the tea polyphenol, in this paper, it was prepared into liposome.Tea polyphenol liposome can enhance bioavailability of tea polyphenol and have a good targeting effect on liver.The main centents and conclusions of this paper are listed as follows:In the research of the conditions optimization of microwave-assisted extracting tea polyphenols from green tea, single factor experiment and orthogonal experiment were used to analysis the effect of facts and the best extraction technology. The microwave intensity, microwave radiate time, frequency and the ratio of tea to water affect the extraction efficiency by using the microwave-assisted technology. The polyphenols increase with the stronger microwave intensity and with the longer time. The polyphenol yield also increases with the microwave radiate frequency increasing, but it consumes too much energy. The ratio of tea to water affects the polyphenol yield, and it consumes much energy in the concentration process. The factors affecting the polyphenol extraction are in the order: microwave radiate time > microwave intensity > the ratio of tea to water > frequency. The optimizing technological parameters are: microwave intensity of 600W, microwave radiate time of 3 minutes, one time and the ratio of 1:20.The technological parameters were investigated using single factor experiments: the ratio of lecithin to tea polyphenols is 1:7-1:9, the ratio of lecithin to cholesterol is 3:1-5:1, PBS PH is 6.5-7.0, PBS concentration is 5mmol ? L-1, ultrasonic time is 3-5 min. On the basis of single factor experiment, response surface analysis was used to optimize the process conditions including four independent variables: the ratio of lecithin to tea polyphenols, ultrasonic time, PBS PH, the ratio of lecithin to cholesterol.The optimal conditions were obtained for the preparation of tea polyphenols liposome by thin film ultrasonic dispersion method: the ratio of lecithin to tea polyphenols 1:8, the ratio of lecithin to cholesterol 4:1, PBS PH 6.62, ultrasonic time 3-5 min, PBS concentration is 5mmol ? L-1. The theoretical optimal embedding rate was 60.36%, the embedding rate in practice by verifying was 60.09±0.69%.The physical and chemical properties of tea polyphenols liposome were investigated using Nano-2S particle size analyzer, FT-IR spectrum, Transmission electron microscopy (TEM). Permeability test indicated that when the liposome was placed in freezer (3-5℃), its state changed very little as permeability was low and it was suitable for long-term storage with strong stability.Transmission electron microscopy images showed that tea polyphenols liposomes was neat vesicles with rounded shape and uniform size.The mean size was 160.4 nm, less than 200 nm, and the dispersion coefficient was 0.281, which indicated that the size distribution was small.ζ- potential value was -67.2, it implyed that the stability of tea polyphenols liposomes prepared was good. It was proved the coacervate was formed by the physical interaction among tea polyphenols,Lecithin and cholesterol using FT-IR spectrum, not chemical interaction. Drug release experiment was analysed by some kinetic equations.For example, the Zero-order equation, the first-order equation, the Higuchi equation, the Niebergull square root equation, the Hixcon-crowell cube root equation and the Weibull equation. The results of data fit indicate that the first-order equation agrees with experimental best.