Preparation And Chemical Modification On Tea Polyphenols And The Study On The Antioxidant Activity Of The Liposoluble Tea Polyphenols

For the novel biological and physiological active functions, the tea polyphenols derived from natural tea leaves are always the focus of world's attention. And with the development to the depth, the fields of applications are becoming larger and larger. Tea polyphenols have many phenolic hydroxyls in their chemical structures, which are not only the reasons for its novel antioxidant function, but also the reasons for its high water-solubility and poor lipid-solubility, which limit their practical application. Therefore a method is introduced to come to the aim of having quite higher solubility in lipid through the change on the chemical molecule level under the condition of non-sacrifice of the outstanding biological and physiological active activities, and provide the possibility of using effectively in the lipidic environment with the tea polyphenols.Recent researches on the tea polyphenols have demonstrated significantly that monomers of the tea polyphenols are inferior to the whole on the antioxidant ability; It was found that assorted catechins show stronger ability to scavenge the free radicals than the monomers of tea polyphenols and the effects are enhanced with more monomers; Moreover, the tea polyphenols derived from natural tea leaves show the strongest synergistic antioxidation against free radicals. After all, it is not easy to separate the various monomers from the mixture. In this thesis, a theoretical and practical method of integrated chemical modification is introduced to modify the tea polyphenols by esterification and the liposoluble tea polyphenols are prepared.On the base of preliminary experiments, the esterification process is investigated systematically through mono-factor and orthogonal experiments. The key influent factors of reaction, such as the ratio ofreactants, quantity of the catalyst and reaction temperature are discussed in detail. Through experiments, the optimum technical processing condition is put forward. The manufacturing process is short, simple, practical and friendly to environment; no toxic reagents are used and with higher atom utility.The liposoluble tea polyphenols are tested by both physical and chemical methods. The results of experiments show that modified products, namely liposoluble tea polyphenols represent good solubility in lipid and have no side effects to the colour, luster and transparence etc. The theory of solubility parameters is introduced in analyzing the solubility of liposoluble tea polyphenols in lipidic environment and the results of experiments are consistent with the theory. In this research the Fourier Transform Infrared Spectrum is applied to characterize the chemical structures of the liposoluble tea polyphenols, and the modified products' chemical characteristics are confirmed.Through intensification experiments, the antioxidant activity of liposoluble tea polyphenols is investigated. The results show that liposoluble tea polyphenols have remarkable inhibition on the lipid peroxidation.The reaction kinetics of the tea polyphenols' esterification are studied in the integral batch-type reactor which is operated under the thermostatic condition. The kinetic model of tea polyphenols' esterification is set up and the parameters in the model are obtained from the experimental data. The characteristics of the kinetics and the engineering realization are discussed preliminarily, and the work is preferable for the further amplificatory investigation.Zhang Xinqiang (Chemical Engineering) Directed by Professor Zhang Xiaolin...