Fluorescent Properties And Analysis Of Anctive Components Of Tea

In this thesis, fluorescence properties of (+)-Catechin (C) and (-)-Epicatechin (EC) were studied. Influence of experimental conditions on fluorescence spectroscopy was inspected. The fluorescence spectra of West Lake Longjing tea and Kuding tea were studied. Two kinds of pigments with red color when irradiated with 365nm UV-irradiation were separated by column chromatography.The main contents of the thesis were as follows:1. The native fluorescence and sensitized fluorescence properties of C and EC were studied.The impacts of acidity, organic solvents, metal ions, surface active agent (SDS andβ-CD) on fluorescence spectroscopy were inspected. Under acidic conditions, catechins solution had a stable fluorescence. The maximum excitation and emission wavelengths were 280 nm and 311 nm. As the acidity of solution changes from pH 5 to pH 9, fluorescence decreases. When pH greater than 9, flurescence disearpered due to phenolic hydroxyl proton ionization. Using L-tryptophan as a reference, fluorescence quantum yields of C and EC were determined to be 0.062 and 0.047, respectively. The fluorescence character of Caffeine and Theophylline in tea was also studied, but no fluorescence was found.2. Three-dimensional fluorescence spectra of 21 kinds of tea were studied. It was found that they had the similar fluorescence peaks at short wavelengths. The fluorescence properties of two types of tea water extract were studied in detail. It was discovered that the main components of tea were catechins. In selected conditions, a good linear relationship between fluorescence intensity and concentration was found, which can be used for the quantitative determination of the fluorescence components of tea.3. Using a method of high-performance liquid chromatography with fluorescence detection, C and EC in the tea were determined at the same time. This new method can also be used for the determination of C and EC in Chinese herbal medicines.4. Using column chromatography method, two kinds of red fluorescence substances in tea were separated. Its three-dimensional fluorescence spectra were investigated, and their molecular character was estimated based on the measurement of 1H-NMR, 13C-NMR, infrared absorption spectroscopy and mass spectrum.