Tea Extract (egcg), Studied The Nature Of The Surfactant Micelle System

1. EGCG extracts and analysisThe feasible extracting technology of ion precipitation for epigallocatechin-3-gallate (EGCG) from Huangshan green tea is investigated. The EGCG extracts are analyzed by UV-vis spectrum, IR spectrum and high performance liquid chromatography. With the ratio of tea and solvent 1:25, the optimal operating conditions of extracting EGCG are found by orthogonal experiment,that is,80% ethanol as solvent,extracting 2 times. In the precipitation, the feasible conditions of the precipitation are: (Al³⁺+Zn²⁺) is as ion-coprecipitating agent. This ensures a higher yield and avoids a serious effect on the security of products at excessive concentration when Al³⁺, Ba2+ and other ions are singlely used. It also can reduce the waste caused by excessive adding metal salts.2. Behaviors of EGCG in Tween 80 micelleThe effects of EGCG on the first critical micelle concentration (cmc1) of nonionic surfactant (Tween 80) are studied by the methods of surface tension, ectrochemistry, UV-vis spectrum and fluorescence spectrum. The location of EGCG in Tween 80 micelles is also investigated. The results show that the cmc1 and the hydrodynamic radius of Tween 80 micelles increase with the increase of EGCG concentration. The partial structure of EGCG is located in the palisades of the micelle because of the hydrogen bond between the polar heads of Tween 80 and the hydroxyl groups of EGCG. When the aggregation of Tween 80 change from the pre-micelle to the spherical micelle, family, to the rod-like micelle, the enrichment of EGCG in micelle leads to the increase of the UV-vis absorption intensities of EGCG and the increase slowly the fluorescence intensities of EGCG. 3. Behaviors of EGCG in SDS micelleThe effects of EGCG on the cmc1 of anionic surfactant (sodium dodecyl sulfate, SDS) are studied by the methods of conductivity, surface tension, UV-vis spectrum and fluorescence spectrum. With the increase of EGCG concentration, the cmc1 and the hydrodynamic radius of SDS micelles increase. When SDS concentration is more than the cmc1, the micropolarity of the probe decreases. These indicate that EGCG is solubilized and located in the interphase bilayer of the micelle. When SDS concentration is up to its second critical micelle concentration, the micropolarity of the probe don't change. EGCG is difficult to located in the outside of the micelle palisade. The obtained results also show that SDS has no obvious influence on the UV–vis spectra of EGCG. SDS can lead to the decrease of the fluorescence intensity of EGCG.4. Behaviors of EGCG in MEG systemThe surface activities of N-Methyl-D-glucamine (MEG) and MEG/EGCG are studied using the methods of surface tension and conductivity. The interaction behaviors of MEG with EGCG are studied by the methods of UV-vis spectrum and fluorescence spectrum. The results show that EGCG has effects on the surface activities. EGCG with MEG can form aggregated assemble, which forms a specific structure. The aggregated assemble leads to the red-shift of the characteristic absorption peak of EGCG. When MEG concentration is low, the hydrophobic interaction exists between MEG and EGCG, which increases the fluorescence intensities of EGCG. With the increase of MEG concentration, the collision of the exciting state caused by the enrichment of EGCG leads to a loss of energy of EGCG molecules and the decrease of fluorescence intensity of EGCG.