الفهرس 
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Abstract
The plant Camellia sinensis yields both green and black tea where the Green tea is produced by lightly steaming the fresh cut leaf. Green tea is very high in polyphenols with potent antioxidant and anti-cancer properties. The chemical composition of green tea varies with climate, season, horticultural practices and age of the leaf where the major components of interest are the polyphenols. The major polyphenols in green tea are flavonoids (e.g., catechin, epi-catechin, epi-catechin-gallate, epi-gallo-catechin-gallate and proanthocyanidins).
The lipids, which are in the liquid-crystal state, trap aqueous solutes in aqueous compartments between a series of lipid bilayers forming spherules called liposomes; which exhibit many of the properties of natural membrane-bounded structures. Thus liposomes constitute a valuable model system with which to study the properties of biological membranes that may be dependent on their lipid components.
The aim of work is to investigate, in vitro, the mechanism of interaction between green tea polyphenols molecules and cell membrane represented by liposomes. The approach of our work is based on 2 phases: first is testing the encapsulation efficiency of liposomes to polyphenols. Second, investigating the structural and phase transition temperature changes for lipid bilayer using FTIR and DSC.
The results showed that each concentration of green tea polyphenol had an effect on both the structure and phase-transition temperature of control DPPC liposomes. Optical density investigation reflected strong insertion of green tea polyphenosl when high concentrations were used. FTIR analysis for CH stretching region showed that control DPPC suffered
little conformational disorder represented by changes in wave number and band width, especially for CH3 symmetric stretching band.
Non-linear curve fitting and peak analysis of carbonyl band in the FTIR spectrum for control DPPC liposomes and polyphenol-containing liposomes showed many estimated components with wide range maxima. Remarkable variations are noticed in both the frequency and band width of estimated components for polyphenol-containing liposomes when compared to control DPPC liposomes. Estimated number of peaks reflects a heterogeneous structure of DPPC incorporated with green tea polyphenols. This heterogeneity suggests the existence of heterogeneous microdomains and reflects the changes in the hydrogen-bonding interactions in the interfacial region.
DSC calorimetry was used to investigate the changes in pre-transition and main-transition temperatures of control DPPC when EGC is incorporated with different concentrations. Both pre-transition and main temperatures (33.14 oC and 41.3) of control DPPC liposomes were highly affected by incorporating green tea polyphenols. Main transition temperature was the most affected one which reached elevated values (above 90 oC) when some polyphenols with certain concentrations were incorporated.