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Abstract

Green tea is well known for its various physiological effects, but there are few studies relating the tastes of tea catechins to their biological activities. We have focused on the interaction of tea catechins with phospholipids to clarify the relationship. The galloyl-type catechins, epicatechin gallate (ECg) and epigallocatechin gallate (EGCg) usually show beneficial properties including chemopreventive, antimutagenic and antioxidant actions more potently than the nongalloyl-type catechins, epicatechin (EC) and epigallocatechin (EGC). The difference in their chemical structures is correlated with their affinity for phospholipid membranes and incorporated amounts into liposomes. This indicates that the interaction of the galloyl-type catechins with phospholipids are always stronger than the nongalloyl-type catechins. Molecular-level insights into how tea catechins interact with lipid membranes were acquired using NMR spectroscopy. Based on solution and solid-state NMR studies with isotropic bicelles and liposomes as models of phospholipid membranes, it is proposed that ECg and EGCg interact with the surface of lipid membranes via the choline moiety of the phospholipids. Since the galloyl-type catechins have been reported to be more bitter and astringent than the nongalloyl-type catechins, both of their tastes and biological activities could be ascribed to the interaction.

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