Analytical study of catechins in lipid bilayers

(1)用脂质体系统研究了茶儿茶素与脂双层的相互作用。作为儿茶素的结构因素，B环上的羟基数目、没食子酰基的存在和C环的立体化学结构决定了脂双层的亲和力。作为外部因素，水介质中的盐浓度、膜的电荷和其他儿茶素的存在也控制着对脂质双层的亲和力。(2)儿茶素如EGC和EGCG被超氧化物氧化，伴随着过氧化氢的形成，它们的细胞毒性作用归因于过氧化氢的形成。(3)用固体核磁共振研究了EGCG与模型膜的相互作用。这些核磁共振观察首次提供了EGCG分子被引入到脂质双层的直接实验证据。(4)用革兰氏阳性菌评价了不同烷基链长的(+)-儿茶素衍生物的抗菌活性。烷基链为4~6个碳的化合物具有很高的抗菌活性。对这些衍生物与脂质双分子层相互作用的研究表明，衍生物的抗菌活性增强是由于对细菌膜的破坏。

(1) Interaction of tea catechins with lipid bilayers has been investigated with liposome systems. As structural factors of catechins, the number of hydroxyl groups on the B-ring and the presence of the galloyl moiety, and the stereochemical structure of the C-ring governed the affinity for the lipid bilayers. As external factors, the salt concentration in an aqueous medium, the electric charge of the membrane, and the presence of other catechins also governed the affinity for lipid bilayers.(2) The gallocatechins such as EGC and EGCg were oxidized by superoxide, accompanied by the formation of hydrogen peroxide, and their cytotoxic effects were ascribed to the hydrogen peroxide formation.(3) The interaction of EGCg with the model membrane of dimyristoylphosphatidylcholine was studied by solid-state ^<31>P-and ^2H-NMR. These NMR observations provide the first direct experimental evidence that an EGCg molecule is incorporated into the lipid bilayers.(4) The antibacterial activity of (+)-catechin derivatives with various alkyl chain lengths was evaluated with Gram-positive bacteria. The antibacterial activity of the compounds with the alkyl chain of 4 to 6 carbons was very high. Investigation of the interaction of these derivatives with lipid bilayers revealed that the reinforcement of the antibacterial activity by the derivatization arises form the damage to bacterial membranes.