Analytical study of catechins in lipid bilayers

(1)用脂质体体系研究了儿茶素与脂质双层的相互作用。作为儿茶素的结构因素，B环上羟基的数量和没食子酰基部分的存在，以及C环的立体化学结构决定了对脂质双层的亲和力。作为外部因素，在水介质中的盐浓度，膜的电荷，和其他儿茶素的存在下也支配的脂双层的亲和力。(2)没食子儿茶素如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)本文用固体核磁共振方法研究了EGCg与二肉豆蔻酰磷脂酰胆碱模型膜的相互作用<31>。这些NMR观测提供了第一个直接的实验证据表明，EGCg分子被纳入脂质双层。(4)用革兰氏阳性菌评价了具有不同烷基链长度的（+）-儿茶素衍生物的抗菌活性。含4 ~ 6个碳原子的烷基链的化合物具有很高的抗菌活性。这些衍生物与脂质双层的相互作用的研究表明，衍生化的抗菌活性的增强来自对细菌膜的损伤。

(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.