Interaction of Plant Polyphenols with Liposomes
Interaction of Plant Polyphenols with Liposomes
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DOI：
10.1016/s1554-4516(06)04004-x
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发表时间：
2006-01-01
期刊：
影响因子：
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通讯作者：
Kumazawa, Shigenori
中科院分区：
文献类型：
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作者：
Nakayama, Tsutomu;Kajiya, Katsuko;Kumazawa, Shigenori
植物多酚的生物活性已通过各种方法在体外和体内检测，以预测其预防人类疾病的能力。在体外实验中发现的活性与培养的哺乳动物细胞应反映的量纳入细胞在孵育过程中。由于在哺乳动物细胞中没有发现植物多酚的特异性转运蛋白，因此推测大多数多酚通过被动转运被掺入细胞中，并且掺入的量与多酚对细胞膜的亲和力有关。通常，测量掺入细胞膜或细胞中的多酚的量是困难和不准确的，因为该量非常低，并且一些多酚不稳定并且在掺入后立即代谢。我们开发了一种方法来测量的多酚类化合物的脂质体与致密的内部水相的脂质双层纳入量。脂质体的相对密度比水的相对密度高，能够在孵育后短时间内通过超离心分离培养基和脂质体。因此，选择性地测量掺入分离的脂质体中的多酚的量。利用该方法对苯丙素类、没食子酸酯类、姜黄素、黄酮类和异黄酮类等植物多酚类化合物的亲和性进行了研究。特别是，茶儿茶素与脂质双层的相互作用进行了详细研究。表儿茶素（EC）、表没食子儿茶素（EGC）、表儿茶素没食子酸酯（ECg）和表没食子儿茶素没食子酸酯（EGCg）是绿色茶浸液中多酚类物质的主要成分。EGCg是这些化合物中最丰富的。报道的EC和EGC的生物活性通常低于它们相应的没食子酸酯，即，心电图和心电图。我们澄清EC和EGC对脂质体的脂双层的亲和力低于ECg和EGCg。这表明茶儿茶素与脂双层的相互作用部分地控制了它们的活性。除了没食子酸酯的存在下，B-环上的羟基基团的数目和C-环的空间位阻特性影响的儿茶素的脂双层的亲和力。此外，外部因素，如作为盐的浓度在水介质中的脂质体悬浮液，脂质双层的电荷和EC的存在支配的EGCg的脂质双层的亲和力。EGCg与模型膜的相互作用也通过固态P-31和H-2NMR进行了研究。这些NMR观察结果提供了直接的实验证据，EGCg分子与脂质双层相互作用。使用具有致密内部水相的脂质体，我们还澄清了ECg和EGCg位于脂质双层的表面上并扰乱膜结构。
The biological activities of plant polyphenols have been examined by various methods in vitro and in vivo for prediction of their ability to prevent human diseases. Their activities found in in vitro experiments with cultured mammalian cells should reflect the amount incorporated into the cells during incubation. Since no transporter specific to plant polyphenols has been found in mammalian cells, it is supposed that most polyphenols are incorporated into the cells by passive transport and the amount incorporated is related to the affinity of the polyphenol for the cell membranes. In general, measurements of the amount of a polyphenol incorporated into the cell membranes or the cells are difficult and inaccurate, because the amount is very low and some polyphenols are unstable and metabolized immediately after incorporation. We developed a method to measure the amount of polyphenols incorporated into the lipid bilayers of liposomes with a dense internal aqueous phase. The higher relative density of the liposomes than that of water enabled to separate the medium and the liposomes by ultracentrifugation for a short time after incubation. Consequently, the amount of a polyphenol incorporated into the separated liposomes was selectively measured. With this method, the affinities of various kinds of plant polyphenols, including phenyl propanoids, gallic acid esters, curcumin, flavonoids and isoflavones have been investigated. In particular, interaction of tea catechins with lipid bilayers has been investigated in detail. Epicatechin (EC), epigallocatechin (EGC), epicatechin gallate (ECg) and epigallocatechin gallate (EGCg) are the major components of polyphenols in green tea infusions. EGCg is the most abundant among these compounds. The reported biological activities of EC and EGC were often lower than those of their corresponding gallic acid esters, i.e., ECg and EGCg. We clarified that EC and EGC had lower affinities for the lipid bilayers of liposomes than ECg and EGCg. This indicates that the interaction of tea catechins with the lipid bilayer partly governs their activities. In addition to the presence of the gallic acid ester, the number of the hydroxyl groups on the B-ring and the steric character of the C-ring affected the affinity of the catechins for the lipid bilayers. Furthermore, the external factors such as salt concentration in an aqueous medium of the liposome suspension, the electric charges of the lipid bilayers and the presence of EC governed the affinity of EGCg for the lipid bilayers. The interaction of EGCg with a model membrane was also examined by solid state P-31 and H-2 NMR. These NMR observations provide direct experimental evidence that EGCg molecule interacts with the lipid bilayers. Using liposomes with a dense internal aqueous phase, we also clarified that ECg and EGCg were located on the surface of the lipid bilayers and perturbed the membrane structure.