Interaction of plant polyphenols with lipids and proteins

(1)测定脂质体的载药量，以确定异黄酮类化合物的亲脂性。在异黄酮类结构中，A环的5位羟基和B环4‘位的甲氧基的存在增加了掺入量。采用V79细胞集落形成实验研究异黄酮类化合物的细胞毒性。(2)(+)-儿茶素类化合物的抗菌活性随烷基链长度的延长而增强。含三个或三个以上碳链的衍生物对脂质体膜表现出很强的亲和力。链长超过五个碳的衍生物破坏了膜。这些结果表明，(+)-儿茶素衍生物的亲脂性和对脂质体膜的破坏能力参与了它们的抗菌活性。(3)通过监测在H_2O_2和高铁肌红蛋白存在下，酚酸、咖啡酸、对香豆酸和阿魏酸在亚油酸胶束中的耗氧量，考察了它们的抗氧化作用。酚酸的主要抗氧化作用归因于在pH 7.4时还原高铁肌红蛋白和在pH 3.4时抑制第二相胶束内发生的链式反应。(4)用固体核磁共振研究了茶儿茶素-表没食子儿茶素没食子酸酯(EGCG)与模型膜二肉豆蔻基磷脂酰胆碱(DMPC)的相互作用。随着EGCG的加入，DMPC磷酸基团的化学位移各向异性减小。DMPC脂质体中[4-2H]EGCG的~2H核磁共振谱表明，与固相中的四极分裂相比，具有更小的四极分裂。这些观察结果提供了EGCG分子与脂质双层相互作用的直接实验证据。

(1) The amount of incorporated into liposomes was measured to determine lipophilicity of isoflavonoids. The presence of a hydroxyl group at 5-position of the A-ring and a methoxyl group at 4'-position of the B-ring in the isoflavonoid structure increased the amount incorporated. The cytotoxicity of isoflavonoids was investigated by a colony-formation assay with V79 cells. The structure-activity relationship of the cytotoxic activity reflected the amount incorporated.(2) The antibacterial activity of (+)-catechin derivatives increased with elongation of the alkyl chain length. The derivatives with a chain of three carbons or more showed strong affinity for the liposome membrane. The derivatives with chains longer than five carbons destroyed the membrane. These results implied that the lipophilicity and disrupting ability of the (+)-catechin derivatives to the liposome membrane participate in their antibacterial activity.(3) Antioxidant effects of the phenolic acids, caffeic acids, p-coumaric acid, and ferulic acid, were investigated by monitoring O_2 consumption in the linoleic acid micelles in the presence of H_2O_2 and metmyoglobin. The main antioxidant effects of the phenolic acids was ascribed to reduction of ferrylmyoglobin at pH 7.4 and inhibition of the chain reaction occurring inside of the micelles in the second phase at pH 3.4.(4) The interaction of a tea catechin, epigallocatechin gallate (EGCg), with the model membrane of dimyristoylphosphatidylcholine (DMPC) was studied by solid-state ^<31>P and ^2H NMR. The ^<31>P chemical shift anisotropy of the DMPC phosphate group decreased on addition of EGCg. The ^2H NMR spectrum of [4-^2H]EGCg in the DMPC liposomes gave deuterium nuclei with much smaller quadrupole splittings than those in the solid phase. These observations provide direct experimental evidence that the EGCg molecule interacts with the lipid bilayers.