Ｅｐｉｇａｌｌｏｃａｔｅｃｈｉｎ　ｇａｌｌａｔｅの膜傷害作用に関する研究　ｐｏｌｙｍｙｘｉｎ　Ｂとの比較

DOI 被引用文献1件 参考文献28件

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タイトル別名
  • Mechanism of membrane damage by (-) epigallocatechin gallate: comparison with polymyxin B.
  • comparison with polymyxin B
  • polymyxin Bとの比較

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We studied the mechanism of membrane damage induced by (-) epigallocatechin gallate (EGCg) isolated from extracts of Camellia sinensis (green tea). The amount of EGCg adsorbed by Staphylococcus aureus was 1.5 to 3 times as much as that of EGCg adsorbed by Escherichia coli and Salmonella Typhimurium. This result indicates that the difference in antibacterial activity of EGCg between Gram-positive and Gram-negative bacteria depends on the amount of EGCg adsorbed across the surface of these organisms. The adsorption of EGCg to S. Typhimurium wild type (SL696) was lower than that of EGCg to S. Typhimurium lipopolysaccharide (LPS) mutants (SL1069 and TA2168). This result suggests that LPS on outer membranes of Gram-negative bacteria inhibit adsorption of EGCg to the surface of organisms. There were, however, no significant differences in MIC of EGCg among these strains of S. Typhimurium. To further explore the mode of action of EGCg, we compared the membrane-damaging activities of EGCg and polymyxin B (PL-B). EGCg damaged phosphatidylcholine (PC) liposome membranes and caused leakage of 5, 6-carboxyfluorescein (CF) encapsulated in the liposomes. However, phosphatidylserine (PS) contained in PC liposomes inhibited CF-release dose-dependently, and the release was inhibited at 5 mol% of PS. On the other hand, CF-release from PC liposomes caused by PL-B was in proportion to the amount of PS contained in the liposome membrane. It seems that the membrane damage induced by EGCg and PL-B depends on the electrical property of the material. We, therefore, assume that the net charge of EGCg is negative, since positively-charged PL-B binds negatively-charged lipid bilayers.

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