title: Interaction of epicatechin gallate with phospholipid membranes as revealed by solid-state NMR spectroscopy.
abstract: Epicatechin gallate (ECg), a green tea polyphenol, has various physiological effects. Our previous nuclear Overhauser effect spectroscopy (NOESY) study using solution NMR spectroscopy demonstrated that ECg strongly interacts with the surface of phospholipid bilayers. However, the dynamic behavior of ECg in the phospholipid bilayers has not been clarified, especially the dynamics and molecular arrangement of the galloyl moiety, which supposedly has an important interactive role. In this study, we synthesized [13C]-ECg, in which the carbonyl carbon of the galloyl moiety was labeled by 13C isotope, and analyzed it by solid-state NMR spectroscopy. Solid-state 31P NMR analysis indicated that ECg changes the gel-to-liquid-crystalline phase transition temperature of DMPC bilayers as well as the dynamics and mobility of the phospholipids. In the solid-state 13C NMR analysis under static conditions, the carbonyl carbon signal of the [13C]-ECg exhibited an axially symmetric powder pattern. This indicates that the ECg molecules rotate about an axis tilting at a constant angle to the bilayer normal. The accurate intermolecular-interatomic distance between the labeled carbonyl carbon of [13C]-ECg and the phosphorus of the phospholipid was determined to be 5.3±0.1 Å by 13C-(31)P rotational echo double resonance (REDOR) measurements. These results suggest that the galloyl moiety contributes to increasing the hydrophobicity of catechin molecules, and consequently to high affinity of galloyl-type catechins for phospholipid membranes, as well as to stabilization of catechin molecules in the phospholipid membranes by cation-π interaction between the galloyl ring and quaternary amine of the phospholipid head-group.
authors.affiliation: Department of Food and Nutritional Sciences and Global COE Program, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan. yuekusa@ims.ac.jp
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Uekusa
authors.forename: Miya
authors.initials: M
authors.lastname: Kamihira-Ishijima
authors.forename: Osamu
authors.initials: O
authors.lastname: Sugimoto
authors.forename: Takeshi
authors.initials: T
authors.lastname: Ishii
authors.forename: Shigenori
authors.initials: S
authors.lastname: Kumazawa
authors.forename: Kozo
authors.initials: K
authors.lastname: Nakamura
authors.forename: Ken-ichi
authors.initials: K
authors.lastname: Tanji
authors.forename: Akira
authors.initials: A
authors.lastname: Naito
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Nakayama
mesh_terms: D001665:Binding Sites; D001667:Binding, Competitive; D002247:Carbon Isotopes; D002392:Catechin / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry / Q000378:metabolism; D057927:Hydrophobic and Hydrophilic Interactions; D008051:Lipid Bilayers / Q000737:chemistry* / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008958:Models, Molecular; D015394:Molecular Structure; D044367:Phase Transition; D010743:Phospholipids / Q000737:chemistry*
chemical_list: D002247:Carbon Isotopes; D008051:Lipid Bilayers; D010743:Phospholipids; D002392:Catechin; C062669:epicatechin gallate; D004134:Dimyristoylphosphatidylcholine