NMR spectroscopic characterization of inclusion complexes comprising cyclodextrins and gallated catechins in aqueous solution: cavity size dependency |
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Authors: | Takashi Ishizu Hiroyuki Tsutsumi Hideji Yamamoto Kazunobu Harano |
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Institution: | 1. Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University, Sanzo Gakuen‐cho 1, Fukuyama, Hiroshima 729‐0292, Japan;2. Department of Applied Biological Science, Faculty of Engineering, Fukuyama University, Sanzo Gakuen‐cho 1, Fukuyama, Hiroshima 729‐0292, Japan;3. Faculty of Pharmaceutical Sciences, Sojo University, 4‐22‐1 Ikeda, Kumamoto 860‐0082, Japan |
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Abstract: | The structure of inclusion complexes of γ‐cyclodextrin (γ‐CD), (–)‐gallocatechin gallate (GCg), and (–)‐epigallocatechin gallate (EGCg) in D2O was investigated using several NMR techniques. GCg formed a 1:1 inclusion complex with γ‐CD in which the A and C rings of GCg were inserted deep at the head of the A ring into the γ‐CD cavity from the wide secondary hydroxyl group side. In the 1:1 inclusion complex with GCg and γ‐CD, the GCg moiety maintained a conformation in which the B and B′ rings of GCg took both pseudoequatorial positions with respect to the C ring. The structure of the inclusion complex of GCg and γ‐CD obtained from NMR experiments supported well that determined from PM6 semiempirical SCF MO calculations. However, 1H NMR experiments suggested that EGCg did not form any inclusion complex with γ‐CD in D2O. The marked difference between GCg and EGCg in inclusion behavior toward γ‐CD may be explained in terms of the stabilization energy calculated with the PM6 method. Copyright © 2008 John Wiley & Sons, Ltd. |
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Keywords: | 1H NMR ROESY NOE (– )‐gallocatechin gallate (– )‐epigallocatechin gallate γ ‐cyclodextrin |
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