NMR Studies on the interaction between (−)-epigallocatechin gallate and cyclodextrins, free and bonded to silica gels Original Research Article

The interaction between (−)-epigallocatechin-3-gallate (EGCG) and β- or γ-cyclodextrin (CD), in free solution and bonded to silica beads, has been studied by 1H HR-MAS NMR spectroscopy. The chromatographic retardation of EGCG on columns packed with CD-silica beads was shown to be due to the interaction of EGCG with the CD ligands because no nonspecific interaction with the silica gel could be observed. EGCG forms a tighter complex with β-CD than with γ-CD and NMR data obtained from hydroxy protons together with mm2 calculations suggest that for β-CD intermolecular hydrogen bonding, in addition to hydrophobic interaction, stabilizes the complex.