NMR Spectroscopic Characterization of Inclusion Complexes of Theaflavin Digallate and Cyclodextrins

Abstract

Cyclodextrins (CDs) are a family of cyclic oligosaccharides which possess the unique ability to include a number of compounds inside their cavities. CDs have been used in tea to mask the bitter taste caused by catechins. In this study we investigated the complexes formed between theaflavin-3,3′-di-O-gallate (TFDg), a major constituent in black tea, and CDs (α-, β-, and γ-CD) using several NMR techniques and a computational simulation. ¹H NMR spectral titration results and DOSY analyses suggested that TFDg interact with each CD. NMR experiments suggested that β-CD binds TFDg more tightly than α- or γ-CD. Additionally, a model for the complex formed between TFDg and β-CD was estimated by NOE measurements. The analysis showed that the galloyl moiety of TFDg was present in the β-CD cavity; this result was supported by computational simulation. The present study characterized the inclusion complex of TFDg and β-CD.