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-, ß-, 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 ß-CD binds TFDg more tightly than α- or γ-CD. Additionally, a model for the complex formed between TFDg and ß-CD was estimated by NOE measurements. The analysis showed that the galloyl moiety of TFDg was present in the ß-CD cavity; this result was supported by computational simulation. The present study characterized the inclusion complex of TFDg and ß-CD. Copyright © 2014, Japanese Society for Food Science and Technology.