Premium
Interaction of gymnemic acid with cyclodextrins analyzed by isothermal titration calorimetry, NMR and dynamic light scattering
Author(s) -
Izutani Yusuke,
Kanaori Kenji,
Imoto Toshiaki,
Oda Masayuki
Publication year - 2005
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/j.1742-4658.2005.05014.x
Subject(s) - isothermal titration calorimetry , chemistry , dynamic light scattering , titration , calorimetry , enthalpy , proton nmr , isothermal process , analytical chemistry (journal) , crystallography , stereochemistry , thermodynamics , chromatography , materials science , physics , nanoparticle , nanotechnology
The physiological phenomenon that the antisweet taste effect of gymnemic acid (GA) is diminished by application of γ‐cyclodextrin (γ‐CD) to the mouth was evaluated at the molecular level using isothermal titration calorimetry, NMR and dynamic light scattering. These analyses showed that GA specifically binds to γ‐CD. Thermodynamic analysis using isothermal titration calorimetry revealed that the association constant of GA and γ‐CD is 10 5 −10 6 m −1 with favorable enthalpy and entropy changes. The heat capacity change was negative and large, despite the change in accessible surface area upon binding being small. These thermodynamics indicate that the binding is dominated by hydrophobic interactions, which is in agreement with inclusion complex formation of γ‐CD. In addition, NMR measurements showed that in solution the spectra of GA are broad and sharpened by the addition of γ‐CD, indicating that unbound GA is in a water‐soluble aggregate that is dispersed when it forms a complex with γ‐CD. Dynamic light scattering showed that the average diameter of unbound GA is > 30 nm and that of GA and γ‐CD complex is 2.2 nm, similar to unbound γ‐CD, supporting the aggregate property of GA and the inclusion complexation of GA by γ‐CD.