Interaction of gymnemic acid with cyclodextrins analyzed by isothermal titration calorimetry, NMR and dynamic light scattering
Interaction of gymnemic acid with cyclodextrins analyzed by isothermal titration calorimetry, NMR and dynamic light scattering
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DOI：
10.1111/j.1742-4658.2005.05014.x
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发表时间：
2005-12-01
期刊：
影响因子：
5.4
通讯作者：
Oda, M
中科院分区：
文献类型：
--
作者：
Izutani, Y;Kanaori, K;Oda, M
采用等温滴定量热法、核磁共振法和动态光散射法，在分子水平上研究了匙羹藤酸（GA）的抗甜味作用被γ-环糊精（γ-CD）降低的生理现象。这些分析表明GA特异性结合γ-CD。热力学分析表明，GA与γ-CD的缔合常数为10（5）~ 10（6）M ~（-1），具有良好的焓变和熵变。热容量的变化是负的和大的，尽管在结合后的可及表面积的变化是小的。这些热力学表明，结合是由疏水相互作用，这是与包合物形成的γ-CD一致。此外，NMR测量表明，在溶液中，GA的光谱是宽的，并且通过添加γ-CD而变得尖锐，这表明未结合的GA是在水溶性聚集体中，当其与γ-CD形成复合物时，该聚集体被分散。动态光散射结果表明，未结合GA的平均粒径> 30 nm，GA与γ-CD复合物的平均粒径为2.2 nm，与未结合的γ-CD相似，支持GA的聚集特性和GA与γ-CD的包合作用。
The physiological phenomenon that the antisweet taste effect of gymnemic acid (GA) is diminished by application of gamma-cyclodextrin (gamma-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 gamma-CD. Thermodynamic analysis using isothermal titration calorimetry revealed that the association constant of GA and gamma-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 gamma-CD. In addition, NMR measurements showed that in solution the spectra of GA are broad and sharpened by the addition of gamma-CD, indicating that unbound GA is in a water-soluble aggregate that is dispersed when it forms a complex with gamma-CD. Dynamic light scattering showed that the average diameter of unbound GA is > 30 nm and that of GA and gamma-CD complex is 2.2 nm, similar to unbound gamma-CD, supporting the aggregate property of GA and the inclusion complexation of GA by gamma-CD.