Properties of Crystal Water of α-, β-, and γ-Cyclodextrin

Abstract

The water vapor sorption isotherms have been established for α-, β-, and γ-cyclodextrin at 40 °C. The powder X-ray diffraction patterns of crystal forms of cyclodextrins stored at various levels of relative humidity (RH) were examined and the results are discussed in terms of the hydration numbers. a-Cyclodextrin hydrate was stable at RH as low as 11%. The water vapor desorption isotherm of β-cyclodextrin showed pronounced hysteresis, which extended to lower RH. The hydrate form of β-cyclodextrin was stable over a wide range of RH in the desorption process, like that of a-cyclodextrin. The crystal form of y-cyclodextrin 7H20 was obtained in addition to the dehydrate form and the 17H2O hydrate form. © 1986, The Pharmaceutical Society of Japan. All rights reserved.