Minimum number of water molecules required for inclusion of d-limonene in the cyclodextrin cavity.

The ratios of inclusion of d-limonene in alpha-, beta-, and gamma-cyclodextrin (CD) cavities were measured under low moisture conditions by a micro-aqueous method, and the minimum numbers of water molecules required for inclusion of d-limonene in alpha-, beta-, and gamma-CD cavities were determined by the auto-catalytic inclusion model. The minimum number of water molecules required for alpha-, beta-, and gamma-CD inclusion calculated from the proposed model were comparable with that in the CD cavity in the crystal state. The effect of ethanol upon the inclusion process was investigated, particularly with a low water content. This is the first study involving measurement of the minimum number of water molecules required for the inclusion of organic molecules (d-limonene) in the CD cavity.