The Stability of Cyclodextrin Complexes in Solution.

Review: a history of cyclodextrins.

If the amylose fraction of starch is degraded by
glucosyltransferases, one or several turns of the
amylose helix are hydrolyzed off and their ends are
joined together, thereby producing cyclic oligosaccharides
called cyclodextrins (CDs) or cycloamyloses
(CAs).

Structures of the Common Cyclodextrins and Their Larger Analogues-Beyond the Doughnut.

The driving forces leading to the inclusion complexation of cyclodextrins were reviewed, which included the electrostatic interaction, van der Waalsinteraction, hydrophobic interaction, hydrogen bonding, release of conformational strain,exclusion of cavity-bound high-energy water, and charge–transferinteraction. It was shown that except for the release of conformation strain and exclusion of cavity-bound water, the otherinteractions were indeed contributive to the complex formation. However, it was concludedthat the enthalpy and entropy changes of the complexation were not good criteria to be used injudging whether a particular driving force was present or important, mainly because of theoccurrence of enthalpy-entropy compensation. On the other hand, the multivariate quantitativestructure-activity relationship analyses usually could illustrate which driving forces wereimportant in certain inclusion complexation systems.

The Driving Forces in the Inclusion Complexation of Cyclodextrins

The association constants and thermodynamic parameters were determined for complexes of α- and β-cyclodextrins (CD) with a variety of alcohols (ROH) by the spectrophotometric examination of the inhibitory effect of ROH on the association of CD with azo dyes, and they were analyzed in connection with the partition coefficients of ROH in a diethyl ether–water solvent system in order to elucidate the binding forces contributing to the association of CD with an organic substrate. Hydrophobic and van der Waals interactions were of primary importance in the complexation. Among them, the latter was preferential in α-CD–1-alkanol adducts, while the former, in β-CD–1-alkanol adducts. As the bulkiness of ROH increased, the stability of the α-CD adduct was lowered owing to van der Waals repulsion between ROH and the relatively small α-CD cavity, whereas that of the β-CD adduct was enhanced by the attainment of the close van der Waals contact of ROH with the relatively large β-CD cavity.

Binding forces contributing to the association of cyclodextrin with alcohol in an aqueous solution.

Topography of cyclodextrin inclusion complexes

Topography of cyclodextrin inclusion complexes : Part II. The iodine-cyclohexa-amylose tetrahydrate complex; its molecular geometry and cage-type crystal structure

http://journals.iucr.org/b/issues/1974/08/00/a11199/a11199.pdf

W. Saenger

Papers

Topography of cyclodextrin inclusion complexes

Topography of cyclodextrin inclusion complexes : Part II. The iodine-cyclohexa-amylose tetrahydrate complex; its molecular geometry and cage-type crystal structure

Topography of cyclodextrin inclusion complexes. IV. Crystal and molecular structure of the cyclohexaamylose–1-propanol–4.8 hydrate complex