Crystal architecture and conformational properties of the inclusion complex, neohesperidin dihydrochalcone-cyclomaltoheptaose (β-cyclodextrin), by X-ray diffraction

The crystal structure of the host-guest noncovalent complex of cyclomaltoheptaose (beta-cyclodextrin, betaCD) with the O-diglycosyl flavonoid neohesperidin dihydrochalcone [(3,5-dihydroxy-4-(3-hydroxy-4-methoxyhydrocinnamoyl)phenyl-2-O-(alpha-L-rhamnopyranosyl)-beta-D-glucopyranoside, NDC] has been determined from single-crystal X-ray diffraction data collected at low temperature (130 K), using synchrotron radiation. The crystal data are as follows: a = 15.125(5), b = 30.523(5), c = 41.332(5) Angstrom, orthorhombic, space group C222(1). The structure contains 19 molecules of water, of which 11 appeared well positioned, whereas 9 are disordered over 23-positions. The betaCD-NDC complex is characterized by one aromatic part of NDC deeply inserted into the hydrophobic cavity of the betaCD through the primary OH rim, and it is present in the crystal as a dimer. The dimeric units, formed by head-to-head assemblies of CD molecules, each with its guest, are self-assembled in columns. The stability of the columns is provided by host-guest and guest-guest attractive interactions, thus showing a key role of the guest molecules in the crystal architecture. The guest conformation in the complex is different from that reported in the literature for uncomplexed NDC. The host-induced conformational changes on NDC provide the optimum geometry requirements for the assembly of the dimeric units. (C) 2004 Elsevier Ltd. All rights reserved.