Studies of the interactions between some flavonols and cyclodextrins

Cyclodextrins (CDs) are recognized as useful pharmaceutical excipients and in the last decade their capability to form inclusion complexes with various drugs has been identified thus, they are used successfully for improvement of some drug properties. In this work the interactions of some natural flavonols with -, - and -CDs have been investigated. Flavonols are quite polar but poorly water-soluble phenolic constituents, widely diffused in nature both as aglycons and glycosides. They are active constituents or represent markers for many herbal drugs and are present in valuable amounts in many vegetables and fruits of the Mediterranean diet. The host molecules investigated were galangin, kaempferol, quercetin and its diglycoside rutin. Inclusion complexes were prepared by different methods: physical mixture, kneading and freeze-drying. The CD-flavonol complexes were characterized using different physico-chemical methods based on differential scanning calorimetry (DSC), IR and NMR (1H-NMR, 13C-NMR, COSY, NOESY, HMQC) spectroscopies. Previously, only a few studies were reported on the complexation of flavonols with cyclodextrins mainly using chromatographic methods which are unable to give full information about host-guest interaction mode.