Complexation of quercetin with three kinds of cyclodextrins: An antioxidant study

The slightly water-soluble flavonoid quercetin (QUE) and its inclusion with either β-cyclodextrin (βCD), hydroxypropyl-β-cyclodextrin (HP-βCD) or sulfobutyl ether-β-cyclodextrin (SBE-βCD) were investigated. The stoichiometric ratios and stability constants describing the extent of formation of the complexes have been determined by phase–solubility measurements; in all cases type-AL diagrams have been obtained (soluble 1:1 complexes). The results showed that the inclusion ability of βCD and its derivatives was the order: SBE-βCD > HP-βCD > βCD.Kinetic studies of DPPH with QUE and CDs complexes were done. The results obtained indicated that the QUE–SBE-βCD complex was the most reactive form.The scavenging capability of QUE and CDs complexes with DPPH and galvinoxyl was studied using ESR spectroscopy. All complexes showed a higher scavenging capability with both radicals, compare quercetin in water. Beside, these results indicated that the complexes formed maintained the quercetin antioxidant activity.