Enhancement of flavonols water solubility by cyclodextrin inclusion complex formation - case study

The phenomenon of solubility increasing of nonpolar flavonol antioxidant – quercetin (QC) in water solutions containing β-cyclodextrin (CD) was studied. Complexation of QC by CD was investigated using phase solubility study. It allows to estimate the apparent formation constant for 1:1 host-guest complex. Additionally thermodynamic properties were evaluated as well showing spontaneous exothermic process of complex formation. Two solubility models were also employ to verify their applicability to predict QC concentration in solution. Those models included modified Apelbalt and Buchowski-Ksiazczak equations. In order to investigate the antioxidant properties of ternary systems QC/CD/water a radical scavenging activity using stable radical of DPPH was performed. Experiments indicated that antioxidant activity is temperature and CD concentration-dependent. It was shown that complexation may inhibit the radical scavenging by QC or changing the scavenging stoichiometry.