On the complexation of quercetin with methyl-??-cyclodextrin: photostability and antioxidant studies

Quercetin, a plant-derived flavonoid, has been extensively investigated for a wide range of potential health benefits linked to its antioxidant properties. Unfortunately the topical administration of this molecule is restricted by its fast photodegradation. In the attempt to overcome this limitation the inclusion complex between quercetin (Q) and methyl-??-cyclodextrin (Me-??-CD) was prepared and previously investigated by a molecular modelling study, a solubility diagram and a DSC analysis. Successively the kinetics of photodegradation, the antiradical, metal chelating and anti-lipoperoxidative activities were studied by comparing the complex with free Q. In addition the accumulation of Q in porcine skin was evaluated after in vitro topical application by means of vertical Franz cells. The complex formation resulted useful in enhancing the solubility of Q without significantly reducing its antioxidant ability. A modest improvement in the photostability was also observed.