In Ukrainian

Abstract

Quercetin and rutin have potent antioxidant and metal ion chelating capacity, possess various biological, biochemical and therapeutic activity, but their application is limited because of low solubility. Anticeptic cationic gemini surfactant ethonium (2-ethylene-bis-(N-dimethylcarbdecyloximethyl) ammonium dichloride) was considered to be a promising solubilizer for flavonoids. The supramolecular interactions of quercetin and rutin with ethonium have been studied spectrophotometrically. The bathochromic shift of quercetin and rutin spectra in pre-micellar ethonium solutions testifies an increase in their polarity. Indeed, the calculated values of quercetin and rutin apparent dissociation constants in ethonium solutions are lower than that in water. In micellar solutions the flavonoid spectral characteristics and protolytic properties remain unchanged, whereas the solubility of quercetin and rutin raises 250 and 5 times, respectively. The binding constants of quercetin (lgK b = 3.71) and rutin (lgK b = 2.52) with ethonium are determined from the solubility data. The formation of supramolecular complexes also causes the essential increase of quercetin and rutin adsorption on silica surface at рН > 5 both in pre-micellar and micellar ethonium solutions in similar ways. This allows us to assume that the structures of surface complexes formed by pre-micellar associates or micelles have no principal differences. The shape of the obtained pH-dependences of quercetin and rutin adsorption suggests that flavonoids as a part of ethonium supramolecular complexes adsorb on silica mainly through the ionic interactions between the positively charged nitrogen atoms and dissociated silanol groups. The results of physico-chemical study may be a base for the development a composition of new medicinal remedies.