Keto-Enol tautomerization of quercetin in solutions of a cationic surfactant,miramistin

Tautomeric transformations of quercetin in solutions of a cationic surfactant, miramistin, have been spectrophotometrically studied. It has been established that, at pH ≥ 6, monoanions of enol-form quercetin are irreversibly transformed into keto-form monoanions, with the rate of this process depending on surfactant concentration and solution pH. It has been shown that the enol tautomer of quercetin is more stable in aqueous solutions, while the ketone form is stabilized in miramistin-containing media. The apparent dissociation constants have been determined for the enol (pK _a ^a= 6.60) and ketone = 5.64) tautomeric forms of quercetin in micellar solutions of miramistin.