Quercetin (3,3′,4′,5,7-pentahydroxyflavone) complexes with calcium (II) and magnesium(II), its potentiometric and spectrophotometric studies

Abstract

In this study, the stability constants of the complexes of quercetin formed with calcium(II) and magnesium(II) were determined potentiometrically by using Calvin-Bjerrum and Irving Rossotti methods and by spectrophotometry. The evaluated protonation constants of the ligand were found: logK 1=9.63±0.11 and logK2 = 8.32±013, at the 25°C. For the calcium and magnesium complexes logarithms of the stability constants were found: for Ca : logK=2.91±0.04, and for Magnesium: logK=3.51±0.07. From the results, the components of quercetin-metal complexes are given 1:1 (quercetin:metal ratio) both Ca(II) and Mg(II).