Spectrophotometric Studies on Flavonoid-Copper (II) Complexes in Methanol Solution

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Complex formation of flavonoids (rutin, quercetin, flavocummelin and flavonol) with copper (II) was studied by spectrophotometry. These flavonoids have some possible chelating sites (such as 3-hydroxy-4-keto, 5-hydroxy-4-keto and 3,4-o-dihydroxy groups denoted as site a, b, and c, respectively) depending on the number and position of hydroxyl substituents in their molecules. Absorption spectra of the flavonoid-copper (II) systems with the changes of Cu^<2+> concentrations were observed, and the molar ratio and continuous variation plots indicated the existence of only 1 : 1 complex in the flavonol-, flavocummelin-, and rutin-copper (II) systems, and both 1 : 1 and 1 : 2 types in the quercetin-copper (II) system. A comparison of the magnitudes of bathochromic shift was compared to consider the sites used for the complex formation. The 1 : 1 complex formation in the flavonol-copper (II) system appears to take place at site a whereas that of the flavocummelin-and the rutin-copper (II) systems at site b. In the case of quercetin, the initial complex formation seems to occur at site a and the subsequent complex formation at site c. In order to compare the relative stability of the flavonoid-copper (II) complexes, the free Cu^<2+> concentrations equilibrated in the mixed solutions of each flavonoid and copper (II) were determined by polarography. The relative stability decreased in the order of quercetin, flavonol, rutin, and flavocummelin.
公益社団法人日本薬学会の論文
1978-08-25

Spectrophotometric Studies on Flavonoid-Copper (II) Complexes in Methanol Solution

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