Experimental and Theoretical Study of the Stability of the Complex Fisetin –Cu(II) and A Comparative Study of Free Ligand and Complex Interaction with Molecular Singlet Oxygen

Flavonoids can exert protection against oxidative damage caused by reactive oxygen species, and this biological activity could be affected by chelation with metallic ions. The stoichiometry and the apparent formation constant of the fisetin –Cu(II) complex were determined. The molecular structure of fisetin shows two possible chelation sites. A molecular modeling analysis of fisetin and its complex was performed to study spectroscopic properties and compared with experimental data. AbstractIn this work, the flavonol fisetin was selected in order to study its reactivity against Cu(II), a metal ion of interest in biological media and industry. The stoichiometry and apparent formation constant of the complex in ethanolic medium at 25 °C were evaluated using spectrophotometric techniques. The resulting stoichiometry was a 1:1 ligand:metal complex, and a logK = 5.17 ± 0.12 was determined. Since two possible chelation sites can be proposed for the complex formation, quantum chemistry calculations were performed on these structures. Calculations suggest that the hydroxyl‐keto site is more stable for the complex formation than the catechol site. Fla vonoids could exert protection against oxidative damage caused by reactive oxygen species, and this biological activity could be affected by chelation with metal ions. This led us to perform a study on the interaction of both, free flavonoid and complex, with reactive oxygen species. Our results sho wed both compounds quench mol...
Source: Photochemistry and Photobiology - Category: Science Authors: Tags: Research Article Source Type: research