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

MUÑOZ, VANESA A.; DIMARCO PALENCIA, FRIDA C. D.; SANCHO, MATIAS; MISKOSKI, SANDRA; GARCÍA, NORMAN A.; FERRARI, GABRIELA V.; MONTAÑA, M. PAULINA

PHOTOCHEMISTRY AND PHOTOBIOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2020 vol. 96 p. 815 - 825

0031-8655

In this work, the flavonol Fisetin was selected in order to study its reactivity against Cu(II), ametal ion of interest in biological media and industry. The stoichiometry and apparentformation constant of the complex in ethanolic medium at 25°C were evaluated usingspectrophotometric techniques. The resulting stoichiometry was a 1:1 ligand:metalcomplex, and a log K = 5.17 ± 0.12 was determined. Since two possible chelation sites canbe proposed for the complex formation, quantum chemistry calculations were performedon these structures. Calculations suggest that the hydroxyl‐keto site is more stable for thecomplex formation than the catechol site. Flavonoids could exert protection againstoxidative damage caused by reactive oxygen species, and this biological activity could beaffected by chelation with metal ions. This led us to perform a study on the interaction ofboth, free flavonoid and complex, with reactive oxygen species. Our results showed bothcompounds quench molecular singlet oxygen photogenerated with visible light, mainly in aphysical fashion. In order to analyze a possible protective effect of flavonoid and itscomplex against oxidative damage in biological environments, the amino acid tryptophan was selected as a model oxidation system. Free flavonoid does not have a markedprotective effect, whereas its complex showed a relevant protective effect.