A comparative photochemical study on the behavior of 3,30 -dihydroxyflavone and its complex with La(III) as generators and quenchers of reactive oxygen species

Authors
Ferrari, Gabriela Verónica; Montaña, Maria Paulina; Dimarco Palencia, Frida Claudia Daniela; Debattista, Nora Beatriz; Pappano, Nora Beatriz; Massad, Walter Alfredo; Garcia, Norman Andino
Publication Year
2013
Language
English
Format
article
Status
Published version
Description
A 1:1 complex between 3,30-dihydroxyflavone (DHF) and La(III) (DHF?La(III)) is formed in methanolic solution with the relatively high apparent stability constant value of 2.3e6 and a calculated standard entropy change of 88.2 J mol-1 K-1, both at 25 C. The photophysical properties of the complex and the free flavonoid are discussed in comparison to the well known related compound 3-hydroxyflavone. The ligand photogenerates O2(1Dg) by energy transfer from its excited triplet state (3DHF) to dissolved ground state oxygen, with a quantum yield of 0.13. 3DHF is quenched by La(III) with a rate constant close to the diffusion-controlled value. The respective abilities of the free flavonoid and DHF?La(III) as quenchers of the riboflavin-photogenerated reactive oxygen species singlet molecular oxygen (O2(1Dg)) and superoxide radical anion (O 2 ) have been investigated. Both individual compounds were photoirradiated with visible light in the presence of the flavin as the only light-absorbing compound. A detailed kinetics and mechanistic study employing polarographic monitoring of oxygen uptake and time resolved detection of O2(1Dg) phosphorescence indicates that DHF and the complex react with O2(1Dg) and O 2 by a non simple mechanism. The former deactivates O2(1Dg) in a predominant physical fashion, a fact that constitutes a desirable property for antioxidants. It was found that metal chelation greatly enhances the ability of DHF as an overall O2(1Dg) quencher.
Fil: Ferrari, Gabriela Verónica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico San Luis. Instituto de Química de San Luis; Argentina
Fil: Montaña, Maria Paulina. Universidad Nacional de San Luis. Facultad de Quimica, Bioquimica y Farmacia. Departamento de Quimica. Area de Quimica Fisica; Argentina
Fil: Dimarco Palencia, Frida Claudia Daniela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico San Luis. Instituto de Química de San Luis; Argentina
Fil: Debattista, Nora Beatriz. Universidad Nacional de San Luis. Facultad de Quimica, Bioquimica y Farmacia. Departamento de Quimica. Area de Quimica Fisica; Argentina
Fil: Pappano, Nora Beatriz. Universidad Nacional de San Luis. Facultad de Quimica, Bioquimica y Farmacia. Departamento de Quimica. Area de Quimica Fisica; Argentina
Fil: Massad, Walter Alfredo. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina
Fil: Garcia, Norman Andino. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina
Subject
3,3'-DIHYDROXIFLAVONE-La(III) COMPLEX
PHOTODEGRADATION
PHOTOSENSITIZATION
REACTIVE OXYGEN SPECIES
RIBOFLAVIN
Físico-Química, Ciencia de los Polímeros, Electroquímica
Ciencias Químicas
CIENCIAS NATURALES Y EXACTAS
Access level
Restricted access
License
https://creativecommons.org/licenses/by-nc-nd/2.5/ar/
Repository
CONICET Digital (CONICET)
Institution
Consejo Nacional de Investigaciones Científicas y Técnicas
OAI Identifier
oai:ri.conicet.gov.ar:11336/5772