fulltext.study @t Gmail

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

Paper ID Volume ID Publish Year Pages File Format Full-Text
30359 44472 2013 8 PDF Available
Title
A comparative photochemical study on the behavior of 3,3′-dihydroxyflavone and its complex with La(III) as generators and quenchers of reactive oxygen species
Abstract

•A 1:1 complex between 3,3′-dihydroxyflavone and La(III) is formed.•3,3′-Dihydroxyflavone photogenerates O2(1Δg) with a quantum yield of 0.13.•No evidence for O2(1Δg) production by the complex was detected.•The ligand and the complex are quenchers of photogenerated O2(1Δg) and O2-.

A 1:1 complex between 3,3′-dihydroxyflavone (DHF) and La(III) (DHF–La(III)) is formed in methanolic solution with the relatively high apparent stability constant value of 2.3 × 106 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(1Δg) 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(1Δg)) and superoxide radical anion (O2-) 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(1Δg) phosphorescence indicates that DHF and the complex react with O2(1Δg) and O2- by a non simple mechanism. The former deactivates O2(1Δg) 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(1Δg) quencher.

Keywords
3,3′-Dihydroxyflavone–La(III) complex; Photodegradation; Photosenitization; Reactive oxygen species; Riboflavin
First Page Preview
A comparative photochemical study on the behavior of 3,3′-dihydroxyflavone and its complex with La(III) as generators and quenchers of reactive oxygen species
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us
Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Photochemistry and Photobiology B: Biology - Volume 124, 5 July 2013, Pages 42–49
Authors
, , , , , , ,
Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us