Riboflavin-Photosensitized Oxidation Is Enhanced by Conjugation in Unsaturated Lipids

Methyl esters of polyunsaturated fatty acids were found to quench triplet-excited riboflavin (3Rib) in efficient bimolecular reactions with rate constants, as determined by laser flash photolysis, linearly depending upon the number of bis-allylic methylene (from 1 to 5). Deactivation of 3Rib is pred...

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Bibliographic Details
Published in:Journal of agricultural and food chemistry 2013-03, Vol.61 (9), p.2268-2275
Main Authors: Cardoso, Daniel R, Scurachio, Regina S, Santos, Willy G, Homem-de-Mello, Paula, Skibsted, Leif H
Format: Article
Language:English
Subjects:
Biological and medical sciences
cholesterol
conjugated linoleic acid
dissociation
ergosterol
Ergosterol - chemistry
esters
Eye
eyes
Fatty Acids, Unsaturated - chemistry
Food industries
Fundamental and applied biological sciences. Psychology
Humans
hydrogen
Linoleic Acids - chemistry
Lipid Peroxides - analysis
Lipid Peroxides - chemistry
oxidation
Oxidation-Reduction
Photochemical Processes
Photolysis
phytosterols
Phytosterols - chemistry
polyunsaturated fatty acids
riboflavin
Riboflavin - chemistry
Skin
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Summary:Methyl esters of polyunsaturated fatty acids were found to quench triplet-excited riboflavin (3Rib) in efficient bimolecular reactions with rate constants, as determined by laser flash photolysis, linearly depending upon the number of bis-allylic methylene (from 1 to 5). Deactivation of 3Rib is predicted by combining the experimental second-order rate constants k 2 determined for acetonitrile/water (8:2, v/v) at 25 °C with density functional theory (DFT) calculations of bond dissociation energy to have an upper limiting value of 1.22 × 107 L mol–1 s–1 for hydrogen abstraction from bis-allylic methylene groups in unsaturated lipid by 3Rib. Still, ergosterol was found to deactivate 3Rib with k 2 = 6.2 × 108 L mol–1 s–1, which is more efficient than cholesterol, with 6.9 × 107 L mol–1 s–1. Likewise conjugated (9E,11E) methyl linoleate (CLA) reacts with 3.3 × 107 L mol–1 s–1, 30 times more efficient than previously found for methyl α-linolenate. Conjugation as in CLA and ergosterol is concluded to enhance 3Rib deactivation, and dietary plant sterols and CLA may accordingly be important macronutrients for eye and skin health, protecting against light exposure through efficient deactivation of 3Rib.
ISSN:0021-8561
1520-5118
DOI:10.1021/jf305280x