Related Experiment Video
Updated: May 14, 2026

Inactivation of Pathogens via Visible-Light Photolysis of Riboflavin-5′-Phosphate
Published on: April 6, 2022
Riboflavin-photosensitized oxidation is enhanced by conjugation in unsaturated lipids
Daniel R Cardoso1, Regina S Scurachio, Willy G Santos
1Instituto de Química de São Carlos, Universidade de São Paulo , Avenida Trabalhador São Carlense 400, CP 780, CEP 13560-970, São Carlos, São Paulo (SP), Brazil.
Abstract:
Methyl esters of polyunsaturated fatty acids were found to quench triplet-excited riboflavin ((3)Rib) 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 (3)Rib is predicted by combining the experimental second-order rate constants k2 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 × 10(7) L mol(-1) s(-1) for hydrogen abstraction from bis-allylic methylene groups in unsaturated lipid by (3)Rib. Still, ergosterol was found to deactivate (3)Rib with k2 = 6.2 × 10(8) L mol(-1) s(-1), which is more efficient than cholesterol, with 6.9 × 10(7) L mol(-1) s(-1). Likewise conjugated (9E,11E) methyl linoleate (CLA) reacts with 3.3 × 10(7) 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 (3)Rib 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 (3)Rib.
More Related Videos
Related Concept Videos
Photochemical Electrocyclic Reactions: Stereochemistry
Selection Rules: Photochemical Activation
Oxidation of Phenols to Quinones
o-hydroxy phenols are oxidized to o-quinones and p-hydroxy phenols to p-quinones. Such redox reactions involve the transfer of two electrons and two protons. The reversible redox property is crucial in...
Conjugate Addition to α,β-Unsaturated Carbonyl Compounds
Biosynthesis of Lipids
UV–Vis Spectroscopy of Conjugated Systems
One of the factors influencing λmax is the extent of conjugation in the...
Cycloaddition Reactions: MO Requirements for Photochemical Activation

