Light radical scavengers

The photobleaching of P-carotene by fluorescent light in fatty acid ester solutions showed an autoxidation kinetic profile with the rate of degradation of P-carotene in the order laurate > oleate > linoleate (Carnevale et al. 1979). The presence of a radical scavenger retarded the autoxidation, thus leading to the view that protection against autoxidation is built into the system by the unsaturation in the fatty acid. 

Pt deposited on WS2-Ti02 mesoporous composites was used for visible-light production of H2 in the presence of Na2S as radical scavenger [188]. Pt-loaded mesoporous zirconium-titanium phosphates also displayed good photoactivity in hydrogen production from carbonate solution [189]. 

UV-filtered light, as in a museum, effectively reduces the amount of oxidation to almost the same level that occurs in darkness. The polymer fraction of mastic was found to reduce the degree of oxidation in the material, possibly by acting as a radical scavenger. 

Antifade agents (free-radical scavengers) in aqueous mounting media prevent photobleaching of fluorophore labels under exposure to excitation light. 

This reduces the rotational broadening and makes the vibrational subspectra apparent as a series of multiple peaks. If hydroxyl radical scavengers such as buffer components, the glass or plastic wall of test tubes, or trace metal contaminants are present, exposure to light will result in the formation of nitric oxide from... 

It is essential that the oxidation of the glycol groupings in the polysaccharide be complete, and that no overoxidation occurs. The latter is excluded by performing the reaction with the exclusion of light, at low temperature, and at a pH of 3-3.5, as described by Bobbitt.73 The use of oxygen-free water and the addition of propyl alcohol, as a radical scavenger, also lessen radical-induced depolymerization during oxidation.75... 

If the photochemical reaction is followed only by measuring the concentration of the light-absorbing ketone, it will indeed appear that the additive (acridine) acts as a quencher in reality it acts as a radical scavenger through a thermochemical reaction which is quite unrelated to the nature of the reactive excited state. 

Autoxidation can lead to deterioration of food, drugs, cosmetics, or polymers, and inhibition of this reaction is therefore an important technical issue. The most important classes of autoxidation inhibitors are radical scavengers (phenols, sterically demanding amines [65, 66]), oxygen scavengers (e.g. ascorbic acid), UV-light absorbers, and chelators such as EDTA (to stabilize high oxidation states of metals and thereby suppress the metal-catalyzed conversion of peroxides to alkoxyl radicals) [67]. 

---