Reactions of OOH Radical with β-Carotene, Lycopene, and Torulene: Hydrogen Atom Transfer and Adduct Formation Mechanisms

Abstract

The relative free radical scavenging activity of beta-carotene, lycopene, and torulene toward OOH radicals has been studied using density functional theory. Hydrogen atom transfer (HAT) and radical adduct formation (RAF) mechanisms have been considered. All the possible reaction sites have been included in the modeling, and detailed branching ratios are reported for the first time. The reactions of hydrocarbon carotenoids (Car) with peroxyl radicals, in both polar and nonpolar environments, are predicted to proceed via RAF mechanism, with contributions higher than 98% to the overall OOH + Car reactions. Lycopene and torulene were found to be more reactive than beta-carotene. In nonpolar environments the reactivity of the studied carotenoids toward peroxyl radical follows the trend LYC > TOR > BC, whereas in aqueous solutions it is TOR > LYC > BC. OOH adducts are predicted to be formed mainly at the terminal sites of the conjugated polyene chains. The main addition sites were found to be C5 for beta-carotene and lycopene and C30 for torulene. The general agreement between the calculated magnitudes and the available experimental data supports the predictions from this work.

A quantum chemical study on the free radical scavenging activity of tyrosol and hydroxytyrosol

“…In non-polar environments, the peroxyl-scavenging activity of HTyr was found to be similar to that of carotenes (*10 5 -10 6 M -1 s -1 ) [126] and canolol (6.8 9 10 5 M -1 s -1 ) [127]; higher than that of sinapinic acid (1.7 9 10 4 M -1 s -1 ) [128]; and much higher than that of melatonin (3.1 9 10 2 M -1 s -1 ) [129], caffeine (3.2 9 10 1 M -1 s -1 ) [123], and Tyr (7.1 9 10 2 M -1 s -1 , this work). Moreover, taking into account that the rate constants corresponding to the Á OOH damage to unsaturated fatty acids are in the range 1.18-3.05 9 10 3 M -1 s -1 [130], HTyr is predicted to protect against peroxyl oxidation of lipids, while the protective effects of Tyr are not expected to be significant.…”

In vitro antioxidant capacity of tomato products: Relationships with their lycopene, phytoene, phytofluene and alpha-tocopherol contents, evaluation of interactions and correlation with reflectance measurements

“…Carotenoids possess a characteristic electron-rich chromophore, which is involved in the AC of these compounds towards different species (Galano & Francisco-Marquez, 2009;Martínez, Stinco, & Mel endez-Martínez, 2014). LYC as an antioxidant has been associated to the possible health benefits derived from the consumption of tomato.…”

Computational consideration on advanced oxidation degradation of phenolic preservative, methylparaben, in water: mechanisms, kinetics, and toxicity assessments

“…At this point, the computational results are expected to interpret the experimental findings and provide theoretical support for the conclusions of the experimental MPB degradation results. In addition, as a approach of cost-effective, convenient, and avoiding the use of animals for toxicological study [22,23], computational approach is frequently adopted to investigate the molecular basis of environmental, chemical, and biological processes [24,25]. To date, no computational study has been reported on the mechanisms and kinetics of MPB degradation using AOPs, as well as the toxicity assessment of its degradation products.…”