On the peroxyl scavenging activity of hydroxycinnamic acid derivatives: mechanisms, kinetics, and importance of the acid–base equilibrium

Abstract

The peroxyl radical scavenging activity of four hydroxycinnamic acid derivatives (HCAD) has been studied in non-polar and aqueous solutions, using the density functional theory. The studied HCAD are: ferulic acid (4-hydroxy-3-methoxycinnamic acid), p-coumaric acid (trans-4-hydroxycinnamic acid), caffeic acid (3,4-dihydroxycinnamic acid), and dihydrocaffeic acid (3-(3,4-dihydroxyphenyl)-2-propionic acid). It was found that the polarity of the environment plays an important role in the relative efficiency of these compounds as peroxyl scavengers. It was also found that in aqueous solution the pH is a key factor for the overall reactivity of HCAD towards peroxyl radicals, for their relative antioxidant capacity, and for the relative importance of the different mechanisms of reaction. The H transfer from the phenolic OH has been identified as the main mechanism of reaction in non-polar media and in aqueous solution at acid pHs. On the other hand, the single electron transfer mechanism from the phenoxide anion is proposed to be the one contributing the most to the overall peroxyl scavenging activity of HCAD in aqueous solution at physiological pH (7.4). This process is also predicted to be a key factor in the reactivity of these compounds towards a large variety of free radicals.

Maclurin protects against hydroxyl radical-induced damages to mesenchymal stem cells: Antioxidant evaluation and mechanistic insight

“…The direct Å OH radical-scavenging tends to undergo SEPT at high Å OH radical levels; while it tends to undergo HAT at low Å OH radical levels. It is further supported by the previous report [46].…”

Thiophenols, Promising Scavengers of Peroxyl Radicals: Mechanisms and kinetics

“…Specie B is a catechol analog, and its rate constant is 84.7 times greater than catechol's. Caffeic acid is a derivative of catechol that is slightly more complex specie and that has proven to be a slightly better antioxidant than simplest catechol . However, it is not significantly better than B: the caffeic acid rate constant is ~1.28 times larger, with respect to the rate constant of specie B. Specie H has acetaminophen as analog and its rate constant is ~5.49 times smaller than the one of compound H. The analog of specie L is resveratrol which is identified as one of the best existing antioxidants .…”

“…a slightly better antioxidant than simplest catechol. [72] However, it is not significantly better than B: the caffeic acid rate constant is~1.28 times larger, with respect to the rate constant of specie B. Specie H has acetaminophen as analog and its rate constant is~5.49 times smaller than the one of compound H. The analog of specie L is resveratrol which is identified as one of the best existing antioxidants. [74,82] Its rate constant is 78 times larger than the one of L. According to our data, the thiophenolic species, which have been tested, in this work, have proved to be good HOO • scavengers and, in most cases, they are even better than their oxygen analogs Supporting Information (Tables S1 and S2).…”

A comparative study of the inhibitory effects by caffeic acid, catechins and their related compounds on the generation of radicals in the reaction mixture of linoleic acid with iron ions

“…(20,21) Meanwhile, the polyphenols are strong antioxidants due to their ability to chelate transition metals like iron as well as their radical scavenging activities. (22) In order to examine the effect of their chelating ability on the formation of lipid-derived free radical in the reaction of linoleic acid with iron ions, we used electron spin resonance (ESR), high performance liquid chromatography-electron spin resonance (HPLC-ESR) and high performance liquid chromatography-electron spin resonance-mass spectrometries (HPLC-ESR-MS) and conducted the comparative study on CA and catechins in antioxidative activities.…”