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

Abstract

The free radical scavenging activity of hydroxytyrosol (HTyr) and tyrosol (Tyr) has been studied in aqueous and lipid solutions, using the density functional theory. Four mechanisms of reaction have been considered: single electron transfer (SET), sequential electron proton transfer (SEPT), hydrogen transfer (HT), and radical adduct formation. It was found that while SET and SEPT do not contribute to the overall reactivity of HTyr and Tyr toward Á OOH and Á OCH 3 radicals, they can be important for their reactions with Á OH, Á OCCl 3 , and Á OOCCl 3 . The Á OOH-scavenging activity of HTyr and Tyr was found to take place exclusively by HT, and it is also predicted to be the main mechanism for their reactions with Á OCH 3 . HT is proposed as the main mechanism for the scavenging activity of HTyr and Tyr when reacting with other Á OR and Á OOR radicals, provided that R is an alkyl or an alkenyl group. The major products of reaction are predicted to be the phenoxyl radicals. In addition, Tyr was found to be less efficient than HTyr as free radical scavenger. Moreover, while HTyr is predicted to be a good peroxyl scavenger, Tyr is predicted to be only moderately for that purpose.

A density functional theory study of the free‐radical scavenging activity of aminoguanidine. Comparison with its reactive carbonyl compound and metal scavenging activities

“…SET reactions are much more endergonic than RAF reactions. The large Δ G 0 differences for the SET reactions in both solvents compare to values previously reported . However, five of the HAT reactions of AG with ˙OCH 3 and four with ˙OOH, as well as the RAF reaction between ˙OCH 3 and AG in water, are exergonic.…”

Computational Study on the Attack of .OH Radicals on Aromatic Amino Acids

“…[22,23] Experimentally, it is difficult to trap radical species, owing to their short half times. [24][25][26][27][28][29][30][31][32] Herein, we report the alternative reaction pathways in the sequential attack of two COH radicals onto phenylalanine, tyrosine, and tryptophan amino acid side chains, all of which are characterized within the framework of density functional theory. [24][25][26][27][28][29][30][31][32] Herein, we report the alternative reaction pathways in the sequential attack of two COH radicals onto phenylalanine, tyrosine, and tryptophan amino acid side chains, all of which are characterized within the framework of density functional theory.…”

On the primary and secondary antioxidant activity from hydroxy‐methylcoumarins: experimental and theoretical studies

“…The results obtained on the radical scavenging activity from HMD with • OOH in lipid media could be employed to compare this activity with other antioxidants, according to this, the HMD is better antioxidant than tyrosol (7.13 × 10 2 M ‐1 s ‐1 ), capsaicin (6.54 × 10 3 M ‐1 s ‐1 ), sinapinic acid (1.66 × 10 4 M ‐1 s ‐1 ), fraxetin (2.43 × 10 4 M ‐1 s ‐1 ), esculetin (4.93 × 10 4 M ‐1 s ‐1 ), sesamol (3.33 × 10 4 M ‐1 s ‐1 ), trans‐Resveratrol (1.42 × 10 5 M ‐1 s ‐1 ), hydroxytyrosol (6.42 × 10 5 M ‐1 s ‐1 ), dopamine (8.16 × 10 5 M ‐1 s ‐1 ), canonol (6.80 × 10 5 M ‐1 s ‐1 ); since the HMD reacts lower than ergosterol (2.05 × 10 6 M ‐1 s ‐1 ) in lipid media.…”