Theoretical Investigation on Antioxidant Activity of Bromophenols from the Marine Red Alga Rhodomela confervoides: H-Atom vs Electron Transfer Mechanism

Abstract

Bromophenols are known as antioxidant radical scavengers for some biomolecules such as those in marine red alga. Full understanding of the role played by bromophenols requires detailed knowledge of the radical scavenging activities in probable pathways, a focus of ongoing research. To gain detailed insight into two suggested pathways, H-atom transfer and electron transfer, theoretical studies employing first principle quantum mechanical calculations have been carried out on selected bromophenols. Detailed investigation of the aforementioned routes revealed that upon H-atom abstraction or the electron transfer process, bromophenols cause an increase in radical species in which the unpaired electron appears to be delocalized as much as possible over the whole aromatic ring, especially in the bromine substituent. The O-H bond dissociation energies (BDEs) and ionization potential energies (IPs) are reported at the B3LYP level of theory, providing the first complete series of BDEs and IPs for bromophenols. The observations are compared to those of other antioxidants for which BDEs and IPs have been previously obtained.

Antioxidant activity of some phenolic aldehydes and their diimine derivatives: A DFT study

“…Reis and his co-workers also theoretically evaluated the antioxidant activity of various phenolic compounds using different levels of calculations [9]. Again, Javan et al investigated computationally the H-atom vs electron transfer mechanism for antioxidant activity of some bromophenols and compared their observation to those for which the antioxidant activity was previously evaluated [10]. Analysis of antioxidant activity of various gallic acid derivatives as well as the values of some density-based reactivity descriptors was carried out by Kar et al and they found that phenolic compounds are more stable in gas phase than in solvent medium [11].…”

Butylated hydroxytoluene enediyne: access to diradical and electrophilic quinone methide intermediates

“…For example, the DFT energetics of the parent enediyne reaction reproduced the experimental value to within 1.5 kcal/mol . Density functional theory has also been successful in calculating energetics of H‐atom transfer reactions such as polyphenols exhibiting antioxidant properties . The B3LYP method is also found to be reliable for Garratt‐Braverman cyclizations and intramolecular H‐atom transfer reactions .…”

“…[4] Density functional theory has also been successful in calculating energetics of H-atom transfer reactions [13][14][15] such as polyphenols exhibiting antioxidant properties. [16,17] The B3LYP method is also found to be reliable for Garratt-Braverman cyclizations and intramolecular H-atom transfer reactions. [18] When searching for whether diradical 7 existed, uBLYP, uM062X, and uM06 functionals were also used.…”

Antioxidant Properties of Lapachol and Its Derivatives and Their Ability to Chelate Iron (II) Cation: DFT and QTAIM Studies

“…is demonstrates the sensitivity of the cation radical forms of isolated ligand (La i ) to the polarity of different solvents used [21,47]. is may be attributed to the lowest value of the enthalpies of solvation of the electron.…”

“…Until now, there is no study on the impact of the metal chelation of these molecular systems on their antioxidant powers. e characterization of the antioxidant activity for large number of antioxidants RX-H, [18][19][20][21][22] has been done by the calculation of the RX-H (X � donor atom such as O, N, ...) bond dissociation enthalpy (BDE). From these calculations, the prediction of the relationship structure-activity and the design of novel possible antioxidant have been carried out.…”