On the energetics of homolytic and heterolytic OH bond cleavage in flavonoids

Characterization and density functional theory study of the antioxidant activity of quercetin and its sugar-containing analogues

“…The BDE value of C4′-OH in B-ring is lower than the OH in A-ring though the hydrogen bond exists between C4′-OH and C3′-OH. These findings are consistent with the results which are found by Dhaouadi et al [23,24]. Judging from the lowest BDE, the number of phenol hydroxyl group for each natural flavonoids and its relative energy values are obtained according to the HAT mechanism; our results are in good agreement with those obtained in the experiment [25][26][27], and we can describe the activities of the flavonoids under study in the following order: quercetin > hyperin > rutin, which are in accordance with the experimental results determined by spectrophotometric assays.…”

Reaction enthalpies of OH bonds splitting-off in flavonoids: The role of non-polar and polar solvent

“…In this mechanism, proton affinity (PA) of the phenoxide anion, ArO À , and electron transfer enthalpy (ETE) represent the reaction enthalpies of the two individual steps. Recently, we performed the systematic study of all three mechanisms in the terms of gas-phase OAH BDEs, IPs, PDEs, PAs and ETEs for eight naturally occurring flavonoids [7] ( Fig. 2): apigenin, luteolin (flavones), fisetin, kaempferol, quercetin (flavonols), epicatechin (flavanol), taxifolin (flavanonol) and cyanidin (anthocyanidin).…”

“…Chosen molecules enabled the investigation of the structural features, such as the presence of hydroxy groups in different positions, C2@C3 double bond and C4@O keto group. The main aim of this work is the estimation of benzene and water solvent effect on the above mentioned reaction enthalpies, because SET-PT and SPLET mechanisms involving charged species are relevant especially in the solution [2, [6][7][8][9]. Solvent is able to affect BDEs of hydroxyl groups participating in intramolecular hydrogen bonds (H-bonds) significantly [6,7,[10][11][12][13].…”

Solvation enthalpies of the proton in polar and non-polar solvents: Theoretical study

“…3.2, is denoted as Electron Transfer Enthalpy, ETE. It was shown that SPLET may play important role in solution phase, especially in polar solvents (Litwinienko and Ingold 2003;Staško et al 2007;Vagánek et al 2012). In chelating action of polyphenols, the proton loss is crucial for the protective activity of these natural antioxidants, too (Procházková et al 2011).…”