H‐atom acceptor capacity of free radicals used in antioxidant measurements

Abstract

Antioxidants are well-known for their beneficial effects on human health. Their capacity to scavenge free radicals mainly depends on their capacity to transfer H atoms to free radicals (R ), and indirectly to labile H-atoms of the R -parent molecule (RAH). The aim of this study was to select an accurate method to estimate bond dissociation enthalpies (BDEs) of ROOAH, LOOAH and DPPHAH. ROO and LOO are radicals involved in lipid peroxidation and DPPH is a free radical used to measure antioxidant activities. BDE(ROOAH) was systematically calculated with more than 20 different methods (HF, post-HF and DFT). This methodology was performed on three ROOAH prototypes (HOOAH, CH 3 OOAH, and CH 3 CH 2 OOAH) for which theoretical BDEs were compared to experimental BDEs. B3P86 and BHandH/6-31þG(d,p) appeared as the best compromises. The influence of R chain length and conjugation degree on BDEs was studied with DFT. Both parameters did not significantly change BDE(ROOAH), except when intra H bonding was formed. The DPPHAH BDE was accurately calculated with B3P86. This functional could definitely be considered as a good compromise since it also gave a reliable estimation of OAH BDE for polyphenols.

Influence of In Vitro Digestion on Composition, Bioaccessibility and Antioxidant Activity of Food Polyphenols—A Non-Systematic Review

“…Radicals can be scavenged by antioxidants by way of three mechanisms [67]: Hydrogen Atom Transfer (HAT), based on breaking the O-H bond:…”

Antiradical and Antioxidative Activity of Azocalix[4]arene Derivatives: Combined Experimental and Theoretical Study

“…Considerable efforts have been devoted to the measurement of O–H BDE using versatile techniques, such as photoacoustic calorimetry [23] and EPR spectroscopy [24,25]. Quantum mechanical methods have also been extensively used for evaluating the O–H BDE [26,27]. In this present work, DFT calculations have been performed at the BP86/6-311+G(d,p) level of theory to calculate the O–H BDEs and the PAs of phenolate anions of azocalixarene derivatives 1 and 2 in an aqueous solution in order to explore the antiradical and antioxidative mechanisms [12,28].…”

Lipocarbazole, an efficient lipid peroxidation inhibitor anchored in the membrane

“…14 The B3P86 functional has been shown to be particularly well-adapted to evaluate the thermodynamics of the reaction between polyphenols and free radicals. 12,14,15 The 6-31+G(d,p) basis set is used since it provides very similar results compared to the larger and more computationally demanding 6-311+G(2d,3pd) basis set; 15 in particular the use of triple-f basis sets and the second diffuse function did not significantly enhance BDE predictions (difference lower than 1 kcal mol À1 ). Geometries, energies including the zero-point correction (V) and enthalpies (H) at 298 K were determined at the (U)B3P86/6-31+G(d,p) level.…”