12 a 17/Nov, 2017, Águas de Lindóia/SP, Brasil A comparative DFT study on antioxidant-related properties of myricetin Iuri N. Soares 1 , Shawan K. C. Almeida 1 , and Gabriel L. C. de Souza 1 1 Departamento de Química, Universidade Federal de Mato Grosso, 78060-900 Cuiabá, Brazil Abstract: It is well known that the antioxidant potential of a given substance can be probed through its capability to scavenge free radicals [1]. The mechanisms related to the referred activity are (mainly): i) hydrogen-atom transfer (HAT), and ii) single electron transfer (SET) [2,3]. For the HAT mechanism, it is established that the weaker the O-H bond, the higher is the antioxidant activity. The bond dissociation enthalpy (BDE) is determined as the difference in the heat of formation between the molecule and corresponding radical, and thus corresponds to the O-H bond-breaking energy. In the SET mechanism, one electron is transferred from the neutral molecule to the free radical: the lower the ionization potential (IP), the easier is the electron abstraction. Hence, probing the bond dissociation energies (BDEs) and ionization potentials (IPs) of flavonols can aid in the identification of compounds that can be applied as phytotherapeutics. In order to compute the referred properties, the density functional theory (DFT) combined with several exchange-correlation functionals have been widely used. In a very recent study, La Rocca et al. [4] benchmarked twenty-one (21) commonly used exchange-correlation functionals for the determination of the BDEs and IPs for two selected molecules that are well known to present antioxidant activity: quercetin and edaravone. The conclusion was that M05-2X [5], M06-2X [6], and LC-ωPBE [7] were the preferred functionals to compute the antioxidant behavior. Hence, in the present work, we decided to apply one of Minnesota family functionals (M06-2X), LC- ωPBE and the widely used B3LYP [8] to investigate the differences among BDEs and IPs determined using these three functionals in the case of another molecule known to be antioxidant: myricetin (chemical structure is shown in Figure 1). Figure 1. Representation of the chemical structure of myricetin. Geometry optimizations, vibrational frequencies and energetics of the neutral molecule and their radicals were carried out using the B3LYP, M06-2X, and LC-ωPBE (UB3LYP, UM06-2X, ULC-ωPBE for the open-shell species) exchange-correlation