Comparative Analysis of the Reactivity of Anthocyanidins, Leucoanthocyanidins, and Flavonols using a Quantum Chemistry Approach

Abstract

Abstract In the present study, we performed a comparative structural, conformational, electronic, and nuclear magnetic resonance analysis of the reactivity of the chemical structure of primary flavonoids, anthocyanidins, and leucoanthocyanidins. We focused our analysis on the following molecular questions: i) differences in cyanidin catechols (+)-catechin, leucocyanidin and quercetin; ii) the loss of a hydroxyl presents in the R1 radical of leucoanthocyanidin due to possible differences in the functional groups linked to C4 (ring C), and, iii) the electron affinity of the 3-hydroxyl group (R7) in the flavonoids delphinidin, pelargonidin, cyanidin, quercetin and kaempferol. For the analysis of the molecular properties, we used the density functional theory (DFT) to evaluate the formation of the covalent bonds and intermolecular forces. A broad analysis of quantum properties was performed using the assessment of the molecular electrostatic potential (MEP) surface, electron localization function (ELF), Fukui functions, descriptors constructed from frontier orbitals, and nucleus independent chemical shift (NICS).