Dimerization of quercetin, Diels-Alder vs. radical-coupling approach: a joint thermodynamics, kinetics, and topological study
2016 (English)In: Journal of Molecular Modeling, ISSN 1610-2940, E-ISSN 0948-5023, Vol. 22, no 8, 190- p.Article in journal (Refereed) Published
Quercetin is a prototypical antioxidant and prominent member of flavonoids, a large group of natural polyphenols. The oxidation of quercetin may lead to its dimerization, which is a paradigm of the more general polyphenol oligomerization. There exist two opposing mechanisms to describe the dimerization process, namely radical-coupling or Diels-Alder reactions. This work presents a comprehensive rationalization of this dimerization process, acquired from density functional theory (DFT) calculations. It is found that the two-step radical-coupling pathway is thermodynamically and kinetically preferred over the Diels-Alder reaction. This is in agreement with the experimental results showing the formation of only one isomer, whereas the Diels-Alder mechanism would yield two isomers. The evolution in bonding, occurring during these two processes, is investigated using the atoms in molecules (AIM) and electron localization function (ELF) topological approaches. It is shown that some electron density is accumulated between the fragments in the transition state of the radical-coupling reaction, but not in the transition state of the Diels-Alder process.
Place, publisher, year, edition, pages
SPRINGER , 2016. Vol. 22, no 8, 190- p.
Antioxidants; Atoms in molecules (AIM); Density functional theory; Electron localization function (ELF); Flavonoids; Kinetics; Thermochemistry
IdentifiersURN: urn:nbn:se:liu:diva-131702DOI: 10.1007/s00894-016-3051-8ISI: 000381203500020PubMedID: 27449669OAI: oai:DiVA.org:liu-131702DiVA: diva2:1010270
Funding Agencies|COST Chemistry project [CMST0804]; Ministry of Education, Youth and Sports [LO1305]; Grant agency of the Czech Republic [P208/12/G016]; Conseil Regional du Limousin2016-10-032016-09-302016-10-03