Characterization of the semiquinones and quinones of (−)-epicatechin by means of computational chemistry

This research was carried out with the purpose to perform a computational characterization of the semiquinones and quinones that can be formed as intermediates in the flavonoid (−)-epicatechin, in order to generate information which can serve as the basis for further experimental work directed to the safe usage of this flavonoid as a natural antifungal and/or antioxidant. To characterize these intermediates, their structural properties as well as some reactivity and energy properties, such as condensed Fukui functions, BDE and total energy, were determined. The computational methodology employed was DFT and the CHIH (medium)-DFT model chemistry. The results showed that the 4′-OH of the catechol group represents the primary site of deprotonation (the most oxidizable), which gives both the most stable and the easiest formed semiquinones. Similarly, the most stable quinones are formed through the primary oxidation of the 4′-OH, followed by the 5-OH or the 7-OH of the resorcinol group.