Spectroscopic and computational study of the major oxidation products formed during the reaction of two quercetin conformers with a free radical

The goal of this research was to determine whether there are differences between the major oxidation products formed during the reaction of quercetin unhydrate (QUH) or quercetin dihydrate (QDH) with the 2,2-diphenyl-1-picrylhydrazyl free radical (DPPH), as well as to identify some properties of these products. The study was carried out employing spectroscopic and computational methods, in order to know the effect of different conformations of quercetin on the mechanism of free radical scavenging. The results demonstrated that although the same oxidation products may be formed from QUH and QDH, their properties and the predominant product were different in each. The o-quinone was the predominant oxidation product of QUH, whereas in QDH it was established an equilibrium between o-quinone and extended p-quinone.

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• The differences in structure of QUH and QDH can prevail in a protic solvent.
• All hydroxyl groups of quercetin can be involved in the reaction with DPPH.
• The predominant products and their properties were different in QUH and QDH.
• The o-quinone was the predominant oxidation product of QUH.
• The o-quinone and extended p-quinone were the predominant products in QDH.