Thermodynamics of radical scavenging effect of deprotonated isoflavones in aqueous solution

Phenoxide anions may play a crucial role in the radical scavenging activity of flavonoids in aqueous solution. Therefore, the thermodynamics of Sequential Proton-Loss Electron-Transfer (SPLET) mechanism for mono-deprotonated isoflavones was investigated in this work. Density functional theory has been used for the calculation of corresponding reaction enthalpies in aqueous solution. For deprotonated forms of fourteen isoflavones, the effect of the structure on SPLET thermodynamics was elucidated. Difference in enthalpies of the first and the second proton loss are in 4-10 kJ mol(-1) range, if two consecutive deprotonations occur in different aromatic rings. Deprotonated isoflavones prefer to enter SPLET reaction pathway to Hydrogen Atom Transfer (HAT) or electron transfer. Obtained results also contribute to the rationalization of pH dependent antioxidant action of flavonoids. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

This study investigated the thermodynamics of SPLET mechanism of isoflavones in aqueous solution, revealing the structural effect on their thermodynamic properties. The findings contribute to understanding the pH-dependent antioxidant action of flavonoids.