Structure, electronic properties, and radical scavenging mechanisms of daidzein, genistein, formononetin, and biochanin A: A density functional study

The structural and electronic properties of daidzein, genistein, formononetin, biochanin A and their radicals were investigated at density functional theory (DFT) method employing B3LYP/6-31+G(d,p) and B3LYP/6-31++G(d,p) methods. This study has concerned the determination of the bond dissociation enthalpy (BDE), adiabatic ionization potential (IP), proton dissociation enthalpy (PDE), proton affinity (PA), electron transfer enthalpy (ETE) and relative energies for each O-H groups, highest occupied molecular orbital (HOMO) and Mulliken spin density are also presented. From the molecular structure and thermodynamic point of view, it was revealed that B-ring of isoflavonoids was the active center and the hydrogen atom transfer (HAT) appeared as a major mechanism in antioxidants action. Analysis of the calculated results suggests that the antioxidant activity is in good agreed with that obtained in TEAC assay values and in the following order: genistein > daidzein > biochanina A > formononetin.