Chrysin is a bioflavonoid which possesses a wide range of important biological activities. In present study, we used a quantum mechanical approach to shed light on the antioxidant ability and antioxidant mechanism of chrysin to scavenge hydroxyl radical (˙OH) in solution phase. The analysis of the theoretical bond dissociation enthalpy (BDE) values and spin density of the radicals to determine the delocalization possibilities at B3LYP/6-311++G** level clearly shows the importance of the A-ring and the 7-OH group in antioxidant reactivity. In the next step, the inclusion of chrysin with β-CD has been investigated extensively using theoretical methods. Density functional theory (M05-2X) employing the 6-31+G* basis set has been used to research the lowest energy geometry for all studied complexes in gas and water mediums. The results of calculations show that the A ring of chrysin with large cavity side of β-CD significantly formed the favorable β-CD/chrysin complex in both phases. Our observations also inferred that hydrogen bonds were the key interactions which stabilized the chrysin/β-CD complex. We used Bader's atoms in molecules (AIM) theory to perform a topological study on chrysin/β-CD complex to emphasize the hydrogen bonds. According to our findings, the process of inclusion increased not only the solubility of chrysin but also its antioxidant potential.

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