Theoretical investigation on the antioxidant behavior of chrysoeriol and hispidulin flavonoid compounds – A DFT study

Over the recent past, the behavior of flavonoids as antioxidants has become the subject of intense research. The biological properties of these compounds are based on the electronic parameters, describing the charge distribution on the rings of the flavonoid molecules. Antioxidative properties of naturally occurring flavonoids such as chrysoeriol and hispidulin have been studied based on the quantum chemical calculations. The B3LYP/6-311G(d,p) protocol has been used for structure optimization and all other computations. Ionization potentials and O–H bond dissociation enthalpies are found to be consistent with antioxidant activity. Ionization potential and hydrogen abstraction enthalpies of the 4′-OH, 5-OH and 7-OH hydroxyl groups are compared and analyzed with the help of an electronic description and a spin density distribution for each structure. The calculated BDE values for all OH sites of chrysoeriol and hispidulin clearly reveal the importance of the B-ring. Their dipole moments and polarizability analyses show that both the compounds are polar in nature and have the capacity to polarize other atoms. Among the two flavonoid compounds, hispidulin is found to be showing higher antioxidant activity than that of chrysoeriol.