Investigations addressing correlation between antioxidant activity and theoretical descriptors are plentiful in the literature. This task is quite ambitious, bearing in mind the rather complicated interactions in living cells. In this study we have tried to simplify the problem by looking for direct correlations between calculated characteristics and scavenging activity, neglecting the specificity of cellular environment. To address the problem of antioxidant activity, a set of 20 phenolic compounds and their phenoxyl radicals were investigated at the unrestricted B3LYP level of theory using the 6-31+G(d,p) basis set. Three important descriptors of the considered compounds were related to the results of the DPPH scavenging activity. Significant linear correlations were obtained in several cases.

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All possible monohydroxycoumarin derivatives are modeled using density functional theory computations in order to investigate the role of the hydroxyl group position for the radical-scavenging and antioxidant activity of these compounds. Geometry optimization is performed using the B3LYP functional with the 6-311++G­(d,p) basis set. The enthalpy changes are assessed in gas phase and in implicit water using the polarized continuum model. Structure–reactivity patterns are delineated. The most reactive isomers as well as the most probable mechanism of interaction between monohydroxycoumarins and free radicals are outlined.

The enthalpies of bond dissociations of the hydroxyl groups, the energy of the highest occupied molecular orbitals and the corresponding radicals spin densities of all possible ten isomeric mono-hydroxyl flavones are calculated by means of 3-parameter Becke, Lee, Yang and Parr functional. The structural factors affecting these descriptors of radical-scavenging activity are outlined. The results obtained show that the hydroxyl groups in ring A and C are more involved in the process of a radical-capturing than recently believed.