Estimation of antiradical properties of series of 4, 7 - dihydroxycoumarin derivatives towards DPPH radical-experimental and DFT study

Different phenolic coumarin derivatives represent a widespread class of compounds that have shown remarkable activity in removing reactive oxygen species. For this reason, within this study, the antiradical activity of previously synthesized phenolic derivatives of 4,7 -dihydroxycoumarin: (E)-3-(1-((2-hydroxyphenyl)amino) ethylidene) -2,4-dioxochroman-7-yl (A-20H), $(E)$ -3-(1((3-hydroxyphenyl)amino)ethylidene)-2,4-dioxochroman-7-yl acetate (A-30H), $(E)$. -3-(1((4-hydroxyphenyl)amino) ethylidene) -2,4-dioxochroman-7-yl (A-40H) acetate against the 2,2-diphenyl-1-picrylhydrazyl (DPPH·) radical was investigated. All research is supported by Density Functional Theory $(\mathbf{DFT}/\mathbf{M06}-\mathbf{2X/6-311++}\mathbf{G}(\mathbf{d, p})$ level of theory and CPCM solvation model-methanol) in combination with global chemical reactivity parameters. The results of experimental scavenging activity towards DPPH· indicate that A-20H shows the best activity. The most probable scavenging route was determined based on the thermodynamic parameters. A good correlation between experiment and theory showed that Hydrogen Atom Transfer (HAT, $\Delta\text{rGHAT}$) was the dominant pathway of the reduction of DPPH·. In general, the results of global chemical reactivity parameters show that the A-40H compound shows the best electron-donating properties, which is correlated with thermodynamic parameters obtained for the Single Electron Transfer (SET, $\Delta{\text{rGSET}}$) mechanism.