The inhibitory potential of 4,7-dihydroxycoumarin derivatives on ROS-producing enzymes and direct HOO/o - radical scavenging activity - a comprehensive kinetic DFT study.

This study examined the antiradical activity of three synthesized coumarin derivatives: ()-3-(1-((2-hydroxyphenyl)amino)ethylidene)-2,4-dioxochroman-7-yl acetate (), ()-3-(1-((3-hydroxyphenyl)amino)ethylidene)-2,4-dioxochroman-7-yl acetate (), and ()-3-(1-((4-hydroxyphenyl)amino)ethylidene)-2,4-dioxochroman-7-yl acetate () against HOO•/O2•- radical species. The investigation included electron spin resonance (ESR) measurements and a DFT kinetic study. Thermodynamic and kinetic parameters of antiradical mechanisms-Formal Hydrogen Atom Transfer (-HAT), Radical Adduct Formation (RAF), Sequential Proton Loss followed by Electron Transfer (SPLET), and Single-Electron Transfer followed by Proton Transfer (SET-PT)-were evaluated using the Quantum Mechanics-based test for Overall Free Radical Scavenging Activity (QM-ORSA) under physiological conditions. ESR results indicated antiradical activity decreased in the sequence (58.7%) > (57.5%) > (53.1%). Kinetic analysis revealed the -HAT mechanism dominated HOO inactivation. A newly formulated Sequential Proton Loss followed by Radical Adduct Formation (SPL-RAF) mechanism described interactions with O. The activity toward O was (1.26 × 10 Ms) > (7.71 × 10 Ms) > (4.22 × 10 Ms). Molecular docking and dynamics studies tested inhibitory capability against enzymes producing reactive species: Lipoxygenase (LOX), Myeloperoxidase (MPO), NAD(P)H oxidase (NOX), and Xanthine Oxidase (XOD). Affinity to enzymes decreased in the order: XOD > LOX > NOX > MPO.