The objective of this research is to examine the function of urolithin D (UroD, 3,4,8,9-tetrahydroxy-6H-benzo[c]chromen-6-one), a metabolite obtained from ellagitannins, in the mitigation of oxidative stress. The research is based on estimating the mechanisms through which UroD acts as an antioxidant under physiological conditions, emphasizing standard antioxidant mechanisms such as formal Hydrogen Aatom Transfer (f-HAT), Radical Adduct Formation (RAF)/Radical Coupling Formation (RCF), and Single Electron Transfer followed by Proton Transfer (SET-PT). This study utilised advanced quantum mechanical techniques, specifically density functional theory (DFT) and the Quantum Mechanics-based test for Overall free Radical Scavenging activity (QM-ORSA) methodology, to assess the thermodynamic and kinetic parameters of UroD in the presence of reactive radical species HOO