Quantum Chemical and Molecular Simulation Insights into Antioxidant Mechanisms and Free Radical Scavenging Activity of Structurally Diverse Flavonols

Oxidative stress-mediated cellular damage is closely associated with the development of several chronic disorders, highlighting the importance of identifying efficient antioxidant molecules. In this study, the antioxidant potential of four structurally different flavonoids namely Kaempferol (MBFL-1), Sudachitin (MBFL-2), Melodorone A (MBFL-3) and Desmoscochinflavone A (MBFL-4) was explained by using integrated computational approach including density functional theory (DFT), molecular docking, molecular dynamics (MD) simulation and MM/PBSA analysis. The DFT calculations revealed significance of hydroxyl group positioning and conjugation pattern in free radical scavenging efficiency via the HAT, SPLET and SET-PT mechanisms. Among them, MBFL-4 exhibited most favoirable antioxidant profile, characterized by the lowest BDE value of 79.21 kcal/mol for HAT mechanism and lowest PA value of 36.02 kcal/mol for initial step of SPLET pathway. The docking analysis of ROS generating enzyme, Xanthine oxidase (PDB ID: 3NVY) showed favorable interactions of MBFL-4 with binding affinities of -8.35 kcal/mol which is consistent with its superior radical scavenging behavior. The studied flavonoids also showed good binding interactions with Keap1 demonstrating binding energies < -6.0 kcal/mol, which might indicate that these flavonoids could be able to modulate the binding interactions of the Nrf2 antioxidant defense pathway. Moreover, 100 ns MD simulation with target protein 3NVY presented MBFL-4 as the most stable and energetically favorable complex with a binding free energy of -17.38 kcal/mol. This highlighting the contribution of enzymatic/signalling pathway modulation in controlling oxidative stress along with free radical scavenging activity, attributed to appropriate hydroxyl configuration and conjugation pattern.