Structural Analyses of Vanillin Derivative Compounds and their Molecular Docking with MPro and RdRp Enzymes of COVID-19

In this work, structural analyses of vanillin (Vanl) and eleven of its derivatives based on the modification of the aldehyde group were investigated using density functional theory (DFT) calculations. In this regard, molecular orbital features and atomic-scale quadrupole coupling constants were evaluated for geometrically optimized structures to see the impact of structural modification on the whole structure. The results indicated that the main impact of such modification was significant only for the modification region, whereas the impact on the rest of the structure was almost negligible. However, electronic features indicated a different tendency for Vanl derivatives for involving in interaction with enzymatic targets. Because of the importance of innovating medication for COVID-19, main protease (MPro) and RNA-dependent RNA polymerase (RdRp) were chosen for the enzymatic target of Vanl ligands for the formation of ligand-target complexes through performing molecular docking (MD) simulations. The results indicated that among the complexes, Vanl 9 (–NHNH2) and 11 (–CH2Cl) could work as the best ligands for interacting with each of RdRp and MPro, respectively. Consequently, optimization of Vanl derivatives could help innovate new compounds for the possible medication of the COVID-19 pandemic.