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Ellagic acid (EA) is an antiplasmodial polyphenol with reported in-vitro activity against Plasmodium falciparum. Studies have reported that EA acts in the late erythrocytic stages of P. falciparum (Pf) when DNA synthesis is taking place. Pf dihydrofolate reductase-thymidylate synthase (PfDHFR-TS) is an important enzyme for DNA synthesis as its inhibition can kill the parasite. As there is no reported study on the molecular interactions between EA and PfDHFR-TS, we aim to study the molecular interactions between EA and PfDHFR-TS (PDB ID: 3DGA) through molecular docking, molecular dynamics (MD) simulations, binding free energy (MM-GBSA) calculations, and density functional theory (DFT) studies. Site-specific and blind docking revealed that EA has a high binding affinity for the active site of PfDHFR-TS. EA formed hydrogen bonds with multiple active site residues. MD simulations for 100 ns revealed that the PfDHFR-TS-EA complex was stable. The average binding free energy of the PfDHFR-TS-EA complex throughout the 100 ns MD simulations was −39.84 kcal/mol. The energy difference (ΔE = 0.04089 eV) obtained from DFT studies indicates the electrical stability and reactivity of EA at the active site of PfDHFR-TS. We conclude that the antiplasmodial activity of EA might be attributed to its ability to potentially bind with PfDHFR-TS. [ABSTRACT FROM AUTHOR]

In this study, a hybrid compound library of 72 phytocompounds from two antiviral medicinal plants (Baccaurea ramiflora and Bergenia ciliata) was computationally investigated for their inhibitory potential against SARS-CoV-2 Mpro. Molecular docking showed that 6-O-vanilloylicariside B5, 6-O-vanilloylisotachioside, leucoanthocyanidin 4-(2-galloyl), and p-hydroxybenzoyl bergenin has good binding affinity for Mpro. However, p-hydroxybenzoyl bergenin did not bind at the catalytic cavity. The RMSD and RMSF data obtained from 100 ns MD simulations revealed stable protein–ligand complexes for 6-O-vanilloylicariside B5, 6-O-vanilloylisotachioside, leucoanthocyanidin 4-(2-galloyl). Ligand trajectory study found 6-O-vanilloylisotachioside and leucoanthocyanidin 4-(2-galloyl) to be stable. Studies on ligand interaction profile and timeline interaction profile showed that 6-O-vanilloylisotachioside and leucoanthocyanidin 4-(2-galloyl) interacted with HIS41–CYS145 dyad and other crucial amino acids of the catalytic site cavity during the entire 100 ns MD simulations. Molecular mechanics generalized born solvent accessibility binding free energy calculations, density functional theory analysis, quantitative structure–property relationship studies, and ADMET profiling of 6-O-vanilloylisotachioside and leucoanthocyanidin 4-(2-galloyl) supported the results generated by molecular docking and MD simulations studies. Based on the current computational investigations, we conclude that that 6-O-vanilloylisotachioside of B. ramiflora and leucoanthocyanidin 4-(2-galloyl) of B. ciliata are two potential inhibitors of SARS-CoV-2 Mpro that are worthy of further investigations. [ABSTRACT FROM AUTHOR]