Synthesis, antimicrobial, molecular docking and molecular dynamics studies of lauroyl thymidine analogs against SARS-CoV-2: POM study and identification of the pharmacophore sites.

Nucleoside precursors and nucleoside analogs occupy an important place in the treatment of viral respiratory pathologies, especially during the current COVID-19 pandemic. From this perspective, the present study has been designed to explore and evaluate the synthesis and spectral characterisation of 5́-O-(lauroyl) thymidine analogs 2-6 with different aliphatic and aromatic groups through comprehensive in vitro antimicrobial screening, cytotoxicity assessment, physicochemical aspects, molecular docking and molecular dynamics analysis, along with pharmacokinetic prediction. A unimolar one-step lauroylation of thymidine under controlled conditions furnished the 5́-O-(lauroyl) thymidine and indicated the selectivity at C-5́ position and the development of thymidine based potential antimicrobial analogs, which were further converted into four newer 3́-O-(acyl)-5́-O-(lauroyl) thymidine analogs in reasonably good yields. The chemical structures of the newly synthesised analogs were ascertained by analysing their physicochemical, elemental, and spectroscopic data. In vitro antimicrobial tests against five bacteria and two fungi, along with the prediction of activity spectra for substances (PASS), indicated promising antibacterial functionality for these thymidine analogs compared to antifungal activity. In support of this observation, molecular docking experiments have been performed against the main protease of SARS-CoV-2, and significant binding affinities and non-bonding interactions were observed against the main protease (6LU7, 6Y84 and 7BQY), considering hydroxychloroquine (HCQ) as standard. Moreover, the 100 ns molecular dynamics simulation process was performed to monitor the behaviour of the complex structure formed by the main protease under in silico physiological conditions to examine its stability over time, and this revealed a stable conformation and binding pattern in a stimulating environment of thymidine analogs. Cytotoxicity determination confirmed that compounds were found less toxic. Pharmacokinetic predictions were investigated to evaluate their absorption, distribution, metabolism and toxic properties, and the combination of pharmacokinetic and drug-likeness predictions has shown promising results in silico. The POM analysis shows the presence of an antiviral (O1δ-, O2δ-) pharmacophore site. Overall, the current study should be of great help in the development of thymidine-based, novel, multiple drug-resistant antimicrobial and COVID-19 drugs.

Methyl ß-D-galactopyranoside esters as potential inhibitors for SARS-CoV-2 protease enzyme: synthesis, antimicrobial, PASS, molecular docking, molecular dynamics simulations and quantum computations.

Carbohydrate esters are significant in medicinal chemistry because of their efficacy for the synthesis of biologically active drugs. In the present study, methyl ß-D-galactopyranoside (MGP) was treated with various acyl halides to produce 6-O-acyl MGP esters by direct acylation method with an excellent yield. To obtain newer products for antimicrobial assessment studies, the 6-O-MGP esters were further modified into 2,3,4-tri-O-acyl MGP esters containing a wide variety of functionalities in a single molecular framework. The chemical structures of the newly synthesized compounds were elucidated by analyzing their physicochemical, elemental, and spectroscopic data. In vitro antimicrobial testing against five bacteria and two fungi and the prediction of activity spectra for substances (PASS) revealed that these MGP estes have promising antifungal functionality compared to their antibacterial activities. The antimicrobial tests demonstrated that the compounds 3 and 10 were the most potent against Bacillus subtilis and Escherichia coli strains, with the minimum inhibitory concentration (MIC) values ranging from 0.352 ± 0.02 to 0.703 ± 0.01 mg/ml and minimum bactericidal concentration (MBC) values ranging from 0.704 ± 0.02 to 1.408 ± 0.04 mg/ml. Density functional theory (DFT) at the B3LYP/3-21G level of theory was employed to enumerate, frontier orbital energy, enthalpy, free energy, electronic energy, MEP, dipole moment which evaluated the effect of certain groups (aliphatic and aromatic) on drug properties. They discovered that all esters were more thermodynamically stable than the parent molecule. Molecular docking is performed using AutoDock Vina to determine the binding affinities and interactions between the MGP esters and the SARS-CoV-2 main protease. The modified esters strongly interact with the prime Cys145, His41, MET165, GLY143, THR26, and ASN142 residues. The MGP esters' shape and ability to form multiple electrostatic and hydrogen bonds with the active site match other minor-groove binders' binding modes. The molecular dynamics simulation validates the molecular docking results. The pharmacokinetic characterization of the optimized inhibitor demonstrates that these MGP esters appear to be safer inhibitors and a combination of in silico ADMET (absorption, distribution, metabolism, excretion, and toxicity) prediction and drug-likeness had promising results due to their improved kinetic properties. Structure activity relationships (SAR) study including in vitro and silico results revealed that the acyl chain, palmitoyl (C16) and 4-chlorobenzoyl (4.ClC6H4CO-) in combination with sugar were found the most potential activates against human and fungal pathogens. After all, our comprehensive computational and statistical analysis shows that these selected MGP esters can be used as potential inhibitors against the SARS-CoV-2.