4. Conclusions
Structural, electronic, topological and vibrational properties together with molecular docking have been studied for both enantiomeric S(-) and R(+) forms of potential antiviral to COVID-19 chloroquine (CQ) combining DFT calculations with SQMFF methodology. The theoretical structures of S(-) and R(+) forms were determined in gas phase and aqueous solution by using hybrid B3LYP/6-311++G** calculations. Energies differences between both forms in gas phase and aqueous solution are of 1.84 and 3.67 kJ/mol, respectively. Calculations in solution predict solvation energy of S(-) form and R(+) respectively of -55.07 and 59.91 kJ/mol. The presence of only four donor and acceptor H bonds groups present in structure CQ probably justifies the low solvation energy values of both forms, as compared with other antiviral agents. MK charges on the Cl1, N2, N3 and N4 atoms and AIM calculations could support the higher stability of R(+) form in solution in agreement with the higher reactivity predicted for the S(-) form in the same medium. Antiviral niclosamide evidences higher reactivity than CQ. Complete vibrational assignments of 153 vibration modes for both forms and scaled force constants have been performed for both forms. Very good concordances were found between the compared 1H-NMR,13C-NMR and UV-Vis spectra with the experimental ones, suggesting in both the presence of the two forms of CQ in solution.
A molecular docking study was performed to identify the potency of inhibition of Chloroquine molecule against COVID-19 virus.
This study clearly shows the antiviral effect, based on binding affinities and interactions formed between amino residues acid and candidate molecule, against COVID-19 virus. The interaction among the chloroquine molecule and COVID-19 are dominated by Van der Waals and hydrogen interactions. Hence, we can use these compounds as antibiotics to a greater extent.