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.