  Virtual screening of phytochemicals was performed through molecular docking,
simulation, in silico ADMET and drug-likeness prediction to identify the
potential hits that can inhibit the effects of SARS-CoV-2. Considering the
published literature on medicinal importance, total 154 phytochemicals with
analogous structure from limonoids and triterpenoids were selected to search
potential inhibitors for the five therapeutic protein targets of SARS-CoV-2,
i.e., 3CLpro (main protease), PLpro (papain-like protease), SGp-RBD (spike
glycoprotein-receptor binding domain), RdRp (RNA dependent RNA polymerase) and
ACE2 (angiotensin-converting enzyme 2). The in silico computational results
revealed that the phytochemicals such as glycyrrhizic acid, limonin,
7-deacetyl-7-benzoylgedunin, maslinic acid, corosolic acid, obacunone and
ursolic acid were found to be effective against the target proteins of
SARS-CoV-2. The protein-ligand interaction study revealed that these
phytochemicals bind with the amino acid residues at the active site of the
target proteins. Therefore, the core structure of these potential hits can be
used for further lead optimization to design drugs for SARS-CoV-2. Also, the
medicinal plants containing these phytochemicals like licorice, neem, tulsi,
citrus and olives can be used to formulate suitable therapeutic approaches in
traditional medicines.
