Table 2.

The dock score of screened phytochemicals binding at the active site of the main protease 3CLpro and their important interactions with various amino acid residues.

Phytochemicals	B.E. (kcal/mole)	Important interactions with residues at the active site, catalytic dyad (HIS41 and CYS145) and GLU166
7-Deacetyl-7-benzoylgedunin	−9.1	Carbon hydrogen bond: GLN189; Hydrogen bond: GLU166, HIS163; VDW: ARG188, ASP187, HIS164, GLY143, SER144, LEU141, ASN142, PHE140, HIS172, LEU167; Pi-Pi T-shaped: HIS41; Alkyl: MET165; Pi-Alkyl: CYS145.
Glycyrrhizic acid	−8.7	Hydrogen bond: HIS163, PHE140, GLU166, ASP197; Carbon hydrogen bond: HIS41, GLN189, MET165; VDW: MET49, HIS164, ASP187, ARG187, ARG188, THR190, ALA191, LEU50, HIS172, SER144, LEU141, ASN142.
Limonin	−8.7	Hydrogen bond: GLU166, HIS163, CYS145; Pi-donor: GLY143; Carbon hydrogen bond: GLN189; VDW: ASN142, HIS164, HIS41, MET49.
Obacunone	−7.5	Hydrogen bond: GLU166, HIS163, CYS145; Pi-donor: GLY143; Pi-Alkyl: CYS145; VDW: MET165, GLN189, ASN142, HIS41, HIS164.