Table 3.

Interactions of COVID-19 Main Protease (PDB ID:6LU7) amino acid residues with ligands at receptor sites.

Ligands	Binding affinity, ΔG (kcal/mol)	Amino acids involved and Distance (A°)
		Hydrogen binding interactions	Hydrophobic interactions
Quadranoside III	−8.6	LYS A:137 (4.60), ASN A:238 (4.52), GLU A:288 (4.82)	LEU A:272 (4.46)
Luteolin-7-glucoside-3′-glucuronide	−8.5	PHE A:219 (5.16), ASN A:221 (3.75, 3.78, 4.67), ASP A:263 (3.50, 3.90)	LEU A:220 (4.22)
Melitric acid A	−8.2	GLN A:110 (4.80, 5.234), ASN A:151 (4.23), ILE A:249 (3.34)	VAL A:104 (7.12), ILE A:106 (5.62), PHE A:294 (4.40), PRO A:293 (4.44), ILE A:249 (4.77)