Table 2.

Binding energy and interacting residues during the inhibition of hMAO-A and hMAO-B by isoliquiritigenin and reference ligands.

Ligands	Binding energya	Interacting residuesb
		H-bond	Hydrophobic
hMAO-A (2BXR)
Isoliquiritigenin (catalytic)	− 7.44	FAD600, Thr336, Tyr444	Ile335 (Pi-Sigma), Leu337 (Pi-Sigma), Phe208 (Pi-Pi Stacked), Tyr407 (Pi-Pi T-shaped)
HRMc (Harmine)	− 6.46	FAD600	Tyr444 (Pi-Sigma), FAD600 (Pi-Sigma, Pi-Pi T-shaped, Pi-Alkyl), Tyr444 (Pi-Pi Stacked), Phe352 (Pi-Pi T-shaped), Tyr407 (Pi-Alkyl), Ile335 (Pi-Alkyl)
hMAO-B (2V60)
Isoliquiritigenin (catalytic)	− 8.69	Cys172, FAD1502, Ile199, Tyr398	Ile199 (Pi-Sigma), Ile171 (Pi-Sigma), Tyr398 (Pi-Pi Stacked), Cys172 (Pi-Sulfur)
Isoloquilitigenin (allosteric)	− 8.03	Pro104, His115, Asn116, Asp123	Arg120 (Pi-Alkyl), Val106 (Pi-Alkyl), Trp119 (Pi-Pi Stacked)
Safinamided	− 9.45	Ile199, Cys172, Pro102	FAD1502 (Halogen: Fluorine), Tyr398 (Pi-Pi Stacked), Tyr435 (Pi-Pi Stacked), Tyr326 (Pi-Pi T-shaped), Leu171 (Pi-Sigma), Cys172 (Pi-Sulfur)
C17e	− 10.60	FAD1502, Ile198	FAD1502 (Pi-Sigma), Tyr398 (Pi-Pi Stacked), Tyr435 (Pi-Pi Stacked), Tyr326 (Pi-Pi T-shaped), Leu171 (Pi-Sigma, Pi-Alkyl, Alkyl), Ile199 (Pi-Sigma, Alkyl), Leu167 (Alkyl), Phe168 (Pi-Alkyl), Cys172 (Pi-Sulfur)

^aThe estimated binding energy (kcal/mol), which signifies the binding affinity of a ligand to the active site of hMAO-A and hMAO-B.

^bThe interacting amino acid residues in the ligand-enzyme complex were determined using the AutoDock 4.2 program.

^cHarmine, reference ligand; 7-methoxy-1-methyl-9H-pyrido[3,4-b]indole.

^dSafinamide, reference reversible hMAO-B inhibitor; (2S)-2-[[4-[(3-fluorophenyl)methoxy]phenyl]methylamino]propenamide.

^eC17, reference ligand; N7-[(3-chlorophenyl)methoxy]-2-oxochromene-4-carbaldehyde.