Discovery of Potent Dengue Virus NS2B-NS3 Protease Inhibitors Among Glycyrrhizic Acid Conjugates with Amino Acids and Dipeptides Esters.

This study investigated a library of known and novel glycyrrhizic acid (GL) conjugates with amino acids and dipeptide esters, as inhibitors of the DENV NS2B-NS3 protease. We utilized docking algorithms to evaluate the interactions of these GL derivatives with key residues (His51, Asp75, Ser135, and Gly153) within 10 Å of the DENV-2 NS2B-NS3 protease binding pocket (PDB ID: 2FOM). It was found that compounds and exhibited unique binding patterns, forming hydrogen bonds with Asp75, Tyr150, and Gly153. Based on the molecular docking data, conjugates with L-glutamic acid dimethyl ester, with β-alanine ethyl ester, and with aminoethantic acid methyl ester were further demonstrated as potent inhibitors of DENV-2 NS3 protease, with IC50 values below 1 μM, using NS3-mediated cleavage assay. Compound was the most potent, with EC50 values of 0.034 μM for infectivity, 0.042 μM for virus yield, and a selective index over 2000, aligning with its strong NS3 protease inhibition. Compound exhibited better NS3 protease inhibition than compound but showed weaker effects on infectivity and virus yield. While all compounds strongly inhibited viral infectivity post-entry, compound also blocked viral entry. This study provided valuable insights into the interactions between active GL derivatives and DENV-2 NS2B-NS3 protease, offering a comprehensive framework for identifying lead compounds for further drug optimization and design as NS2B-NS3 protease inhibitors against DENV.