The Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is a fast-spreading viral pathogen and poses a serious threat to human health. New SARS-CoV-2 variants have been arising worldwide; therefore, is necessary to explore more therapeutic options. The interaction of the viral spike (S) protein with the angiotensin-converting enzyme 2 (ACE2) host receptor is an attractive drug target to prevent the infection via the inhibition of virus cell entry. In this study, Ligand- and Structure-Based Virtual Screening (LBVS and SBVS) was performed to propose potential inhibitors capable of blocking the S receptor-binding domain (RBD) and ACE2 interaction. The best five lead compounds were confirmed as inhibitors through ELISA-based enzyme assays. The docking studies and molecular dynamic (MD) simulations of the selected compounds maintained the molecular interaction and stability (RMSD fluctuations less than 5 Å) with key residues of the S protein. The compounds DRI-1, DRI-2, DRI-3, DRI-4, and DRI-5 efficiently block the interaction between the SARS-CoV-2 spike protein and receptor ACE2 (from 69.90 to 99.65% of inhibition) at 50 µM. The most potent inhibitors were DRI-2 (IC₅₀ = 8.8 µM) and DRI-3 (IC₅₀ = 2.1 µM) and have an acceptable profile of cytotoxicity (CC₅₀ > 90 µM). Therefore, these compounds could be good candidates for further SARS-CoV-2 preclinical experiments.

Background: To date, COVID-19 has caused over 772 million cases, with approximately 7 million deaths, according to the World Health Organization. Therefore, there is a need to develop new drugs to address the challenges posed by this disease. Objective: To propose new antiviral agents based on the natural product curcumin as potential protein-protein interaction inhibitors between the SARS-CoV-2 spike receptor binding domain (RBD) and the ACE2 receptor. Methods: A curcumin-based virtual screening was performed (Tanimoto coefficient= 0.9), and molecular docking analysis were carried out using the RBD as a receptor. Molecular dynamics (MD) using GROMACS were conducted for 120 ns. The SwissADME server was used to predict pharmacokinetics. To validate predictions, an in vitro enzyme assay measuring the relative inhibition of the interaction between the RBD and the ACE2 receptor was performed. Results: More than 1300 ligands were evaluated through molecular docking. The docking results were analyzed, and the ligands were classified according to their score and profile of interactions with residues of the RBD of the SARS-CoV-2 S glycoprotein. The top ten with the best scores and interactions were selected to verify the commercial availability. The lead compound Cu-1 demonstrated significant interactions with the RBD and stability in MD simulations, was acquired and evaluated in vitro. Compound Cu-1 inhibited 36 ± 0.7 % the interaction between the SARSCoV- 2 spike and the ACE2 receptor. In addition, Cu-1 was shown to have an acceptable druglikeness and pharmacokinetic profile. Conclusion: Curcumin provides a scaffold for identifying novel compounds with potential antiviral activity. Further studies on compound Cu-1 could yield on optimizing its structure to increase activity targeting the RBD of the S glycoprotein.