Repositioning therapeutics for COVID-19: virtual screening of the potent synthetic and natural compounds as SARS-CoV-2 3CLpro inhibitors

The widespread transmission of SARS-CoV-2 has sparked alarm worldwide. Attaining the best drugs to treat COVID-19 at the shortest possible time is one of the most critical issues in this urgent situation. Molecular docking investigation of the therapeutic potential of marketed drugs is a fast and cost-effective approach to provide a solution to this problem. The recent research efforts have led to the resolving of the 3CLpro structure as a key protease in the lifecycle of coronavirus, which could facilitate in silico evaluation of drug candidates. Herein, the similarity between the SARS-CoV-2-3CL main protease and the other SARS-CoV receptors was evaluated via multiple sequence alignment and phylogenetic tree. The reported structure of the 3CLpro was considered as a target to identify potential inhibitors for treating COVID-19 using molecular docking based virtual screening protocol. Accordingly, a database of 50 synthetic compounds with various pharmacological usage such as antiviral, anti-inflammatory, anti-human immunodeficiency viruses, antimalarial, antibacterial, anticancer, and antioxidant including approved drugs and those undergoing clinical trials, and 40 natural compounds particularly those employed in traditional Iranian medicine was constructed. The output of multiple sequence alignment analysis showed that SARS-CoV-2 main protease shares a similarity of 96% with SARS-CoV. Also, the docking results indicated that the licofelone acyl glucuronide as an anti-inflammatory drug and delta-bilirubin as an antioxidant and anti-inflammatory agent as well as kappa-carrageenan conformer, beta-D-galactopyranosyl and calycosin 7-O-glucoside as natural compounds with minimal side-effects, according to in vitro studies, are good candidates to block the enzymatic activity of SARS-CoV-2 3CLpro. Moreover, the compound 1 with the highest negative binding energy is a chemical compound that due to its favorable interactions with the 3CLpro can be identified as a representative potential drug candidate for COVID-19. GRAPHIC ABSTRACT: [Image: see text] SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s13738-021-02235-7.