In-silico docking studies of selected phytochemicals against papain like protease of SARS-Cov-2

The SARS-Cov-2 virus, which is evolving continuously and causing adverse effects throughout the world, needs an effective drug molecule for its treatment. There are several receptors of SARS Cov-2 which are targeted for its inhibition by many lead molecules both in-vitro and in-vivo. Papain like Protease (PLpro) is one of the two SARS-Cov-2 proteases that can be used as a drug target for SARS Cov-2. It is a coronavirus enzyme that plays a role in the cleavage and maturation of viral polyproteins, assembly of the replicase-transcriptase complex and disruption of host responses. PLpro has also been linked to the cleavage of proteinaceous post translational modifications on host proteins as a means of evading antiviral immune responses. Structure-based drug discovery can be one of the effective methods to screen for various molecules against the target receptors. In this study, PLpro of SARS CoV-2 was chosen as the target for docking. Forty phytochemicals from various plant sources and four synthetic drugs have been screened for their inhibitory potential against PLpro using AutoDock Vina. Phytochemicals such as Tinosponone, Rhoifolin, Rosmanol, Berberin, Nimbin and two other existing drugs Elbasvir and Declatasvir showed higher inhibitory potential in terms of higher binding affinities. ADME and toxicity analysis were also performed to predict the pharmacokinetics and drug likeliness properties. It was concluded from the study that Tinosponone possesss potential inhibitor property of papain-like proteases (PLpro) of SARS CoV-2. Tinosponone from the plant Tinospora cordifolia had a binding affinity of - 9.3 kcal/mol and obeyed the Lipinski rules, making it an effective lead molecule for treating SARS CoV-2. Molecular Dynamics simulation of Tinosponone with PLpro has proved the stability and validity of the binding with RMSD value in range of 0.2 nm when it was run for 50 ns using GROMACS. Therefore, Tinosponone could be considered as a potential inhibitor of PLpro of SARS CoV-2.