Analysis of natural compounds against the activity of SARS-CoV-2 NSP15 protein towards an effective treatment against COVID-19: a theoretical and computational biology approach.

Coronavirus infectious disease 2019 (COVID-19), a viral infection caused by a novel coronavirus (nCoV), continues to emerge as a serious threat to public health. This pandemic caused by SARS-CoV-2 (severe acute respiratory syndrome-coronavirus-2) has infected globally with 1,550,000 plus deaths to date, representing a high risk to public health. No effective drug or vaccine is available to curb down this deadly virus. The expedition for searching for a potential drug or vaccine against COVID-19 is of massive potential and favour to the community. This study is focused on finding an effective natural compound that can be processed further into a potential inhibitor to check the activity of SARS-CoV-2 with minimal side effects targeting NSP15 protein, which belongs to the EndoU enzyme family. The natural screening suggested two efficient compounds (PubChem ID: 95372568 and 1776037) with dihydroxyphenyl region of the compound, found to be important in the interaction with the viral protein showing promising activity which may act as a potent lead inhibitory molecule against the virus. In combination with virtual screening, modelling, drug likeliness, molecular docking, and 500 ns cumulative molecular dynamics simulations (100 ns for each complex) along with the decomposition analysis to calculate and confirm the stability and fold, we propose 95372568 and 1776037 as novel compounds of natural origin capable of getting developed into potent lead molecules against SARS-CoV-2 target protein NSP15.

Molecular basis for drug repurposing to study the interface of the S protein in SARS-CoV-2 and human ACE2 through docking, characterization, and molecular dynamics for natural drug candidates.

A novel coronavirus (SARS-CoV-2) identified in Wuhan state of China in 2019 is the causative agent of deadly disease COVID-19. It has spread across the globe (more than 210 countries) within a short period. Coronaviruses pose serious health threats to both humans and animals. A recent publication reported an experimental 3D complex structure of the S protein of SARS-CoV-2 showed that the ectodomain of the SARS-CoV-2 S protein binds to the peptidase domain (PD) of human ACE2 with a dissociation constant (Kd) of ~ 15 nM. In this study, we focused on inhibitors for ACE2: S protein complex using virtual screening and inhibition studies through molecular docking for over 200,000 natural compounds. Toxicity analysis was also performed for the best hits, and the final complex structures for four complexes were subjected to 400 ns molecular dynamics simulations for stability testing. We found two natural origin inhibitors for the S protein: human ACE2 complex (Andrographolide and Pterostilbene) which displayed better inhibition potential for ACE2 receptor and its binding with the S protein of SARS-CoV-2. Comparative studies were also performed to test and verify that these two drug candidates are also better than hydroxychloroquine which is known to inhibit this complex. However, we needed better potential drug candidates to overcome the side effects of hydroxychloroquine. Supplementary experimental studies need to be carried forward to corroborate the viability of these two new inhibitors for ACE2: S protein complex so as to curb down COVID-19.

In silico virtual screening, characterization, docking and molecular dynamics studies of crucial SARS-CoV-2 proteins.

The ongoing pandemic COVID-19 (COrona Virus Immuno Deficiency-2019) which is caused by SARS-CoV-2 (Severe Acute Respiratory Syndrome-CoronaVirus-2) has emerged as a pandemic with 400,000 plus deaths till date. We do not have any drug or vaccine available for the inhibition of this deadly virus. The expedition for searching a potential drug or vaccine against COVID-19 will be of massive potential and favor. This study is focused on finding an effective natural origin compound which can put a check on the activity of this virus. We chose important proteins from the SARS-CoV-2 genome such as NSP4, NSP15 and RdRp along-with the human ACE2 receptor which is the first point of contact with the virus. Virtual screening and followed up molecular docking resulted in Baicalin and Limonin as the final lead molecules. 200 ns of MD simulation for each protein-ligand complex provides the insights that Baicalin has a potential to target NSP4, NSP15 and RdRp proteins. Limonin which is largely used in traditional Indian medicine system is found to inhibit the human ACE2 receptor (making it inefficient in binding to the receptor binding domain of SARS-CoV-2). Our studies propose Baicalin and Limonin in combination to be studied in vitro and in vivo against COVID-19.Communicated by Ramaswamy H. Sarma.