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Withanone from Withania somnifera Attenuates SARS-CoV-2 RBD and Host ACE2 Interactions to Rescue Spike Protein Induced Pathologies in Humanized Zebrafish Model

Authors Balkrishna A, Pokhrel S, Singh H, Joshi M, Mulay VP, Haldar S, Varshney A

Received 20 November 2020

Accepted for publication 19 January 2021

Published 11 March 2021 Volume 2021:15 Pages 1111—1133

DOI https://doi.org/10.2147/DDDT.S292805

Checked for plagiarism Yes

Review by Single anonymous peer review

Peer reviewer comments 2

Editor who approved publication: Dr Anastasios Lymperopoulos


Video abstract of "Anti-viral efficacy of the phytochemical Withanone" [ID 292805].

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Acharya Balkrishna,1,2 Subarna Pokhrel,1 Hoshiyar Singh,1 Monali Joshi,1 Vallabh Prakash Mulay,1 Swati Haldar,1 Anurag Varshney1,2

1Drug Discovery and Development Division, Patanjali Research Institute, Haridwar, 249405, Uttarakhand, India; 2Department of Allied and Applied Sciences, University of Patanjali, Haridwar, 249405, Uttarakhand, India

Correspondence: Anurag Varshney; Swati Haldar
Drug Discovery and Development Division, Patanjali Research Institute, Roorkee-Haridwar Road, Haridwar, 249405, Uttarakhand, India
Tel +91-1334-244107, Ext. 7458
; +91-1334-244107, Ext. 7481
Fax +91-1334-244805
Email [email protected]; [email protected]

Purpose: SARS-CoV-2 engages human ACE2 through its spike (S) protein receptor binding domain (RBD) to enter the host cell. Recent computational studies have reported that withanone and withaferin A, phytochemicals found in Withania somnifera, target viral main protease (MPro) and host transmembrane TMPRSS2, and glucose related protein 78 (GRP78), respectively, implicating their potential as viral entry inhibitors. Absence of specific treatment against SARS-CoV-2 infection has encouraged exploration of phytochemicals as potential antivirals.
Aim: This study aimed at in silico exploration, along with in vitro and in vivo validation of antiviral efficacy of the phytochemical withanone.
Methods: Through molecular docking, molecular dynamic (MD) simulation and electrostatic energy calculation the plausible biochemical interactions between withanone and the ACE2-RBD complex were investigated. These in silico observations were biochemically validated by ELISA-based assays. Withanone-enriched extract from W. somnifera was tested for its ability to ameliorate clinically relevant pathological features, modelled in humanized zebrafish through SARS-CoV-2 recombinant spike (S) protein induction.
Results: Withanone bound efficiently at the interacting interface of the ACE2-RBD complex and destabilized it energetically. The electrostatic component of binding free energies of the complex was significantly decreased. The two intrachain salt bridge interactions (K31-E35) and the interchain long-range ion-pair (K31-E484), at the ACE2-RBD interface were completely abolished by withanone, in the 50 ns simulation. In vitro binding assay experimentally validated that withanone efficiently inhibited (IC50=0.33 ng/mL) the interaction between ACE2 and RBD, in a dose-dependent manner. A withanone-enriched extract, without any co-extracted withaferin A, was prepared from W. somnifera leaves. This enriched extract was found to be efficient in ameliorating human-like pathological responses induced in humanized zebrafish by SARS-CoV-2 recombinant spike (S) protein.
Conclusion: In conclusion, this study provided experimental validation for computational insight into the potential of withanone as a potent inhibitor of SARS-CoV-2 coronavirus entry into the host cells.

Keywords: ACE2-RBD complex, Withania somnifera, withanone, docking and MD simulation, ELISA, SARS-CoV-2 S-protein, humanized zebrafish model

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