In vitro virucidal activity of Echinaforce®, an Echinacea purpurea preparation, against coronaviruses, including common cold coronavirus 229E and SARS-CoV-2
Authors: Hulda R Jonsdottir
Roland Schoop
Nicole Lenz
Johanna Signer
Marc Strasser
Werner C Albrich
Olivier B Engler
Andreas Suter
Roland Züst
Denise Siegrist
Sarah Ryter
Rahel Ackermann-Gäumann
Journal: Virology Journal (2020)
Discipline: MICROBIOLOGY
Keywords: Antivirals; Common cold; Coronavirus; Echinacea; HCoV-229E
Affiliations: SPIEZ LABORATORY, Austrasse, 3700, Spiez, Switzerland., SPIEZ LABORATORY, Austrasse, 3700, Spiez, Switzerland. ., Division of Infectious Diseases and Hospital Epidemiology, Kantonsspital St. Gallen, St. Gallen, Switzerland., A.Vogel AG, Roggwil, Switzerland.

Abstract:  Background: Coronaviruses (CoVs) were long thought to only cause mild respiratory and gastrointestinal symptoms in humans but outbreaks of Middle East Respiratory Syndrome (MERS)-CoV, Severe Acute Respiratory Syndrome (SARS)-CoV-1, and the recently identified SARS-CoV-2 have cemented their zoonotic potential and their capacity to cause serious morbidity and mortality, with case fatality rates ranging from 4 to 35%. Currently, no specific prophylaxis or treatment is available for CoV infections. Therefore we investigated the virucidal and antiviral potential of Echinacea purpurea (Echinaforce®) against human coronavirus (HCoV) 229E, highly pathogenic MERS- and SARS-CoVs, as well as the newly identified SARS-CoV-2, in vitro. Methods: To evaluate the antiviral potential of the extract, we pre-treated virus particles and cells and evaluated remaining infectivity by limited dilution. Furthermore, we exposed cells to the extract after infection to further evaluate its potential as a prophylaxis and treatment against coronaviruses. We also determined the protective effect of Echinaforce® in re-constituted nasal epithelium. Results: In the current study, we found that HCoV-229E was irreversibly inactivated when exposed to Echinaforce® at 3.2 μg/ml IC50. Pre-treatment of cell lines, however, did not inhibit infection with HCoV-229E and post-infection treatment had only a marginal effect on virus propagation at 50 μg/ml. However, we did observe a protective effect in an organotypic respiratory cell culture system by exposing pre-treated respiratory epithelium to droplets of HCoV-229E, imitating a natural infection. The observed virucidal activity of Echinaforce® was not restricted to common cold coronaviruses, as both SARS-CoV-1 and MERS-CoVs were inactivated at comparable concentrations. Finally, the causative agent of COVID-19, SARS-CoV-2 was also inactivated upon treatment with 50μg/ml Echinaforce®. Conclusions: These results show that Echinaforce® is virucidal against HCoV-229E, upon direct contact and in an organotypic cell culture model. Furthermore, MERS-CoV and both SARS-CoV-1 and SARS-CoV-2 were inactivated at similar concentrations of the extract. Therefore we hypothesize that Echinacea purpurea preparations, such as Echinaforce®, could be effective as prophylactic treatment for all CoVs due to their structural similarities. 

Retracted: No

PubPeer comments:
 There is no  solvent-only control in the whole paper (including supplementaries). Therefore the only real observations at this point would be that *65% Ethanol has a virucidal activity* which has nothing to do with the advertised compound. On Twitter, the authors laboratory claim the following:  We have of course tested the solvent in the appropriate dilution as a control. -- But if they do not want (?) to make this control public, this study should be retracted put on hold, due to *lack of an appropriate control* (crucial for the main point of the paper). , 
 #1 Addendum to the comment above: The lack of reporting of an appropriate control should indeed cause concern. However, it should be noted that according to the description in the paper, the solution was diluted before application, i.e. the ethanol concentration used was much lower. ,