Echinacea inhibits influenza viruses in vitro, no resistance: study


Echinacea purpurea

Luebeck/Germany (bb) - A special extract of the traditionally used medicinal plant Echinacea purpurea exerts a potent antiviral activity in vitro, according to Prof. Dr. Stephan Pleschka, University of Giessen/Germany. Both the virus inhibiting activity of Echinacea, which was studied by his group, and the only recently discovered inflammation modulating and antibacterial effects of the herbal extract could extend the preventive and therapeutic spectrum of antiviral drugs, including influenza.

Study  The aim of the in vitro-study presented at an international Conference on Antivirals (ICAV-9) in Luebeck (1) was to evaluate both the antiviral activity of a standardized Echinacea preparation against different influenza viruses and the possible mechanism responsible for this. Pleschka and colleagues used renal epithelial cells (MDCK cells) as cellular infection model. All tested influenza strains (including the new pandemic H1N1 strain) were clinically relevant, some highly pathogenic and a few with pandemic potential (A/Thailand/KAN-1/04 (H5N1), A/FPV/Bratislava/79 (H7N7), A/Hamburg/1/09 (H1N1)). The echinacea fresh plant extract was added to the cultured cells at different times and in varying concentrations. After viral inoculation, the extent of infection inhibition was measured.

Results  It was found that all tested viral strains were almost completely inactivated by the echinacea fresh plant extract. The necessary extract concentration for the inhibition of viral infectivity was far below under the recommended dosage for oral application of the respective echinacea product. Further tests showed that the H5N1 strain had developed no resistance against echinacea, even not after multiple cell culture rounds. In control experiments, the viruses were treated with the neuraminidase inhibitor oseltamivir. In this case, almost all viruses developed resistance with the third passage. However, even these oseltamivir-resistant viruses, Pleschka said, were completely inhibited by the echinacea extract. The research in the possible mechanisms showed that the echinacea extract nonspecifically inactivates the viral surface protein hemagglutinin and thus the viral adhesion to the cellular HA-receptors, which finally inhibits a central pathogenetic step of influenza infections.

Summary  These insights into the molecular mechanisms of the echinacea antimicrobial effects confirm earlier observations on the medical use in this regard - especially acute infections, inflammations and infection risks following traumatic injuries. It seems, that the often-cited stimulation of the immune system is less important for these effects, then both a non-specific inhibition of infection (both viral and bacterial) and a symptoms relieving normalization of excessive inflammatory responses ("cytokine storm"). The therapeutic relevance of the specific echinacea fresh plant extract in these indications should now be further evaluated.

Plant extract  A standardized alcoholic extract of fresh herb (95%) and roots (5%) of the traditional medicinal plant Echinacea purpurea (L.) Moench (Echinaforce®, A. Vogel Bioforce AG, Switzerland) was tested. In many countries the approved indications mainly concern the prevention and treatment of infections including common cold. In addition to anti-viral effects (2), the extract used has anti-bacterial and marked anti-inflammatory properties (3).

Literature (1) International Conference on Antivirals for Neglected and Emerging Viruses (9th ICAV Symposium). Luebeck/Germany, October 10 - 13, 2010 (
(2) Pleschka S, Stein M, Schoop R, Hudson JB: Anti-viral properties and mode of action of standardized Echinacea purpurea extract against highly pathogenic avian influenza virus (H5N1, H7N7) and swine-origin H1N1 (S-OIV). Virol J. 2009 Nov 13;6:197.
(3) Sharma SM, Anderson M, Schoop SR, Hudson JB: Bactericidal and anti-inflammatory properties of a standardized Echinacea extract (Echinaforce): dual actions against respiratory bacteria. Phytomedicine. 2010 July; 17(8-9): 563-8.

Scientist Prof. Dr. Stephan Pleschka is a virologist at the Justus Liebig-University in Giessen/Germany. Important scientific activities in virology and microbiology are:
* Identification, characterization and assessment of viral and cellular factors and mechanisms regulating viral multiplication in infected cells and thus influence the viral replication.
* Viral spread and consecutive immune reactions of infected hosts including infection syndromes in different animal models.
* In addition to his research in pathogenesis of influenza and new therapeutic approaches, other relevant work applies to the importance of influenza for lung diseases and the innate immunity.

Key words infection blockade, virus inhibition, antiviral, antibacterial, inflammation modulation, Echinacea purpurea (L.) MOENCH, Echinaforce, fresh plant extract, hemagglutinin, molecular mechanisms, influenza, pandemic, prophylaxis, resistance, swine flu, disease control, therapy

Autor/In: Rainer H. Bubenzer, Heilpflanzen-Welt (19.10.2010)