Synergistic inhibition of Influenza replication cycle with Echinacea purpurea and Sambucus nigra

Introduction

Hemagglutinin and neuraminidase enzyme present therapeutic targets for the prevention and treatment of influenza. Echinacea purpurea extracts have been shown to inhibit hemagglutinin activity and viral infectivity [1]. In this study we examined the possibility that Sambucus nigra juice could additionally affect other parameters of influenza replication cycle and consequently enhance antiviral activity.

Methods

An ethanol extract (65% V/V) from freshly harvested E purpurea herb and roots (EF), the juice from Sambucus nigra (SAM) fructus and a fixed combination thereof (Echinaforce® Hotdrink, EF+SAM), were all assayed for interaction with viral hemagglutinin and neuraminidase activities, and inhibition of influenza virus (H1N1) replication in MDCK cells as described in [1].

Results

Lower concentrations of EF+SAM (0.0005% EF/0,02%SAM) were required to inhibit 50% of H1N1 replication than the single extracts with 0.006% for EF and 0.41% for SAM indicating super-additive effects of the EF+SAM combination. We observed varying kinetics, with early blockade of infection by Echinacea, while Sambucus' activity developed over time: EF activity was attributed to hemagglutinin blockade, indicating an early stage interference with infection. In contrast, SAM had no measurable activity on receptor interaction (HA activity) but inhibited activity of neuraminidase by 40% and more strongly than EF at the same concentration of 0.04%.

Conclusion

E purpurea ethanol extract and juice of Sambucus nigra have complementary points of activity to inhibit the influenza replication cycle. In combination the extracts inhibit both hemagglutinin and neuraminidase activities, i.e. virus entry and release of progeny virions, demonstrating synergistic effects in inhibition of influenza virus.

Reference:

[1] Pleschka S, Stein M, Schoop R, Hudson JB. Virology Journal 2009;6:197.