Echinacea extracts contain significant and selective activities against human pathogenic bacteria

Abstract

Echinacea (Asteraceae) extracts have been advocated traditionally for use in individuals suffering from sore throats, coughs, and various other respiratory symptoms that could be due to bacterial infections. We therefore evaluated six different commercial Echinacea extracts, with defined composition of standard marker compounds, for their ability to inactivate 15 different human pathogenic bacteria and two pathogenic fungi. The extracts were derived from E. angustifolia roots or mixtures of E. purpurea roots and aerial parts and contained different relative amounts of alkylamides and polysaccharides and similar overall concentrations of caffeic acid derivatives. Five bacteria, Streptococcus pyogenes, Haemophilus influenzae, Legionella pneumophila, Clostridium difficile, and Propionibacterium acne, were very sensitive to one or more of the extracts, but the patterns of sensitivity were quite different for the various extracts. Furthermore, there were no correlations between bacterial sensitivity and the concentrations of marker compounds in the extracts. The other bacteria and fungi were either slightly sensitive to one or more extracts or were totally resistant. In conclusion, certain preparations of Echinacea, especially ethanol formulations, could provide useful protection or symptom alleviation in cases of various upper and lower respiratory infections, such as sinusitis, bronchitis, pharyngitis, tonsillitis, and pneumonia, as well as cutaneous infections, by means of their selective bactericidal activities, although we do not know which components of the extracts are responsible for these activities. © 2008 Informa Healthcare USA, Inc.