Extracts of Echinacea purpurea are among the most widely used herbal medicines throughout Europe and North America for the prevention or treatment of common cold, coughs, bronchitis and other upper respiratory infections. Popular preparations include expressed juice from the aerial parts of the plant (which contain polysaccharides) and alcoholic tinctures from roots (containing caffeic acid derivatives and alkylamides). Since immune modulation has been reported for similar extracts, cytokine antibody arrays were used to investigate the changes in the pro-inflammatory cytokines and chemokines released from a cultured line of human bronchial epithelial cells exposed to Rhinovirus 14 and two different chemically characterized Echinacea extracts. Virus infection stimulated the release of at least 31 cytokine-related molecules, including several important chemokines known to attract inflammatory cells. Most of these effects were reversed by simultaneous exposure to either of the two Echinacea extracts, although the patterns of response were different for the two extracts. These results could explain the antiinflammatory properties of Echinacea extracts. Furthermore, a number of these cytokines were stimulated by the same Echinacea preparations in uninfected cells. These observations therefore provide support for the alleged beneficial uses of Echinacea extracts.
In preparation for a clinical trial on the efficacy of Echinacea products with a pediatric population, a rational method for selection of test products was developed, based on phytochemical and bioassay evaluation. Ten currently available commercial products of Echinacea angustifolia (EA) or Echinacea purpurea (EP) were selected, and 3 bottles of each of 2 different lots were purchased for each product. Investigators were blinded to product identity before phytochemical analysis. Lot-to-lot variation was small, but product variation due to species and formulation was large. Products derived from ethanol extracts had low polysaccharide content and high levels of alkamides (EA), echinacoside (EA), cynarin (EA), cichoric acid (EP), and caftaric acid (EP). These products possessed high antiviral activities that differed between EA and EP products, but limited immune activation properties. In contrast, products derived without ethanol extraction had higher polysaccharide levels, but low levels of other components. These aqueous compounds showed immunostimulant activity as measured in a mouse macrophage model and a somewhat different antiviral profile. The choice of Echinacea product for clinical trial must therefore consider the impact of immune enhancement, the specific viral infection targeted, and the potential to reduce symptoms via antiinflammatory activity. Product selection may also depend on whether the intent of the trial is prophylaxis or treatment.
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