Anti-inflammatory activities of Echinacea extracts do not correlate with traditional marker components

Numerous preparations of Echinacea (Asteraceae), mainly derived from three species, Echinacea purpurea ( L.) Moench, Echinacea angustifolia (D.C.) and Echinacea pallida (Nutt.) Nutt., are available for the treatment of symptoms of colds and influenza which, along with a number of other respiratory conditions, have been ascribed to the induction of pro-inflammatory cytokines. We evaluated various chemically characterized extracts and fractions, derived from the three species of Echinacea, for their possible inhibitory effects on the secretion of pro-inflammatory cytokines IL-6 and IL-8 (CXCL-8) by human bronchial epithelial cells infected with rhinovirus type 14. All of the E. purpurea fractions, comprising aqueous or ethanol extracts of roots, leaves and stems, but to a lesser degree flowers, strongly inhibited the secretion of both cytokines. In contrast, corresponding fractions derived from E. angustifolia and E. pallida showed relatively weak cytokine-inhibitory activity, whereas their aqueous fractions significantly enhanced cytokine secretion, both in virus-infected and in uninfected cells. These properties did not correlate with the presence or absence of alkylamides or specific caffeic acid derivatives, although the alkylamide rich fraction of E. angustifolia showed a significant inhibitory effect. However, there was some correlation between anti-cytokine effects and our previously reported anti-viral activities. Thus, none of the groups of compounds traditionally used as "markers" for Echinacea are responsible for anti-inflammatory activity. Consequently, we believe that other constituents of Echinacea should be evaluated.