Echinacea purpurea (L.) Moench., E. angustifolia DC., E. pallida (Nutt.) Nutt.

Asteraceae (Compositae)

Black Sampson; Coneflower; E. purpurea, E. angustifolia: purple coneflower; E. angustifolia: Kansas snakeroot; narrow-leaf purple coneflower; E. pallida: pale coneflower; pale purple coneflower; sometimes it is also called Rudbeckia, which is, however, another genus of the Asteraceae.

Echinacea herba; Echinacea radix

E. purpurea: rhizome and root/fresh flowering aerial parts/dried herb/fresh expressed juice; E. pallida: root; E. angustifolia: herb

The phytochemical composition of the various species is slightly different and this leads to confusion as to the potential for drug interactions. E. purpurea: The root contains alkamides, including dodecatetraenoic acid isobutylamide, caffeic acid derivatives and saturated (non-hepatotoxic) pyrrolizidine alkaloids. The herb contains similar alkamides to the root, caffeic acid derivatives and polysaccharides. The pressed juice (from the aerial parts) contains heterogeneous polysaccharides, inulin-type compounds, arabinogalactan polysaccharides and glycoproteins. E. pallida: The root contains similar caffeic acid esters and glycosides to E. purpurea. Polyenes and polyacetylenes, including a range of ketoalkenes and ketopolyacetylenes, have been reported and polysaccharides and glycoproteins are also present. E. angustifolia: The root contains alkamides and similar caffeic acid esters and glycosides to E. purpurea. Alkylketones and the saturated pyrrolizidine alkaloids are also present (Barnes et al. 2005; Williamson et al. 2013).

Clinical evidence for its use as an immunomodulator is available for some of the standardised extracts. Overall, Echinacea preparations appear to be efficacious both in the treatment (reducing symptoms and duration) and prevention of the common cold. However, Echinacea preparations tested in clinical trials differ greatly. Better evidence is shown with preparations based on the aerial parts of E. purpurea as they might be effective for the early treatment of colds in adults, but the results are not fully consistent (Barnes et al. 2005; Linde et al. 2006; Nahas and Balla 2011). A randomised, double-blind, placebo-controlled trial assessed the safety and efficacy of a specific E. purpurea