The three medicinal species of Echinacea contain multiple pharmacologically-active constituents in their flowerheads, leaves, and roots. The chief constituents include water-soluble polysaccharides (inulin in E. angustifolia with arabinogalactans and arabinoxylan in the other two species), caffeic and ferulic acid derivatives (e.g. cichoric acid, echinoside), glycoproteins, and fat-soluble alkylamides along with volatile oils, flavanoids, and trace amounts of 1,2 saturated pyrrolizidine alkaloids (not the unsaturated alkaloids implicated in hepatotoxicity).^3-6

The constituents vary between species, by part of the plant examined (i.e., above ground plant vs. root), and by growing conditions, time of harvest, etc.⁷ All three species have alkylamides, primarily unsaturated isobutylamides, though the concentration is highest in E. angustifolia roots.⁸ All three species also produce polysaccharides, such as echinacin B, in their leaves and flowers, but the concentration is greatest in E. purpurea. E. angustifolia root contains higher concentrations of caffeic acid esters (0.6-2.1%), including echinoside⁹ and cynarin.¹⁰ In a comparison study of the three species, Sloley found that cichoric acid and verbascoside were prominant in E. purpurea root though cynarin and dodeca-2E,4E,8Z,10Z/E-tetraenoic acid isobutylamides were present in E. angustifolia root extracts. E. pallida root extracts contained predominantly echinacoside and 6-O-caffeoylechinacoside.¹¹

The mechanism of action of the Echinacea constituents is not clearly understood, though researchers have advanced several theories. In vitro and animal studies suggest that Echinacea enhances nonspecific immunity.¹² Its activities include: increase in natural-killer cells and monocytes,¹² inhibition of tissue and bacterial hyaluronidase,⁴ increase in granulocyte phagocytosis,¹³ increase in WBC mobility,⁴ increase in release of tumor necrosis factor (TNF) and interferon,¹⁴ stimulation of fibroblasts,⁴ stimulation of macrophage activity,⁸ increase in cytokine production,¹⁵ stimulation of antibody production,⁵ antioxidant activity,¹¹ and inhibition of tumor cells.¹⁶ Other researchers contend that Echinacea serves as an immunomodulator with both stimulatory and anti-inflammatory activity.^8,17-20

Toxicity studies are underway at the National Toxicology Program and at Gaia Herbal Research Foundation. Previous results revealed no significant toxicity from oral administration of E. purpurea juice (LD₅₀ >15,000 mg/kg) with sedation and dyspnea at very high doses intravenously ( LD₅₀ >5,000 mg/kg in rats).²¹ Echinacin, a German pharmaceutical, did not cause mutations or chromosomal abnormalities.²²