Echinacea (Purple Coneflower)

James Meschino DC, MS, ROHP

General Features

Echinacea is a wildflower that is native to North America, although the majority used in herbal supplements comes from cultivated plants.  It is a perennial herb, whose medical ingredients are found in the whole plant, including the root and aerial portions.  It is primarily used as a short-term supplement to arrest the onset of a cold or flu (upper respiratory tract infection) in the early stages, or as means to shorten the duration of these self-limiting conditions.^1,6,7

Principle Active Constituents

1. Echinacoside – a compound composed of caffeic acid, a caffeic acid derivative (similar to catechol), glucose and rhamnose, all attached to a central glucose molecule. Other caffeic acid derivatives important to the pharmacology of Echinacea include cichoric acid, chlorogenic acid and cynarin.  A significant degree of Echinacea’s immune modulating properties are attributable to the presence of echinacoside.
2. Polysaccharides – a number of immunostimulatory polysaccharides have been isolated including inulin (Echinacea root contains ~ 20% inulin), which has been shown to stimulate the alternate complement pathway, enhancing the movement of white blood cells into areas of infection. Arabinogalactan has been shown to increase interferon, tumor necrosis factor and interleukin-1.
3. Various Flavonoids ^1,6,7,8

Clinical Application and Mechanism of Action

1. Immunostimulation

Inulin stimulates alternative complement pathway of the immune system, which has been shown to enhance the action of white blood cells to fight infection and other pathogens.

Echinacea enhances T cells production of interferon and other immune potentiators.  The result is enhanced T cell replication, macrophage activity, antibody binding, and increased numbers of circulating neutrophils.

The non specific T cell activation by Echinacea also increases activity of natural killer cells.

Echinacea enhances macrophage phagocytosis and stimulates macrophages to produce a number of immune-potentiating compounds (i.e. tumor necrosis factor, interferon, and interleukin-1).

Echinacea Inhibits hyaluronidase enzyme, which is normally secreted by microorganisms in an attempt to breakdown tissue barriers between cells ( known as the cement substance, ground substance or proteoglycans), enabling the microorganism to more easily spread and invade new cells.^2,3,4,5,6,7

2. Therapeutic Application

Treatment of Upper Respiratory Tract Infections (URI)- a review of 16 clinical trials, involving a total of 3396 patients, provided evidence that Echinacea can abort a cold or flu (upper respiratory tract infection) in the early stages and/or shorten the duration and severity of upper respiratory tract infections in a significant number of cases. ⁹ In one study involving 80 individuals, it was shown that Echinacea shortened the duration of cold symptoms from 6 days on average, compared to 9 days in the placebo group. ¹⁰ However, there is insufficient evidence to suggest that Echinacea can prevent colds and related URI, if taken prophylactically over a long period of time (e.g., throughout the winter). Studies examining this possible benefit have mostly reported negative results in that Echinacea has not demonstrated an ability to reduce the number of URI, colds or flus in clinical trials where it has been tested as a preventive agent in this regard^{. 11} Thus, at this time Echinacea is not recommended as a supplement to be taken for long periods, but is rather used most effectively as a short-term intervention to rally the immune system during the early (prodromal) stages of an upper respiratory tract infection.^1,6,7

Best Variety:  Some experts suggest that Echinacea Purpurea is the best variety because it provides the greatest range of active compounds and has the greatest level of clinical research support. ¹

Dosage and Standardized Grade

Upper Respiratory Tract Infection – as an agent to help arrest the onset, or to help shorten the duration and minimize the severity of the common cold or flu, taking 300 mg of Echinacea every two hours for the first day of illness, then 300 mg three times per day for the duration of symptoms is a common practice.  If taken as a capsule or caplet the standardized extract should contain 3.5 percent or greater echinacoside content and not less than 2.4% soluble beta-1,2 d-5 fructofuranosides, per 300 mg tablet or capsule.  ⁶

 Author’s Note: Anecdotal evidence suggests that many people take much higher doses of Echinacea at the beginning of cold symptoms and during the cold cycle.  It is not uncommon to encounter individuals using doses as high as 900 mg of Echinacea every two hours at the outset of a cold, and maintaining this level of intake until the symptoms begin to subside. Fortunately, Echinacea appears to be generally safe, even when taken in very high doses, as indicated below.

Adverse Side Effects, Toxicity and Contraindications

Echinacea is regarded as being generally safe, even when taken at high doses.  It has not been found to cause any toxic effects and reported side effects of high dose supplementation are infrequent and usually limited to minor gastrointestinal symptoms, and increased urination. ^12,13 Some minor allergic symptoms have also been reported.  In Australia, one survey found that 20% of allergy-prone individuals were allergic to Echinacea upon testing.  On rare occasions severe allergic reactions have occurred with Echinacea supplementation, some of them life threatening. ^6,7,14

Other concerns are based upon the long-term administration of Echinacea and the possibility of over-stimulating the immune system in at risk individuals.  As such, Echinacea should not be used by people with autoimmune disorders (Lupus, Rheumatoid Arthritis, etc.) and patients with multiple sclerosis, as there is evidence to show that it may trigger or aggravate such conditions. ¹⁵   A reported case also implicated the use of Echinacea in triggering recurrent episodes of erythema nodosum, an inflammatory condition that involves tender nodules under the skin. ¹⁶

As prolonged use of Echinacea may over-stimulate immune function and trigger underlying or hidden pathologies, the daily use of Echinacea for long periods as may occur in patients with impaired immune function (i.e., chronic fatigue), should not exceed eight weeks.  The customary cycle of use in these cases is as follows: After one week of abstaining from Echinacea supplementation patients can begin another eight week cycle of supplementation, followed by one week off and so on.¹

Thus, a primary concern of long-term use of Echinacea is rooted in the risk of sustained immune system enhancement, which may trigger some auto destructive consequences (i.e., attacking healthy body tissues, reawakening of dormant herpes viruses and/or, triggering autoimmune reactions).1

Drug-Nutrient Interactions

1. Immunosuppressive Drugs – Echinacea counters the effects of these drugs and should not be used concurrently.^17,18
2. Corticosteroid Medications – Echinacea may counter the effects of these drugs in patients with autoimmune conditions and should not be taken concurrently.¹⁹

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3. Tubaro A, et.al. Anti-inflammatory activity of a polysaccharide fraction of echinacea angustifolia root.  J Pharm Pharmacol 1987;39:567-9.
4. Roesier, J, et.al. Application of purified polysaccharides from cell cultures of the plant echinacea purpurea to mice medicates protection against systematic infections with listeria monocytogenes and candida albicans.  Int J Immunopharmacol 1991;13:27-37.
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18. See DM, et al. In vitro effects of Echinacea and ginseng on natural killer and antibody-dependent cell cytotoxicity in healthy subjects and chronic fatigue syndrome or acquired immunodeficiency syndrome patients. Immunopharmacology. 1997; 35 (3): 229-35.
19. Bauer R. Echinacea Drugs—effects and active ingredients. Z Arztl Fortbild. (Jena). 1996; 90 (2): 111-15.