Echinacea purpurea

Echinacea purpurea (Eastern purple coneflower or Purple coneflower) is a species of flowering plant in the genus Echinacea.[1]Its cone-shaped flowering heads are usually, but not always purple.[2]It is native to eastern North America[1] and present to some extent in the wild in much of the eastern, southeastern and midwest United States.[3] It is also grown as an ornamental plant, and numerous cultivars have been developed for flower quality and plant form.[2]

Medicinal effects

Marketed and studied medicinal products contain different species (E. purpurea, E. angustifolia, E. pallida), different organs (roots and herbs) and different preparations (extracts and expressed juice). Their chemical composition is very different.[5][6]

Multiple scientific reviews and meta-analyses have evaluated the published peer reviewed literature on the immunological effects of Echinacea. Reviews of the medicinal effects of Echinacea are often complicated by the inclusion of these different products.[7] Evaluation of the literature within the field suffers generally from a lack of well-controlled trials, with many studies of low quality.[7][8][9][10]

A 2007 study by the University of Connecticut combined findings from 14 previously reported trials examining Echinacea and concluded that Echinacea can cut the chances of catching a cold by more than half, and shorten the duration of a cold by an average of 1.4 days.[8][11] However, Dr. Wallace Sampson, an editor of Scientific Review of Alternative Medicine and a Stanford University emeritus clinical professor of medicine, says that the referenced trials lack the similarities necessary to provide definitive results when combined into one report. “If you have studies that measure different things, there is no way to correct for that. These researchers tried, but you just can’t do it.”[12]

A 2003 controlled double-blind study from the University of Virginia School of Medicine and documented in the New England Journal of Medicine[13] stated that echinacea extracts had “no clinically significant effects” on rates of infection or duration or intensity of symptoms. The effects held when the herb was taken immediately following infectious viral exposure and when taken as a prophylaxis starting a week prior to exposure. In a press release, Dr. Michael Murray, the Director of Education for Factors Group of Nutritional Companies, a manufacturer of Echinacea-related products, calls the study “faulty and inaccurate.”[14] According to Dr. Murray, none of the three extracts used on the 399 study participants contained all three of the components of Echinacea responsible for its immune-enhancing effects: polysaccharides, alkylamides and cichoric acid. In addition, Dr. Murray said “the standard dosage for dried Echinacea angustifolia root is normally three grams per day or more and this study used less than one gram.”

An earlier University of Maryland review based on 13 European studies concluded that echinacea, when taken at first sign of a cold, reduced cold symptoms or shortened their duration.[15] The review also found that three of four published studies concluded that taking echinacea to prevent a cold was ineffective.

The European Medicines Agency (EMEA) assessed[16] the body of evidence and approved the use of expressed juice and dried expressed juice from fresh flowering aerial parts of Echinacea purpurea for the short-term prevention and treatment of the common cold. According to their recommendations:

It should not be used for more than 10 days. The use in children below 1 year of age is contraindicated, because of theoretically possible undesirable effect on immature immune system. The use in children between 1 and 12 years of age is not recommended, because efficacy has not been sufficiently documented although specific risks are not documented. In the absence of sufficient data, the use in pregnancy and lactation is not recommended.[17]

Popular belief and traditional use

Echinacea is popularly believed to be an immunostimulator, stimulating the body’s non-specific immune system and warding off infections and also being utilized as a laxative. A study commonly used to support that belief is a 2007 meta-analysis in The Lancet Infectious Diseases.[8] The studies pooled in the meta-analysis used different types of echinacea, different parts of the plant, and various dosages. This review cannot inform recommendations on the efficacy of any particular type of echinacea, dosage, or treatment regimen. The safety of echinacea under long-term use is also unknown.[18]

History

Echinacea angustifolia was widely used by the North American Plains Indians for its general medicinal qualities.[19]Echinacea was one of the basic antimicrobial herbs of eclectic medicine from the mid 19th century through the early 20th century, and its use was documented for snakebite, anthrax, and for relief of pain. In the 1930s echinacea became popular in both Europe and America as a herbal medicine. According to Wallace Sampson, MD, its modern day use as a treatment for the common cold began when a Swiss herbal supplement maker was “erroneously told” that echinacea was used for cold prevention by Native American tribes who lived in the area of South Dakota.[12] Although Native American tribes didn’t use echinacea to prevent the common cold, some Plains tribes did use echinacea to treat some of the symptoms that could be caused by the common cold: The Kiowa used it for coughs and sore throats, the Cheyenne for sore throats, the Pawnee for headaches, and many tribes including the Lakotah used it as an analgesic.[20]

Native Americans learned of E. angustifolia by observing elk seeking out the plants and consuming them when sick or wounded, and identified those plants as elk root.[21]

Active substances

Like most crude drugs from plant or animal origin, the constituent base for echinacea is complex, consisting of a wide variety of chemicals of variable effect and potency. Some chemicals may be directly antimicrobial, while others may work at stimulating or modulating different parts of the immune system. All species have chemical compounds called phenols, which are common to many other plants. Both the phenol compounds cichoric acid and caftaric acid are present in E. purpurea, other phenols include echinacoside, which is found in greater levels within E. angustifolia and E. pallida roots than in other species. When making herbal remedies, these phenols can serve as markers for the quantity of raw echinacea in the product. Other chemical constituents that may be important in echinacea health effects include alkylamides and polysaccharides.

The immunomodulatory effects of echinacea preparations are likely caused by fat-soluble alkylamides (alkamides), which occur mostly in E. angustifolia and E. purpurea but not in E. pallida.[22] Alkylamides bind to human CB2 and CB1cannabinoid receptors and thus inhibit tumor necrosis factor α TNF-alpha.[23] These Alkylamides have similar potency to that of THC at the CB2 receptor, with THC being around 1.5 times stronger (~40 nm vs ~60 nm affinities). However, potency is dramatically less than that of THC at the psychoactive CB1 receptor (~40 nm vs ~ >1500 nm affinities).

As with any herbal preparation, individual doses may vary significantly in active chemical composition. In addition to poor process control which may affect inter- and intra-batch homogeneity, species, plant part, extraction method, and contamination or adulteration with other products all lead to variability between products.[24][25]

Root or whole plant

As with any plant, the chemical makeup of echinacea is not consistent throughout the organism. In particular, the root has been promoted as containing a more efficacious mixture of active chemicals. A 2003 study in the Journal of the American Medical Association (Taylor et al. 2003[26]) found that when echinacea products made from the entire plant were taken after the second cold symptom appeared they provided no measurable beneficial effect for children in treating the severity or duration of symptoms caused by the common cold virus. The study has been criticized for using whole-plant extracts instead of root extracts, and the dosages studied were lower than those recommended by herbalists.[citation needed] A 2005 study in the New England Journal of Medicine (Turner, 2005[13]) focused on several root extracts, but still found no statistically significant effects on duration, intensity, or prevention of symptoms.

Frequency of administration

Proponents of echinacea assert that it is not a “one-dose” treatment, and that in order to work effectively, a dose should be taken at the very first sign of a cold symptom. Subsequent doses are called for every two to four hours after the first dose, including during the overnight sleeping period, until the cold symptoms have disappeared.[citation needed]

The several species of echinacea differ in their precise chemical constitution, and may provide variable dosages of any active ingredients.

{Information courtesy Wikipedia}