Echinacea (Echinacea purpurea, Echinacea angustifolia, Echinacea pallida)
The genus Echinacea belongs to the family Compositae, commonly referred to as the sunflower family. Of the known species, E. purpurea, E. angustifolia, and E. pallida are commonly used in herbal medicine. Extracts derived from the root and aerial parts are widely used in Europe and the United States as nonspecific immunostimulants and to prevent or treat the common cold and influenza.
Depending on how this Asteraceae family member is classified, there are up to 12 different species of Echinacea. The most commonly used species for medicinal purposes is Echinacea purpurea, which is easy to cultivate and therefore, product demand does not put stress on native populations of Echinacea species that are difficult to cultivate. Most preparations found in the market are derived from the above-ground, or aerial, parts of E. purpurea and/or underground parts of E. purpurea; these preparations account for 80% of commercial production. In addition, E. angustifolia and E. pallida are also utilized in commerce but much less than E. purpurea. All three species of Echinacea seen in commercial preparations have undergone chemical and pharmacological studies. However, there are several other species of Echinacea that have little to no research on their chemistry and pharmacology.
Internal: Supportive therapy for colds and chronic infections of the respiratory tract and lower urinary tract.
External use: Poorly healing wounds and chronic ulcerations.
The native Americans utilized Echinacea for several uses including as an anesthetic, analgesic, for coughs and sore throats, and as an antidote for poisons such as snake venom. The physicians of the early 20th century learned many of these uses from the native Americans and utilized Echinacea for many indications, including sepsis, as well as less severe infections. At this time, Echinacea spp. has been documented in therapeutic use for more than a century by physicians for a variety of infections.
Indications given are for E. purpurea root.
The common cold, flu, and upper respiratory tract infections.
General immune system function.
Vaginal candidiasis in combination with an antifungal.
Non-healing wounds (topical or oral formulation).
Prophylaxis of common cold, flu, and upper respiratory tract infections. (weak evidence)
The complex chemical composition of the roots and herbs of Echinacea involves alkamides, ketoalkenes, caffeic acid derivatives, polysaccharides, and glycoproteins, which are believed to be responsible for noted immunostimulatory and anti-inflammatory activities.
Preclinical studies suggest immunostimulatory and anti-inflammatory effects. A standardized echinacea preparation inactivated influenza viruses and may improve respiratory activity. In animal models, echinacea stimulated erythropoiesis, increased blood-oxygen transport, produced anxiolytic effects, and exhibited wound-healing properties.
Clinical data indicate that echinacea is ineffective in preventing the common cold caused by rhinoviruses or in treating upper respiratory infections. Studies of its ability to reduce the incidence and duration of the common cold yielded mixed results. Other analyses do not indicate any benefits for treating colds, and weak evidence for a prophylactic benefit, but a large, randomized trial found an echinacea formulation to be as effective as oseltamivir for influenza, and with fewer adverse events in the echinacea group. In a review of 17 clinical trials involving 3,363 participants, echinacea supplements were found to affect reductions in pro-inflammatory cytokines that play a role in the progression of cytokine storm and acute respiratory distress syndrome.
Other studies have shown that a standardized echinacea root extract has immunomodulating activity; an echinacea/sage spray was useful in treating acute sore throats, and a formula containing dry root extracts of Echinacea purpurea and Echinacea angustifolia may be useful as an adjuvant therapy for decreasing relapse incidence in patients treated for genital condylomatosis. A topical echinacea extract was reported effective in alleviating symptoms associated with atopic eczema. Echinacea may also have anticancer potential evidenced by the cytotoxic effects exerted by an extract and a major compound, cichoric acid, in human colon cancer cells.
Some studies suggest that echinacea could decrease plasma levels, affect therapeutic efficacy, or cause adverse effects with some anticancer drugs. In HIV-infected patients, co-administration with etravirine was found to be safe and well-tolerated. In a large population-based study, use of echinacea was associated with a slight increase in diastolic blood pressure. There is insufficient evidence regarding the efficacy and safety of echinacea during pregnancy.
Echinacea’s active constituents include cichoric and caftaric acids, polysaccharides, and alkylamides. Immune-modulating effects of a standardized echinacea root extract include upregulation of interleukin (IL)-2 and IL-8 and downregulation of pro-inflammatory cytokines tumor necrosis factor (TNF)-alpha and IL-6. Immunemodulation by alkylamides occurs through binding to human cannabinoid receptors 1 and 2, and by inhibiting TNF-alpha. Alkylamides may also be responsible for anti-inflammatory effects. Although echinacea does not appear to have significant ergogenic or anabolizing effects, it appears to enhance the immune system and decrease oxidative damage.
In vitro and in vivo, echinacea extracts were shown to stimulate phagocytosis, enhance mobility of leukocytes, stimulate TNF and IL-1 secretion from macrophages and lymphocytes, and improve respiratory activity. However, their effects on innate immunity such as phagocytosis could not be confirmed, and showed only minimal effects on tumor progression, although echinacea did stimulate natural killer cell activity. Other studies suggest that bacterial components of echinacea are responsible for immune benefits, as total bacterial load differences and content of bacterial lipopolysaccharides within echinacea samples have correlated with NF-kappaB activation in THP-1 cells.
In human colon cancer cells, cichoric acid decreased telomerase activity and induced apoptosis via DNA fragmentation, caspase-9 activation, poly-ADP-ribose polymerase (PARP) cleavage, and beta-catenin downregulation.
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