Latin name: Echinacea purpurea
Pharmacopoeial name: Echinaceae purpureae radix
Other names; Echinacea root, purple coneflower root
E. purpurea is the best known of the dozen or so species of perennial prairie wildflowers native to the central grasslands of North America. E. purpurea is characterized by erect main stems up to 2 meters in height, alternate leaves on long stalks, and solitary spiny, reddish-orange flowers surrounded by purplish bracts.
E. purpurea is cultivated widely throughout the United States, Canada and Europe. Prior to European colonization, a number of Native American nations used various Echinacea preparations for a variety of purposes (1). European settlers learned about native botanical species from their indigenous teachers, soon bringing Echinacea into the colonial pharmacopoeia. Echinacea is used most widely as prevention or treatment for the common cold, with the proposed mechanism of action relating to its reported ability to stimulate the immune system (2).
Echinacea purpurea is best known for its effects on the immune system (3). Stimulation of various immune cells such as macrophages, other monocytes, and natural killer (NK) cells has been demonstrated repeatedly in vitro (4). However, if and how these “immunostimulating” effects translate into better human health is less well understood (5), and “immunomodulation” may be a more appropriate term for Echinacea’s effects.
Activation of human macrophages was reported by Möse (6). More recent work has reported activation of NK cell as well as macrophage phagocytosis following exposure of ex vivo human immune cells to E. purpurea extracts (7). Reports of increased macrophage phagocytic activity have been accompanied by several reports of enhanced cytokine production (8).
The first, a single-blind study reported a 20% increase in phagocytotic activity at day 4 in an Echinacea group injected intravenously with an E. purpurea preparation. The second study, reported as double-blinded and randomized, subjected 24 men to oral dosing, with 30 drops 3 times daily for 5 days, with either an ethanolic extract of E. purpurea root or a similar-appearing placebo (9). Increases in PMN phagocytic activity were reported, reaching peak levels at day 5. No changes in white cell counts or other blood measurements were noted.
Melchart and colleagues reported the results of five separate studies in a single 1995 report (10). Finding mostly negative results, this team suggested using sick or immunocompromised “patients” rather than “healthy volunteers” for future studies. In 1998, Berg et al. reported a trial in which 42 triatheletes were randomly administered magnesium,placebo or E. purpurea daily during 28 days of training and directly before and after a competition (11). While three of 13 in the magnesium group and four of 13 in the placebo group got colds, none of the athletes taking Echinacea developed respiratory infections. This trend toward benefit was not statistically significant.
Anti-inflammatory and antioxidant effects
Echinacea’s claims as an anti-inflammatory rest on both theoretical and observed inhibition of inflammatory mechanisms. (12,13). Enhancement of free-radical scavenging activity has been reported by laboratories in the U.S. and Canada (14,8). Hu and Kitts reported anti-oxidant and free-radical scavenging activity, including suppression of oxidation of human low-density lipoprotein (14).
Extracts from E. purpurea have been attributed significant antifungal activities in a series of in vitro experiments testing activity against various Saccharomyces cerevisiae and various Candida species, including Candida albicans (15). Other laboratories have also reported anti-Candida activity (16).
Coeugniet and Kühnast reported a trial testing an expressed juice of E. purpurea to effect recurrent vaginal yeast infections (17). Women with laboratory-confirmed Candida infections were treated with topical econazole, then administered either oral or injected Echinacea extract. Treatments continued for 10 weeks, and recurrence of yeast infection and response to the treatments were measured. Treated groups demonstrated increased skin reactivity and decreased recurrence of vaginal candidi- asis over the 6-month monitoring period. While 60% of controls got new infections, only 5–17% of women in the treatment groups were diagnosed with recurrent vaginal infections.
Bronchitis and pertussis
In 1988 Baetgen reported a retrospective analysis of 1280 children who had received either E. purpurea juice as an in- tramuscular injection, antibiotics alone or a combination of the two (18). The duration of illness in the Echinacea-only group was reported as shorter than that in the Echinacea-plus-antibiotics group, which was shorter than in the antibiotics-only group. In 1984 Baetgen reported a retrospective analysis of 170 people with clinically-defined pertussis (whooping cough) who again received either E. purpurea juice as an intramuscular injection, antibiotics alone or a combination of the two (19,20). Again, the author claimed a duration benefit for the Echinacacia only groups.
Eichler and Krüger reported that cultured cells infected with virus and exposed to E. purpurea juice demonstrated an increased rate of presentation of viral antigen (21). Extracts of E. purpurea were reported to inhibit viral replication in animal cell viral culture models (22). Activity against influenza virus has also been reported (23).
Turner and colleagues reported a trial testing the efficacy of Echinacea in preventing or ameliorating the effects of experimental colds induced by a cultured rhinovirus (24) The authors claim that their experiment demonstrates the “ineffectiveness of Echinacea for prevention of experimental colds”. However, if the observed trends were real and generalizable to naturally acquired colds, a 13% effect is arguable clinically significant, similar to the benefits expected with many standard treatments, such as antibiotics for middle-ear or sinus infection (25,26).
In 1992, Schöneberger reported a trial testing the preventive efficacy of E. purpurea juice among 108 patient which demonstrated a significant preventive efficacy, with 32.5% of the Echinacea group versus 25.9% of the placebo group remaining healthy, alongside severity and duration benefits of similar magnitude (27). According to Schöneberger, participants with a T4/T8 ratio of less than 1.5 prior to the study benefited the most.
In 1998 Melchart, Linde and colleagues reported a 3- armed preventive double-blind, randomized, controlled trial comparing extracts of E. purpurea root and E. angustifolia root with placebo (28). 302 healthy volunteers were recruited and randomized to 1 of 3 groups. Extracts were produced using a 30% ethanol solution and a 1:11 plant extract ratio. In the E. purpurea group, 29% experienced at least one cold, compared with 32% in the E. angustifolia group and 37% in the placebo group.
Upper respiratory infection
In 1992, Bräunig et al. reported a randomized controlled trial that tested two doses of an ethanol-water extract of E. purpurea root among 180 patients with upper respiratory infection (29). Compared to placebo, statistically significant reductions in self-reported symptom severity were reported in the “high dose” group, with effect sizes ranging from 10% to 50%. Trends to benefit were noted in the “low dose” Echinacea group.
In 1995 Scaglione and Lund reported a single-blind randomized trial of a combination product containing E. purpurea extract, rosemary, eucalyptus, fennel and vitamin C (30). Participants in the Echinacea group showed a mean duration of 3.37 days compared with 4.37 days in the placebo group. Hoheisel and colleagues in 1997 reported a trial of standardized E. purpurea juice versus placebo among 120 participants with new onset common cold (31). The authors claim a 20% absolute and 50% relative reduction in the number of active group participants who went on to develop “a real cold”. Of those who developed a “real cold”, a median duration of 8 days is reported for the placebo group versus 4 days for the Echinacea group.
Brinkeborn et al. (1999) reported a double-blind, randomized trial comparing three formulations of E. purpurea tablets with a similar-appearing placebo (32). Reported benefits for Echinacea were greater for physician-assessed than for patient-assessed symptoms. Also in 1999, Henneicke-von Zepelin and co-authors reported a multicentre, double-blind, randomized controlled trial (33). An intention-to-treat analysis yielded statistically significant benefit to echinacea for all symptom-based outcome variables (rhinitis score, bronchitis score, overall severity, general wellbeing), with effect sizes ranging from 20% to 33%.
Schulten and colleagues published an account of a “double blinded” randomized trial of 5mL of Echinacea, “pressed juice from fresh flowering purple coneflower [1.7–2.5 : 1], stabilized by ethanol … twice daily for 10 days” (34). As the major finding, the authors claim a 6.0-day median duration URTI in the Echinacea group versus 9.0 days in the placebo group.
Echinacea appears to be a relatively safe herbal medicine, although there have been several reports of allergic reactions (35). Safety of Echinacea in pregnancy has not been determined
Keywords:- Immunomodulation; Anti-inflammatory; antioxidant; Anti-fungal; Bronchitis and pertussis; Anti-viral; Upper respiratory infection
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