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Echinacea

GlossarySuccess Chemistry Staff

Echinacea is a herbal medicine that has been used for centuries, customarily as a treatment for common cold, coughs, bronchitis, upper respiratory infections (URIs), and inflammatory conditions. It belongs to Heliantheae tribe of the Asteraceae (Compositae) family, and the nine species of these perennial North American wildflowers have a widespread distribution over prairies, plains, and wooded areas.
BACKGROUND Three species of Echinacea are used medicinally: E. purpurea (Fig. 1), E. pallida (Fig. 2), and E. angustifolia (Fig. 3). In the United States of America, Echinacea preparations have been the best selling herbal products in health food stores. However, an analysis reveals that completely different preparations are sold under the name Echinacea using different plant parts and different extraction solvents (1). The most investigated preparation, which is mainly available on the German market, contains the expressed juice of E. purpurea aerial parts. Besides this, hydro alcoholic tinctures of E.purpureaaerial parts and roots, as well as from E. pallida and E. angustifolia roots, can be found (2,3). In North America, especially, it is also common to sell encapsulated powders from aerial parts and roots of these three species. Preclinical studies indicate that Echinacea constituents modulate immune mechanisms and there is increasing evidence that Echinacea preparations containing alkamides can suppress stress-related cellular immune responses. As reviewed by Chicca et al. (4), the interaction of alkamides with the cannabinoid receptor type-2 (CB2), which is a modulator of inflammation, may provide a mechanistic basis for the anti-inflammatory and immuno modulatory effects exerted by purple cone flower. Echinacea alkamides are now considered as a new class of cannabinomimetics (5,6). Recent findings suggest that Echinacea has a modulatory role on the innate immune system, able to both stimulate and inhibit the immune response. Since Echinacea-derived alkamides significantly suppressed T-lymphocytes(7),it is apparentt hat the multiplicity and diversity of parts of various plants, methods of extraction, and solvents used, as well as the components on which the extracts have been standardized, have hampered clear recommendations regarding Echinacea usage. Several reviews on the evidence regarding the effectiveness of orally ingested Echinacea extracts in reducing the incidence, severity, or duration of acute URIs have been published. The majority of trials investigated whether Echinacea preparations shorten the duration or decrease the severity of symptoms of the common cold (for reviews see 5,8–12). A recent Cochrane review (10) concluded thate specially preparations based on the aerial parts of E. purpurea might be effective for the early treatment of colds in adults, but results are not fully consistent. Beneficial effects of other Echinacea preparations for preventative purposes might exist, but have not been shown in independently replicated rigorously randomized trials. Therefore, further clinical studies are needed to evaluate the therapeutic role of Echinacea preparations. Many of the in vivo studies performed so far used phytochemically insufficiently characterized Echinacea preparations. The regulatory status of Echinacea products is variable. In the United States, they are considered as dietary supplements, and manufacturers can therefore produce, sell, and market herbs without demonstrating safety and efficacy first, as is required for pharmaceutical drugs. In Canada, they are regulated as Natural Health Products (NHPs),and in several European countries they have drug status. The EMEA (EuropeanMedicinesAgency)Committeeon Herbal Medicinal Products(HMPCs)has published the following guidance documents for Echinacea products (www.emea.europa.eu):  Community Herbal Monograph on Echinacea purpurea (L.) Moench, herba recens (13)  Community Herbal Monograph on Echinacea purpurea (L.) Moench, radix (14)  Community Herbal Monograph on Echinacea pallida (Nutt.) Nutt., radix (15)  Community List Entry for Echinacea purpurea (L.) Moench, herba recens (16) For HMPCs published as a Community Herbal Monograph,the industries in general have still more possibilities in change. In contrast, entries in the Community List are legally binding to applicants and competent authorities.
ACTIVE PRINCIPLES, PHARMACOLOGICAL EFFECTS, AND STANDARDIZATION The constituents of Echinacea, asinanyotherplant, cover a wide range of polarity, ranging from the polarpolysaccharides and glycoproteins, via the moderately polar caffeic acid derivatives, to the rather lipophilic polyacetylenes

Echinacea Species Echinacea purpurea

and alkamides. This makes it necessary to study separately the activity of different polar extracts of Echinacea, such as aqueous preparations,alcoholic tinctures, and hexane or chloroform extracts.
Polysaccharides and Glycoproteins Systematic fractionation and subsequent pharmacological testing of the aqueous extracts of the aerial parts of E. purpurea led to the isolation of two polysaccharides (PS I and PS II) with immuno stimulatory properties. They were shown to stimulate phagocytosis in vitro and in vivo, and enhance the production of oxygen radicals by macrophages in a dose-dependent way. Structural analysis showed PS I to be a 4-O-methylglucuronoarabinoxylan with an average MW of 35,000

Echinacea pallida chinacea angustifolia

Da, while PS II was demonstrated to be an acidic arabinorhamnogalactan of MW 45,000 Da. A xyloglucan, MW 79,500 Da, was isolated from the leaves and stems of E. purpurea (17), and highly water-soluble fructans have been recently isolated from E. purpurea (L.) Moench roots (18). Polysaccharides from E. angustifolia have also been found to possess anti-inflammatory activity (19). In a Phase-Iclinicaltrial, a polysaccharide fraction (EPOVIIa), isolated from E. purpurea tissue culture and injected at doses of 1 and 5 mg, caused an increase in the number of leukocytes, segmented granulocytes, and tumor necrosis factor-alpha (TNF-) (20). Three glycoproteins, MW 17,000, 21,000, and 30,000 Da, have been isolated from E. angustifolia and E. purpurea roots. The dominant sugars were found to be arabinose (64–84%), galactose (1.9–5.3%), and glucosamines (6%). The protein moiety contained high amounts of aspartate, glycine, glutamate, andalanine(21).Anenzyme-linkedimmunosorbentassay (ELISA)methodhasbeendevelopedforthedetectionand determination of these glycoproteins in Echinacea preparations (22). In 2005, an arabinogalactan protein (AGP) and an arabinan were isolated from the roots of E. pallida (Nutt.) Nutt (23). Most AGPs contain mostly carbohydrate moieties (>90%) along with a small amount of protein(<10%).Also information concerning the protein– polysaccharide linkage type has recently been published,
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and hydroxyproline (42.9% w/w) was detected as the dominant amino acid and was identified as the major amino acid responsible for the binding between the protein and the AG subunits via an O-glycosidic linkage (24). Purified extracts containing these glycoprotein– polysaccharide complexes exhibited B-cell stimulating activity and induced the release of interleukin-1 (IL-1), TNF-, and interferon-, (IFN-,) in macrophages, which could also be reproduced in vivo in mice (21). In a study performed in 2002, the influence of an oral administration of a herbal product, consisting of an aqueous-ethanolic extract of the mixed herbal drugs Thujaesummitates, Baptisiaetinctoriaeradix, E.pupureaeradix, and E. pallidae radix, standardized on Echinacea glycoproteins, on cytokine induction, and antibody response against sheepred blood cells was investigated by Bodinet etal.(25)inmice. This administration caused a significant enhancement of the antibody response against sheep red bloodcells, inducingan increase in the numbers of splenic plaque forming cells and the titers of specific antibodies in the sera of the treated animals (25). The influence of the same extract on the course of Influenza A virus infection in Balb/c mice was also tested. The data show that the oral treatment with this aqueous-ethanolic extract induced a statistically significant increase in the survival rate, prolonged the mean survival time, and reduced lung consolidation and virus titer (26). An Echinacea polysaccharide enriched fraction isolated from E. purpurea aerial parts was able to exert an antiviral action on the development of recurrent herpes simplex virus type-1 (HSV-1) disease when supplied prior to infection (27). Hwang et al. (28) showed that macrophages respond to purified polysaccharide and also alkamide preparations. Adherent and non adherentmouse splenocyte populations were incubated in vitro with E.purpurealiquidextract(freshEchinacearootjuice,mature seed, fresh leaf, and fresh fruit juice extracted in 40–50% alcohol), or with water or absolute alcohol (25 mg dry powder/mLofsolvent) soluble E.purpureadriedrootand leaf extract preparations. The immune stimulatory ability of components contained within these Echinacea extracts offers insight into possible therapeutic potential to regulate non adherent lymphocytes in immune responses and activation events. The use of flow cytometry demonstrates a link between the polysaccharides in Echinacea and the immunostimulatory effect that has therapeutic relevance. It was suggested that the main immunostimulatory activity of Echinacea resides in the water-soluble materials rather than the lipoidal small molecules (29).
Caffeic Acid Derivatives Alcoholic tinctures of Echinacea aerial parts and roots are likely to contain caffeic acid derivatives (Figs. 4–6). Extracts of different species and plant parts of Echinacea can be distinguished by thin layer chromatography (TLC) or high-performance liquid chromatography (HPLC) analysis (2). Also, capillary electrophoresis [micellar electrokineticchromatography(MEKC)]hasbeensuccessfullyappliedfortheanalysisofcaffeicacidderivativesinEchinacea extractsandenablesthediscriminationofthespecies(30). The roots of E. angustifolia and E. pallidahavebeenshown to contain 0.3–1.7% echinacoside (1) (2). Both species can
O OR
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1 Glucoside (1,6-) Echinacoside Rhamnose (1,3-)

2 Rhamnose (1,3-) H Verbascoside
Figure 4 Main phenylpropanoid glycosides found in Echinacea species.
be discriminated by the occurrence of 1,3- and 1,5-Odicaffeoyl-quinic acids (3, 4), which are only present in the roots of E. angustifolia. Recently, it has been reported thatcynarin,the1,3-dicaffeoyl-quinicacid,blocked the interaction between the CD28 of T-cell receptor and CD80 of antigen presenting cells under the condition of 1:1ratio of T-cell and B-cell in vitro. This Echinacea component is the first small molecule that is able to specifically block theCD28-dependentpathwayofT- cell activation and has therefore great potential as an immunosuppresive agent (31).Echinacosidehasanti-oxidant(32),lowantibacterial, and antiviral activity, but does not show immunostimulatory effects (17). It is also reported that echinacoside inhibits hyaluronidase (33) and protects collagen type III from free radical-induced degradation in vitro (34). The aerial parts of E.angustifolia and E.pallidahavebeenshown to contain verbascoside (2), a structural analog of echinacoside (1). The roots of E. purpurea do not contain echinacoside, butcichoricacid (2R,3R-dicaffeoyl-tartaricacid;6) and caftaric acid (monocaffeoyl tartaric acid; 5). Cichoric acid (6) is also the major polar constituent in the aerial parts of Echinacea species. Echinacoside (1) and cichoric acid (6) have also been produced in tissue cultures of E. purpurea and E. angustifolia (17). The latter acid (6) has been shown to possess phagocytosis stimulatory activity in vitro and in vivo, while echinacoside (1), verbascoside (2), and 2-caffeoyl-tartaric acid (5) did not exhibit this activity(17).Robinson described cichoric acid as an inhibitor
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Quinic acid derivatives from Echinacea species.
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COOH
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Figure 6 Tartaric acid derivatives from Echinacea species.
of human immunodeficiency virus type-1 (HIV-1) integrase (35). It is especially abundant in the flowers of all Echinacea species and the roots of E.purpurea(1.2–3.1%and 0.6–2.1%, respectively). Much less is present in the leaves and stems. E. angustifolia contains the lowest amount of cichoric acid (2). The content, however, strongly depends on the season and the stage of development of the plant and is highest at the beginning of the vegetation period and decreases during plant growth (36). N¨usslein et al. found that polyphenoloxidases(PPO)are responsible for the oxidative degradation of exogenous and endogenous caffeic acid derivatives (37,38). Apart from cichoric acid, echinacoside (1) and cynarin (3) fromE. angustifolia roots are also highly susceptible to enzymatic degradation and oxidation in hydroalcoholic solutions during the extraction process. During the 16 days after extraction of E. angustifoliarootswith60%(v/v)ethanol/waterandstorage at 4◦C, a decline to 0 was observed in the content of echinacoside(1)andcynarin(3)from0.25mg/mLextractand 0.09 mg/mL extract, respectively (39). In order to standardize Echinacea preparations and guarantee a consistent content of caffe icacidderivatives,itisvitaltocontrolthis enzymatic activity.
Alkamides Striking differences have been observed between the lipophilicconstituentsofE.angustifolia(alkamides;Fig.7) and E. pallida roots (ketoalkenynes; Fig. 8). E. purpurea roots also contain alkamides, however, mainly with two doublebondsinconjugationtothecarbonyl group,while E.angustifoliaprimarilyhascompoundswitha2-monoene chromophore. The chief lipophilicconstituents of E.pallida roots have been identified as ketoalkenes and ketoalkyneswithacarbonylgroupinthe2-position(2).The main components are tetradeca-8Z-ene-11,13-diyn-2-one (17), pentadeca-8Z-ene-11,13-diyn-2-one (18), pentadeca8Z,13Z-diene-11-yn-2-one (19), pentadeca-8Z,11Z,13Etriene-2-one(20),pentadeca-8Z,11E,13Z-triene-2-one(21), and pentadeca-8Z,11Z-diene-2-one (22). They occur only in trace amounts in E. angustifolia and E. purpurea roots. Therefore, they are suitable as markers for the identification of E. pallida roots. However, it has been observed
7
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Undeca-2E-ene-8,10-diynoic acid-isobutylamide
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Pentadeca-2E,9Z-diene-12,14-diynoic acid isobutylamide
Figure 7 MainalkamidesfoundinEchinaceaaerialpartsandE.purpurea and E. angustifolia roots.
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17 Tetradeca-8Z-ene-11,13-diyn-2-one
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19 Pentadeca-8Z,13Z-diene-11-yn-2-one
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21 Pentadeca-8Z,11E,13Z-triene-2-one
22 Pentadeca-8Z,11Z-diene-2-one
23 Heptadeca-8Z,11Z-diene-2-one
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R=
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R= Figure 8 Ketoalkenes and ketoalkynes found in E. pallida roots.
that these compounds undergo auto-oxidation when the roots are stored in powdered form. Then, the hydroxylated artifacts, 8-hydroxy-9E-ene-11,13-diyn-2-one (25), 8-hydroxy-pentadeca-9E-ene-11,13-diyn-2-one (26), and 8-hydroxypentadeca-9E, 13Z-diene-11-yn-2-one (27), can beprimarilyfound(Fig.9),oftenwithonlysmallresidual quantities of the native compounds. Hence, the roots of E. pallida are best stored in whole form. Approximately 15 alkamides have been identifiedas important lipophilic constituents of E. angustifolia roots. They are mainly derived from undeca- and dodecanoic acid,anddifferinthedegreeofunsaturationandtheconfigurationofthedoublebonds(Fig.7).The mainstructural typeisa2-monoene-8,10-diynoicacidisobutylamide,and some 2-methyl-butylamides have also been found. In
25 8-Hydroxytetradeca-9E-ene-11,13-diyn-2-one R=
O OH R
26 8-Hydroxypentadeca-9E-ene-11,13-diyn-2-one R=
27 8-Hydroxypentadeca-9E,13Z-diene-11yn-2-one R =
Figure 9 8-Hydroxy-ketoalkenynesformedviaauto-oxidationinpowdered E. pallida roots.
E. purpurea roots, 11 alkamides have been identified with theisomericmixtureofdodeca-2E,4E,8Z,10E/Z-tetraenoic acidisobutylamides(11,12)asthemajorcompounds(17). The aerial parts of all three Echinacea species contain alkamides of the type found in E. purpurea roots, and also with dodeca-2E,4E,8Z,10E/Z-tetraenoic acid isobutylamides (11, 12) as the main constituents (2). A series of pharmacological experiments have shown that Echinacea extracts containing alkamides have significant anti-inflammatory and immunomodulatory properties. Among the many pharmacological effects reported, modulation of macrophagesandpolymorphonucleocytes (PMN) immune cells and effects on cytokine/chemokine expression in human cells have been demonstrated most convincingly. Furthermore, inhibition of cyclooxygenase is known as an effective strategy to suppress pain and inflammation. Alkamidesisolated from the roots of E. angustifolia inhibited cyclooxygenase-2 (COX-2)-dependent prostaglandinE2 formation,butdidnotinhibitCOX-2expression at the transcriptional or translational level (5,8, 9,40–42). Determination of the alkamide content (dodeca2E,4E,8Z,10E/Z-tetraenoicacidisobutylamides)in the different plantparts showed thatitaccumulatesprimarilyin the roots and inflorescences, the highest being found in E. angustifolia. E. pallida roots contain only trace amounts, rootsofE.purpurea0.004%to0.039%,andthoseofE.angustifolia0.009%to0.151%.Theyieldintheleavesis0.001%to 0.03%(17).Inarecentstudy,62commercialdriedrootand aerial samples of E. purpurea grown in eastern Australia wereanalyzedforthemedicinallyactiveconstituents.Totalconcentrationinrootsampleswas6.2±2.4mg/g,and in aerial samples was 1.0±0.7 mg/g (43). In 2001, Dietz et al. (44) reported the presence ofdodeca-2E,4E,8Z,10E/Z-tetraenoicacidisobutylamides (11, 12) in human blood after oral administration of an ethanolic extract of E. purpurea. More recently, a study showed that the absorption maximum (Cmax) of dodeca2E,4E,8Z,10E/Z-tetraenoic acid isobutylamides (11, 12) is reached 30 minutes after oral application. Due to these results, the mucous membrane of the mouth is most likely the major area of absorption (45). Jager et al. investigated the permeability of isobutylamides(11,12)through Caco2 monolayers. They found that the alkamides were almost completely transported from the apical to the basolateral side of the monolayer in six hours by passive diffusion and that no significant metabolism occurred (46). Matthias et al. (47) investigated the bioavailability of caffeic acid derivatives and alkamides also using Caco-2 monolayers. The caffeic acid conjugates (caftaric acid, echinacoside, and cichoric acid) permeated poorly through the Caco-2 monolayers although one potential metabolite,cinnamic acid,diffusedreadilywithanapparent permeability (Papp) of 1× 10–4 cm/sec, while alkamides were found to diffuse with Papp ranging from 3 × 10–6 to3×10–4 cm/sec.Closemonitoringofthetransport forsixhoursrevealedanearlycompletetransfertothebasolateral side without significant metabolism. Transport experiments performed at 4◦C showed only a slight decrease, which is a strong hint that dodeca-2E,4E,8Z,10E/ Z-tetraenoic acid isobutylamides (11, 12) cross biological membranes by passive diffusion. These data suggest that alkamides are more likely than caffeic acid conjugates to
Echinacea Species
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pass through the intestinal barrier and thus be available for influencing an immune response (47). Based on these invitro studies and the performance of eight pharmacokinetic studies since 2005, evidence is given that alkamides are bioavailable in relevant concentrations after oraladministration of Echinacea preparations orpurecompounds(5).Inallpharmacokineticstudiesperformed so far, the time to reach the mean concentration maximum after administration of liquid Echinacea preparations (E. angustifolia or E. purpurea) was approximately 30minutes. Tmax afteradministrationof Echinacea tablets, which has been investigated in two clinical studies, was varying within 45 minutes to 2.3 hours (5). As it has also been shown for Echinacea tinctures that more concentrated preparations needed longer to attain Tmax. Besides bioavailability,informationconcerningthedistributionin tissues is an important issue in the evaluation of the systemic exposure and a prerequisite for the interpretation of in vitro pharmacological testing. The pharmacokinetic and tissue distribution of the dodeca-2E,4E,8Z,10E/Ztetraenoic acid isobutylamides (tetraenes), the main alkamides in Echinacea preparations, has been recently investigated and demonstrated a rapid absorption and distribution to the examined tissues (liver and four different brain regions) with a passage across the blood-brain barrier (BBB). The highest concentration was found in the striatum. The total amount of tetraenes in plasma was calculated as area under the curve (AUC0-∞) (794 min·ng/mL)andapproximately13%∼45%ofthatfound in different brain parts (1764–6192 min · ng/mL), and 63% of that in liver tissues (1254 min · ng/g). The Cmax in plasma was 26.4 ng/mL, while the Cmax in the different brain regions varied between 33.8 ng/g and 46.0 ng/g. The appearance in brain tissues offers new pharmacological options of alkamides containing Echinacea preparations with the emphasis on cannbinoid receptor interaction between the immune system and the central nervous system (48). Since alkamides show structural similarity with anandamide, an endogenous ligand of cannabinoid receptors, it was found that alkamides bind significantly to CB2 receptors, which is now considered as a possible molecular mode of action of Echinacea alkamides as immunomodulatory agents (5,49). At the same time, Gertsch et al. demonstrated the modulation of TNF- gene expression and multiple signal transduction pathways by Echinacea alkamidesand postulated a mechanism related to cannabinoid receptors. To ascertain whether CB2 was the receptor subtype involved in the observed effects, a CB2 antagonist was used in combination with the dodeca-2E,4E,8Z,10E/Z-tetraenoic acidisobutylamides.Thespecificantagoniststronglyabolished TNF- transcription and thus indicated a strict peripheral cannabinoid-mediatedprocess (40,41). Effectson CB2 receptor-containing immune cells in humans were evaluatedinarandomized,singledose,crossoverexvivo study with lipopolysaccharide (LPS)-stimulated blood cellsafterinvivoadministrationoftwoE.purpureapreparationsstandardizedon0.07mgdodeca-2E,4E,8Z,10E/Ztetraenoic acid isobutylamides (EchinaforceTM tincture and tablets). Both forms of medication led to a significant decrease in production of proinflammatory cytokines (IL-8 and TNF-), while changes in IL-6 concentrationwerenotstatisticallysignificant(5).IL-8andTNF
 are proinflammatory cytokines. Therefore, the effect of the Echinacea preparations can be considered as an antiinflammatory action and corresponds with the observed invitroeffectsofalkamides.Alsothedirecteffectsofalkamides on T-lymphocytes, which are key mediators of antiviral immunity, have been investigated by testing inhibition of IL-2 production (50). This can explain why the symptoms of a common cold, like sore throat, can be reduced. In summary, a lot of recent pharmacological data suggest that Echinacea alkamides may not only have immunostimulatory but also anti-inflammatory and antiviral activity by a reduction in NO, TNF-, IL-8, IL-2, and COX-dependent prostaglandin E2 formation in different cell types and assays used. From the above, it is obvious that not a single, but severalconstituents,likethealkamides,cichoricacid,glycoproteins, and polysaccharides, are responsible for the immunostimulatoryactivityofEchinaceaextracts,andthe applicationofextractsappearstobereasonable.However, conformity of these extracts is a must for generating consistent products and reproducible activity.
CLINICAL EFFICACY Several dozen human experiments—including a number of blind randomized trials–have reported health benefits of Echinacea preparations. So far, clinical efficacy has been studied in randomized controlled clinical trials for cold pressed juice and hydroalcoholic tincture/extract of E. purpurea aerial parts, a standardized extract from E. purpurea roots (hydroalcoholic tincture/extract), a hydroalcoholic extract of E. pallida roots, and for E. angustifolia root tinctures. All of them have used a variety of different Echinacea preparations and study designs. Most importantly,thephytochemicalprofileofthepreparations wasnotdeterminedornotreportedinmostofthestudies. Since different Echinacea preparations have varying phytochemicalprofilesduetotheuseofdiversespecies,plant parts,andextractionprocedures,thevariationinreported clinical effectiveness may be due to discrepancies in the chemical profile. In 16 randomized controlled trials summarizedinthelatestCochranedatabase,onlyeight(50%) reported the exact characterization of the herbal remedy being used (10). In three experimental infection studies pooled by Schoop et al. (51), only one (33%) has been included without content details of the tested Echinacea product. In the 14 randomized clinical trials included in the meta-analysis by Shah et al. (11), five (36%) reported the chemical profiling of the herbal product used. Therefore,thenewlypublishedmeta-analysispooledresultsfor all Echinacea preparations, although the original publication did not adequately describe the preparations tested. This lack of information needs to be taken into account when research on Echinacea is evaluated. The most robust data come from trials testing E.purpureaextractsinthetreatmentforacuteURI.Arecent Cochranereview(10)summarized16randomizedclinical trials of Echinacea to assess whether there is evidence that Echinaceapreparationsare(i)moreeffectivethannotreatment, (ii) more effective than placebo, (iii) similarly effective to other treatments in the prevention and treatment of the common cold. The authors concluded that there is
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someevidencethatpreparationsbasedontheaerialparts ofE. purpureamightbeeffectivefortheearlytreatmentof colds in adults. Besides the Cochrane database review, two further meta-analyseshavebeenpublished.Inonemeta-analysis, all performed clinical trials were pooled regardless of the product tested or the trial approach used (11), the second included only trials with experimentally induced infections (51). The meta-analysis by Shah et al. included two sets of studies: nine studies investigating whether Echinacea compounds prevent colds and seven studies investigating whether they shorten their duration. It has been stated that there is a significant improvement of common cold after taking Echinacea. In detail, Echinacea decreased the odds of developing the common cold by 58% and the duration of a cold by 1.4 days (11). The other metaanalysisofthreepreventativetrialsusinganexperimental viruschallengemodelshowedthattheoddsofexperiencingaclinicalcoldwere55%higherwithplacebothanwith Echinacea (51). In this meta-analysis a study, published in the New England Journal of Medicine, evaluating the effect ofchemicallydefinedextractsfromE.angustifoliarootson rhinovirus type 39 infection was included. Without pooling, the extracts did not have clinically significant effects oninfectionwitharhinovirusorontheclinicalillness(52). These results and information should be a motivation to conduct larger prevention trials in the future. As with most medications for the treatment of the common cold, the clinical data on Echinacea so far are not conclusive. There is a clear indication that preparations fromtheaerialpartsandrootsofE.purpureamaybeeffective. Preparations from E. angustifolia and E. pallida roots need further controlled clinical trials, in order to provide a better evidence for clinical efficacy (12).
CLINICAL PARTICULARS Dosage Information For internal use, the daily dose for aerial parts of E. purpurea for adults is 6 to 9 mL of pressed juice or equivalent preparations, 3×60 drops of a tincture (1:5, ethanol 55% v/v) or dried expressed juice equivalent to 8 to 18 g of the herbal substance, divided in two to four doses (13). For dried roots, the recommended daily dose is 3 × 300 mgonechewabletabletcontaining40mgextract(6.5:1)of E. purpurea roots and corresponding to 260 mg of herbal substance, every second hour (maximum nine tablets a day) (14). For external use, semisolid preparations with a minimum of 15% of pressed juice are recommended (16).ForE.pallidaroots,therecommendeddailydosageof CommissionEistincture1:5with50%(v/v)ethanolfrom nativedryextract(50%ethanol,7–11:1),correspondingto 900mgherb(53),threetimesdailyonetabletcontaining30 mg dry extract (4–8:1) of E. pallida roots, four times daily two tablets containing 12 mg dry extract (4–8:1), or five times daily 25 drops containing 100% tincture (1:5) (15). Theuseinchildrenyoungerthan1yeariscontraindicated, and the use in children between 1 and 12 years of age is not recommended. The therapy should start at first signs of common cold. If the symptoms persist longer than 10 days during the use of the medicinal product, a doctor or a qualified health care practitioner should be consulted.
Adverse Effects and Herb–Drug Interactions The safety profile of Echinacea has been based on the very fewreportedseriousadverseeventsandreportsfromseveral clinical trials that showed a low frequency of side effects. Parnham (54) reported 13 adverse events that were possibly associated with Echinacea use in Germany between1989and1995,and4weredeterminedtobecausal. Alltheadverseeventswerereportedasallergicreactions. Taylor et al. (55) found an increased risk of rash when childrenof2to11yearsreceivedEchinaceacomparedwith those who received placebo. Mullins and Heddle (56) reported 51 possible cases of Echinacea-related allergy, of which 26 were suggestive of possible immunoglobulin E-mediated hypersensitivity. Allergic cross-reaction with daisy family members has been reported. Some possible side effects from the German health authorities list (53):
 In rare cases, hypersensitivity reactions might occur. For drugs with preparations of Echinacea, rash, itching, rarelyfaceswelling,shortnessofbreath,dizziness,and blood pressure drop have been reported.  In case of diabetes, the metabolic status may worsen (53).
Perri et al. (57) reviewed the evidence for the use of Echinaceaduringpregnancyandlactationviasevenelectronic databases. They found good scientific evidence from a prospective cohort study that oral consumption of Echinacea during the first trimester does not increase the risk for major malformations. They reported that Echinacea is nonteratogenic when used during pregnancy. Caution should be maintained while using Echinacea during lactation until further high-quality human studies can determineitssafety.Incontrast,in2007,therewasthefirststudy conducted to evaluate whether pharmaceuticals containingalcoholicextractsofE.purpureagiventopregnantmice influence angiogenic activity and may then lead to severedevelopmentaldisturbances.Theyfoundanincrease in angiogenic activity of tissue homogenates in Esberitox group and a diminution in case of Immunal forte. The growth factor concentration was lower in all groups compared to the control. They concluded that there is some possibility that pharmaceuticals containing E. purpurea might influence fetal development in human also, because they may interfere with embrional angiogenesis, and should not be recommended for pregnant women (58). The German Commission E monograph cautions the use of Echinacea in persons who have autoimmune diseases, progressive systemic diseases, such as tuberculosis, multiple sclerosis, leukoses, collagenoses, and HIV infection.Thewarningsarebasednotonsolidclinicalevidence but on the theoretical possibility that the immunemediated inflammatory mechanism of these diseases can be exacerbated by the immunostimulating properties of Echinacea. Nosignificantherb–druginteractionswithEchinacea have been reported. Four studies were clinical trials and nine were in vitro assays, but most of the studies did not contain complete information about the concentration of extract used (59). No phytochemical analysis of the extracts was reported and limit the inferences that can be
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drawn from these studies. A common problem of many herb–drug interaction reports is that investigators fail to report species,plantpartused,preparation type,and concentrations assayed, and/or dose, each of which may affect the accuracy of reporting and the potential for herb– drug interactions. Currently, there are no rational reports available on herb–drug interactions of any Echinacea product. Both E. purpurea aerial parts and roots appear to have a relatively low potential to generate cytochrome P450 (CYP 450) herb–drug interactions in vivo involving CYP1A2 andCYP3A4(60).ThereislittleifanyeffectofE.purpurea on systemic p-glyocprotein-mediated transport mechanism in vivo (61,62). Itcanbeconcludedthatthereisaverylowincidence of side effects associated with E. purpurea, since, in comparisonwiththelargeproportionofthepopulationusing Echinaceayearly(>10million),wherehaveibeen no known reported major outbreaks of side effects or death. Also in long-term treatment, the expressed juice of E. purpurea was shown to be well tolerated (54).
CONCLUSIONS Echinacea,oneofthemostpopularbotanicalsupplements in North America, is employed as an immunemodulator, with antimicrobial and anti-inflammatory properties. So far, the overall therapeutic activity of Echinacea cannot be attributed to any single constituent. Pharmacological effects related to immune functions have been demonstrated for both high- and low-molecular-weight constituents. Compounds from the classes of caffeic acid derivatives, alkamides, polysaccharides, and glycoproteins are regarded as the most relevant constituents. Recent experiments have demonstrated that alkamides are detectable in human blood in relevant concentrations after oral administration of Echinacea preparations. Moreover, it has been shown that the main alkamides cross the BBB and bind to CB receptors, which is now considered as a possible molecular mode of action of Echinacea alkamides as immunomodulatory agents.Employing Various Species,plant parts,and extraction procedures results in different Echinacea preparations having distinguished phytochemical profiles. Clinical effectiveness may vary becauseofdiscrepanciesinthechemicalprofile.Standardization of botanicals should guarantee that preparations containtherapeuticallyeffectivedosesofactiveprinciples and should assure consistent batch-to-batch composition andstabilityoftheactiveconstituents.Also,clinicaltrials should be performed only with well-characterized Echinacea preparations.