Source: Data from Stuart, D.L. and Wills, R.B.H., 2000, J. Herbs, Spices Med. Plants, 7: 91-101.
Source: Data from Stuart, D.L. and Wills, R.B.H., 2000, J. Herbs, Spices Med. Plants, 7: 91-101.
Letchamo et al. (1999) studied the accumulation of active ingredients during the development of the flower heads of the American-grown E. purpurea. The quality of Echinacea was strongly influenced by floral development, which was divided into four stages, from early flower buds to the senescent stage. The highest content of cichoric acid was found at Stage 1, and the content of isobutylamide was highest at Stage 3 and 4. The maximum content of chlorogenic acid and echinacoside occurred at Stages 1 and 2, respectively. To obtain optimal yields of both hydrophilic and lipophilic components, Echinacea flowers should be harvested at Stage 3.
A number of recent studies have showed how varying methods of extraction, drying, and storage affect levels of active components (He et al., 1998; Hevia et al., 2002; Hudaib et al., 2003; Kim et al., 2000a, 2000b; Livesey et al., 1999; Menon et al., 2002; Perry et al., 2000; Stuart and Wills, 2000b, 2003; Sun et al., 2002). All these factors caused diversity in the plant material and final products. Chapter 8 in this book by Perry et al. describes these factors in detail.
As mentioned above, Echinacea contains a considerable number of phytochemicals, some of which are water soluble. Therefore, the processing methodology will affect the level of the different components extracted. The level of polysaccharides will be much lower if alcohol extraction is used during preparation.
Brovelli et al. (2001) compared two types of press to make juice from U.S.-grown E. purpurea: the hydraulic bag press and a mechanical screw press. The results showed differences not only in physical parameters but also in the chemical nature of the juices. Juice extracted by screw press had twice the concentration of cichoric acid as the juice extracted by the bag press. There was also a qualitative and quantitative difference in the alkamide fraction in favor of the screw press.
Over the last several years, the market for Echinacea has grown rapidly. As a result, there has been an increase in species misidentification or adulteration in the Echinacea trade. Inadequate quality control means that ineffective or adulterated products can reach the market. The literature and the media have revealed examples of Echinacea preparations of poor quality and low amounts of characteristic constituents.
Roots of Parthenium integrifolium L., commonly known as American feverfew, have been found to be adulterants/substitutes for Echinacea root (Turner, 2001). Its roots are larger and easier to harvest than Echinacea roots. This adulterant/substitute can be recognized by the absence of any caffeoyl derivatives (Giancaspro, 2000) or through the presence of the sequiterpene esters cin-namoylechinadiol, cinamoylepoxyechinadiol, cinnamoylechinaxathol, and cinnamoyl dihydroxy-nardol.
Wolf et al. (1999) described the discrimination of the three main species of Echinacea by random amplified polymorphic DNA (RAPD) analysis. Individual Echinacea species are easily identified by RAPD analysis. Adulterations due to drug mixtures also can be detected. Laasonen et al. (2002) have developed a near-infrared reflectance spectroscopic method for the fast (analysis within 1 minute) qualitative identification of E. purpurea dried milled roots. An adulterated E. purpurea sample can be detected at a minimum of 10% adulteration.
The phytochemical studies on Echinacea have revealed tremendous diversity in the quality of Echinacea products derived from various sources (Bergeron et al., 2000; Gilroy et al., 2003; Letchamo et al., 1999; Weil, 1999). The potency of Echinacea products can vary from manufacturer to manufacturer and from lot to lot from a single manufacturer, all of which can be attributed to quality diversity.
Echinacea is available to consumers in many forms, including tinctures, pressed juice, liquid, tablets, pills, powders, capsules, lozenge, beverage, spray, soft gel, ointments, lotions, creams, toothpastes, and teas. In earlier publications, products for the parenteral administration of Echinacea existed in Germany (Parnham, 1996). Now, many hundreds of products are available worldwide (Bauer, 1998). Even in Australia, there are hundreds of Echinacea products listed in the Australian Register of Therapeutic Goods (ARTG) containing Echinacea alone or in combination with other herbs, vitamins, or minerals (Cameron, 1998). Tinctures or extracts of Echinacea in alcohol are the form most herbal authorities recommend. In the U.S., the most commonly used preparation is a liquid extract made from the root of E. purpurea (Kligler, 2003). In Germany, freshly pressed E. purpurea juice is popular (Bauer, 1999).
Different formulations of Echinacea preparations may have different contents of active ingredients and exert diverse pharmacological effects in the human body. Products derived from an extract containing more than 50% ethanol are not considered capable of the effects of water-soluble polysaccharides since in this concentration polysaccharides are insoluble (Stuart and Wills, 2000a). Freshly pressed Echinacea purpurea juice may contain certain levels of polysaccharides (Bauer, 1999).
Like the other herbal medicines, one problem of quality control and standardization in Echina-cea products is that many countries have their own regulatory criteria and are not prepared to accept products from other countries that have been assessed by different criteria. The quality control of Echinacea thus varies by country and manufacturer. In the U.S., neither the Food and Drug Administration (FDA) nor any other federal or state agency routinely tests herbal medicines or other dietary supplements for quality prior to sale (Goldman, 2001). It was not until March 1999 that the FDA required that the labeling of herbal products provide information identifying the species of the herb, the part of the plant used, and the concentration of the herb.
Gilroy et al. (2003) investigated 59 single-herb preparations of Echinacea purchased from 11 stores in the Denver area over a 2-day period in August 2000. The samples included tablets, capsules, soft gels, and liquid. The results of thin layer chromatography (TLC) analysis showed that six samples (10%) contained no measurable Echinacea at all. The concentration of cichoric acid in the samples of the E. purpurea species ranged from 0% to 1.46%. In addition, the recommended daily dose of these samples ranged from 45 to 5,380 mg while German Commission E recommends a daily dose of 900 mg. The price per recommended dose ranged from $0.02 to 2.99.
Bauer (1999) analyzed six commercial preparations (one to four batches each) containing E. purpurea (aboveground parts) expressed juice, and found that they varied dramatically in cichoric acid and alkamide content. HPLC analysis showed that the content of dodeca-2E,4E,8Z,10E/Z-tetraenoic acid isobtylamide in the preparation ranged from 0.08 to 1.84 mg/100ml and cichoric acid varied from 0.0% to 0.4%.
In a recent issue of Consumer Reports, 12 brands of Echinacea pills on the U.S. market were compared. Levels of phenolic compound (caffeoyl-tartaric acid, chlorogenic acid, cichoric acid, and echinacoside) were assessed. Results showed that the average total percentage of phenolics varied from 0.8% to 4.5% depending on brand. Even within a brand, pills in different bottles had different levels of phenolics (Weil, 1999).
The independent ConsumerLab.com based in White Plains, New York, recently reviewed 25 commercial Echinacea products sold in the U.S., and tested them for the quality and quantity of Echinacea and levels of microbial contamination (ConsumerLab.com, 2001). Only 14 products (56%) passed this review. Others had inadequate labeling or lower levels of components than claimed on labels.
For 25 commercial Echinacea-containing remedies, Osowski et al. (2000) quantified cichoric acid and alkamide contents. Results showed large differences (up to 10,000-fold) in cichoric acid (Gilroy et al., 2003) or alkamide contents. Moreover, large differences among comparable products of different manufacturers and among different lots of the same product were noted.
This variation is caused in part by the enzymatic degradation by polyphenol oxidase (PPO; EC 126.96.36.199) during the processing of fresh plant material (Kreis et al., 2000). Enzymatic degradation during extraction could reduce the measured levels of phenolic compounds by more than 50%. Nusslein et al. (2000) have investigated the causes of cichoric acid degradation in Echinacea products and recommended a process to stabilize E. purpurea products.
Because of great diversity in Echinacea product quality, it is no wonder that the results of clinical trials are inconsistent. A number of clinical trials and reviews have indicated that Echinacea preparations are efficacious in preventing and treating the common cold and other respiratory infections, while other clinical trials (Barrett et al., 2002; Del Mar et al., 2002; Grimm and Muller, 1999; Turner et al., 2000) showed no significant effects. There are also a number of unpublished trials of Echinacea preparations with negative results (Melchart et al., 2001). In spite of this inconsistency, clinical studies of the effect of Echinacea on the common cold remain a valid subject (Turner, 2002); over 40 clinical studies have been published so far.
Schulten et al. (2001) reported a placebo-controlled, randomized, double-blind clinical trial evaluating the efficacy of the pressed juice from the fresh flowering E. purpurea in 80 patients with the common cold. The results showed that the duration of all symptoms was significantly reduced (9.0 days to 6.0 days) and the disease was less severe in the active treatment group than in the placebo group.
In a study by Brinkeborn et al. (1999), acute treatments of the common cold with two tablets containing crude extracts of E. purpurea (95% herb, 5% root) three times daily were shown to significantly reduce cold symptoms compared to the placebo, while a preparation of E. purpurea root did not.
Another study on the prophylactic efficacy of Echinacea was carried out in the flu season with 647 students from the University of Cologne. The result showed a 15% reduction in the number of colds in the group given Echinacea compared to the placebo group (Winslow and Kroll, 1998).
In a 12-week, double-blind, placebo-controlled trial, 302 healthy volunteers were given E. purpurea or E. angustifolia root extracts or a placebo pill, and any effect on prevention of upper respiratory infections was noted. Subjects taking Echinacea lasted slightly longer before suffering infection and had slightly fewer colds than those given the placebo, but the differences were not significant (Melchart et al., 1998). Sixteen controlled clinical trials (involving 3,396 patients) from a total of 40 trials were chosen and evaluated in a Cochrane Library systematic review (Melchart et al., 2001). Most trials showed positive results, suggesting that Echinacea products may have some beneficial effects on prevention and treatment of the common cold. However, quality data in about two-thirds of the trials was considered insufficient. The biggest problem is the great diversity and the unclear comparability of the investigated products. The use of different Echinacea preparations made comparability of the results difficult. It was recommended (Dennehy, 2001; Osowski et al., 2000) that preclinical and clinical studies with Echinacea-containing herbal medicines should always indicate the species and plant parts used, formulation, method of extraction and quantification of potentially active components, and so on. These procedures will help to reduce inconsistencies in clinical trials and allow future research to focus on preparations that appear most promising.
Legislation, Pharmacopoeias, and Monographs
Considerable diversity also exists in the legislation, pharmacopoeias, and monographs of various countries. "There is no international consensus on how to regulate natural health products. The U.S. lists them as dietary supplements, with the onus on manufacturers to have data supporting their claims. At the other extreme, Germany regulates the products as drugs" (Sibbald, 2001). At present, in many countries, Echinacea is considered to be a food supplement, not a drug. Even so, as one of the most important herbal medicines in Western countries, Echinacea has been listed in some monographs as shown in Table 9.11.
In the U.S., Echinacea is classified as a dietary supplement according to the Dietary Supplement and Health Education Act (DSHEA) approved in 1994 (FDA, 1995). Dietary supplements are treated as foods by the FDA; if they were on the market before 1994, they did not have to undergo any evaluation (Roll, 2002). Therefore, it is a manufacturer's responsibility to ensure that Echinacea products are safe and properly labeled prior to marketing. This complicates verifying product purity, safety, and consistency. In 2001, the U.S. Pharmacopoeia (USP, 2002) created the Dietary Supplement Verification Program (DSVP) to help inform and safeguard the growing number of consumers who use dietary supplements. The program responds to the need to assure the public that dietary supplement products contain the ingredients stated on the product label (Thompson, 2001). As of March/April 2002, the botanical list in the U.S. Pharmacopoeia and National Formulary (USP-NF) had not yet included an official monograph of Echinacea products (DSVP, 2002).
In Canada, herbal products are divided into four groups under current Canadian Food and Drug regulation. Echinacea products are in the third group, which are nonprescription, traditional herb
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