Introduction Popularity of Echinacea Publications Cultivation Consumers Market Diversity of Echinacea Species
Variety and Other Factors Methodology and Laboratories Regions Plant Parts
Component Levels at Plant Development Stage
Legislation, Pharmacopoeias, and Monographs Quality Standardization of Echinacea
Active Markers Standardization Conclusion Acknowledgments References introduction
During the last decade, along with growing interest in CAM (complementary and alternative medicine) therapy and changes in the regulation of dietary supplements, Echinacea has become one of the most popular herbal medicines throughout the Western countries, particularly in Europe and in North America, its original source (Asher et al., 2001; Barrett, 2003; Borchers et al., 2000; Kessler et al., 2001; Kligler, 2003). Echinacea is also becoming popular in Australia (Wilkinson and Simpson, 2001). In North Africa, South America, and China, people are also paying increasing attention to this herb (Berti et al., 2002; Dou et al., 2001; El-Gengaihi et al., 1998; Hevia et al., 2002; Li et al., 2002; Luo et al., 2003; Shalaby et al., 1997a, b; Wang et al., 2002; Zhang et al., 2001).
The activities of Echinacea in modulating the immune system include (1) stimulating in vitro and in vivo phagocytosis; (2) cytokine production in macrophages; (3) antiviral activity; (4) enhancing natural killer cell activity; (5) inhibiting hyaluronidase, HIV integrase, prostaglandin, and leukotriene formation; and (6) antioxidant activity (Barrett, 2003; Bauer, 2000). Echinacea has been frequently used in preventing and treating uncomplicated upper respiratory tract infections. Its efficacy has been reported in a number of clinical trials, although some results of its effectiveness are inconclusive and inconsistent (Barrett et al., 2002; Bone, 1997a, b; Brinkeborn et al., 1999; Melchart et al., 1998, 2001; Schulten et al., 2001; Schwarz et al., 2002; Turner et al., 2000; Turner, 2001, 2002).
Like many other herbal medicines, it is still not clear how and which of Echinacea's complex range of components exert direct or synergistic effects (Bauer, 1999). This lack of clarity produces difficulty in standardizing plant components and functional end products of Echinacea. The situation is further complicated by the fact that different parts (root or the aerial portions) of different species (mainly Echinacea purpurea, Echinacea angustifolia, and Echinacea pallida) that are cultivated in different areas and harvested at different times have been used in producing various dosage forms with varying strengths (tinctures, juice, tablets, pills, etc.) by diverse preparation procedures that include various extracting solvents (alcohol or water). All of these factors can affect the constituents contained in the raw materials or their end products, and might be the causes of the inconsistent results observed in clinical trials (Bauer, 1999; Dennehy, 2001; Kim et al., 2000a, b; Nusslein et al., 2000; Osowski et al., 2000; Perry et al., 2001; Sloley et al., 2001).
Increasing interest in Echinacea is propelling research that will, on the one hand, identify its active constituents and further elucidate its mechanism of action, as well as clarify issues concerning positive/negative indications, most effective doses, and safety, thus guiding a rational use of this herb. On the other hand, it will reveal the diversity in the plant material and in the entire process from planting to the end products (Baugh and Ignelzi, 2000). Therefore, a standardized quality of plant material and end products is doubtlessly needed for such a popular and diversified herbal medicine.
popularity of ECHINACEA
So far, over 800 scientific studies on Echinacea have been published including botanical, chemical, analytical, pharmacological, clinical aspects, and so on. Results of searches for publications about Echinacea in the databases Pub-Med, National Library of Medicine (www.ncbi.nlm.nih.gov/PubMed) and ISI Web of Science (www.isinet.com) are shown in Table 9.1 and Table 9.2, respectively.
Although Echinacea has a long tradition as a folk medicine among Native Americans and is now the most popular herb in North America, research on Echinacea in these countries was rare until the 1990s. Before the 1980s, most research on Echinacea was pioneered and conducted in Germany and published in German (Bauer and Wagner, 1991). More recently, studies on Echinacea have been carried out worldwide and are published mostly in English (Table 9.1 and Table 9.2).
Scientific publications about Echinacea are increasing rapidly. The annual number of publications on this herb found in Pub-Med in 2002 is 50 to 80 times greater than during the 1970s and 1980s. Searching the database CAplus (stneasy.fiz-karlsruhe.de) also showed that studies on Echinacea are increasing rapidly. During the 30 years between 1967 and 1997, 131 publications related to Echinacea were found (4.4/year), while in the 4 years between 1997 and 2001, more than 200 publications were found (50/year), even though a number of publications were not included in this database. This increasing frequency is just a beginning, and it can be predicted that more studies will be published as the exciting results of new research work are revealed (Binns et al., 2002; Currier and Miller, 2002; Gan et al., 2003; Goel et al., 2002; Pomponio et al., 2002; Speroni et al., 2002).
While searching the Internet with three of the most popular search engines, we encountered duplicated Web pages and advertising. However, by carefully setting the search terms, it is possible to find a large quantity of useful and scientific information. Among these search engines, Google is a satisfactory one in obtaining valuable information on Echinacea. The number of Web pages
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