Fall 2008

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STORIES online Extra: Putting science behind botanical supplements

(The following report outlines additional information on the work of the Iowa Botanical Center, provided by authors Diane Birt and Mark Widrlechner)

Echinacea is native exclusively to North America, with populations extending from the southeastern US west through the Great Plains to the foothills of the Rocky Mountains and north to southern Canada. Historically, indigenous peoples of North America used Echinacea roots medicinally. Three species of Echinacea: E. angustifolia, pallida, and purpurea are commonly used medicinally today, typically to treat or prevent upper respiratory infections or as general immunostimulants. Echinacea is one of the most commonly used botanical supplements, and in 2004 more than $23 M was spent by US consumers on Echinacea supplements.

Our studies at Iowa State University show that very different chemicals are found in the various Echinacea species used in supplements. Extracts from Echinacea roots were found to have activity on a cellular pain receptor that is important in sensing the pain of inflammation and is a prime therapeutic target for analgesic and anti-inflammatory drugs. Anti-inflammatory activity differed by Echinacea species, with E. angustifolia, pallida, and sanguinea exhibiting the greatest activity. This activity was explained in part by a class of fat-like chemicals called alkamides.

The most widely used and researched species of Hypericum is H. perforatum (commonly known as St. John's wort), a perennial native to Europe. The plant has a long history of medicinal use in treating an array of ailments, including insomnia, depression, rheumatism, and gastritis, as well as being externally applied for treatment of wounds and other conditions. Currently, H. perforatum is most commonly used for depression, with an estimated 4.3 million adults in the US reporting use in 2002 during the past year; its sales were estimated at $9 million in 2004.

Research at the University of Iowa in the Iowa Botanical Center identified water-soluble compounds in Hypericum that have anti-viral activity in the dark. This is of interest because earlier studies primarily focused on anti-viral activity that required light to be effective.

Two species of Prunella have been studied for their medicinal value: P. vulgaris (also known as self-heal) and P. laciniata. Whole flowering plants of P. vulgaris have been used for inflammatory bowel disease, fever, headache, diarrhea, liver disease, and mouth and throat ailments. Studies with cultured cells have also demonstrated the efficacy of P. vulgaris in inhibiting herpes simplex virus 1 and 2, as well as HIV infection and replication.

Because of the reported uses and activities of Echinacea, Hypericum and Prunella and our Center's strength in studying infection, a key focus of our research has been in the area of botanical supplements and infection. The management of infection is a critical element of both traditional and modern medicine. With the emergence of new infectious agents and increased resistance to conventional drug therapies, this issue takes on added importance.

Both Echinacea and Hypericum have been studied clinically for potential health benefits, and, in general, the studies have yielded mixed results, with some suggesting a health benefit but others reporting no measurable impact on the indicators of infectious disease. For example, recent large clinical trials have not supported using Echinacea to fight colds, and research is ongoing to identify key bioactive and interfering constituents. Selecting appropriate supplements for these trials has been particularly challenging because investigators lack a basic understanding of the chemical profiles that would most likely be successful in preventing or reducing specific disease symptoms. Furthermore, variability among botanical supplements makes comparisons among trials difficult, if not impossible. Thus, it is our Center's objective to identify chemical profiles and the key compounds that define their bioactivity, and to provide a context that can be used to reinterpret past studies and serve as a foundation for future research.

While the variation in plants used for botanical supplements probably contributes to the poor reproducibility of past clinical studies, the range of variation in these plants, when systematically analyzed, provides a strong foundation on which to develop the strategies and tools needed to produce the most effective products for a growing body of consumers.

Learn more:

Learn more:

Center for Research on Botanical Dietary Supplements

North Central Regional Plant Introduction Station