Nature's Pharmacopeia: A World of Medicinal Plants
The purple coneflower is a perennial herbaceous plant native to central and eastern North America.101 The genus is composed of several species, some of which are similar in appearance and partially overlapping in range. The species Echinacea angustifolia grows a series of oblong, lance-shaped leaves close to the ground and then produces flowering heads on stems 10 to 60 centimeters in length. The flowering heads are made up of dozens of small flowers, the outermost flowers growing long, thin, violet or pink petals, giving a flowering head about 10 centimeters in diameter (figure 14.12). The pale purple coneflower (E. pallida) is similar in appearance, with slightly taller stems and flowering heads with longer petals. E. purpurea has larger, more oval-shaped leaves.102 Both the aboveground portion of the plant and the root have been used in medicine, and purple coneflower is a popular horticultural plant, growing well in temperate zone gardens.
FIGURE 14.12 A purple coneflower.
Numerous indigenous American groups employed purple coneflower in medicine and hygiene.103 Among the Omaha and Ponca of present-day Nebraska and Oklahoma, the plant was called mika-hi (comb plant) because people used the mature flower head to brush the hair. Applications to treat illnesses were diverse: among Indians of the upper Missouri River region, the macerated root was used to treat snakebite and insect stings, the Dakota (Sioux) of the upper Great Plains used the root (probably applied to the skin) to treat bites and wounds, and the Lakota (Sioux) used it to ease toothache, bellyache, and other sorts of pain. Other groups in the central North American plains used Echinacea root for colic, colds, and sore throat and as a stimulant when traveling at night.104 Indigenous American medicinal uses for purple coneflower were diverse. However, Europeans took very little note of its value in native health care, and only in the mid-nineteenth century did American physicians and botanists remark on its possible therapeutic utility.105
While mainstream medical practice in the West slowly shifted away from a humoral understanding of the body and became enamored with the advances in biochemistry emerging in Europe, a group of physicians and pharmacists in the United States developed a uniquely American school of medical thought during the nineteenth century. In this form of medicine, called eclectic medicine, local and indigenous botanic remedies and noninvasive therapies were favored over the violent purging, bloodletting, and strong drugs that sometimes characterized the patient’s experience at the hands of conventionally trained physicians.106 To the eclectic practitioners, native American herbs were appealing additions to the pharmacopeia, and they wrote extensively of the value of purple coneflower, one early adopter calling it a “blood purifier” and “antiseptic for internal and external use.”107 By 1915, eclectic physicians had documented dozens of therapeutic applications for Echinacea root extract, whether applied to the surface of the body, taken orally or rectally, or injected hypodermically. It was lauded as a sedative, cure for hair loss, and treatment for a diverse array of infections, including malaria, syphilis, spinal meningitis, and rabies.108
A school of American medical practice that advocated the use of North American herbal treatments during the nineteenth and early twentieth centuries
The American Indians and eclectic physicians primarily used E. angustifolia root (the latter extracting the root in alcohol and water) in their medical preparations, but by the 1930s, European practitioners transformed the use of the herb in two important ways. First, German and Swiss entrepreneurs brought back to Europe seeds of E. purpurea (instead of E. angustifolia), from which they prepared chemical isolates. Second, they made alcohol and water extracts from the aerial portions of the blooming plant rather than the roots.109 Today, the diversity of purple coneflower preparations complicates their comparison in laboratory and clinical tests. Furthermore, the growing location and time of harvest influence the chemical profile of herbal extracts, rendering analysis of experimental outcomes somewhat challenging.110
Purple coneflower extracts contain an assortment of chemical constituents, including a volatile oil, fatty acid–derived alkamides, polyalkenes, polyalkynes, caffeic acid derivatives (including chicoric acid), flavonoids, polysaccharide carbohydrates, and a low concentration of alkaloids.111 The relative concentration of these components differs among species and source (root versus aerial portion) of plant material.112Much of the current research on purple coneflower seeks to determine whether the herb can prevent or treat symptoms of upper-respiratory viral infections, such as those associated with the common cold and influenza. The particular chemical compound or combination of compounds responsible for Echinacea’s proposed biological activity have not been defined, but recent data indicate that commercial formulations of water-alcohol coneflower extracts can kill viruses, prevent their adhesion to human cells, and interfere with their ability to induce an inflammatory response in the laboratory setting.113
Clinical trials on purple coneflower and the common cold have been conducted by the dozens, but the results are mixed, with some studies showing effectiveness in reducing the incidence or severity of the illness and others showing no difference between the treatment and control groups. Among the largest studies performed to date, the investigators employed dissimilar dosing schemes, used diverse formulations of plant material, and examined different aspects of the progress of upper-respiratory infection.114
Once widely employed by indigenous people for infections and adopted by American physicians seeking native cures for difficult illnesses, the purple coneflower is among the most controversial of botanicals. Ongoing research in the laboratory and clinic should help define its possible bioactive components, and the standardization of experimental approaches would help generate a more robust dataset to allow a better understanding of its efficacy against viral challenges and perhaps also against those ailments for which it was recognized by generations of both indigenous and more recently arrived Americans.