ETHNOPHARMACOLOGY. Although the medicinal uses of plants can be traced to earliest human history and many modern pharmaceuticals are based in botanicals (about 30 percent), Western scientists have been reluctant to extend credibility to the therapeutic potential of plants from other cultures. During the last quarter of the twentieth century, however, attitudes about botanical sources of pharmaceuticals and other medicines shifted dramatically in the West. Renewed interest in plant medicines is substantiated in ethnopharmacology, the study of the chemistry and physiologic actions of (primarily plant) medicines used by native populations. Ethno denotes cultural group, and pharmacology refers to the science of drug sources, activities, and uses (Etkin, 1996; Rivier and Bruhn, 1979; Rivier and Anton, 1991). Scholarly journals that publish research and reviews on the topic include the Journal of Ethnopharmacology, Pharmaceutical Biology, Economic Botany, Planta Medica, Phytotherapy Research, and Fitoterapia.
Ethnopharmacologists represent diverse academic traditions, most prominently anthropology, pharmacology, and botany, and some commercial domains, including the pharmaceutical industry and the rapidly expanding market for "herbal" (botanical) medicines and medicinal foods. Given the diversity of contributors to ethnopharmacology, the field has considerable breadth in objectives and approaches. At one end of a continuum, anthropologists and a small percentage of ethnobotanists link the ethnography of health and illness to the chemistry and physiologic action of plant medicines. This extends traditional ethnomedical research that addressed the cultural basis of therapeutics and the social relations of healing and that treated plants largely as cultural objects. Anthropological ethnopharmacology has come to include the biodynamic qualities of plants, to acknowledge that tangible attributes may be as important as symbols in the selection of particular species and the interpretation of their physiologic actions.
This biocultural perspective on ethnopharmacology takes into account that native peoples, like Western scientists, are keen observers of their natural environments who embellish the cultural meaning of plants by marking and managing bitter, wound healing, symptom mediating, and other physical attributes. Yucatec Maya populations, for example, distinguish medicinal from nonmedicinal species (including foods) by smell and taste, noting especially astringent, aromatic, and sweet characteristics. These culturally defined clues not only encode information about which symptoms a particular plant treats best but also juxtapose cultural salience to bioactivity. For example, constituents (polyphenols) present in the plants used by Yucatec Maya for digestive complaints are responsible for both astringent taste and efficacy in the treatment of intestinal disorders (Ankli et al., 1999; Brett and Heinrich, 1999). Anthropologists discern these subtleties through extensive field studies (ethnography) of indigenous peoples to understand the complex cultural and environmental circumstances that shape plant selection and use. They have observed that many medicinal species are used for other purposes as well, thus extending human exposure to pharmacologically active constituents.
Medicines overlap especially with foods, and some cultural groups, for example, the Hausa in Nigeria, acquire knowledge of some wild food plants through their experiences with those species as medicines (Etkin and Ross, 1994). In other circumstances the incorporation into cuisines of "novel" plants, such as unusually bitter, astringent, or otherwise unpalatable plants, takes advantage of the healthful effects of bioreactive species, some of which may later be used as medicine proper (Johns, 1994). The point is not to judge whether or not some indigenous group "got it right," that is, used pharmacologically active plants in a way consistent with the principles of biomedicine, but to apply the techniques of bioscience as one aspect of comprehensive research based in extensive field study.
At the other end of the continuum are ethnopharmacologists whose primary objective is drug development. Logically this is the perspective of researchers who do want to know whether or not some indigenous group "got it right" and if so how that lead can be pursued to discover new pharmaceuticals. Bioprospecting pharmacologists have begun to collaborate with botanists, who offer chemo-taxonomic insights to guide the search for new sources of known drugs (on the principle that closely related plants have similar chemical profiles) and new plant compounds. For example, the potential to develop medicines for diabetes is suggested in plants that have insulin-stimulating effects, inhibit carbohydrate-digesting enzymes in the intestine, or increase glucose utilization (Raman and Skett, 1998). This research is primarily entrepreneurial (discovering products rather than indigenous knowledge) and necessarily involves only short-term field study with greater emphasis on laboratory and clinical phases. As such this version of ethnopharmacology is not as likely to uncover overlapping uses and the potential pharmacologic significance of certain indigenous food plants.
In the West the bioscientific perspective of ethnopharmacology is applied also to the study of foods. For example, researchers have found that the antioxidant lycopene, which gives tomatoes their red color, diminishes the risk of cardiovascular disease and cancers of the digestive tract and prostate (Rao and Agarwal, 1999). Similarly sulforaphane in broccoli has anticancer activity; hesperidin in grapefruit inhibits poliomyelitis, herpes, and influenza viruses; capsaicin in chili pepper lowers the risk of stomach cancer; sulfides in garlic and onion inhibit blood clotting; and glucaric acid in orange lowers serum cholesterol (Debrovner, 1993; Montanari et al., 1997).
These examples of healthful constituents in everyday (nonexotic) foods overlap the rapidly expanding public and scientific interest in complementary and alternative medicines (CAM), many of which are variably promoted as functional foods, medical foods, supplements, nutraceuticals, health foods, pharmafoods, phytofoods, and phytochemicals ("phyto-" denotes plant). Although the popularity of CAM has been primarily commercially driven, these products increasingly are subjected to scientific scrutiny. For example, studies suggest that constituents of saw palmetto protect against prostrate cancers and that dandelion extracts are diuretic. Pharmacologic studies of previously uncharacterized medicinal foods also reveal potential risks. For example, the blood-thinning and insulin-promoting actions of ginseng may act synergistically with drugs prescribed for the same effects; Saint-John's-wort decreases the effectiveness of some pharmaceuticals, including Indinavir (used to treat HIV/AIDS); and licorice may increase the side effects of oral contraceptives (Newall et al., 1996).
Ethnopharmacologists of all persuasions want to move beyond catalogs of plant use and action to address issues of context. How are the activities of plant components affected by preparation according to real instructions for use? What is the outcome when foods, medicinal foods, medicines, and other biodynamic substances are combined? These are complex questions. They are also the most interesting questions, and their answers will have the broadest implications for people who interact with biodynamic foods and medicines in their daily lives.
See also Botanicals ; Health and Disease ; Health Foods ; Medicine ; Neutraceuticals .
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Nina L. Etkin