Viral diseases, including emerging and chronic viruses, are an increasing worldwide health concern. As a consequence, the discovery of new antiviral agents from plants has assumed more urgency than in the past. A number of native Amazonian medicines of plant origin are known to have antimicrobial and anti-inflammatory activity, although only a few have been studied for their antiviral properties and immunomodulating effects. Those most studied include: sangre de grado (drago) (Croton lechleri) in the Euphorbiaceae family and una de gato (Uncaria tomentosa) in the Rubiaceae family. This article reviews the chemical composition, pharmacological properties, state of current research, clinical use, and potential antiviral and immunomodulating activity of these and other plants from the Peruvian Amazon. (Altern Med Rev 2001;6(6):567-579)
Co-evolution between plants and their natural enemies -- including insects, bacteria, fungi, nematodes, animals, humans, and viruses -- is considerably more far reaching than current theories of reciprocal interactions suggest. Counter-resistance, genetic adaptability, polymorphic immune capacity, and pleomorphism among microbial agents allow for immense diversity of species and endless biochemical possibilities. (1) In order to adapt to environmental insults, plants produce a vast number of natural products that have antimicrobial and immunomodulating potential. (2) These include isoflavonoids, indoles, phytosterols, polysaccharides, sesquiterpenes, alkaloids, glucans, tannins, a variety of vitamins and trace minerals that function as antioxidants and co-enzymes, and many other phytochemical substances. In addition, there are a number of parallels between plant immunological activity and the immune systems of mammals, including adaptive mechanisms for viral resistance. (3)
Both the attribute of reciprocal natural co-evolution and the concept of shared chemistry among species are characteristics that allow humans to use plants as antiviral and immunomodulating medicines. (4) In an age of emerging new viruses with stunning virulence, natural antiviral and immunomodulating substances could play a significant role in human disease prevention and treatment.
The Amazonian region of northwestern Peru is among the earth's richest zones of biodiversity. It includes plants, animals, insects, as well as microbial organisms, and is one of nature's perfect evolutionary laboratories for plant biology. Ethnobotany has a long and distinguished history throughout the Amazon basin and its tributaries. Richard Evans Schultes (1915-2001), a tireless supporter of Amazonian ethnobotany, (5) began his investigation in the northwestern Amazon in 1941. (6) In previous centuries much of our knowledge of Amazonian flora is credited to Alexander von Humboldt of Germany (1769-1859) and Richard Spruce of England (1849-1863), as well as to Henry Hurd Rusby of Columbia University (1885-1928). Contemporary authorities on Amazonian ethnobotany include James Duke (7) and Mark Plotkin. (8)
Natural Product Selection
There are two ways natural products are selected for investigation. The classical method is laboratory based and relies on previous taxonomic findings, phytochemical factors, immunopharmacological studies, and random screening methods. The other, which is gaining popularity among investigators, is searching traditional texts and herbal medicine usage, including oral interviews with traditional indigenous healers -- the ethnobotanical route. (9,10) In one study, researchers found that an ethnobotanically driven approach led to a higher...