Ethnobotany: Source of therapeutic drugs

Plants are sources of many medicinal drugs that have been discovered by ethnobotanical research

It can easily take many years for a substance to become commercially available as a therapeutic drug. Many new medicinal agents derived from ethnobotanical research will be introduced in the future as have been in the past.

• In the mid-1980s, most pharmaceutical manufacturers had abandoned exploring folk uses of plants in their search for new drugs.
• Now it appears that there is a new appreciation for plants that are used in traditional medicine which can serve as a source of novel therapeutic agents.
• Such appreciation has emerged in part because of recent discoveries made by a small but growing group of ethnobotanists.
• Fieldwork exploring the medicinal uses of plants by indigenous peoples in remote parts of the world, coupled with the introduction of sophisticated assays able to determine whether plants exert a biological effect, has facilitated the discovery of bioactive molecules made by medicinal plants.
• Some of these molecules show promise as possible therapies for a range of diseases, including AIDS and cancer.
• It can easily take many years for a substance to become commercially available as a drug.
• There seems little doubt that in the future several new agents derived from ethnobotanical research will be introduced.
• In the past, almost all pharmaceutical research relied heavily on vascular plants as sources of medicines.
• Flowering plants and ferns (as opposed to microscopic organisms and fungi) produced many commercially sold drugs.
• Many of these agents are now synthesized in several pharmaceutical laboratories, but others are still isolated from plants.
• Most were discovered by studying indigenous uses of plants.
• Plants have been a rich source of medicines because they produce a host of bioactive molecules, most of which probably evolved as chemical defenses against predation or infection.
• Several forces have conspired by the close of the 1970s to cause plants to lose much of their appeal as drug sources for the pharmaceutical industry.
• Microorganisms and fungi that inhabit soil, which are easy to collect and culture, had provided a vast array of antibiotics.
• Advances in synthetic chemistry and molecular biology promised to supply new means for designing drugs in the laboratory.
• In the late 1970s and early 1980s, several groups of scientists independently set off to different courners of the world for the express purpose of finding innovative drugs through ethnobotanical research.

The ethnobotanical approach is actually one of several methods that can be applied in choosing plants for pharmacological studies.

• It is estimated that 265,000 flowering species inhabit the earth.
• Of these, less than half of one percent have been studied exhaustively for their chemical compositions and medicinal values.
• In a world with limited financial resources, it is impossible to screen each of the remaining species for biiological activity.
• Investigators, for example, can gather vegetation randomly in an area supporting rich biological diversity.
• Unfortunately, random searches yield relatively few new drug possibilities.
• Other plant-collecting methods, including the ethnobotnical approach, are more targeted.
• In phylogenetic surveys, researchers choose close relatives of plants known to produce useful compounds.
• In ecological surveys, they select plants that live in particular habitats or that display characteristics indicating that they produce molecules capable of exerting an effect on animals.
• Collectors might, for example, focus on specimens that seem to be immune from predation by insects.
• The absence of predation suggests a plant may produce toxic chemicals.
• Many chemicals that are toxic to insects also show bioactivity in humans, which means they might be capable of achieving some therapeutic effects.
• Finally, the ethnobotanical approach assumes that the indigenous uses of plants can offer strong clues to the biological activiites of those plants.
• The history of drug discovery implies that the ethnobotanical approach is the most productive of the plant-surveying methods, and recent findings confirm that impression.

How do ethnobotanists choose the societies they study?

1. First, the societies should be located in a floristically diverse area; such as, a tropical rain forest. Such diversity dramatically increases the number of plants available; it therefore enhances the likelihood that plants with pharmacologically active molecules will be pressed into service.
2. Second, the societies should have remained in the region for many generations. Groups who have resided in one place for a long time presumably have had ample opportunity to explore and experiment with local vegetation.
3. Third, the cultures must have a tradition in which healers transmit their plant knowledge from generation to generation, usually through apprentices. Such repetitive, long-term use of botanical species can be expected to have identified both the most effective medicinal plants and those that are too toxic for safe use.

Ethnobotanists interested in drug discovery often rely on healers to identify plants that are likely to contain potent bioactive chemicals. There is some urgency to this work: many healers are elderly and lack apprentices. As they die, much of their knowledge of local vegetation dies, too.

In spite of its apparent successes, ethnobotany is unlikely to ever become a major force behind commercial drug discovery programs.

Its application is limited by the scarcity of properly trained ethnobotanists who have the time to conduct rigorous, long-term fieldwork in remote areas of the world. Also, many funders of drug research still perceive the ethnobotanical approach as archaic, unscientific, and unworthy of attention.

Sadly, plant knowledge seems to be disappearing even faster than the forests themselves!

The unit or lists of ethno- words and definitions are located here.