Ethnobotany, Ethnopharmacology and Drug Discovery

1. Introduction

     Throughout human history, people used various materials from nature to cure their illnesses and improved their health. Substances were derived from flora, fauna and mineral sources located in people’s immediate surroundings but also in remote areas [1]. Nature has been the source of medicinal agents for thousands of years, and an impressive number of modern drugs have been isolated from natural sources, many based on their use in traditional medicine. These plant based traditional medical systems continue to play an essential role in health care, with about 80% of the world’s inhabitants relying mainly on traditional medicines for their primary health care [2], though medicinal plants form the principle component of traditional medicine.

     Medicinal folklore over the years has proved to be an invaluable guide in the present day screening of drugs. Many important modern drugs like digitoxin, reserpine, tubocurarine, ephedrine, ergometrine, atropine, vinblastine and aspirin have been discovered by following leads from the folk uses [3].

     Farnsworth and colleagues indicated that globally there were 119 compounds from 90 plants which were used as single entity medical agents. Significantly, 77% of these were obtained as a result of examining the plants, based on ethnomedical uses and are employed in manners that approximate those uses [4].

     In recent years, we have called attention to the lack of information on the relative importance of a medicinal plant (or other useful plants) within a culture and the need for comparing the use of plants inter-culturally. Such studies have important implications for research in the field of natural products, since these ethnobotanical studies point out to the  species which most urgently should be studied phytochemically and which we consider them to be the most likely ones to contain bioactive compounds. Indigenous people use a wide range of plants therapeutically to maintain their health. There is great promise for new drug discovery based on traditional plant uses. Also, plants may be used as food, and it is difficult to draw a line between these two groups; food may be medicine and vice versa [5].

     The loss of language and traditional knowledge due to acculturation and plant habitat destruction is a major concern, particularly among smaller and more vulnerable tribes and indigenous groups. Serious dangers exist for the survival of such people and their cultures and the ecosystems which nurture them and provide western and traditional medicine with novel plant products for human well-being everywhere. Loss of indigenous knowledge has an impact on the modern medicine. As indigenous cultures become increasingly fragmented and threatened by modern development pressures in developing countries, folk knowledge may be lost for ever. Like the current spasm of plant and animal species extinction, the practitioners of ethnomedicine appear to be at a great risk of extinction than even forests and other biomes. Knowledge of the use of plants is disappearing faster than themselves [3]. In this race against ecosystem destruction, researchers in many disciplines must rally to provide the impetus to save global diversity while at the same time accelerating studies of ethnomedicine in consort with biomedical and chemical terms for developing new natural products and drugs needed by humans. It behooves us to study the practice of indigenous populations before they are lost, through either human indifference or our relentless ability to change and destroy the vegetation around us. We hope that this writing will stimulate those interested in ethnobotany, ethnopharmacology and human welfare to look closely and seriously at the data awaiting our scrutiny.

2. Ethnobotany

     The term ethnobotany was first introduced by American botanist John Harshberger in 1896 as “the study of plant use by humans”. Ethnobotany studies the relationship between humans and plants in all its complexity and is generally based on a detailed observation and study of the use a society makes of plants, including all the beliefs and cultural practices associated with this use. It is useful for ethnobotanists to live with indigenous people, to share the everyday life of their community and, of course, to respect the underlying cultures. Ethnobotanists have a responsibility both to scientific community and to the indigenous cultures.

     The discipline of ethnobotany is a much broader discipline which is interested in all studies about the relationship between people and plants. Ethnobotany focuses not only on medicinal plants, but also on other natural products derived from nature, such as: food, plants used in rituals, coloring agents, fiber plants, poisons, fertilizers, building materials for houses, household items, boat, etc. [6].

     Because plants play an important role in almost every realm of human activity, ethnobotany encompasses many fields including botany, biochemistry, pharmacognosy, toxicology, medicine, nutrition, agriculture, ecology, evolution, comparative religion, sociology, anthropology, linguistics, cognitive studies, history and archeology. The multidisciplinary nature of ethnobotany allows for a wide array of approaches and applications and leaves the way open for many scientists to study the plant uses in different ways [7]. But medicinal plants have always been the main research interests of ethnobotany and the study of these resources has also made significant contributions to the theoretical development of the field [6].

     It is clear that inter- and multidisciplinary approaches can lead to more fruitful, thorough and systemic approximations in the study of plant-people interactions. Despite or perhaps because of its many challenges, ethnobotany remains a fascinating and promising area of study [7].

2.1. Quantitative ethnobotany

     Some wild plant resources are severely threatened by habitat loss and species-selective overexploitation. In addition, indigenous knowledge about the use of wild plant resources is rapidly disappearing from traditional communities. In the context of conservation and sustainable and equitable use of wild plant resources, quantitative ethno-botany can contribute to the scientific base for management decisions. In order to enhance the indicative value of ethnobotanical studies, there have been attempts in recent years to improve the traditional compilation-style approach through incorporating suitable quantitative methods of research in ethnobotanical data collection, processing and interpretation. Such quantitative approaches aim to describe the variables quantitatively and analyze the observed patterns in the study, besides testing hypotheses statistically.

     The concept of quantitative ethnobotany coined out in 1987 by Prance and co-workers. It is defined as “the application of quantitative techniques to the direct analysis of contemporary plant use data”. Quantification and associated hypothesis-testing help to generate quality information. The techniques used in this respect include, cluster and principal analysis, regression analysis, analysis of variance and log-linear modeling [8-10].

2.2. Applied ethnobotany

     Besides developing quantitative methods, ethnobotany has moved towards a wider approach, including other aspects of the natural world. Ethnobotanists quite often identify themselves more and more as ethno-biologists or ethnoecologists because these disciplines offer more opportunities to analyze human interactions with the overall environment as well as people’s relation to external factors such as the impact of tread systems on local economics and ways of life.

     Since 1992, the people and plants initiative has coined the phrase “applied ethnobotany” which actually relates to studies and methods which enable work with the knowledge holders in a participatory way, to analyze knowledge and set up improved management systems which build on local sets of practices and social dynamics. Applied ethnobotany also strives to bridge the gap between traditional knowledge and scientific knowledge and to understand the relationship between local practices and knowledge systems and policies, rules and economic trends at the national and international level [11].

2.3. Ethnoecology

     Recently, the term ethnoecology has coined out. Martine (1995) describes ethnoecology as a discipline which integrates many diverse academic fields. The term ethnoecology is used to encompass all studies which describe local people’s interaction with the natural environment, including subdisciplines such as ethnobiology, ethnobotany, ethnoentomology and ethnozoology [12]. In fact ethnoecology is the science of how people understand the relationship between humans, animals, plants and physical elements of a locale [13].

3. Ethnopharmacology

    Ethnopharmacology as a specifically designated field of research has a relatively short history. The term was first used in 1967 in the title of a book on hallucinogens. The observation, identification, description and experimental investigation of the ingredients, and the effects of the ingredients, and the effects of such indigenous drugs is a truly interdisciplinary field of research which is very important in the study of traditional medicine. Ethnopharmacology is defined as “the interdisciplinary scientific exploration of biologically active agents traditionally employed or observed by man”.

     This definition draws attention to the bioscientific study of indigenous drugs but does not explicitly address the issue of searching for new drugs. Medicinal plants are important elements of indigenous medical systems in many parts of the world, and these resources are usually regarded as a part of traditional knowledge of a culture [6].

     Four general types of herbal medicine exist which are Asian, European, Indigenous and Non-Western. Many like the Asian and European systems go back thousands of years, appear in the pharmacopoeia, and with such a tradition of use are better understood than those of indigenous origins that are often only orally or secondarily recorded. Indigenous medical systems are the most diverse and are still practiced where such cultures are intact, but are continuously evolving as contact with other cultures continuous. The knowledge may reside exclusively with traditional healers, or be generally known [14].

    Studies dealing with medical and other useful plants and their bioactive compounds have used many concepts and methodologies. These are interdisciplinary or multidiscipli-nary studies but the relative lack of progress in interdisciplinary and applied domains derives in part from the fact that ethnophar-macologists represent diverse intellectual traditions most prominently pharmacology, anthropology and botany. In addition, some are connected to commercial enterprises, including the pharmaceutical industry and the rapidly expanding market for herbals and medicinal foods. Will it be possible in future to use those combined voices to forge a more interdisciplinary field of inquiry, i.e. how realistic is the vision that calls for an ethnopharmacology that yields collaboration among different researchers as well as the application of that knowledge to practical ends for both scientific and indigenous communities [15].

3.1. Examples of ethnopharmacological studies

     An interesting example of an early ethnopharmacological approach is provided by the study of the botanical origin of the arrow poison curare, its physiological effects and the compound responsible for these effects. Curare was used by certain wild tribes in South America for poisoning their arrows and many early explores documented this usage. The botanical source of curare was eventually identified as the climbing vine

Chondrodendron tomentosum Ruiz and Pavon; other species of the Menispermanceae (Curarea spp. and Abuta spp.) and Loganiaceae (Strychnos spp.) are also used in the production of curares of varying types [6]. Another example is drown from ethnobotanical work in Turkmen Sahra area in north-east of Iran, with Turkmen people. Turkmens use the seeds of Salvia viridis L. (Lamiaceae) for treatment of inflammatory eye diseases and cleansing eyes from dusts and straws [16]. The seeds are approximately 2 mm wide and 3 mm long; and people use them directly to the eyes, but before using, seeds are soaked in water or milk for about 1 h or so and then applied. At the first glance, this seems an unlikely remedy for eye problems, but the rationale behind it becomes evident when considering the morphological and chemical makeup. The genus Salvia is well known for having the property of ‘Myxocarpy’ (production of mucilage when getting wet), even it could be considered as a taxonomic character. The mucilaginous layer around the seeds contains complex polysaccharides which form a soft layer around seeds. This layer may well have a cleansing effect, and polysaccharides are known to be useful in the treatment of inflammatory conditions and bacterial or viral infections. Although there are no pharmacological data from experimental studies available to corroborate this use, information on the histochemical structure of the seed make it likely that the treatment has some scientific basis.

      Discovery of reserpine from a traditional medicinal plant (Rauvolfia serpentina) is very interesting. This plant which is called Chota-chand in Hindi, have been used by local people of Himalayan Mountains for snakebite. A local legend claims that in ancient times mangooses were observed to feed on the plant before engaging in combat with cobra. Copying the reputed activity of the mangoos, local people found that the shrub could serve as a potent antidote to snakebite. In Bihar Province of India people use the plant to treat insanity, epilepsy and insomnia [17]. Reserpine isolated from Rauvolfia is a potent drug for hypertension. Interestingly, there is a similar legend among Turkmens of Iran concerning a different plant, Verbascum, called Segher-ghureg in Turkmeni. Verbascum species are also used to treat snakebites [18]. Despite the Rauvolfia which finally captured the attention of scientists, Verbascum sp. are still waiting for scientists to have a closer and detailed look on them. Also, ethnophar-macology as a science bridging the gap between natural sciences and anthropology, should look at symbolic and cognitive aspects. People may select plants because of their specific pharmacological properties, but also because of the symbolic power they may believe is in a plant. Understanding these aspects requires cognitive and symbolic analysis of field data [6]. Another example from field studies in Turkmen Sahra area is the use of the seeds of Peganum harmala L. for evil eye. The seeds are known to contain a variety of alkaloides, but these seeds are not taken by the local people, instead they are grilled and smoked; and believed that the smoke of seeds is a powerful symbol for   repealing evil eyes and as a part of the healing process.

     One more example is the use of tubers of Leontice leontopetalum L. subsp. ewersmannii (Bunge.) Coode. People believe that the plant exist as male and female and men should use the tubers of female plants and women should use the tubers of male plant, otherwise the plant has no effect [18].

     The role of ethnopharmacology can be extended beyond that defined previously. It looks not only at empirical aspects of indigenous and popular plant use, but also at the cognitive foundations of this use. Only if these issues are to be included will it be a truly interdisciplinary field of research [6].

3.2. Ethnopharmacology and bioprospecting

     Bioprospecting focuses on the development of new drugs for huge markets of the Northern hemisphere. Potentially, highly profitable pharmaceutical products are developed, based on the biological and chemical diversity of the various ecosystems of the earth; this requires an enormous financial input. The search starts with the collection of biogenic samples (plants, fungi, other micro-organisms and animals), progresses through analysis of the chemical, biological and pharmacological activities to the development of drug templates or new drugs. A key process in this search is high-throughput screening systems such as those that have been established by major international pharmaceutical companies. Huge libraries of compounds (and sometimes extracts) are screened for biological activity against specific targets. Active natural products are only one of the many sources of material for these batteries of tests but serve as a starting point for drug development. Currently, some companies envision screening 500000 samples a week against a single target; thus it becomes essential to have an enormous number of chemically diverse samples available. In bioprospecting programs, which are directed specifically towards infectious diseases, the use of ethnobotanical information is very useful and promising.

      Ethnobotanical studies generally result in the documentation of a rather limited set of well-documented useful plants, mostly medicinal, but also those known to be toxic or used in nutrition. In ethnopharmacology, an important goal is the development of improved preparations for use by local people. Thus it is essential to obtain information on the bioactive compounds from these plants, their relative contribution to the effects of the extract (including for example, synergic or antagonistic effects), the toxicological profile of the extract and its constituents. By restricting ethnopharmacology to the bioscientific study of indigenous uses, attention is drowning to the need for improving indigenous phytochemical systems, especially in developing countries. This requires research strategies for studying indigenous medical plants and their uses. Truly multidisciplinary research on the medicinal plants requires the inclusion of other methodologies from such fields as medical or pharmaceutical anthropology or sociology. Not only do we need a detailed understanding, incorporating social scientific and bioscientific methods, but we also need to support all means available of making better use of these products.

4. Geographical coverage and perspectives

     Considering the distribution of ethnobotanical and ethnopharmacological work throughout the world, most of the works have been done on the Latin America and Africa. Also the number of published studies in ethnobotany varies across Latin America. A survey published in 1994, of articles on ethnobotany which have appeared in international journals revealed that 41% of all studies in Latin America have been in South America, 14% in Central America. 36% in Mexico and 9%in the Caribbean (Σ= 2768). Mexico is easily the country with the greatest level of activity (36% in total), followed by Peru (11%), Colombia (9%) and Guatemala (5%). Ranking the ethnobotanical studies in Latin America by theme is as follows: (1) medicinal plants, (2) domestication and origin of agriculture, (3) archaeobotany, (4) edible plants, (5) general ethnobotanical studies, (6) agro-forestry and home-gardens, (7) forest use, (8) cognitive studies, (9) historical studies, and (10) market survey. Table 1 shows the number of studies on different themes in ethnobotany in Latin America. In Asia, ethnobtanical studies have been done in few countries. In India, ethnobotany emerged as a distinct discipline in the early of 1970s. Ethnobotanical research started in Nepal in about 1970 and has since become a popular