Nature has been a source of medicinal agents for thousands of years, and an impressive number of modern drugs have been isolated from natural sources
“Nature has been a 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 medicine 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. Plant products also have an important role in the health care systems of the remaining 20%, who reside in developed countries. About 25% of prescription drugs dispensed from community pharmacies in the United States from 1959 to 1980 contained plant extracts or active principles derived from higher plants.
At least 119 chemical substances derived from 90 plant species are important drugs currently in use. Of these 119 drugs, 74% were discovered as a result of research directed at the isolation of active compounds from plants used in traditional medicine.18 Based on 1991 sales, half of the leading pharmaceuticals were either derived from natural products or contained a pharmacopoeia that was based on natural products (O’Neill MJ, Lewis JA. 1993). In 1993, 57% of the top 150 brand-name products prescribed contained at least one major active compound, or were derived or patterned after compounds, reflecting biological diversity (Grifo F. et al. 1997). Many researchers have discussed the importance of medicinal plants as sources of new therapeutic agents (Cragg GM, Newman DJ. 2001) and others have effectively focused on the potential of specific chemical classes (e.g., alkaloids) in drug discovery. Recent research continues to validate an ethnobotanically targeted approach to the initial discovery of pharmaceuticals (Lewis W.H. 1999). Still others estimate that of about 375 total drugs of pharmaceutical significance in the rain forests of the world, only one-eighth have been discovered. Assessing the worth to humanity of drugs already known and used might be even more relevant. Subsequently, Cinchona bark has been used since the seventeenth century. In 1820, when Caventou and Pelletier identified its active alkaloid quinine, and later quinidine, along with their analogs, isomers, semi synthetics, and synthetics to treat malaria, heart conditions, and other ailments, sales escalated. Worldwide use of these drugs against malaria and arrhythmia generated untold wealth, relieved much suffering, and saved millions of lives. Further, use of the antimalarial drugs led to the successful habitation of vast areas of tropical to warm temperate regions, making possible new opportunities for progress and riches. Sales of these drugs to the present time amount to an astounding net figure in the tens, if not hundreds, of billions of dollars.
Medical Ethnobotany Indigenous peoples use a wide range of plants therapeutically to maintain their health. There is great promise for new drug discoveries based on traditional plant uses (Lewis W.H, Elvin-Lewis M.P. 1995). To be allowed to use this knowledge, researchers must recognize that both intangible resources (knowledge) and tangible resources (genetic material) are being provided. In 1992, the United Nations Convention on Biological Diversity confirmed the rights of source nations over the genetic materials found within their boundaries. That convention also required that local and indigenous knowledge, practices, and innovations be protected and recognized (Lewis W.H. 2000). Before conducting ethnobotanical research, it is essential to obtain agreements among all parties, addressing prior informed consent, confidentiality, ownership of intellectual property and tangible biological materials, collecting area scope, conservation of medicinal plants and habitats, responsibilities of parties, benefit sharing, compensation due parties at all stages of research, development, and commercialization, and supplier of materials. Appropriate models exist for guidance in developing collaborative agreements, so that the discovery of new natural products.
A number of phytochemicals (castanospermine, calanolides, prostratin) are potentially useful in the treatment of human autoimmune deficiency syndrome (AIDS). Cell modifiers of plants that act as mutagens, teratogens, lectins, or mitogens are described. Antimutagenic compounds have important potential roles in cancer chemoprevention. Indeed, the greatest advancement in cancer therapeutics in the last quarter of a century has been the incorporation of compounds and analogs isolated from plants sources and their semi synthetic derivatives.
Many texts and monographs have been studied carefully in selecting the examples of plants useful, harmful, and enjoyable to humans. From these works we have gleaned what our forefathers learned the hard way and passed on to us. They performed experiments over thousands of years by trial and error, and we, with broader insight and scientific expertise, have a much greater opportunity to utilize these data than any who preceded us. Valuable data, however, are not always recorded. It behooves us to study the practices 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 book will stimulate those interested in Ethnobotany and human welfare to look closely and seriously at the field data awaiting our scrutiny.
Natural products and their derivatives represent more than 50% of the drugs in clinical use in the world (Cowan, 1999, Sofowora, 1984). One of the paramount reasons for pursuing natural products chemistry resides in the actual or potential pharmacological activity to be found in alkaloids, terpenoids, coumarins, flavonoids, lignans and the like. Since the advent of antibiotics in the 1950’s, the use of plant derivatives as a source of antimicrobials has been virtually non-existent (Cowan, 1999). Antimicrobial plant extracts have been recognized as a future source of new antimicrobials in the event of the current downturn in the pace at which these are being derived from microorganisms. The public is also becoming more aware of problems with overprescription and misuse of traditional antibiotics (Cowan, 1999). Resistance to anti-microbial agents is recognized at present as a major global public health problem. Infective diseases account for approximately one-half of all deaths in countries in tropical regions. In industrialized nations, despite the progress made in the understanding of microorganisms and their control, incidents of epidemics due to drug resistant microorganisms and the emergence of hitherto unknown disease causing microbes, pose enormous public health concerns (Iwu et al; 1999). The number of resistant strains of microbial pathogens is also growing since penicillin resistance and multiresistant pneumococci caused a major problem in South African hospitals in 1977 (Berkowitz, 1995). Berkowitz, (1995) referred to the emergence of drug resistant bacteria as a medical catastrophe. Leggiadro (1995) stated that effective regimens might not be available to treat some enterococci isolates and that it is critically important to develop new antimicrobial compounds for these and other organisms before we enter the post antibiotic era. The cost of drugs is a sizable proportion of total health expenditure in most developing countries. In some of these countries, drug related expenses account for up to 30-50% of the total cost of health care (Sofowora, 1984). This situation is becoming increasingly unbearable to many nations including South Africa. The World Health Organization (WHO), have observed that up to 80% of the rural populace in the developing countries depend on herbal or alternative medicine and requested member countries to explore safe indigenous medicines for their national health care (Sofowora, 1984).
Plants have served as a source of new pharmaceutical products and inexpensive starting materials for the synthesis of some known drugs. Components with medicinal properties from plants play an important role in conventional Western medicine. In 1984, at least 25% of the Western medicine issued in the US and Canada were derived from or modeled after plant natural products and 119 secondary metabolites were used globally as drugs (Farnsworth, 1994). It has been estimated that 14-28% of higher plant species are used medically. Only 15% of all angiosperms have been investigated chemically and 74% of pharmaceutically active plant derived components were discovered after following up on ethnomedical use of the plant (Farnsworth, 1991). The traditions of collecting, processing and applying plant and plant-based medications have been handed down from generation to generation. In many African countries, traditional medicines, with medicinal plants as their most important components, are sold in marketplaces or prescribed by traditional healers (without accurate dose value) in their homes (Herdberg and Staugard, 1989). Because of this strong dependence on plants as medicines, it is important to study their safety and efficacy (Farnsworth, 1994). The value of ethnomedicine and traditional pharmacology is nowadays gaining increasing recognition in modern medicine because the search for new potential medicinal plants is frequently based on an ethno-medicinal basis. In the ethno-pharmacological approach, local knowledge about the potential uses of the plants is very useful as compared to the random approach where indigenous knowledge is not taken into consideration. Compounds inhibiting microorganisms, such as benzoin and emetine have been isolated from plants (Cox, 1994). It is possible that antimicrobial compounds from plants may inhibit bacteria by a different mechanism than the presently used antibiotics and may have clinical value in the treatment of resistant microbial strains. For this reason, it is therefore important to investigate plants as alternative sources of anti-microbial compounds. Preliminary work done on the southern African members of the section Hypocrateropsis (Eloff, 1999a) indicated that most of the members of this section had substantial antibacterial activity against Gram-positive and Gram-negative bacteria. Bioautography studies indicated that members of the section Hypocrateropsis have different antibacterial compounds from members of other sections. Substantial antibacterial activity of some species further motivated this study. Fossils of plants date back as early as 3.2 billion years ago. These plants provided the foundation upon which animal life and later, human life were based on. They provide bodybuilding food and calories as well as vitamins essential for metabolic regulation. Plants also yield active principles employed as medicines [Shultes, 1992] Fossils of plants date back as early as 3.2 billion years ago. These plants provided the foundation upon which animal life and later, human life were based on. They provide bodybuilding food and calories as well as vitamins essential for metabolic regulation. Plants also yield active principles employed as medicines [Shultes, 1992].
Finding healing powers in plants is an ancient idea. Hundreds, if not thousands, of indigenous plants have been used by people on all continents as poultices and infusions dating back to prehistory. There is evidence of Neanderthals, living 60 000 years ago in present-day Iraq, using hollyhock (Alcea rosea L.), which is still in ethnomedicinal use around the world today [Cowan, 1999]. The Bible offers descriptions of at least 30 healing plants of which frankincense (Boswellia sacra L.) and myrrh (Commiphora myrrha L.) were employed as mouthwashes due to their reported antiseptic properties. The fall of ancient civilizations resulted in the destruction or loss of much of the documentation of plant pharmaceuticals but many cultures continued in the excavation of the older works as well as building upon them. Native Americans were reported to have used 1625 species of plants as food while 2564 found use as drugs, while the Europeans started turning towards botanicals when treatment in the 1800s became dangerous and ineffective [Cowa n, 1999]. Today some 1500 species of medicinal and aromatic plants are widely used in Albania, Bulgaria, Croatia, France, Germany, Hungary, Spain, Turkey and the United Kingdom [Hoareau, 1999].