Implications of ethnobotanical studies on bioprospecting strategies of new drugs in semi-arid regions more

The Open Complementary Medicine Journal, 2010, 2, 21-23 21 Open Access Implications of Ethnobotanical Studies on Bioprospecting Strategies of New Drugs in Semi-Arid Regions Ulysses Paulino de Albuquerque* Departamento de Biologia, Área de Botânica, Universidade Federal Rural de Pernambuco, Rua Dom Manoel de Medeiros s/n, Recife, Brazil Abstract: Many strategies are currently used by researchers and pharmaceutical companies to search for new drugs for medical and pharmaceutical purposes. The choice of a strategy depends primarily on the costs involved, team background in a given area, and/or promising results pointed at certain approaches. Ethnobotanical/ethnopharmacological studies are proving to be powerful tools in the search for new drugs. However, despite being scientifically recognized claimed approaches, it is necessary to recognize that the relationship among people, their traditions, and the use of natural resources for medical purposes can be quite complex. In this opinion article, our intention is to show the implications of some findings of our research group that may be relevant to the search for new drugs in semi-arid regions. Keywords: Caatinga, ethnopharmacology, phytochemistry. INTRODUCTION The relationships between people and plants are complex, often involving adaptive responses to ecological and evolutionary forces [1] (Fig. 1); in addition to these adaptations, our culture is also a powerful force that can shape these complex relationships. Our research group has been asked to frequent: how ecological and evolutionary may have shaped the relationship between people and plants throughout the evolution of different societies and cultures? Therefore, in this opinion article, we aim to review some of the assumptions with which our group has been working in semi-arid northeastern Brazil and to highlight the potential implications for drug discovery from ethnobotanical and/or ethnopharmacological studies. In this sense, we believe that principles of evolution and ecology constitute an interesting theoretical framework for understanding the relationship between people and plants. Although the documentation collected over the past 100 years indicates that the relationships between people and plants are highly complex processes that differ from culture to culture, evidence also suggests that some processes may predictably follow general patterns. According to Gottlieb and Borin’s [2] approach: “Considering our very serious losses in biodiversity to exceed vastly the limits of natural sustainability, our plight is understandable. Appropriate financing of our efforts would be helpful, but not sufficient. We need, most of all, coordination of efforts. Our holistic work aims to provide an outline of the basic strategy: the reduction of the problem to a manageable size via understanding of the mechanisms of nature”. Our approach is similar in the sense that we are trying to understand how the people select medicinal plants, to reduce the efforts of biosprospection. The connection *Address correspondence to this author at the Departamento de Biologia, Área de Botânica, Universidade Federal Rural de Pernambuco, Rua Dom Manoel de Medeiros s/n, Recife, Brazil; Tel: 55-81-3320 6350; Fax: 55-813320-6361; E-mail: upa@db.ufrpe.br 1876-391X/10 among phytochemistry, evolution ecology and ethnobotany is possible and desirable (see, for example, [2-4]). People How Ecology and Evolution affects... Interrelationship Plants Fig. (1). An example of model to understand people and plant interactions. CLIMATE SEASONALITY AND THE SELECTION OF MEDICINAL PLANTS The hypothesis of climate seasonality postulates that people who live in markedly seasonal climates generally employ foraging strategies (for medical resources) focused on woody plants that are perpetually offered in nature [5]; an example of this type of climate is the caatinga, a region with semi-arid vegetation in northeastern Brazil. There are two types of evidence supporting this hypothesis: the first is based on ethnobotany, with studies indicating people’s preference for plants, or even certain organs of a plant, that are continuously available, even when a number of other species with similar functions are also available [5,6]. At first, one might view this as a very obvious prediction, but considering the scenario of seasonal forests, such as the caatinga, where herbs become an abundant resource in certain periods of the year, one may wonder why during the period of abundance these herbs are not used as extensively as tree resources [7]. It is possible that this same scenario is true in other seasonal forests as well. Another issue is that 2010 Bentham Open 22 The Open Complementary Medicine Journal, 2010, Volume 2 Ulysses Paulino de Albuquerque this behavior may have been selected for as a result of ecological pressures. Albuquerque [5] collected evidence that plants with similar uses are not equally valued by people. A second type of evidence supporting this hypothesis is that people tend to use native and perennial resources, even though herbs are more abundant, more easily accessible and locally perceived with equal efficiency at certain times of year [6]. The caatinga herbal stratum is dynamic, variable in time and space and limited to only a few months (2-4 months) per year due to rain availability [8-10]. The herbaceous flora can vary between and within years in the same area [6,8]. This local variability in availability, which does not allow local people to predict if a given resource will be available for use, may have allowed the evolution of specialized behavior in foraging for woody plants and perennial structures. Some findings from our group show, for example, that people in the caatinga region prefer to use the stem bark of an important medicinal plant, the "aroeira" (Myracrodruon urundeuva Allemão), even when leaves are available. We found that the concentration of tannins is markedly higher in the leaves than in the stem bark [10-12]. What seems to be a cultural decision based on and perpetuated by tradition might be justified in the local ecological context. Our findings allow us to hypothesize that not only is the use of a medicinal plant in pharmacopeia construction determined by the perception of plant effectiveness, its availability (abundance, for example) and its accessibility but also the idea of security that the resource will always be temporal available is a critical factor. If true, this assumption has important implications for seasonal environments: it is more important to have a resource that is always available than to have a resource that is biologically more efficient (therapeutic activity). If indeed these trends are confirmed with well-designed studies in several seasonal forests, it will be possible to understand the ecological and evolutionary dynamics behind people's decisions at the moment they gain ownership of natural resources. From a practical perspective, knowledge of these dynamics would be useful in the selection of prospecting strategies directed toward specific resources. DIVERSIFICATION OF USES From a chemical perspective, the findings of our group were also interesting in that they revealed an apparent tendency of people to include exotic plants to diversify their pharmacopeias [13,14]. Thus far, we have accumulated two types of evidence: evidence based on chemistry and evidence based on ethnobotany. In terms of chemistry, we found that the exotic plants used in a local pharmacopeia introduce different classes of compounds, thus adding chemical diversity to the pharmacopeia [14]. From an ethnobotanical point of view, our findings suggest that exotic plants are often used to treat conditions for which there is no indication of use for native plants or when these plants are less preferred [15]. In studies of the pharmacological activities of caatinga plants, there was a clear predominance of phenolic compounds (particularly tannins) in a significant percentage of the plants studied; the presence of phenolic compounds seems to be associated with some of the biological activities reported by people in ethnobotanical studies [16]. If, due to the ecogeographic conditions that characterize the caatinga, there is a trend toward specialization of metabolic pathways for phenolic compound production, it would be reasonable to assume that the introduction of exotic plants is a possible diversification strategy, and a new question would appear: is it possible that this "metabolic specialization”, focused on phenolic compounds, has led to a specialization of the possible therapeutic uses of native plants in this region, leading people to introduce new plants as a diversification strategy? One line of evidence supporting this apparent specialization is the fact that the indication for antiinflammatory purposes is predominant among native plants of the caatinga [14-17]; this anti-inflammatory activity is also strongly related to the presence of phenolic compounds, especially tannins. An alternative path is that given the ability of phenols to bind to different types of proteins, it is possible that the spectrum of biological activity of these compounds is much wider than we believe, because the presence of a wider range of biological activities of a plant is not always due to a greater diversity of compounds present in the plant. These ideas need to be tested because they have strong implications not only for understanding the dynamics of medicinal strategies developed by people but also for directing bioprospecting investigations. THE APPARENCY HYPOTHESIS Other hypotheses that we tested, such as the hypothesis of apparency, have failed to explain the criteria that lead people to select certain plants for their traditional pharmacopeia [13, 18,19]. The apparency hypothesis was developed as a result of herbivory studies and was later suggested as a possible explanation for the inclusion of certain herbs in the medicinal systems of some cultures [20]. The basic prediction is that herbs and plants with short life cycles would develop defense strategies based on highly toxic compounds with low molecular weight (such as alkaloids). However, if this is correct, we would expect to find this trend among the medicinal plants used by a particular group of people. Our findings in the caatinga do not support such predictions and furthermore suggest that such compounds are more likely to occur in woody plants with long life cycles [16,18]. In conclusion, these data reinforce earlier findings that there are well-defined trends for medicinal plants selection by local people, at least for the caatinga of northeastern Brazil. Thus, it would be appropriate to test these ideas in other semi-arid regions because confirmation of these ideas would have major implications for bioprospecting: researchers would expect to find certain groups of biological activities and/or phytocompounds in the medicinal plants used by people in a given region. This type of knowledge would result in logistical, scientific and economic gains (cost reduction due to directed studies with greater probabilities of success). These ideas can only be preliminary approaches, and more studies are necessary to test if these “patterns” can be generalized to caatinga and others semi-arid regions of the world. The small number of studies with standardized methods reduces our potential for generalizations. ACKNOWLEDGEMENTS The author would like to thank the CNPq for financial support (“Edital Universal”) and productivity grants; to my Implications of Ethnobotanical Studies on Bioprospecting Strategies of New Drugs The Open Complementary Medicine Journal, 2010, Volume 2 23 students at the Laboratory of Applied Ethnobotany (UFRPE) for the fruitful discussions; and to Dr. Elcida de Lima Araújo (UFRPE) and Dr. Elba Lucia Cavalcanti de Amorin (UFPE) for the scientific cooperation. REFERENCES [1] Albuquerque UP, Hurrell JA. Ethnobotany: one concept and many interpretations. In: Albuquerque UP, Hanazaki N, Eds. Recent developments and case studies in ethnobotany 1 ed. Sociedade Brasileira de Etnobiologia e Etnoecologia/NUPEEA: Recife Brazil 2010; pp. 87-99. Gottlieb OR, Borin MR. Medicinal products: regulation of biosynthesis in space and time. Mem Inst Oswaldo Cruz 2000; 95: 115-20. Gottlieb OR, Borin MR, Brito NR. Integration of ethnobotany and phytochemistry: Dream or reality? Phytochemistry 2002; 60: 14552. Gottlieb OR, Borin MR. Quantitative chemobiology: a guide into the understanding of plant bioactivity. J Braz Chem Soc 2002; 13: 772-6. Albuquerque UP. Re-examining hypotheses concerning the use and knowledge of medicinal plants: a study in the caatinga vegetation of NE Brazil. J Ethnobiol Ethnomed 2006; 2: 1-10. Albuquerque UP, Andrade LHC, Silva ACO. Use of plant resources in a seasonal dry forest (Northeastern Brazil). Acta Bot Brasil 2005: 19: 1-16. Santos LL, Ramos MA, Silva SI, Sales MF, Albuquerque UP. Caatinga Ethnobotany: anthropogenic landscape modification and useful species in Brazil’s Semi-Arid Northeast. Econ Bot 2009; 63: 363-74. Reis AMS, Araújo EL, Ferraz EMN, Moura AN. Inter-annual variations in the population structure of an herbaceous of caatinga vegetation in Pernambuco Brazil. Rev Bras Bot 2006; 29: 497-508. Araújo EL, Silva KA, Ferraz EMN, Sampaio EVSB, Silva SI. Diversidade de herbáceas em microhabitats rochoso plano e ciliar em uma área de caatinga Caruaru-PE. Acta Bot Brasil 2005; 19: 282-97. [10] [11] [12] [13] [2] [3] [4] [5] [6] [7] [14] [15] [16] [17] [18] [8] [9] [19] [20] Araújo E L, Albuquerque UP, Castro CC. Dynamics of Brazilian caatinga - a review concerning the plants environment and people. Funct Ecosyst Commun 2007; 1: 15-29. Monteiro JM, Lins Neto EMF, Albuquerque UP, Amorim ELC, Araújo EL. Use patterns and knowledge of medicinal species among two rural communities from Northeastern Brazil semi-arid region. J Ethnopharmacol 2006; 105: 173-86. Monteiro JM, Lins Neto EMF, Albuquerque UP, Amorim ELC, Araújo EL. The effects of seasonal climate changes in the caatinga on tannin levels in Myracrodruon urundeuva and Anadenanthera colubrina. Rev Bras Farmacogn 2006; 16: 338-44. Almeida CFCB, Silva TCL, Amorim ELC, Maia MBSM, Albuquerque UP. Life strategy and chemical composition as predictors of the selection of medicinal plants from the caatinga (Northeast Brazil). J Arid Environ 2005; 62: 127-42. Alencar NL, Araújo TS, Amorim ELC, Albuquerque UP. The inclusion and selection of medicinal plants in traditional pharmacopoeias evidence in support of the diversification hypothesis. Econ Bot 2010; 64: 68-79. Albuquerque UP, Oliveira RF. Is the use-impact on native caatinga species in Brazil reduced by the high species richness of medicinal plants? J Ethnopharmacol 2007; 113: 156-70. Araújo TS, Alencar NL, Amorim ELC, Albuquerque UP. A new approach to study medicinal plants with tannins and flavonoids contents from the local knowledge. J Ethnopharmacol 2008; 120: 72-80. Albuquerque UP, Medeiros PM, Almeida ALS, et al. Medicinal plants of the caatinga (semi-arid) vegetation of NE Brazil: a quantitative approach. J Ethnopharmacol 2007; 114: 325-54. Alencar NL, Araújo TS, Amorim ELC, Albuquerque UP. Can the apparency hypothesis explain the selection of medicinal plants in an area of caatinga vegetation? A chemical perspective. Acta Bot Brasil 2009; 23: 908-09. Albuquerque UP, Lucena RFP. Can apparency affect the use of plants by local people in tropical forests? Interciencia 2005; 30: 506-10. Stepp JR, Moerman DE. The importance of weeds in ethnopharmacology. J Ethnopharmacol 2001; 75: 25-31. Received: March 29, 2010 © Ulysses Paulino de Albuquerque; Licensee Bentham Open. Revised: April 14, 2010 Accepted: April 20, 2010 This is an open access article licensed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/bync/3.0/), which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.