Joabe Gomes de Melo

Caatinga revisited: ecology and conservation of an important seasonal dry forest.

Besides its extreme climate conditions, the Caatinga (a type of tropical seasonal forest) hosts an impressive faunal and floristic biodiversity. In the last 50 years there has been a considerable increase in the number of studies in the area. Here we aimed to present a review of these studies, focusing on four main fields: vertebrate ecology, plant ecology, human ecology, and ethnobiology. Furthermore, we identify directions for future research. We hope that the present paper will help defining actions and strategies for the conservation of the biological diversity of the Caatinga.

Antiproliferative Activity, Antioxidant Capacity and Tannin Content in Plants of Semi-Arid Northeastern Brazil

The objective of this study was to evaluate antiproliferative activity, antioxidant capacity and tannin content in plants from semi-arid northeastern Brazil (Caatinga). For this study, we selected 14 species and we assayed the methanol extracts for antiproliferative activity against the HEp-2 (laryngeal cancer) and NCI-H292 (lung cancer) cell lines using the (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazole) (MTT) method. In addition, the antioxidant activity was evaluated with the DPPH (2,2-diphenyl-2-picrylhydrazyl) assay, and the tannin content was determined by the radial diffusion method. Plants with better antioxidant activity (expressed in a dose able to decrease the initial DPPH concentration by 50%, or IC50) and with higher levels of tannins were: Poincianella pyramidalis (42.95 ± 1.77 µg/mL IC50 and 8.17 ± 0.64 tannin content), Jatropha mollissima (54.09 ± 4.36µg/mL IC50 and 2.35 ± 0.08 tannin content) and Anadenanthera colubrina (73.24 ± 1.47 µg/mL IC50 and 4.41 ± 0.47 tannin content). Plants with enhanced antiproliferative activity (% living cells) were Annona muricata (24.94 ± 0.74 in NCI-H292), Lantana camara (25.8 ± 0.19 in NCI-H292), Handroanthus impetiginosus (41.8 ± 0.47 in NCI-H292) and Mentzelia aspera (45.61 ± 1.94 in HEp-2). For species with better antioxidant and antiproliferative activities, we suggest future in vitro and in vivo comparative studies with other pharmacological models, and to start a process of purification and identification of the possible molecule(s) responsible for the observed pharmacological activity. We believe that the flora of Brazilian semi-arid areas can be a valuable source of plants rich in tannins, cytotoxic compounds and antioxidant agents.

Medicinal plants used as antitumor agents in Brazil: an ethnobotanical approach.

We describe the medicinal plants that have been reported to be antitumor agents and that have been used in ethnobotanic research in Brazil to answer the following questions: what is the abundance of plants reported to be antitumor in Brazil? Have the plant species used for tumor treatment in traditional Brazilian medicine been sufficiently examined scientifically? Our analysis included papers published between 1980 and 2008. A total of 84 medicinal plant species were reported to be used for cancer and tumor prevention or treatment; 69.05% of these were cited as being used for the treatment of tumors and cancer in general and 30.95% for specific tumors or cancers. The plants that were cited at a higher frequency were Aloe vera, Euphorbia tirucalli, and Tabebuia impetiginosa. At least, one pharmacological study was found for 35.71% of the species. Majority of the studies selected were conducted in rural communities and urban areas and in areas with traditional healers in Brazil. We found the following molecules to be the most studied in vitro and in vivo: silibinin, β-lapachone, plumbagin and capsaicin. The species addressed here constitute interesting objects for future studies to various professionals in the field of natural products.

Levels of Tannins and Flavonoids in Medicinal Plants: Evaluating Bioprospecting Strategies

There are several species of plants used by traditional communities in the Brazilian semiarid. An approach used in the search for natural substances that possess therapeutic value is ethnobotany or ethnopharmacology. Active substances that have phenolic groups in their structure have great pharmacological potential. To establish a quantitative relationship between the species popularly considered to be antimicrobial, antidiabetic, and antidiarrheal, the contents of tannins and flavonoids were determined. The plant selection was based on an ethnobotanical survey conducted in a community located in the municipality of Altinho, northeastern Brazil. For determination of tannin content was utilized the technique of radial diffusion, and for flavonoids, an assay based on the complexation of aluminum chloride. The group of plants with antimicrobial indications showed a higher content of tannins compared to the control groups. The results evidence suggests a possible relationship between these compounds and the observed activity.

Native medicinal plants commercialized in Brazil – priorities for conservation

A majority of the native medicinal plants that are commercialized in Brazil are harvested from natural populations. In addition to this essentially unrestrained collecting, these plants have been heavily impacted by the cutting and the fragmentation of forest formations throughout the country. Considering the limited availability of natural resources, threats to species diversity, and the necessity of conservation efforts in light of the rapid exhaustion of natural ecosystems, it is becoming exceedingly important to establish conservation priorities. The present work sought to identify the native medicinal plants harvested for industrial purposes and to establish conservation priorities for the species of highest commercial value. To that end, a survey of Brazilian industrial products that use medicinal plants was undertaken in 54 shops in the city of Recife (Pernambuco, NE Brazil). The survey noted information concerning the commercial name of the product, its plant composition and pharmaceutical presentation, therapeutic indications, as well as the laboratory that produced it. Only native species were considered. A total of 74 different native species used to produce more than 300 types of products were encountered in the present survey. Twelve species demonstrated significant versatility (Species which had the highest numbers of different therapeutic indications and body systems), and 58.33% of these plants were trees. Destructive collecting predominates (58.11%), greatly affecting taxa collected exclusively from wild populations (86.49%). The intensive use of exclusively wild species and the destructive harvesting techniques employed in gathering them create serious problems that will threaten the availability of these resources to future generations.

New strategies for drug discovery in tropical forests based on ethnobotanical and chemical ecological studies.

ETHNOPHARMACOLOGICAL RELEVANCE Hypotheses from ethnobotany and chemical ecology can increase our ability to predict the pharmaceutical potential of tropical flora. In order to illustrate how bioprospecting studies can benefit from the incorporation of these hypotheses, especially in tropical dry forests, we discuss evidence from ethnobotanical studies that examine hypotheses about the ecology of plant defense against herbivory. MATERIALS AND METHODS We focus on two hypotheses regarding defense patterns in plants-the plant apparency hypothesis and the resource availability hypothesis-and analyze how these can help us understand the use of medicinal plants by traditional communities. RESULTS The evidence suggests that medicinal plants in the dry forest are a rich source of drugs in which phenolic compounds, especially tannins, are directly responsible for the therapeutic activity. Phenolic compounds and their potential therapeutic activity are likely good candidates for bioprospecting efforts. CONCLUSION We believe that following strategies to link ethnobotanical and chemical ecological approaches will increase the efficiency of bioprospecting studies in tropical forests.

Intracultural Variation in the Knowledge of Medicinal Plants in an Urban-Rural Community in the Atlantic Forest from Northeastern Brazil

This study assessed the intracultural knowledge of the use of medicinal plants in an urban-rural community in an Atlantic forest fragment in northeastern Brazil. We examined the importance of native and exotic species and the effects of gender and age on that knowledge. We also compared data obtained from different groups of informants (local experts and general community). We conducted 194 interviews between June 2007 and January 2008, using the freelist technique and semistructured forms to collect ethnobotanical data. Information obtained from the community was compared with that from six local experts who participated in a survey in 2003. From a total of 209 ethnospecies, exotic and herbaceous plants presented higher richness. With respect to the number of citations, women and older informants were shown to know a higher number of medicinal plants. Comparing knowledge of local experts with that of the general community, we noted that experts know a similar wealth of plant families and therapeutic indications, but the community knows a greater species richness. These results indicate that local experts may provide useful information for studies that search for a quick diagnosis of the knowledge of a given community.

Citation behavior in popular scientific papers: what is behind obscure citations? The case of ethnobotany

Citation studies have become an important tool for understanding scientific communication processes, as they enable the identification of several characteristics of information-retrieval behavior. This study seeks to analyze citation behavior using two popular ethnobotany articles, and our analysis is guided by the following question: when an author references a work, is he pointing out the work’s theoretical contribution, or is bias a factor in citing this reference? Citation analysis reveals an interesting phenomenon, as the majority of citing texts do not consider the theoretical contributions made by the articles cited. Two possible conclusions can be drawn from this scenario: (1) citing authors read the original texts that they cite only superficially, and (2) the works cited are not read by the vast majority of people who reference them. Thus, it is clear that even with sufficient access to reference texts; ethnobotanical studies highlight elements less relevant to the research and reproduce discussions in a non-reflective manner.

Functional aspects of the use of plants and animals in local medical systems and their implications for resilience

ETHNOPHARMACOLOGICAL RELEVANCE This study sought to understand the role of plants and animals in traditional medical systems and evaluate the capacity of these systems to absorb impacts and maintain their identity by determining the existence of functional substitutes. MATERIAL AND METHODS Ethnobiological data were collected through semi-structured interviews and free lists at a rural community in the semiarid region of northeastern Brazil. The data were subjected to the utilitarian redundancy model and analyzed by tests of proportion and variance. RESULTS We found that most of the therapeutic targets treated with animal-based remedies were also treatable by plant-based remedies; these targets were perceived as very usual, although they were not considered dangerous. Furthermore, people considered the plants and animals to be equally effective at curing overlapping therapeutic targets, but the plant remedies were used more frequently. The findings show that local knowledge about medicinal plants and animals follows similar patterns regarding the utilitarian redundancy, with high functional overlap among these features. However, the ease of access to the medicinal resource influences the choice of treatment, leading to an increased preference for plants over animals. In addition, we suggest that during the cultural evolution process, people concentrated their efforts on experimenting with different resources for the treatment of diseases that were very frequent locally, even if not very severe, which contributed to the resilience of the local medical system. CONCLUSION Furthermore, we infer that plants may effectively perform the function of healing, whereas animals act as reserves of resilience for the system, maintaining system function in the face of disturbances that may affect the availability of plant species.

The Influence of the Environment on Natural Resource Use: Evidence of Apparency

This chapter evaluates the mechanisms by which certain characteristics of a specific natural resource (particularly a plant), such as its environmental availability or chemical composition, can affect its local use. An evaluation of the factors that influence people’s decision to select and try a natural resource and, possibly, incorporate it in their social-ecological systems is the main guiding issue for this chapter. To address this issue, we explore the assumptions of the ecological apparency hypothesis (EAH), the optimal foraging theory (OFT) and the resource availability hypothesis (RAH). EAH, OFT and RAH were first introduced in classic ecological research but were subsequently adapted to the fields of human ecology and ethnobiology. We also discuss how these ideas can complement one another to explain people’s choices for plant resource use and management. Finally, we bring some evidence from the available literature in favor or against these assumptions, especially to what concerns the EAH.