The conservation of native priority medicinal plants in a Caatinga area in Ceará , northeastern Brazil

Much of the Brazilian semiarid region faces a considerable process of degradation of natural resources, and ethnobotanical studies have collaborated with important information about the use and traditional knowledge, serving as a tool to design conservation strategies of native plant species. Thus, this study aimed to determine medicinal species meriting conservation priorities in a “Caatinga” area in the northeastern of Brazilian territory. The ethnobotanical data were collected through semi-structured interviews with key subjects selected through the “snowball” technique. The availability and species conservation priority was verified by relative density, risk of collection, local use and use of diversity in the forest fragment sampled. It was recorded 42 native medicinal plants and conservation priority score was calculated for seven species, including Mimosa tenuiflora, Hymenaea courbaril, Ximenia americana and Amburana cearensis need immediate conservation and attention, since their collection does not occur in a sustainable way. In order to ensure the perpetuation of the species and the sustainability of traditional therapeutic practice there needs to be a development of conservation practices of caatinga remaining to better conserve the species of the biome.


INTRODUCTION
In recent years, many studies have been intensified focused on medicinal plants (Souza et al. 2013, Ribeiro et al. 2014a) and ethnobotany has been highlighted in the evaluation of traditional therapies and the development of strategies for the conservation of medicinal flora through local practices (Oliveira et al. 2007, Albuquerque et al. 2011).Approximately 25% of pharmaceutical drugs are chemicals derived from vegetable, where 85% of the population uses traditional systems herbal healing, increasing the use and exploitation of biodiversity every day (Oliveira 2010).
Excessive collection of this feature can affect plant populations modifying their structure, thus, changing the dynamics of the same over time and in terms of individual, affecting their growth and reproductive capacity (Shahabuddin and An Acad Bras Cienc (2017) 89 (4)

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MARIA O. SANTOS et al.Prasad 2004), may cause natural and sometimes irreversible losses.However, recovery strategies can be developed and conservation of these areas from surveys of the potential of plant resources available to a particular community (Roque et al. 2010).Brazil, which is the country holder of one of the greatest biodiversity in the world, has among its biomes, the caatinga, as one of the most exploited and threatened that needs, given the conditions, recommendations and strategies for conservation of natural resources (Albuquerque et al. 2011), for the misuse of caatinga resources have caused irreversible damage to the process of desertification now affects about 15% of the area; Predatory extraction and irrecoverable loss of the diversity of flora (Schober 2002).
Current studies show the importance of savanna vegetation for the conservation of Brazilian biodiversity, due to the high level of endemism of the species having the lowest number and the less extent protected from all Brazilian biomes (Leal et al. 2005), due to the increasing waste, caused mainly by human activities on the natural resources available (Albuquerque et al. 2011).Among the many uses of this vegetation are the timber, medicinal and widely referred to forage in ethnobotanical surveys in rural communities.Thus, this study aimed to determine medicinal species meriting conservation priorities in a caatinga area in northeastern Brazil.

STUDY AREA
The survey was conducted in Nazareth community, next to the Legal Reserve of Nazareth Farm, on the banks of the a federal road (BR 116), located 5 km far from the city of Milagres, between coordinates 7º18 'S and 38º56' W (2015) The ethnobotanical survey was conducted through semi-structured interviews, where knowledge of subjects was granted after reading, permission and signature of informed consent and informed.It is important to mention that this research was submitted to the Research Ethics Committee of the Regional University of Cariri and approved with Opinion No. 019980.Interviews were conducted with 30 key informants and local experts (23 females and 7 males), aged 23-71 years selected by the snowball technique.It was also made some informal interviews with local residents to get information about using wood available species.To assess the local availability of medicinal species in the ethnobotanical survey was selected an area of caatinga apparently kept close to the community studied.
The availability was based on the relative density of species in the forest fragment maintained, obtained through the phytosociological study, which was applied the method of multiple plots for a total of 12 plots of 10x10m, which included all individuals alive and standing dead with stem diameter at the DNS ground level ≥ 3 cm and height ≥ 1 m.The analyzed phytosociological parameters were density, dominance and importance value index using the Fitopac 1.0 that characterized the area (Shepherd 1995).
FLORISTIC SURVEY Species that were collected were in reproductive stages with flower and/or fruit, accompanied by duplicates to follow with herborization process.The herborization process occurred in accordance with the standard methods recommended by Mori et al. (1989).The identification was made through specialized bibliography, as compared to previously identified plant material and / or sent to taxonomists.The witness material was incorporated into the collection of the Caririense Dardano de Andrade Lima Herbarium of the Regional University of Cariri (HCDAL-URCA).

Conservation priorities for medicinal plants
The conservation priority (CP) was performed according to Dzerefos andWitkowski (2001), Oliveira et al. (2007), Albuquerque et al. (2011).Based on the analyzes of phytosociological parameters for the plant community (density), the conservation priority (CP) of the species was calculated, with criteria described in Table I: CP = 0.5 (BS-biological score) + 0.5 (RU-risk of use).
Where: SB = D x 10 (score for relative density) RU = 0.5 (H) + 0.5 (U) x 10 (H is the risk of colletion, and U is the value of use).
H (Table I) U = L (local importance) + V (diversity usage) / 2 In order to obtain the calculation of the relative density were included living individuals and those who presented partially cut, but with conditions to be yet collected for some utility.The average of the sum of the local importance (L) and the diversity of use (V) determined the value of use (U), which together with the collection risk score (H) provided the risk of use (RU) score.The risk of use score was obtained by the following formula: RU = 0.5 (H) + 0.5 (U) x 10.
The value of the collection risk (H) was based on the biological consequences of collection according to the removed vegetal part (Table I).The value of the local importance (L) was determined by the percentage of the number of informants who indicated a particular species as medicinal and the diversity of use (V) was based on the number of types of use attributed to a species, varying its score of 1 To 10.Wood usage for some species was associated with the calculations by adding 10 points (Table I).
The score allowed to classify medicinal plants into three categories (Dzerefos and Witkowski 2001): Category 1: with value > 80, where species that require high priority conservation controlled collection, associated with the establishment of alternatives are framed; Category 2: where are included the species with between 60 and 80, with the potential to be collected according to the location and specific quotas; Category 3: species obtained value < 60, includes appropriate species for more intense sampling.

RICHNESS OF PLANT MEDICINAL, HABITS AND PARTS UTILIZED
It was recorded 42 native medicinal species belonging to 34 genera and 24 families (Table SI -Supplementary Material).Fabaceae (07 spp.) and Euphorbiaceae (04 spp.) had the largest number of species, and is also commonly found in other ethnobotanical work carried out in areas of caatinga (Cartaxo et al. 2010, Lós et al. 2012, Ribeiro et al. 2013, 2014b), suggesting that representatives of Fabaceae are extremely important for medicinal use and have great potential for bioactive compounds (Moerman and Estabrook 2003), as well as timber and fodder (Almeida et al. 2012).
In the habit of species, the arboreal predominated with 46%, followed by herbaceous (20%), scandent (15%), shrubs (11%) and subshrub (8%).The predominance of arboreal habit becomes indicative of the increasing use of native species for local therapeutic practices.This fact can be justified by the greater willingness of forest resources throughout the year and considerable resistance to sudden changes in the environment, such as the prolonged drought that occurs commonly in the Northeast (Silva and Proença 2008).
Turning attention to the parts of the plant, root stood out with 32.3% of the use of quotations, then peel and stem bark which together had 38.9% and sheet with 20.3%, the rest of the plant parts (flower, heart, fruit peel, fruit and latex) amounted to 8.5%.The roots represent the plant parts most used in studies by Marinho et al. (2011), different situation from other studies in caatinga areas that has among its main uses bark and the inner bark of the stem (Almeida andAlbuquerque 2002, Ribeiro et al. 2013).

AVAILABILITY OF MEDICINAL SPECIES
In a sampled forest fragment was recorded 28 species in 10 families and 24 genera (Table II).
Fabaceae (8 spp.) and Euphorbiaceae (4 spp.) were the most representative families in relation to number of species.These families are commonly found in floristic studies, structure and medicinal plant surveys in the caatinga area as having the highest number of species (Sampaio 1996, Figueiredo et al. 1997, Alcoforado-Filho et al. 2003), having medicinal species value (Albuquerque et al. 2009, Roque et al. 2010, Oliveira et al. 2010).A considerable demand for these families for medical  use may be linked to a wide diversity added the availability of the species in the environment.
Aspidosperma pyrifolium, Auriculata luetzelburgia and Anadenanthera colubrina were considered rare in the fragment, due to the occurrence of only one individual in the area evaluated.In other studies in the area of caatinga, A. pyrifolium and Anadenanthera colubrina presented values ranging from 04 to 1199 and 05 to 123 individuals respectively (Amorim et al. 2005, Araújo et al. 2012, Rodal et al. 2008, Souza and Medeiros 2013, Queiroz et al. 2006, Pereira et al. 2001, Pereira Júnior et al. 2012).
Among the species available, 21 had fewer than ten individuals in the sampled area, among them, Hymenaea courbaril, Amburana cearensis, Ximenia americana and Mimosa tenuiflora, having been frequently cited by informants studied, for medical use.The limited availability of the species in the area may is related to the frequent use of therapeutic practices and other purposes, thus deserving attention as the conservation of these species.
Among the medicinal species, 35 were not available in the area, some as Myracrodruon urundeuva, Cereus jamacaru, Passiflora cincinnata and Hybanthus ipecacuanha got the most nominations in ethnobotanical survey.Although these species are not available, the use of their relationship in the local community can still be recurring, because according to Torre-Cuadros and Islebe (2003), not all plants are used related to their availability, often acquired in other ways and in other environments.
According to Andrade et al. (2005) and Albuquerque et al. (2011), M. urundeuva is among the ten most important in phytosociological studies in northeastern Brazil, is most commonly found in protected areas, private and well maintained and hardly emerging in anthropogenic environments, which can be justified by their widespread use.According to Nunes et al. (2008), the unavailability of M. urundeuva perhaps related to an intense process of predatory exploitation, causing the devastation of their natural populations.

MEDICINAL SPECIES WITH PRIORITY OF CONSERVATION
Among all of the 28 species available, seven of them had medicinal use in the studied community and have associated timber use.For the same applied to the conservation priority score (CP) (Table III).Among them, six have bound to use perennial structures (bark, inner bark and roots), while a (Bauhinia cheilantha) using only overhead structures (Table SI).The collection of perennial structures of plants can affect the regenerative process of the species when it comes to clear them from the environment (Oliveira et al. 2007, Albuquerque et al. 2011, Júnior et al. 2011).According Albuquerque et al. (2010), the use of non-perennial structures is considered a less harmful activity to the species.
In the medicinal available species, Mimosa tenuiflora (CP = 91.25),Hymenaea courbaril (CP = 87.5),Ximenia americana (CP = 83.75)and Amburana cearensis (CP = 82.5)require high priority conservation (CP) and are included in category 1 (scores> 80) indicating that the collection of these species may present a risk of local extinction.All species in this category are not readily available in the art (DR = 0 ≤ 1), cited by less than 25% of the local responders (L = 1).M. tenuiflora is among the species that have great importance in the field of caatinga in the northeastern semi-arid region (Souza and Rodal 2010).In its natural habitat has been exploited for the production of poles and firewood, and also considered one of the important component of goat diet, sheep and cattle, especially grazing younger sprouts at the beginning of the rains, as well as dried leaves and pods during the period dry season (Pereira Filho et al. 2005).
Hymenaea courbaril has great economic and medicinal importance, with wide range of use (V = 10), and was cited by the majority of local informants also a source of income for many communities.Their exploitation is mainly caused by the timber and medicinal use, with the list of endangered species of the Brazilian Institute of Environment and Renewable Natural Resources (IBAMA 1992).
Ximenia americana and Amburana cearensis are included in the category of extinction risk, and their reported uses for bark and stem bark, which may use affects them negatively as well as the people who depend on these natural subsidies.These species are widely used in health care within the northeastern communities, often being reported its uses in ethnobotanical studies (Cartaxo et al. 2010, Ribeiro et al. 2014b), mainly linked to perennial structures such as bark and inner bark for own consumption or commercial purpose (Albuquerque andAndrade 2002, Ribeiro et al. 2013).
In category 2 (CP between 60 and 80), which are included the species with the potential to be collected according to the location and specific quotas were not registered any kind.Category 3 (value <60) were grouped three species Croton blanchetianus (CP = 50), Bauhinia cheilantha (CP = 46.25)and Pityrocarpa moniliformis (CP = 35), being considered appropriate to collect, it is believed that consumption no threat to conservation.C. blanchetianus and P. moniliformis proved widely available in the area (DR ≥7).C. blanchetianus showed high availability on site, although it had importance for the community (IL = 4) between the evaluated species and a wide Although some species do not appear as priorities to be preserved, most in this area are at risk of collection, being exploited their perennial parts: bark, inbark and roots, a fact that may compromise the conservation of these species, and this form of management improper, possibly already manifested its effects, and may be related to the scarcity of some species of reports before easily found.
According to Albuquerque et al. (2011), estimate priority species for conservation is a useful tool in helping communities to conservation stamp decisions about environmental resources favoring growth studies related to this subject that has risen in ethnobotany literature (Dhar et al. 2000, Dzerefos and Witkowski 2001, Oliveira et al. 2007, Albuquerque et al. 2010, Júnior et al. 2012, Ribeiro et al. 2013).
Ecology and genetics information in natural populations of tropical tree species are incipient in the literature, due to the high diversity and complexity of species, causing difficulties in sampling and in the appropriate methodologies for their study.This knowledge is essential for the understanding of the genetic structure of populations and, therefore, for the design of strategies for conservation, breeding and sustainable management (definition of stock size, adequate management of species, recovery of degraded areas, collection of seeds for planting with native species) (Kageyama et al. 2003).
The pressure on the genetic resources of the caatinga biome is quite pronounced, either due to the socio-economic conditions of the inhabitants or due to the pressure to establish productive activities.The first damage occurs due to the gradual loss of genetic variability for all species of the biome, which may result in a second disappearance of a species under intense use.There have been few studies on the collection, use, characterization, phylogenetic and genetic studies, use of derivatives and pre-improvement of endemic or spontaneous species in the region (EMBRAPA 2000).
Santos et al. ( 2007) (Amburana cearensis (Fr.Allem.)AC Smith, Myracrodruon urunueva M. Allem., Schinopsis brasiliensis Engl.and Spondias tuberosa) concluded that these species are not uniformly distributed throughout the Brazilian semiarid region, suggesting that the need for a greater number of areas for in situ preservation of the genetic variability of the species studied.Positive relationships between genetic distances and ecogeographic regions have been reported for populations of Amburana cearensis, Myracrodruon urundeuva and Schinopsis brasiliensis (Santos et al. 2007).
Strategies for conservation of genetic resources can be defined based on the information obtained with the DNA markers: when the variability is within the populations, a larger network of environmental preservation areas (APAs) is needed for in situ preservation of genetic variability; when the variability is between the regions, that is, when there is grouping of individuals independently of the collection region, it is indicated that few APAs are necessary (Santos et al. 2007).

CONCLUSIONS
The study presented a considerable amount of native medicinal species used, showing that the informants are knowledgeable and users of the local flora.However, the low number of medicinal species available and the small number of individuals may be related not only to medicinal or other uses, but also to the gradual loss of genetic variability for the biome species, which may result in a second disappearance of a given species under intense use.Strategies that result in establishing a greater number of areas for in situ preservation or sampling of a smaller number of individuals in various landscape units should be considered for ex situ preservation of genetic variability.
Among the species, Mimosa tenuiflora, Hymenaea courbaril, Ximenia americana and Amburana cearensis were considered priority for conservation, since they presented high diversity of use and collection risk.In this way, it is necessary to develop conservation practices of caatinga remnants, seeking improvements in the quality of the biome, and also as a strategy for the recovery of endemic species that would be important for the health of the local communities that use them.
, situated in South mesoregion of Ceará state, with an area of 577 square kilometers (IBGE 2010).It makes boundaries with some other cities like Aurora, Barro, Mauriti, Brejo Santo, Abaiara and Missão Velha.It has a hot tropical semiarid climate with annual average temperature of 26 °C.The annual average rainfall is 939 mm, with the rainy season from February to April.The relief includes Araripe and backwoods depression.The soils are mostly litholic, read-yellow podizolic, and Vertisol (IPECE 2015).Its vegetation consists of forest Deciduous Thorny and semi deciduous forest Tropical Rain (IPECE in 2012).

TABLE I Criteria and scores used to calculate priorities conservation of medicinal plants arising of the phytosociological survey in the community Nazaré, Milagres-CE.
Collection of perennial aerial structures such as leaves, which may affect the plant's energetic investment, survival, and reproductive success in the long term.4Collection of transitory structures as flowers and fruits.The regeneration of the population may be altered in the long term by collecting the seed supply, but the individual itself is not affected.

TABLE II List of species recorded in survey phytosociological in the Nazaré community, City of Milagres, Ceará, Brazil.
N: Number of individuals; RD: relative density; RDO: relative dominance; RF: relative frequency; IV: importance value; No of sample.MARIA O. SANTOS et al.