Ecogeographic research and essential oil production of Medusantha martiusii (Benth.) Harley & J.F.B.Pastore (Lamiaceae)

The semiarid region of Brazil is marked by scarce rainfall and high temperatures. The Caatinga biome, established in this region, has great diversity of plants with economic potential and applications, such as in herbal medicine. Plant representatives include those of the family Lamiaceae, which has 240 genera and 7200 species. The essential oil of the species Medusantha martiusii, popularly known as “alfazemas de caboclo”, has often been found to have biological activities, such as cytotoxic, antimicrobial and insecticidal effects, thus making this species economically important. The objective of this study was to characterize the climatic, geographical and edaphic aspects of sites where M. martiussi naturally occurs in the state of Bahia in order to understand the possible relationships and interactions between the environment and plant growth, development and production of essential oils. Vector files with climate, geomorphology, phytophysiognomy, and soil data were examined and the data were systematized and analyzed. The species occurs in semiarid areas with nutrient-poor, acidic and well-drained soils. The species has broad range of thermal adaptation, occurring from mountainous regions with high relief to low altitudes and in climatic zones characterized by scant and poorly distributed rainfall. The essential oil content showed a quantitative variation across the surveyed sites, with an average of 2.07% by dry weight of leaves and flowers, and a moderate and significant interaction of the essential oil with Fe and Zn concentrations present in the soil were also observed.