Leaf essential oils and volatiles, histochemistry and micromorphology of Neomitranthes obscura (DC.) N. Silveira (Myrtaceae) growing in sandy coastal plains of Rio de Janeiro

We evaluated the chemical composition of leaf essential oils and volatiles in Neomitranthes obscura from different sandy coastal plains in Rio de Janeiro State. These sites present different environmental conditions. Leaf essential oils and volatiles were characterized by GC/MS after simultaneous distillation-extraction (SDE) and hydrodistillation (HD). All samples were rich in sesquiterpenes, mainly those from cadinene, germacrene and caryophyllene cyclization pathways, including (E)-caryophyllene, α-copaene, β-selinene, α-cadinene, selina-3,7 (11)-diene, germacrene B and caryophyllene oxide. Chemical profiles of N. obscura from different restingas presented high variation in the relative amount of some compounds. Fewer compounds were produced in a semi-arid climate (Massambaba restinga). Comparing samples collected during different seasons in Marambaia restinga, (E)-caryophyllene presented highly variable concentrations. The highest concentration was observed in August, which is the month of least rainfall. In contrast, germacrene B presented the lowest concentration in August. Leaf secretory structures were described using light and scanning microscopy and histochemical tests. The main sites of lipophilic and terpenoid accumulation are located in the secretory cavities of mesophyll. Our data indicate that the production of essential oils and volatiles in N. obscura is influenced by both plant developmental stage and environmental conditions.