Wettability and morphology of the leaf surface in cashew tree from the Amazon, Northern Brazil / Molhabilidade e morfologia da superfície da folha em cajueiro da Amazônia na Região Norte do Brasil

Leaves surfaces, which represent an interface with plants and the environment, have several structures with specific functions. Some foliar properties, including wettability and mechanical containment, are inferred in terms of cellular adaptation and the presence or absence of cuticular wax. Various morphological parameters, ranging from macro- to nano scales, are analyzed and contribute to the study of taxonomy, pharmacognosy, and ecology of plants. The aim of this paper was to analyze the effect and influence of epicuticular wax granules on the hydrophobicity of Anacardium occidentale L. leaf surfaces. Leaf specimens were directly examined with an environmental scanning electron microscope without metal coating. Images revealed epidermis ornament, stomata type, was, and trichomes. Static contact angle between water and the surface was also measured on both sides. On the adaxial side, an angle of 104.09° ± 0.95° was found, suggesting that adaxial surface is hydrophobic. On the abaxial side, the angle was 62.20° ± 1.60°, which indicates a hydrophilic nature, probably because of the greater amount of epicuticular wax on the adaxial leaf surface. The present investigation provided an important contribution to morphological and ultrastructural characterization of leaves of cashew tree, which is a plant of great medicinal and economic importance.

Superfícies de folhas têm diversas estruturas com funções específicas e contribuem para a relação delas com o meio ambiente. Algumas propriedades foliares, incluindo molhabilidade e contenção mecânica, são inferidas em termos de adaptação celular e da presença ou ausência de cera cuticular. Diversos parâmetros morfológicos, variando da macroescala até a nanoescala, são analisados e contribuem para o estudo de taxonomia, farmacognosia e ecologia de plantas. O objetivo deste trabalho foi analisar o efeito e a influência de grãos de cera epicuticular na hidrofobicidade da superfície de folhas de Anacardium occidentale L. Amostras de folha foram examinadas com um microscópio eletrônico de varredura ambiental sem recobrimento metálico. As imagens evidenciaram algumas características (epiderme, tipo de estômato, cera e tricomas). O ângulo de contato estático entre a água e a superfície também foi medido em ambos os lados. No lado adaxial, foi encontrado um ângulo de 104,09° ± 0,95°, sugerindo que esta é hidrofóbica. No lado abaxial, o ângulo foi de 62,20° ± 1,60°, que indica uma natureza hidrofílica, provavelmente devido à grande quantidade de cera epicuticular na superfície abaxial da folha. A presente investigação forneceu uma contribuição importante para a caracterização morfológica e ultra-estrutural de folhas de cajueiro, que é uma planta de grande importância econômica.

Hydroxylation of 1,8-cineole by Mucor ramannianus and Aspergillus niger

The monoterpenoid 1,8-cineole is obtained from the leaves of Eucalyptus globulus and it has important biological activities. It is a cheap natural substrate because it is a by-product of the Eucalyptus cultivation for wood and pulp production. In this study, it was evaluated the potential of three filamentous fungi in the biotransformation of 1,8-cineole. The study was divided in two steps: first, reactions were carried out with 1,8-cineole at 1 g/L for 24 h; afterwards, reactions were carried out with substrate at 5 g/L for 5 days. The substrate was hydroxylated into 2-exo-hydroxy-1,8-cineole and 3-exo-hydroxy-1,8-cineole by fungi Mucor ramannianus and Aspergillus niger with high stereoselectivity. Trichoderma harzianum was also tested but no transformation was detected. M. ramannianus led to higher than 99% of conversion within 24 h with a starting high substrate concentration (1 g/L). When substrate was added at 5 g/L, only M. ramannianus was able to catalyze the reaction, but the conversion level was 21.7% after 5 days. Both products have defined stereochemistry and could be used as chiral synthons. Furthermore, biological activity has been described for 3-exo-hydroxy-1,8-cineol. To the best of our knowledge, this is the first report on the use of M. ramannianus in this reaction.

Chemical composition and insecticidal activity of Cymbopogon citratus essential oil from Cuba and Brazil against housefly / Composição química e atividade inseticida do óleo essencial de Cymbopogon citratus de Brasil e Cuba contra mosca doméstica

Essential oil of Cymbopogon citratus collected from Brazil and Cuba was tested to a chemical characterization and then was tested on the post-embryonic development of Musca domestica. The chemical composition analysis by GC-MS of the oils from Brazil/Cuba allowed the identification of 13 and 12 major constituents respectively; nine of them common to both. In the both oils, the main components were the isomers geranial and neral, which together form the compound citral. This corresponds to a total of 97.92%/Brazil and 97.69%/Cuba of the compounds identified. The monoterpene myrcene, observed only in the sample of Cuba, presented a large relative abundance (6.52%). The essential oil of C. citratus (Brazil/Cuba) was dissolved in DMSO and tested at concentrations of 5, 10, 25, 50, 75 and 100% and citral was prepared by mixing 16.8 mg with 960 µL DMSO. Both essential oils and monoterpene citral were applied topically to newly-hatched larvae (1µL/larva). The results showed a lethal concentration (LC50) of 4.25 and 3.24% for the Brazilian and Cuban essential oils, respectively. Mortalities of larval and newly-hatched larvae to adult periods were dose-dependent for the two both oils as for monoterpene citral, reaching 90%. Both essential oils and citral caused morphological changes in adult specimens.

O óleo essencial de Cymbopogon citratus, coletado no Brasil e em Cuba, foi caracterizado quimicamente e testado no desenvolvimento pós-embrionário de Musca domestica. A análise da composição química dos óleos essenciais (Brasil/Cuba), por Cromatografia Gasosa acoplada ao espectrômetro de massa (GC-EM), permitiu a identificação de 13 e 12 componentes principais, respectivamente; nove deles comuns aos dois. Em ambos os óleos, os principais componentes foram os isômeros geranial e neral, que, juntos, formam o composto citral. Esse corresponde a um total de 97,92%/Brasil e 97,69%/Cuba dos compostos identificados. O monoterpeno mirceno, observado na amostra cubana, apresentou grande abundância relativa (6,52%). O óleo de C. citratus (Brasil/Cuba) foi dissolvido em DMSO, obtendo–se as concentrações de 5, 10, 25, 75 e 100%; e o citral (16,8 mg) foi misturando com 960mL de DMSO. Tanto o óleo essencial como o monoterpeno citral foram aplicados topicamente nas neolarvas (1µL/larva). Os resultados mostraram uma concentração letal (CL50) de 4,25% e 3,24% para o óleo essencial brasileiro e cubano, respectivamente. As mortalidades do período larval e o de neo-larva a adulto foram dose-dependentes, tanto para os óleos como para o monoterpeno citral, podendo chegar a 90%. Ambos os óleos essenciais e citral causaram alterações morfológicas nos espécimes adultos.