BACKGROUND Recent studies showed that essential oils from different pepper species (Piper spp.) have promising leishmanicidal and trypanocidal activities. OBJECTIVES In search for natural compounds against Trypanosoma cruzi, different forms of the parasite were incubated for 24 h at 28ºC or 4ºC with Piper aduncum essential oil (PaEO) or its main constituents linalool and nerolidol. METHODS PaEO chemical composition was obtained by GC-MS. Drug activity assays were based on cell counting, MTT data or infection index values. The effect of PaEO on the T. cruzi cell cycle and mitochondrial membrane potential was evaluated by flow cytometry. FINDINGS PaEO was effective against cell-derived (IC50/24 h: 2.8 μg/mL) and metacyclic (IC50/24 h: 12.1 μg/mL) trypomastigotes, as well as intracellular amastigotes (IC50/24 h: 9 μg/mL). At 4ºC - the temperature of red blood cells (RBCs) storage in blood banks - cell-derived trypomastigotes were more sensitive to PaEO (IC50/24 h = 3.8 μg/mL) than to gentian violet (IC50/24 h = 24.7 mg/mL). Cytotoxicity assays using Vero cells (37ºC) and RBCs (4ºC) showed that PaEO has increased selectivity for cell-derived trypomastigotes. Flow cytometry analysis showed that PaEO does not affect the cell cycle of T. cruzi epimastigotes, but decreases their mitochondrial membrane potential. GC-MS data identified nerolidol and linalool as major components of PaEO, and linalool had trypanocidal effect (IC50/24 h: 306 ng/mL) at 4ºC. MAIN CONCLUSION The trypanocidal effect of PaEO is likely due to the presence of linalool, which may represent an interesting candidate for use in the treatment of potentially contaminated RBCs bags at low temperature.

RESUMOOs óleos essenciais apresentam potencial para serem empregados como bioherbicidas, possuindo vantagens em função da sua biodegradabilidade, elevada diversidade estrutural e reduzida resistência natural às plantas daninhas. Os óleos essenciais das folhas e dos rizomas de Hedychium coronarium, planta invasora exótica adaptada a diferentes regiões do Brasil, foram extraídos por hidrodestilação e caracterizados quimicamente por Cromatografia Gás-Líquido e Cromatografia Gás-Líquido/Espectrometria de Massas. As atividades alelopáticas foram determinadas pelas metodologias que avaliam os efeitos voláteis e o contato direto dos mesmos sobre a germinação de sementes e vigor de plântulas de alface. Os constituintes majoritários do óleo essencial das folhas foram o β-pineno (46,9%), o α-pineno (19,2%) e o β-cariofileno (13,2%) e o dos rizomas, o β-pineno (41,5%), o 1,8-cineol (23,6%) e o α-pineno (13,1%). Analisando os efeitos voláteis dos óleos essenciais, observou-se que o aumento das concentrações dos mesmos não alterou a primeira contagem de plântulas germinadas e a germinação total. Em relação ao IVG, à massa seca e ao comprimento das partes radiculares e aéreas das plântulas, o óleo essencial dos rizomas foi mais efetivo que o óleo essencial das folhas nas reduções da resposta das variáveis. Ao avaliar o efeito do contato direto dos óleos essenciais observou-se que ambos reduziram a resposta de todas as variáveis avaliadas e que, adicionalmente, o óleo dos rizomas provocou reduções superiores à do óleo das folhas em todas as variáveis. Estes resultados podem ser atribuídos ao maior conteúdo monoterpênico presente no óleo essencial dos rizomas, destacando-se a presença do 1,8-cineol.

ABSTRACTEssential oils have the potential to be used as bioherbicides, and possess the advantage of their biodegradability, high structural diversity and reduced natural resistance to weeds. The essential oils of the leaves and rhizomes of Hedychium coronarium, an exotic invasive plant adapted to different regions of Brazil, were extracted by hydrodistillation and characterised chemically by Gas-Liquid Chromatography and Gas-Liquid Chromatography/Mass Spectrometry. Allelopathic activity was determined using methodologies that evaluate the effects of volatility and direct contact on seed germination and seedling vigour in the lettuce. The major constituents of the essential oil from the leaves were β-pinene (46.9%), α-pinene (19.2%) and β-caryophyllene (13.2%) and from the rhizomes, β-pinene (41.5%), 1.8-cineole (23.6%) and α-pinene (13.1%). When analysing the volatile effects of the essential oils, it was seen that their concentration did not affect seedling first germination count or total germination. The essential oil from the rhizomes was more effective than the essential oil from the leaves in reducing seedling response for SGI, dry weight, and length of the roots and shoots. When evaluating the effect of direct contact with the essential oils, it was seen that both oils reduced the response of all the variables under evaluation, and that in addition, the oil from the rhizomes caused greater reductions than that from the leaves, again for all variables. These results can be attributed to the higher levels of monoterpenes present in the essential oil from the rhizomes, mainly the presence of 1.8-cineole.

Tendo em vista a importância dos óleos essenciais, objetivou-se, com este trabalho, avaliar a atividade antioxidante e os efeitos fungitóxicos do óleo essencial de capim-limão e do seu constituinte majoritário citral sobre a inibição micelial dos fitopatógenos Fusarium oxysporum cubense, Colletotrichum gloeosporioides, Bipolaris sp. e Alternaria alternata. A atividade antioxidante foi realizada, empregando os métodos de redução do radical livre DPPH e o ensaio de oxidação do sistema b-caroteno/ácido linoléico. Para cada metodologia, utilizou-se o delineamento inteiramente casualizado em esquema fatorial de 4 x 5, sendo quatro compostos (óleo essencial, citral, timol e α-tocoferol) e cinco concentrações (5; 10; 25; 50 e 100 µg L-1), com três repetições Os ensaios para verificação das atividades fungitóxicas foram realizados aplicando o teste de fumigação in vitro sobre a inibição micelial dos fungos fitopatogênicos estudados. Os tratamentos foram dispostos de forma inteiramente casualizada, com três repetições e em esquema fatorial com arranjo variável entre os fitopatógenos. O óleo essencial e o citral apresentaram pequena atividade antioxidante perante a metodologia que avalia a redução do radical estável DPPH, no entanto, perante a metodologia que emprega o sistema emulsificado β-caroteno/ácido linoléico estes compostos apresentaram atividades antioxidantes significativas. Nas atividades fungitóxicas, o óleo essencial e o citral apresentaram uma maior atividade sobre o fitopatógeno Alternaria alternata. Em relação aos valores de IC50 os menores valores apresentados pelo óleo essencial (75,83 µg mL-1) e pelo citral (58,24 µg mL-1) foram sobre o Bipolaris sp. O citral causou as maiores inibições miceliais, para todos os fitopatógenos.

Given the importance of essential oils, this study evaluated the antioxidant activity and fungitoxic effects of lemongrass essential oil and its main constituent citral on mycelial inhibition of phytopathogens Fusarium oxysporum cubense, Colletotrichum gloeosporioides, Bipolaris sp. and Alternaria alternata. The antioxidant activity was evaluated by employing the DPPH free radical reduction method and oxidation tests of the system β-carotene/linoleic acid. For each method, a completely randomized design in a 4 x 5 factorial arrangement was used with four compounds (essential oil, citral, thymol and α-tocopherol) and five concentrations (5; 10; 25; 50 and 100 Mg L-1), with three replicates. The tests to determine fungitoxic activities were performed by applying the in vitro fumigation test on mycelial inhibition of studied phytopathogens. The treatments were arranged in a completely randomized design with three replicates and a factorial arrangement. The essential oil and citral showed little antioxidant activity by the methodology that measures the reduction of the stable radical DPPH; however, by the methodology that employs the emulsified β-carotene/linoleic acid system, these compounds showed significant antioxidant activities. At fungitoxic activities, the essential oil and citral showed greater activity against the phytopathogen Alternaria alternata. When compared to the values of IC50, the lowest values presented by the essential (75.83 µg mL-1) and citral (58.24 µg mL-1) oils were found for Bipolaris sp. Citral caused the greatest mycelial inhibition on all phytopathogens.