Corymbia citriodora and Cymbopogon nardus essential oils samples were analyzed by GC and GC-MS and their qualitative and quantitative compositions established. The main component of essential oils of C. citriodora and C. nardus was citronellal, at 61.78% and 36.6%, respectively. The essential oils and citronellal were tested for their fumigant antifungal activity against Pyricularia (Magnaporthe) grisea, Aspergillus spp., and Colletotrichum musae. The minimum inhibitory concentration (MIC) ranged from 100 to 200 ppm for the essential oils and 25 to 50 mg·mL−1 for citronellal. The contact assay using the essential oils and citronellal showed growth inhibition of the three fungal species. However, a concentration of 1.47 mg·mL−1 only reduced the inhibition of Aspergillus growth to 90% at 14 days of exposure. For the fumigant assay, 0.05, 0.11, and 0.23 mg·mL−1 of essential oils and citronellal drastically affected growth of P. grisea, Aspergillus spp., and C. musae. Harmful effects on the sporulation and germination of the three fungi were seen, and there was complete inhibition at 0.15 mg·mL−1 with both oils and citronellal. This showed that the crude component of essential oils of C. citriodora and C. nardus markedly suppressed spore production, germination, and growth inhibition of P. grisea, Aspergillus spp., and Colletotrichum musae.

Resumo: Neste estudo, os extratos metanólicos de dez espécies de plantas medicinais coletadas em Gurupi, Tocantins, Brasil, foram submetidos aos ensaios de neutralização dos radicais ABTS e DPPH, redução do ferro (FRAP) e poder redutor, para investigação do potencial antioxidante. Os resultados revelaram que as plantas avaliadas apresentam pronunciadas atividades antioxidantes, sendo as espécies Buchenavia tetraphylla, Buchenavia tomentosa e Lippia sidoides as que apresentaram as maiores atividades, bem como os maiores teores de compostos fenólicos e de flavonoides. Por meio da determinação dos coeficientes de Person, foi possível observar correlação entre os teores de compostos fenólicos e as atividades antioxidantes perante todos os ensaios. Por outro lado, não foram observadas correlações satisfatórias entre os teores de flavonoides e tais atividades, sugerindo que os compostos fenólicos são os principais contribuintes para o potencial antioxidante apresentado pelos extratos das plantas medicinais estudadas. Palavras-chave: Buchenavia; Lippia sidoides; Ensaios antioxidantes. AbstractIn this study, methanolic extracts of ten species of medicinal plants collected at Gurupi, Tocantins state, Brazil, were subjected to assays of neutralization of ABTS and DPPH radicals, ferric reducing antioxidant power (FRAP), and reducing power to investigate their antioxidant potential. The results revealed that the plants that were investigated exhibited strong antioxidant activities. The species Buchenavia tetraphylla, Buchenavia tomentosa, and Lippia sidoides displayed the highest activities, as well as the largest contents of phenolic compounds and flavonoids. Using Pearson's correlation coefficient, we could observe correlations between the contents of phenolic compounds and the antioxidant activities in all the assays. On the other hand, we could not observe satisfactory correlations between the flavonoid contents and these activities, which suggest that the phenolic compounds provide the main contributions to the antioxidant potential displayed by the medicinal plant extracts that were studied.

Fumonisins are mycotoxins (MTs) produced mainly by the fungus Fusarium verticillioides, the main pathogens of maize which cause ear rot. The aim of this work was to evaluate some factors that may lead to high fumonisin production by F. verticillioides in maize grains, correlating the pathogen inoculation method with different genotypes grown in four Brazilian states. Experiments were conducted in 2015–2016 in maize crops from experimental maize fields located in four distinct states of Brazil. Results showed that contamination by fumonisin mycotoxins occurred even on symptomatic or asymptomatic grains. In all municipalities, the samples showed levels of fumonisin B1 that were higher than would be tolerable for the human consumption of corn products (the current tolerance limit for fumonisin is 1.5 μg g−1). High severity of grains infected with F. verticillioides does not always show high concentrations of fumonisins. Environments with higher temperatures may influence the production of high concentrations of fumonisin in maize hybrids. Spray inoculation methods and inoculation at the center of spikes did not influence fumonisin concentrations. Results showed that the hybrids P3630H, P32R48 and P3250 presented higher disease severity, as well as higher mycotoxin levels in the studied locations with higher temperatures.

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Melon cultivation is frequently heavily reliant on synthetic fungicides, including products used to control gummy stem blight caused by Stagonosporopsis cucurbitacearum. The essential oils used in controlling plant pathogens may offer an alternative to chemical pesticides. This study evaluated the effectiveness of essential oils to control the gummy stem blight in melon plants. In vitro tests were carried out using essential oils obtained from ripe noni fruit (Morinda citrifolia) and dehydrated leaves of the following plants: lemon grass (Cymbopogon citratus), citronella grass (Cymbopogon nardus), basil (Ocimum basilicum) and Mexican tea (Chenopodium ambrosioides) at different concentrations. A synthetic fungicide was used as control treatment. Results showed that the essential oils from noni and lemongrass had the highest effect on mycelial growth inhibition in S. cucurbitacearum. When applied on melon plants as a preventive measure, the essential oils from noni and lemongrass controlled gummy stem blight at the following concentrations: 0.03, 0.05, 0.1 and 0.3%. These results highlight the potential of essential oils to manage melon fungal diseases, which may result in reduction of pesticide application.

The use of plant essential oils has been adopted as less hazardous to the environment and human health than synthetic insecticides used for the control of insects that transmit diseases. Despite of exerting insecticidal activities against several insect disease vectors, the potential impacts on non-target organisms exerted by essential oils extracted from Lippia sidoides (Cham.) have not received adequate attention. Here, we evaluated the susceptibility and potential changes in consumption rates of honey bees, Apis mellifera (L.), when exposed to essential oils extracted from L. sidoides. Was exposed forager bees to honey syrup (50% v/v) containing L. sidoides essential oil for 5 h. After this exposure period, the bees received regular honey syrup for another 19 h period. Six essential oil concentrations was used, namely 1.0, 1.5, 2.0, 2.5, 3.0 and 3.5 µL of essential oil/mL of syrup, and evaluated the syrup consumption and bees mortality in both periods (at the 5th and 24th h). The results reveal that independent of the essential oil concentration, the forager bees fed significantly less on L. sidoides essential oil-containing honey syrup. However, feeding on L. sidoides essential oil-containing honey syrup did not cause significant mortality when compared with bees that were not exposed to the essential oils. Thus, the results demonstrate that L. sidoides essential oils exhibited adequate selectivity against honey bees.

The objective of this study was to evaluate the transmissibility of F. verticillioides, in corn seeds, when inoculated in different phenological stages. The plants were inoculated with the pathogen at the following stages: V7, V9, R1, R2, R4, and R6. The experiments were conducted in pots, in a completely randomized design, with six replications. The fungus infection rate in the seeds was verified through the health test (Blotter Test). The significance of the contrast between the phenological stages and in the two experiments (rainy season and dry season), and productivity showed plant-seed transmission of F. verticillioides in all phenological stages. The PCR technique was able to reveal up to the lowest level, 1% incidence of F. verticillioides in corn seeds. There was a significant difference between the times of plant inoculation and the incidence of the fungus in the seeds. Plants inoculated in the reproductive phase transmitted F. verticillioides for seeds with the highest rate of infection, in the two experiments, in the rainy season (V7 - 48; V9 - 46; R1 - 77.33; R2 - 84; R4 - 96; R6 - 96.67; and Test - 14.67%), and dry season (V7 - 46.67; V9 - 66; R1 - 75.33; R2 - 95.33; R4 - 98; and R6 - 97.33%). In this way, the present work demonstrated that in the reproductive phenological stages R2, R4, and R6, the corn plant was more susceptible to infection with F. verticillioides, and that it also resulted in a decrease in grain productivity.

PHYSICAL AND CHEMICAL CHARACTERIZATION OF ESSENTIAL OIL OF Siparuna guianensisAublet. Thermal and spectroscopic analyses of essential oil extracted from Siparuna guianensis Aublet, an aromatic plant belonging to medicinal ethnobotany family Siparunaceae, were carried out. The plant is known throughout the North and Northeast of Brazil by the name negramina and has wide application as a natural insect repellent. Thermogravimetric analyses were correlated with the Arrhenius Equation to provide kinetic parameters of evaporation, including activation energy and frequency factor. Differential scanning calorimetric analysis showed the presence of an exothermic oxidation peak, probably as a result of transformations and decomposition of the solid structure before melting.Keywords: negramina; Siparuna guianensis Aublet; essential oil; thermogravimetric analysis. INTRODUÇÃOSiparuna guianenis Aublet pertencente à família Siparunaceae é uma espécie neotrópica utilizada para indicações etnobotânicas e para conservação de biomas. No Brasil, localiza-se, principalmente, no Cerrado, onde estas plantas são nativas e abundantes. No entanto, as suas reservas encontram-se ameaçadas por não estarem legalmente protegidas. 1 É possível que, num futuro próximo, esta e outras espécies não possam ser encontradas e tampouco estudadas, especialmente por suas características popularmente tidas como terapêuticas. Óleos essenciais de folhas frescas e secas de S. guianensis são extraídos para diversos fins, sendo que sua composição pode mudar conforme a região e as estações do ano. 1De uma forma geral, os óleos essenciais são comercialmente importantes devido à presença de terpenóides, alcalóides e compostos fenólicos em grandes quantidades e aos seus usos em indústrias de condimentos, perfumes, drogas e outros. Conforme Croteau (2002) 2 e seus colaboradores, existem em torno de 55 mil terpenóides já isolados fazendo parte tanto do metabolismo primário quanto do secundário deste gênero de planta com, aproximadamente, 12 mil alcalóides e 8 mil compostos fenólicos já reconhecidos. 2A principal reação de decomposição dos extratos vegetais está relacionada com a oxidação dos seus compostos quando os mesmos são processados inadequadamente. Em geral, a presença de luz, oxigênio, calor e umidade dificultam a conservação dos óleos essenciais, sendo que, para manter sua qualidade, um armazenamento apropriado é de fundamental importância. 3Altas temperaturas promovem a oxidação dos óleos, o que, consequentemente, seguem para uma oxi-polimerização e uma decomposição termo-oxidativa. 4 A estabilidade destes óleos tornase um fator importante a ser considerado, pois suas propriedades são utilizadas para a produção de alimentos, aromatizantes, dentre outras. A oxidação é uma reação exotérmica que pode ser medida por análise térmica.5 Os métodos termoanalíticos são empregados para o controle da qualidade dos óleos vegetais, os quais podem fornecer informações relevantes a respeito de sua estabilidade quando em aquecimento. Assim, Dyszel (1990Dyszel ( , 1993,...