Rafaela Karin Lima

Influência da luz e da temperatura sobre a oxidação do óleo essencial de capim-limão (Cymbopogon citratus (D.C.) Stapf)

The identification of the chemical compounds of the essential oil was performed with a gas chromatograph coupled to a mass spectrometer. The oil was left in the presence and absence of light and submitted to different temperatures to evaluate its stability. The yields of the major compounds were evaluated every fifteen days. Citral and myrcene, the major compounds of the essential oil, were degraded over time in both the presence and absence of light, but temperature only influenced the degradation of myrcene.

Atividade inseticida do óleo essencial de pimenta longa (Piper hispidinervum C. DC.) sobre lagarta-do-cartucho do milho Spodoptera frugiperda (J. E. Smith, 1797) (Lepidoptera: Noctuidae)

The objectives of this research were to evaluate the chemical composition and bioactivity of the essential oil from the longpepper leaves (Piper hispidinervum) and its effect on the comportment and/or mortality of the fall armyworm (Spodoptera frugiperda). The essential oil was obtained by steam stream distillation, using the modified Clevenger apparatus, the chemical composition was analyzed by GC-MS and GC. Tests of ingestion and topical application in fall armyworm of 1 st and 3 rd instar were made. The results showed that the long-pepper essential oil has insecticide activity on S. frugiperda, causing mortality and food reduction, and safrole (82%) as its majority constituent. Mortality was found in the ingestion test in larvae of 1 st instar LC 50 = 16.2 mg/mL for larvae of 3 rd instar LC 50 = 9.4 mg/mL, with reduced food CD 50 = 0.72 mg/mL; and acute toxicity test of the contact topic with LD 50 = 277.91 μg/larvae, after an interval of 96 hours, neurotoxicity symptoms were also observed, as knock-down effect.

Efeito do óleo essencial de pimenta longa (Piper hispidinervum C. DC) e do emulsificante Tween® 80 sobre o crescimento micelial de Alternaria alternata (Fungi: Hyphomycetes)

The object of this work was to evaluate the effectof essential oils from Long-pepper leaves Piper hispidinervum on the mycelial growth of Alternaria alternata and to analyze the influence of emulsifier Tween® 80 concentration in the control of this phytopathogen. The essential oil was obtained by steam stream distillation, using a modified Clevenger apparatus, and the chemical composition was analyzed by gas chromatography coupled to mass spectroscopy GC-MS and GC. For biological tests, the bioanalytical in vitro method was used, observing the growth or inhibition of such phytopathogen in BDA culture media, in the presence of different essential oil concentrations (0, 100, 250, 500, e 1000 mgL -1) under different Tween® 80 concentrations. Factorial scheme with four repetitions, in entirely randomized outline was adopted. The essential oil of Long-pepper inhibited the micellial growth of the A. alternata fungus at all of the concentrations tested. A 100% inhibition at the 1000 mgL -1 concentration was observed, and the percentage of emulsifier (Tween® 80) influenced the fungitoxic activity at the 250 mgL-1 and 500 mgL -1 concentrations of the essential oil.

Composition of the essential oil from the leaves of tree domestic varieties and one wild variety of the guava plant (Psidium guajava L., Myrtaceae)

The compositions of the essential oils from the leaves of three domestic varieties of the guava tree Psidium guajava L. (Paluma, Seculo XXI and Pedro Sato) and of one wild variety were compared. Essential oils were extracted by steam distillation, the components were identified by gas chromatography coupled to mass spectrometry GC-MS, and the apparent concentrations were determined by gas chromatography with a flame ionization detector. The results demonstrated that the three essential oils contained many common substances with a prevalence of 1,8-cineole, whereas the essential oil of the Paluma variety contained 1,8-cineole (42.68%) as the major constituent, as well as α-terpineol (38.68%). The principal components of the essential oil of the Seculo XXI variety were 1,8-cineole (18.83%), trans-caryophyllene (12.08%), and selin-11-en-4-αol (20.98%), while those of the Pedro Sato variety and of the wild plant were 1,8-cineole (17.68%) and (12.83%), caryophyllene oxide (9.34%) and (9.09%), and selin-11-en-4-α-ol (21.46%) and (22.19%), respectively.

Caracterização química do óleo essencial de folhas de goiabeira (Psidium guajava L.) e seus efeitos no comportamento da lagarta-do-cartucho do milho Spodoptera frugiperda (J. E. Smith, 1797) (Lepidoptera: Noctuidae)

The aim of this research was to obtain and characterize essential oil from leaves of Psidium guajava cv. Pedro Sato, and its possible effects on fall armyworm Spodoptera frugiperda behavior. The essential oil was obtained through steam distillation, by using a modified Clevenger apparatus, and the chemical composition was later analyzed by gas chromatography coupled to mass spectroscopy GC-MS. In order to evaluate the essential oil effect on the armyworm of 1st instars behavior, four treatments were tested; two with oil at 0.01 and 0.001 % in ethanol/water 1:1 concentration; two controls with water and the other with ethanol/water 1:1. The results showed that the above analyzed essential oil constituted of a-terpineole (0.9%), 1,8-cineole (7.0%), â-caryophyllene (7.2%) and the caryophyllene oxide (13.8%). It was also found that the essential oil showed a repellent effect toward the fall armyworm at 0.01% concentration.

Efeito de doses de silício sobre a produtividade e características agronômicas da soja [Glycine max (L.) Merrill]

A soja [Glycine max (L.) Merrill] e o principal produto agricola da exportacao brasileira, portanto, torna-se importante a realizacao de estudos que contribuam para a minimizacao dos efeitos que possam causar a diminuicao do rendimento e a depreciacao da qualidade dessa oleaginosa, como a ocorrencia de pragas e doencas, problemas com a fertilidade do solo e adversidades climaticas, entre outros. Sabe-se que as plantas diferem na sua capacidade de absorver silicio (Si), sendo assim diferentemente classificadas. A influencia do Si no desenvolvimento vegetativo em plantas de soja ainda e pouco conhecida, existindo poucos estudos descritos na literatura. Diante disso, objetivou-se, neste trabalho, avaliar a resposta da soja a diferentes doses de Si no plantio, por meio da produtividade e caracteristicas agronomicas das plantas no campo. O delineamento experimental utilizado foi o de blocos casualizados (DBC), com tres repeticoes, tendo como tratamentos 11 doses de Si (0, 50, 100, 150, 200, 250, 300, 350, 400, 450 e 500 kg ha-1) na semeadura da soja, cultivar BRS MG 68 Vencedora. As doses de Si utilizadas nao proporcionaram aumentos significativos na produtividade de graos, peso de mil sementes, numero de sementes por legume, o mesmo nao se verificando com o numero de legumes por planta, altura de planta e altura de insercao do primeiro legume que apresentaram efeito significativo, com o aumento das doses nessas caracteristicas. A aplicacao de Si nao proporcionou efeitos fitotoxicos visiveis na planta de soja.