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URI permanente para esta coleçãohttps://locus.ufv.br/handle/123456789/11800
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Item Características físico-químicas de ácidos húmicos em diferentes etapas da vermicompostagem(Eclética Química, 2010) Reis, E. L.; Reis, C.; Brighenti, C. R. G.Amostras de materiais coletados em diferentes estádios de vermicompostagem foram submetidas a procedimentos de extração de ácidos húmicos. Técnicas de titulação potenciométrica, termogravimetria (DTG), difração de raios X e espectrofotometria no uv/visível e no infravermelho foram utilizadas no estudo desses materiais. Os dados de titulação foram submetidos ao ajuste por regressão não-linear, determinando-se, assim, cinco valores de pKa característicos de cinco classes de grupos tituláveis. Nas curvas DTG, foram observadas duas etapas, sendo a primeira característica da separação de estruturas alifáticas e, ou, alicíclicas e a segunda, a decomposição de estruturas aromáticas. A difratometria de raios X apresentou diferenças marcantes nos resultados, principalmente nos três primeiros picos onde parecem ocorrer reorganização estrutural e polimerização ao longo do processo de vermicompostagem. Os espectros do infravermelho não apresentaram diferenciação entre os espectros. Os valores da razão E4/E6 encontrados estão de acordo com os característicos dos ácidos húmicos, mas não fornecem informações que possam contribuir para a elucidação da estrutura e formação desses ácidos.Item Synthesis and phytotoxicity of 4,5 functionalized tetrahydrofuran-2-ones(Journal of the Brazilian Chemical Society, 2012-12) Resende, Gabriela C.; Alvarenga, Elson S.; Galindo, Juan C. G.; Macias, Francisco A.In this work we report a versatile synthesis of fourteen γ-lactones all structurally related, nine of which are novel compounds, accomplished from the readily available furfural. The phytotoxic activity of the synthesized compounds was evaluated in vitro by the influence on the growth of wheat coleoptiles. The percentages of inhibition were mostly small and not statistically different from control after the third dilution (100 µmol L-1). In general, α,β-unsaturated lactones presented better activities than the saturated ones. The most active compounds presented 51, 68 and 76% of inhibition in 1000 µmol L-1. The results indicate that regardless of saturation, the presence of the γ-lactone moiety is important for the bioactivity, but their presence has no implications with potency.Item Remoção dos corantes Reactive Blue 21 e Direct Red 80 utilizando resíduos de sementes de Mabea fistulifera Mart. como biossorvente(Revista Ambiente & Água, 2012-01) Silveira Neta, Julieta de Jesus da; Silva, Carlos Juliano da; Moreira, Guilherme Costa; Reis, César; Reis, Efraim LázaroNeste estudo empregou-se resíduos de Mabea fistulifera Mart. como bioadsorvente para a remoção dos corantes Reactive Blue 21 (RB 21) e Direct Red 80 (DR 80) em soluções aquosas e em amostras de efluentes reais fortificados com estes corantes. Foram investigados os ensaios da influência do pH, cinéticos e adsortivos para a remoção dos corantes por meio de uma série de experimentos de batelada. O bioadsorvente exibiu máxima adsorção em pH = 2,0 para ambos os corantes. O tempo de equilíbrio da adsorção foi estabelecido em 300 minutos para o DR 80 e 120 minutos para o RB 21. O modelo de Langmuir descreveu com maior fidelidade o comportamento do sistema sortivo, apresentando coeficiente de determinação (R 2 ) superior a 0,98. Por meio da Isoterma de Langmuir, foi possível obter a capacidade máxima de adsorção dos corantes Direct Red 80 e Reactive Blue 21 pelo bioadsorvente sendo encontrados os valores de 4,92 mg g-1 e 11,13 mg g-1 , respectivamente. O modelo cinético de pseudo-segunda ordem melhor descreveu o processo de adsorção do corante RB 21 sob o bioadsorvente, embora a difusão intra-partícula também esteja envolvida no mecanismo de adsorção. Já para o corante DR 80 o modelo de difusão de Morris e Weber sugeriu que a difusão intra-partícula é predominante em todo o processo de adsorção. Depois de otimizadas as condições adsortivas, o bioadsorvente foi empregado a amostras de efluentes têxteis reais fortificadas com soluções aquosas dos corantes, obtendo-se 85 % de remoção do RB 21 e 94 % de remoção do DR 80 na matriz do efluente.Item Síntese e avaliação da atividade antimicrobiana de furanonas halogenadas e de compostos análogos aos nostoclídeos(Química Nova, 2010) Barbosa, Luiz C. A.; Maltha, Célia R. A.; Demuner, Antônio J.; Pinheiro, Patrícia F.; Varejão, Jodieh O. S.; Montanari, Ricardo M.; Andrade, Nélio J.Considering the broad spectrum of biological activity of gamma-butyrolactone derivatives, we presented the synthesis of 3,4-dihalo-5-arylidenefuran-2(5H)-ones (17-21) and analogues (24-28) of the natural product nostoclide (7,8). Furanones 17-21 were synthesized from the condensation of aromatic aldehydes with lactones 14 and 15, that were obtained from mucobromic and mucochloric acids. Lactone 15 was converted into the intermediate 23 in 36% overall yield. Compound 23 was then transformed into the nostoclide analogues 24-28. Some of the compounds prepared showed antimicrobial activities against Escherichia coli, Staphylococcus aureus and Bacillus cereus comparable to commercial antibiotics.Item Influência dos constituintes químicos dos extratos de diferentes matrizes na resposta cromatográfica de agrotóxicos(Química Nova, 2010) Neves, Antônio Augusto; Queiroz, Maria Eliana L. R.; Starling, Maria Antônia V. M.; Pinho, Gevany Paulino de; Silvério, Flaviano OliveiraMultiresidue methods for pesticides monitoring by GC are commonly employed, however, it is well known that the presence of compounds of the matrix introduces errors during the quantiûcation. The main consequence of matrix effect is an increasing or decreasing analyte signal after the GC saturation with extracts of matrix. In this paper, the influence of constituents of nine matrices on the quantification of the four pesticides by GC-ECD was studied. Variation of signal was evaluated by PCA and HCA, and results showed that the constituents of tomato increased the signal (until 300%), while extracts of apple decreased (until -20%). Variation the analyte signal in the presence of the matrix in respect to the same analyte in solvent (standard solution) also was observed, mainly for liver extract (until 270%).Item Determinação de constituintes químicos em madeira de eucalipto por Pi-CG/EM e calibração multivariada: comparação entre redes neurais artificiais e máquinas de vetor suporte(Química Nova, 2011) Nunes, Cleiton Antônio; Lima, Claudio Ferreira; Barbosa, Luiz Cláudio de Almeida; Colodette, Jorge Luiz; Fidêncio, Paulo HenriqueMultivariate models were developed using Artificial Neural Network (ANN) and Least Square - Support Vector Machines (LS-SVM) for estimating lignin siringyl/guaiacyl ratio and the contents of cellulose, hemicelluloses and lignin in eucalyptus wood by pyrolysis associated to gaseous chromatography and mass spectrometry (Py-GC/MS). The results obtained by two calibration methods were in agreement with those of reference methods. However a comparison indicated that the LS-SVM model presented better predictive capacity for the cellulose and lignin contents, while the ANN model presented was more adequate for estimating the hemicelluloses content and lignin siringyl/guaiacyl ratio.Item Activity of essential oil of Lippia triplinervis Gardner (Verbenaceae) on Rhipicephalus microplus (Acari: Ixodidae)(Parasitology Research, 2013-02) Lage, Tiago Coelho de Assis; Montanari, Ricardo Marques; Fernandes, Sergio Antonio; Monteiro, Caio Márcio de Oliveira; Senra, Tatiane de Oliveira Souza; Zeringota, Viviane; Calmon, Fernanda; Matos, Renata da Silva; Daemon, ErikThe objective of this work was to characterize and investigate the acaricidal activity of the essential oil of the aerial parts of Lippia triplinervis at different concentrations on unengorged larvae and engorged females of Rhipicephalus microplus. The essential oil yielded 2.21 % (w/w to dry matter) and was composed mainly of carvacrol (31.9 %), thymol (30.6 %), and p-cymene (12.3 %). Two tests were performed to assess the acaricidal activity: the modified larval packet test, with concentrations of 2.5, 5.0, 10.0, 15.0, and 20.0 mg/mL and the female immersion test, with concentrations of 10.0, 20.0, 30.0, 40.0, and 50.0 mg/mL. There were ten repetitions for each concentration, and for each test, a control group was formed in which the ticks were treated with Tween 80 (20 mg/mL). The experimental groups were kept in a climate-controlled chamber (27 ± 1 °C and RH >80 %). The mortality of the larvae was above 95 % in all the groups tested and reached 100 % as of the 5.0 mg/mL concentration, while the control group exhibited 0 % mortality. In the female immersion test, there was a significant decline (p < 0.05) in the egg mass weight, egg production index, and hatching percentage starting at the concentration of 30.0, 40.0, and 20.0 mg/mL, respectively, and the control percentage at the concentrations of 40.0 and 50.0 mg/mL were above 90 and 95 %. The L. triplinervis oil as thus an alternative source of the monoterpenes thymol, carvacrol, and p-cymene, and its toxicity on R. microplus larvae and females makes it promising possibility for control of this tick.Item Evaluation of the catalytic activity of oxide nanoparticles synthesized by the polymeric precursor method on biodiesel production(Journal of Materials Research, 2012-12-14) Nascimento, Gabriela Santilli do; Mambrini, Giovanni Pimenta; Paris, Elaine Cristina; Peres, Juliano Aurelio; Colnago, Luis Alberto; Ribeiro, CaueThis paper shows a comparison between different nanostructured oxides, obtained by polymeric precursor method, regarding their activity for biodiesel conversion from oil–methanol mixtures. The basicity/acidity and surface area (SA) of the oxides were taken in account to analyze the catalytic activity in the transesterification reaction. The temperature dependence for the heterogeneous catalysts was analyzed, where only CaO showed activities at 70 °C (∼98% of conversion), while the other oxides, SnO2, ZnO, TiO2, CaTiO3, were observed active only at 150 °C for the reaction parameters adopted. The results revealed that the highest activity observed is not associated to SA only but mainly with the surface basicity. This suggest that, for oxides synthesized by the polymeric precursor method, the surface basicity surpasses the particle size effects in catalysis in a way to promote the transesterification reaction.Item Composition, antifungal activity and main fungitoxic components of the essential oil of Mentha piperita L.(Journal of Food Safety, 2011-12-11) Freire, Marcelo Moreira; Jham, Gulab Newandram; Dhingra, Onkar Dev; Jardim, Carolina Marangon; Barcelos, Rosimeire Coura; Valente, Vânia Maria MoreiraTwenty-one components (93.9% of the total chromatographic peak area) were tentatively identified in the essential oil (EO) of Mentha piperita L., based on Kováts retention indices (RIs), a mass spectral database (gas chromatography-mass spectrometry, GC-MS) and visual comparison of the mass spectra of the sample peaks with those of the database. The presence of 15 compounds (corresponding to 90.7% of the total chromatographic peak area) was confirmed by authentic standards. The EO presented a good activity against the following important postharvest deteriorating fungi: Aspergillus flavus, Aspergillus glaucus, Aspergillus niger, Aspergillus ochraceous, Colletotrichum gloesporioides, Colletotrichum musae, Fusarium oxysporum and Fusarium semitectum. At a concentration of 0.2% of the EO, all the fungi were completely inhibited, except for A. glaucus and C. musae which were inhibited 90 and 98%, respectively. TLC-bioautography yielded three subfractions that prevented fungal growth, suggesting the presence of antifungals. Bioassay data of the crude EO were compared with those of the three subfractions. Based on these tests, it was concluded that several fungitoxics were responsible for the antifungal activity of M. piperita, with the principal ones being menthone, neomenthol, menthol and carvone. However, participation of other compounds cannot beruled out. This is the first study in the literature that presents data on the activity of the crude EO against eight important postharvest deteriorating fungi, characterizing the amounts and types of comounds. In addition, also for the first time, the active fractions of the crude EO were isolated, identified and the components quantified. More detailed fungal tests are being conducted to confirm the tentative preliminary antifungal data.Item Essential oils from pequi fruits from the brazilian Cerrado ecosystem(Food Research International, 2013-11) Geőcze, K. C.; Barbosa, L. C. A.; Fidêncio, P. H.; Silvério, F. O.; Lima, C. F.; Barbosa, M. C. A.; Ismail, Fyaz M. D.The composition of the essential oils of pequi fruits gathered from the Brazilian Cerrado ecosystem in the states of Maranhão (MA), Minas Gerais (MG) and Tocantins (TO) was investigated. The oils were obtained by steam distillation, and each component was speciated using GC-MS. The oil content varied from 0.13% to 1.15%. Interestingly, the major substance found within samples from two of the states was ethyl hexanoate (MA, MG), whereas isopropyl hexanoate and isopentyl-2-methylbutanoate were specific for the samples from TO. Both principal components analysis (PCA) and hierarchical cluster analysis (HCA) were used for exploratory analysis of the oils, and, consequently, the pequi fruits were classified according to their place of origin. The PCA showed that 51.5% of the variance accumulated in the PC1 and PC3, and the group formation obtained using HCA confirmed that the oil composition is influenced by geographic and/or plant genetic factors. Such analyses could assist in the selection of more flavoursome and healthy variants of pequi.