In view of the increasing global challenge of bacterial resistance, there exists an urgent need for the rationale development of antibacterial compounds with either novel or multiple mechanisms of action. Two chalcone-derivatives, F1 and F23, demonstrated MICs within the range of 16 to >512 μg/ml against two plant pathogens (P. caratovoram and C. michiganensis subsp. michiganensis) as well as important clinical bacterial species. Both compounds displayed an MIC of 32 μg/ml against quinolone-resistant S. aureus. Whilst possessing weak activities individually, each semi-synthetic agent displayed notable synergistic action with polymyxin B against S. aureus, C. violaceum, E. coli and Ps. aeruginosa, thereby recording FICs within the range of <0.093 to 2 that indicated the existence of synergism in some instance. These chalcone compounds applied with polymyxin B displayed a notable FICindex of <0.093 against the Neisseriaceae C. violaceum, and a potential noteworthy capacity to extend the spectrum of activity of the latter antibiotic to include Gram-positive S. aureus species. F1 inhibited staphylococcal replication in broth and the combination of either of both chalcone-derivatives with polymyxin B instituted a metabolic blockage in S. aureus and other bacterial species as determined through a modified MTT reduction assay. The combined agents inflicted major disruptions to the S. aureus cytoplasmic membrane bilayer as evidenced by the release of intracellular potassium as well as the influx of Sytox Green fluorescent stain. Notable levels of cell membrane potential dissipation, leakage of intracellular potassium ions and blockage of reducing enzymes activities occurred within the first 30 minutes, well in advance of significant loss in cell viability that was recorded usually after 4 – 8 hours, suggesting these activities were prerequisites to cell death. In erythrocyte lysis assay, the synergistic combinations of 128 μg/ml of either of both chalcone derivatives with 128 μg/ml polymyxin B displayed the lowest degree of haemolysis, followed by that occurring with 32 μg/ml of the chalcone-derivatives combined with 256 μg/ml of the polypeptide antibiotic. In conclusion, further structure activity modifications aimed at improving the aqueous solubility of these chalcone-derivatives as well as the antibacterial activity recorded for certain combination concentrations of polymyxin B with either of these semi-synthetic agents may be required before considerations are made for the possibility for potential external formulations. Such preparations may include antiseptic creams, lotions, ointments, as well as aerosols that can be applied with nebulizers in targeted delivery for such cases like cystic fibrosis.

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Made available in DSpace on 2015-05-14T13:21:30Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 12264651 bytes, checksum: c1dad0a27d50ddb05acdcc8e21042b61 (MD5) Previous issue date: 2012-09-11 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / In this work the potential of the Digital Image-Based Flame Emission Spectrometry (DIB-FES) is demonstrated through two completely separate applications. The first one consists in the indirect determination of three drugs in injectable form: sodium dicofenac, sodium dipyrone and clacium gluconate and the second in the combination of DIB-FES with Multiple Linear Regression (MLR) for the simultaneous determination of sodium and calcium in powder milk. Up to the present moment the literature does not report the use of traditional FES in: indirect determination of organic substances, simultaneous determination of analytes using a unique detector and overcoming the problem of spectral interference. In DIB-FES digital images of the flame are captured by webcam in its oxidant region (2,5 cm over the burner of the flame photometer) and are associated with the radiation emitted by metals present in the air-butane flame. Based on Red-Green-Blue (RGB) colour system, univariate and multivariate calibration models were developed, which were validated and then applied to real samples. In each application the results were compared with the results obtained by their respective reference methods. There were no statistically significant differences between the results when the paired t-test at the 95% confidence level. The estimated precision was better than the respective reference methods and accuracy was assessed by high values of bias and recovery rates between 97 and 104% in the two applications. / Neste trabalho a potencialidade da Espectrometria de Emissão em Chama Baseada em Imagens digitais (DIB-FES) é demonstrada por meio de duas aplicações completamente distintas. A primeira consiste na determinação indireta de três fármacos em soluções injetáveis: diclofenaco sódico, dipirona sódica e gluconato de cálcio e a segunda na combinação da DIB-FES com Regressão Linear Múltipla (MLR) para a determinação simultânea de sódio e cálcio em amostras de leite em pó. Até o presente momento a literatura não reporta a utilização da FES tradicional na: determinação indireta de substâncias orgânicas, determinação simultânea de analitos utilizando um único detector e superação do problema de interferência espectral. Na DIB-FES as imagens digitais da chama são capturadas pela webcam na região oxidante da mesma (2,5 cm acima do queimador do fotômetro) e estão associadas às radiações emitidas pelos metais presentes na chama ar-butano. Com base no sistema de cores Vermelho-Verde-Azul (RGB) foram desenvolvidos modelos de calibração univariada e multivariada, os quais foram validados e então aplicados em amostras reais. Em cada aplicação os resultados obtidos foram comparados com os resultados obtidos por seus respectivos métodos de referência. Não houve diferenças estatisticamente significativas entre resultados ao aplicar o teste t emparelhado ao nível de 95% de confiança. A precisão estimada foi melhor do que a de seus respectivos métodos de referência e a exatidão foi verificada por altas taxas de tendência e fatores de recuperação entre 97 e 104% nas duas aplicações.