Percorrer por autor "Dantas, Daniela"
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- Electrochemical characterization of imidazole-based carboxamidrazones in aqueous and organic solutions and structure-activity relationshipPublication . Rodrigues, Rui; Dantas, Daniela; Carvalho, Filipe; Ribeiro, Ana; Zille, Andrea; Silva, Renata; Remião, Fernando; Dias, Alice; Pinto, Eugénia; Cerqueira, Fátima; Geraldo, Dulce
- Mechanism and structure-activity relationship of the antimicrobial imidazole-based carboxamidrazonesPublication . Dantas, Daniela; Rodrigues, Rui; Carvalho, Filipe; Ribeiro, Ana; Zille, Andrea; Silva, Renata; Remião, Fernando; Geraldo, Dulce; Pinto, Eugénia; Cerqueira, Fátima; Dias, Alice
- Mechanism of antifungal activity by 5-aminoimidazole-4-carbohydrazonamide derivatives against candida albicans and candida kruseiPublication . Cerqueira, Fátima; Maia, Marta; Gabriel, Carla; Medeiros, R.; Cravo, Sara; Ribeiro, Ana Isabel; Dantas, Daniela; Dias, Alice Maria; Saraiva, Lucília; Raimundo, Liliana; Pinto, EugéniaSystemic mycoses are one major cause of morbidity/mortality among immunocompromised/debilitated individuals. Studying the mechanism of action is a strategy to develop safer/potent antifungals, warning resistance emergence. The major goal of this study was to elucidate the mechanism of action of three (Z)-5-amino-N’-aryl-1-methyl-1H-imidazole-4-carbohydrazonamides (2h, 2k, 2l) that had previously demonstrated strong antifungal activity against Candida krusei and C. albicans ATCC strains. Activity was confirmed against clinical isolates, susceptible or resistant to fluconazole by broth microdilution assay. Ergosterol content (HPLC-DAD), mitochondrial dehydrogenase activity (MTT), reactive oxygen species (ROS) generation (flow cytometry), germ tube inhibition and drug interaction were evaluated. None of the compounds inhibited ergosterol synthesis. Ascorbic acid reduced the antifungal effect of compounds and significantly decreased ROS production. The metabolic viability of C. krusei was significantly reduced for values of 2MIC. Compounds 2h and 2k caused a significant increase in ROS production for MIC values while for 2l a significant increase was only observed for concentrations above MIC. ROS production seems to be involved in antifungal activity and the higher activity against C. krusei versus C. albicans may be related to their unequal sensitivity to different ROS. No synergism with fluconazole or amphotericin was observed, but the association of 2h with fluconazole might be valuable due to the significant inhibition of the dimorphic transition, a C. albicans virulence mechanism.
- Synergistic antimicrobial activity of silver nanoparticles with an emergent class of azoimidazolesPublication . Ribeiro, Ana Isabel; Dantas, Daniela; Carvalho, Luís Filipe; Padrão, Jorge; Silva, Renata; Remião, Fernando; Pinto, Eugénia; Cerqueira, Fátima; Dias, Alice; Zille, AndreaThe combination of two or more agents capable of acting in synergy has been reported as a valuable tool to fight against pathogens. Silver nanoparticles (AgNPs) present a strong antimicrobial action, although their cytotoxicity for healthy cells at active concentrations is a major concern. Azoimidazole moieties exhibit interesting bioactivities, including antimicrobial activity. In this work, a class of recently described azoimidazoles with strong antifungal activity was conjugated with citrate or polyvinylpyrrolidone-stabilized AgNPs. Proton nuclear magnetic resonance was used to confirm the purity of the compounds before further tests and atomic absorption spectroscopy to verify the concentration of silver in the prepared dispersions. Other analytical techniques elucidate the morphology and stability of AgNPs and corresponding conjugates, namely ultraviolet-visible spectrophotometry, scanning transmission electron microscopy and dynamic light scattering analysis. The synergistic antimicrobial activity of the conjugates was assessed through a checkerboard assay against yeasts ( and ) and bacteria ( and ). The conjugates showed improved antimicrobial activity against all microorganisms, in particular towards bacteria, with concentrations below their individual minimal inhibitory concentration (MIC). Furthermore, some combinations were found to be non-cytotoxic towards human HaCaT cells.