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- Domino synthesis of a new class of red-shifted and antimicrobial imidazole-based azo dyes from 5-aminoimidazole-4-carboxamidrazones.Publication . Pereira da Silva, Mariana; Silva, Bárbara; Costa, Inês; Coutinho, Paulo; Cerqueira, Fátima; Pinto, Eugénia; Dias, AliceCombining antimicrobial activity with halochromic properties offers an enticing opportunity to both combat and detect microbial infection in the medical field. Previous research has identified a class of compounds that demonstrate potent antimicrobial activity, particularly against pathogenic yeasts. Notably, these compounds also exhibit vibrant pink-blue colours and a halochromic behaviour within the therapeutic pH range. Aiming at developing a more sustainable synthetic method and to generate better red-shifted and pH-responsive imidazole-based azo dyes, a new domino reaction was discovered yielding a novel class of green-coloured 2-aminoimidazole azo-dyes. A strategy based on circular chemistry was achieved by introducing the accessible and environmentally benign O/KI oxidant system, which is able not only to regenerate the oxidants but also minimize side reactions. The isolation of two key intermediates was also an important achievement in comprehending the underlying mechanisms. As expected, this new class of 2-aminoimidazole dyes also presented significant solvatochromism and pronounced halochromism with colours changing from green to purple as the pH decreases. molecular quantum mechanics calculations supported the data obtained experimentally. A great number of compounds (12 in 18 compounds) showed potent fungicidal activity against and moderate activity against.
- 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.