Design, synthesis, and biodistribution studies of new analogues of marine alkaloids: Potent in vitro and in vivo fungicidal agents against Candida spp.

Invasive candidiasis, such as intra-abdominal candidiasis (IAC), is a significant cause of morbidity and mortality worldwide. IAC is still poorly understood, and its treatment represents a challenge for public health. In this study, we showed the in vitro anti-Candida activity of four alkaloid synthetic derivatives and their antifungal potential in a murine model of IAC. The biological effects of alkaloids were evaluated against Candida spp. through the determination of the minimum inhibitory concentration (MIC). For the alkaloids that showed antifungal activity, the fungicidal concentration, time-kill curve, synergism with azoles and polyenes, phenotypic effects, and the effect against virulence factors were also determined. The most active alkaloids were selected for in vivo assays. The compounds 6a and 6b were active against C. albicans, C. glabrata, and C. tropicalis (MIC 7.8 µg/mL) and showed promising antifungal activity against C. krusei (MIC 3.9 µg/mL). The compound 6a presented a potent fungicidal effect in vitro, eliminating the yeast C. albicans after 8 h of incubation at MIC. An important in vitro synergistic effect with ketoconazole was observed for these two alkaloids. They also induced the lysis of fungal cells by binding to the ergosterol of the membrane. Besides that, 6a and 6b were able to reduce yeast-to-hyphal transition in C. albicans, as well as inhibit the biofilm formation of this pathogen. In the in vivo assay, the compound 6a did not show acute toxicity and was mainly absorbed by the liver, spleen, and lung after a parenteral administration. Also, this analogue significantly reduced the fungal load of C. albicans on the kidney and spleen of animals with IAC. Therefore, these results showed that the compound 6a is a potent anti-Candida agent in vitro and in vivo.

Antibacterial, antifungal, and antiviral activities of chalcone-bearing tetrahydropyranyl and 2,4-dihydroxyl moieties / Actividad antibacteriana, antifungica y antiviral de las chalconas que contienen los grupos tetrahidropiranilo y 2,4-dihidroxilo / Atividades antibacteriana, antifúngica e antiviral de chalconas funcionalizadas com os grupos tetrahidropiranil e 2,4-dihidroxil

SUMMARY Chalcones highlights as an important structure in medicinal chemistry and thus has been widely used as a template in the development of new drugs. In this study, we aim to determine the antibacterial, anti-Candida, and anti-Dengue potential of new chalcone-bearing 2,4-dihydroxyl and tetrahydropyranyl moieties. Antimicrobial activity assays showed that microorganism of the Staphylococcus genus (including methicillin-resistant strains) were susceptible to 2,4-dihydroxychalcones, with minimum inhibitory concentrations (MICs) ranging of 19.5 to 125 µg.mL-1. Compound 4e, which showed the highest bacteriostatic effect, also has bactericidal activity from of 80 µg.mL-1. The growth of oral isolates of Candida albicans was also efficiently inhibited with compound 4e (MIC: 15.6-32.3 µg.mL-1), which was fungicidal at 15.6 µg.mL-1. However, the presence of the tetrahydropyranyl moiety impaired both the antibacterial and antifungal effects. None of the chalcones tested were actives against Dengue virus serotype 2. In conclusion, the compound 4e showed good anti-Staphylococci and anti-Candida activity and may be a promising prototype for the development of new antimicrobial agents.

RESUMEN Las chalconas se destacan como una estructura importante en la química médica y, por lo tanto, se ha empleado como prototipo para el desarrollo de nuevos fármacos. En este estudio, nuestro objetivo fue determinar el potencial antibacteriano, anti Candida y anti-Dengue de las nuevas chalconas que poseen los grupos 2,4-dihidroxilo y tetrahidropiranilo. El ensayo de actividad antimicrobiana mostró que las bacterias del género Staphylococcus (incluidas las cepas resistentes a la meticilina) fueron sensibles a las 2,4-dihidroxicalconas estudiadas, con concentraciones inhibitorias mínimas (CIM) que oscilan entre 19,5 y 125 µg.mL-1. El compuesto 4e, que tuvo el mejor efecto bacteriostático, también mostró un efecto bactericida a partir de la concentración de 80 µg.mL-1. El crecimiento de los aislamientos orales de Candida albicans también se inhibió eficientemente con el compuesto 4e (CIM: 15.6-32.3 µg.mL-1), que fue fungicida a una concentración de 15.6 µg.mL-1. Sin embargo, la presencia del grupo tetrahidropiranilo perjudicó la actividad antibacteriana y anti-fúngica de los análogos de la chalcona. Además, ninguno de los compuestos evaluados mostró un efecto contra el virus del dengue serotipo 2. En conclusión, el compuesto 4e muestra una buena actividad anti-estafilocócica y anti-Candida y puede ser un prototipo prometedor para el desarrollo de nuevos agentes antimicrobianos.

RESUMO As chalconas se destacam como uma importante estrutura na química medicinal e dessa forma tem sido empregada como um protótipo para o desenvolvimento de novos fármacos. Nesse estudo, nós objetivamos determinar o potencial antibacteriano, anti-Candida, e anti-Dengue de novas chalconas que possuem os grupos 2,4-dihidroxil e tetrahidropiranil. O ensaio de atividade antimicrobiana mostrou que bactérias do gênero Staphylococcus (incluindo linhagens resistentes a meticilina) foram sensíveis para as 2,4-dihidroxichalconas estudadas, com concentrações inibitórias mínimas (CIM) variando de 19,5 para 125 Dengue potential of new chalcone µg.mL-1. O composto 4e, o qual apresentou o melhor efeito bacteriostático, também mostrou efeito bactericida a partir da concentração de 80 µg.mL-1. O crescimento de isolados orais de Candida albicans foi também eficientemente inibido com o composto 4e (CIM: 15.6-32.3 µg.mL-1), o qual foi fungicida a concentração de 15,6 µg.mL-1. Entretanto, a presença do grupo tetrahidropiranil prejudicou a atividade antibacteriana e antifúngica dos análogos de chalcona. Adicionalmente, nenhum dos compostos avaliados mostrou efeito contra o vírus da dengue sorotipo 2. Em conclusão, o composto 4e apresenta boa atividade anti-estafilocóccica e anti-Candida, e pode ser um promissor protótipo para o desenvolvimento de novos agentes antimicrobianos.

Pharmacologic potential of new nitro-compounds as antimicrobial agents against nosocomial pathogens: design, synthesis, and in vitro effectiveness.

Nosocomial infections are an important cause of morbi-mortality worldwide. The increase in the rate of resistance to conventional drugs in these microorganisms has stimulated the search for new therapeutic options. The nitro moiety (NO2) is an important pharmacophore of molecules with high anti-infective activity. We aimed to synthesize new nitro-derivates and to evaluate their antibacterial and anti-Candida potential in vitro. Five compounds [3-nitro-2-phenylchroman-4-ol (3); 3-nitro-2-phenyl-2H-chromene (4a); 3-nitro-2-(4-chlorophenyl)-2H-chromene (4b); 3-nitro-2-(4-fluorophenyl)-2H-chromene (4c), and 3-Nitro-2-(2,3-dichlorophenyl)-2H-chromene (4d)] were efficiently synthesized by Michael-aldol reaction of 2-hydroxybenzaldehyde with nitrostyrene, resulting in one ß-nitro-alcohol (3) and four nitro-olefins (4a-4d). The antibacterial and anti-Candida potentials were evaluated by assaying minimal inhibitory concentration (MIC), minimum fungicidal concentration (MFC), and minimum bactericidal concentration (MBC). Mono-halogenated nitro-compounds (4b and 4c) showed anti-staphylococcal activity with MIC values of 15.6-62.5 µg/mL and MBC of 62.5 µg/mL. However, the activity against Gram-negative strains was showed to be considerably lower and our data suggests that this effect was associated with the outer membrane. Furthermore, nitro-compounds 4c and 4d presented activity against Candida spp. with MIC values ranging from 7.8-31.25 µg/mL and MFC of 15.6-500 µg/mL. In addition, these compounds were able to induce damage in fungal cells increasing the release of intracellular material, which was associated with actions on the cell wall independent of quantitative changes in chitin and ß-glucan. Together, these findings show that nitro-compounds can be exploited as anti-staphylococcal and anti-Candida prototypes.