Abstract Klebsiella pneumoniae is a species of Gram-negative bacteria related to a wide range of infections and high rates of drug resistance. The combined use of antibacterial agents is one of the strategies that has been analyzed in recent years as part of the alternatives in the treatment of drug-resistant infections. Recently, the antibacterial activity of of 2-chloro-N-(4-fluoro-3-nitrophenyl)acetamide has been demonstrated against K. pneumoniae, also indicating that this acetamide did not show significant cytotoxic potential in preliminary tests. Thus, it becomes an interesting substance for future studies that explore its antimicrobial capacity, including investigating its association with antibacterial drugs. Based on this, this research aimed to analyze the effects of the association of 2-chloro-N-(4-fluoro-3-nitrophenyl)acetamide (CFA) with ciprofloxacin, cefepime, ceftazidime, meropenem and imipenem against K. pneumoniae strains. The results showed additivity when the substance was combined with ciprofloxacin and cefepime, indifference when associated with ceftazidime and synergistic effect when combined with meropenem and imipenem. Thus, the acetamide was able to optimize the effects of antibacterial drugs, reducing the concentrations necessary to cause bacterial death. These data indicate a potential future clinical use of these combinations, and further studies are needed to analyze this viability.

Four new piperine derivatives, PC1-PC4, were synthesized, and their structures were fully characterized by infrared (IR) and 1H and 13C nuclear magnetic resonance (NMR) spectroscopies. Quantum chemical calculations were performed using density functional theory (DFT) with the B3LYP-D3/6-31G(d,p) and 6-311+G(2d,p) basis sets. Electronic properties, such as the energy gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) and some global chemical reactivity descriptors, were evaluated to study the reactivity and stability of the compounds. 1H and 13C NMR chemical shifts were calculated by using the gauge-invariant atomic orbital (GIAO) method and compared with experimental values. In addition, the compounds were evaluated in an antifungal study against Candida, Trichophyton and Microsporum strains, and only PC4 showed 70% inhibition in ten tested strains, with a minimum inhibitory concentration (MIC) ranging from 1.23-2.46 μmol mL-1 and a minimum fungicide concentration (MFC) ranging from 9.84-19.68 μmol mL-1, and presented a fungistatic effect.

Abstract Aspergillus genus causes many diseases, and the species Aspergillus flavus is highly virulent. Treatment of aspergillosis involves azole derivatives such as voriconazole and polyenes such as amphotericin B. Due to an increase in fungal resistance, treatments are now less effective; the search for new compounds with promising antifungal activity has gained importance. The aims of this study were to evaluate the effects of the synthetic amide 2-chloro-N-phenylacetamide (A1Cl) against strains of Aspergillus flavus and to elucidate its mechanism of action. Thus, the minimum inhibitory concentration, minimum fungicidal concentration, conidial germination, associations with antifungal agents, cell wall activities, membrane activities and molecular docking were evaluated. A1Cl presented antifungal activity against Aspergillus flavus strains with a minimum inhibitory concentration of between 16 and 256 μg/mL and a minimum fungicidal concentration between 32 and 512 μg/mL. The minimum inhibitory concentration of A1Cl also inhibited conidial germination, but when associated with amphotericin B and voriconazole, it promoted antagonistic effects. Binding to ergosterol on the fungal plasma membrane is the likely mechanism of action, along with possible inhibition of DNA synthesis through the inhibition of thymidylate synthase. It is concluded that the amide 2-chloro-N-phenylacetamide has promising antifungal potential.

A series of fifteen new piperine-derived diesters was synthesized through the substitution reaction between the salt of piperic acid, obtained through piperine basic hydrolysis, with the δ-chloro-esters, obtained through the cleavage of tetrahydrofuran (THF) with acyl chlorides in the presence of ZnCl2. The final compounds were obtained with yields ranging from 50 to 84% and were characterized by infrared (IR) and 1H and 13C nuclear magnetic resonance spectroscopy (NMR). The new compounds were evaluated in silico in regard to their ADME (absorption, distribution, metabolism, and excretion) properties, and in vitro for their antimicrobial activity against bacteria strains (Staphylococcus aureus and Pseudomonas aeruginosas), yeast fungi (Candida albicans and C. tropicalis) and filamentous fungi (Aspergillus fumigatus, A. flavus and A. niger). The results from the in silico studies of Lipinski’s rule of five showed that most compounds present good pharmacological possibilities, and the results from in vitro antimicrobial activity showed that 8 of the 15 synthesized compounds displayed antimicrobial activity, inhibiting the growth of 40-80% of tested strains, with a minimum inhibitory concentration (MIC) interval ranging from 1024 to 256 µg mL−1.

Ten imides derived from safrole, 4a-4j, were synthesized and their structures were fully characterized by infrared (IR) spectroscopy, 1H and 13C nuclear magnetic resonance (NMR) spectroscopy and high resolution mass spectrometry (HRMS) analysis. Among the ten imides studied, eight are new. The compounds were evaluated in an in silico study and showed strong to moderate antifungal activity against various strains of Candida and Cryptococcus. In particular, compounds 4b, 4c and 4h exhibited strong antifungal activity, with minimum inhibitory concentration (MICs) between 0.17-0.73 µmol mL-1. The compound 4j exhibited antifungal activity with MIC 1.28 µmol mL-1 for all strains tested. In silico studies of the parameters of Lipinski’s rule of five indicated that these compounds are potential new drug candidates. The predict oral bioavailability can be evaluated through these parameters. In addition, a computational study helped assigning the stereochemistry of compound 4j, where the synthesized mixture is composed by two stereoisomers, 4j(1) (SRR) and 4j(2) (RSS).

Piperine, previously extracted from black pepper (Piper nigrum L.), was used as a precursor for the synthesis of twelve new diester derivatives. The final products were obtained through the bimolecular nucleophilic substitution reaction (SN2) of the alkyl 2-chloroacetates and the salt of piperic acid, obtained from the basic hydrolysis of piperine. The compounds were synthesized with yields of 55-84% and characterized by infrared spectroscopy and 1H and 13C nuclear magnetic resonance. The evaluation of the compounds’ potential as new drug candidates was done through an in silico study of ADME properties (absorption, distribution, metabolization and excretion) and evaluation of antimicrobial activity against bacterial strains (Staphylococcus aureus and Pseudomonas aeruginosa), yeasts (Candida albicans and Candida tropicalis) and filamentous fungi (Aspergillus fumigatus, Aspergillus flavus and Aspergillus niger). The in silico study showed that the compounds were good drug candidates and antimicrobial evaluation demonstrated that 9 of the 12 compounds exhibited a minimum inhibitory concentration (MIC) ranging 1024-256 μg mL-1.

New diesters derived from phthaloylglycine (7a-7i) were synthesized and their structures characterized by infrared, 1H and 13C nuclear magnetic resonance (NMR) spectroscopy. The compounds were evaluated in an in silico study, which demonstrated positive features indicating a possible drug candidate. The diesters showed antifungal activity ranging from moderate to strong against strains of Candida. Compounds 7a, 7b, 7c, 7e and 7i had a moderate minimum inhibitory concentration (MIC) of 1024 µg mL−1 against all fungal strains, while 7h showed a very good MIC of 256 µg mL−1 against Candida albicans, Candida parapsilosis and Candida krusei and 64 µg mL−1 against Candida tropicalis. However, only 7h and 7i were able to inhibit bacterial growth of strains of Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa and Escherichia coli with an MIC of 1024 µg mL−1.

Nine new compounds derived from selenoglycolic acid were synthesized, and their structures were fully characterized by elemental analysis, infrared (IR), 1H and 13C nuclear magnetic resonance (NMR). The compounds were evaluated in an in silico study and showed strong to moderate antibacterial activity against several strains of Staphylococcus aureus. In particular, three compounds exhibited excellent antibacterial activity, with minimum inhibitory concentrations (MICs) between 16 and 64 µg mL-1. Furthermore, two of the nine compounds showed antifungal activity, with MIC of 1024 and 512 µg mL-1. In silico studies of the parameters of Lipinski's rule of five indicate that these compounds have potential to be new drug candidates.

Abstract Fungal infections have become a concern for health professionals, and the emergence of resistant strains has been reported for all known classes of antifungal drugs. Among the fungi causing disease, we highlight those that belong to the genus Aspergillus. For these reasons, the search for new antifungals is important. This study examines the effects of a coumarin derivative, 4-acetatecoumarin (Cou-UMB16) both alone and together with antifungal drugs, and its mode of action against Aspergillus spp. Cou-UMB16 was tested to evaluate its effects on mycelia growth, and germination of Aspergillus spp. fungal conidia. We investigated its possible action on cell walls, on the cell membrane, and also the capacity of this coumarin derivative to enhance the activity of antifungal drugs. Our results suggest that Cou-UMB16 inhibits Aspergillus spp. virulence factors (mycelia growth and germination of conidia) and affects the structure of the fungal cell wall. When applying Cou-UMB16 in combination with azoles, both synergistic and additive effects were observed. This study concludes that Cou-UMB16 inhibits mycelial growth and spore germination, and that the activity is due to its action on the fungal cell wall, and that Cou-UMB16 could act as an antifungal modifier.

A phytochemical investigation from aerial parts of Casearia arborea (Rich.) Urb. (Salicaceae) led to isolation and identification of: sitosterol, 4-en-stigmast-3-one, 13-hydroxy-trans-ent-cleroda-3,14-diene,3-hydroxy-2-oxo-trans-ent-cleroda-3,14-diene (kolavelone), a mixture of 13-hydroxy-trans-ent-cleroda-3,14-diene and an ester ethyl hexadecanoate, kaempferol-3-O-a-L-arabinofuranoside and 4',5,7-trihydroxy-3',5'-dimethoxyflavone (tricin). The compounds have been described for the first time in this species. Five trihydroxy-flavone-hexoside derivatives have been identified by LC-ESI-HR-MS. The antimicrobial activity of kolavelone was evaluated against strains of Staphylococcus, Bacillus, Pseudomonas, Shigella and Candida spores, and its minimum inhibitory concentration (MIC) was determined. The results showed the antimicrobial activity of kolavelone against several bacteria and Candida tropicalis indicating its potential use as antimicrobial agent.

A series of ten new compounds have been synthetized in satisfactory yields (85-95%) through the treatment of isopropyl mesoionic 1,3-thiazolium-5-thiolate with 2-chloro-N-arylacetamides and characterized by elemental analysis, infrared (IR), 1H and 13C nuclear magnetic resonance (NMR) spectroscopies. The newly synthesized compounds were evaluated as new drug candidates in in silico study and for their antifungal activity against several strains of Candida albicans. In silico study indicates that no compound has potential to be a new drug while four compounds showed medium to strong activity with minimum inhibitory concentration (MIC) range of 256-1024 µg mL-1.

RESUMOAo longo do tempo, se modificou a etiologia das onicomicoses, leveduras do gênero Candida têm emergido como agentes etiológicos importantes. O objetivo desse trabalho foi determinar a frequência de onicomicoses causadas por leveduras em João Pessoa, Paraíba, Brasil de 1999 a 2010. Um estudo retrospectivo de janeiro de 1999 a dezembro de 2010 avaliou os resultados de exames micológicos diretos (EMD) positivos para leveduras provenientes de onicomicoses, realizados no Laboratório Clínico Hemato(r). As mulheres foram as mais afetadas por onicomicoses, as unhas dos pés são os alvos preferidos e ocorrem preferencialmente em adultos. As leveduras prevalentes foram Candida tropicalis e C. krusei.

ABSTRACTOver time, as the etiology of onychomycosis has developed, yeasts from the genus Candida have emerged as important etiological agents. This study aimed to determine the frequency of yeast caused onychomycosis in Joao Pessoa, Paraíba, Brazil from 1999 to 2010. A retrospective study from January 1999 to December 2010 evaluated the results of onychomycosis positive direct mycological exams (DME) - for yeast and realized in the Hemato(r) Clinical Laboratory. Women were the most affected by onychomycosis which occur preferentially in adults, and the toenails are the favorite yeast targets. The prevalent yeasts were Candida tropicalis and C. krusei.

Uma série de 21 derivados, 1,3,4-oxadiazolinas, foi sintetizada pela ciclização de N-acilhidrazonas com anidrido acético e avaliada in vitro quanto à sua atividade antifúngica contra seis espécies de Candida: Candida albicans (ATCC 90028 e LM V-42), Candida krusei (ATCC 6258 e LM 12 C) e Candida tropicalis (ATCC 13803 e LM 14). As espécies de Candida foram consideradas sensíveis a uma série dos compostos, os quais inibiram o crescimento de 50 a 90%, com um intervalo de concentração inibitória mínima (MIC) de 64 a 512 µg mL-1. As estruturas dos compostos foram totalmente confirmadas e caracterizadas pelas técnicas de infravermelho com transformada de Fourier (FTIR), ressonância magnética nuclear (NMR) de ¹H e 13C, e espectrometria de massa (MS).

A series of 21 1,3,4-oxadiazoline derivatives was synthesized by cyclization of N-acylhydrazones with acetic anhydride and evaluated for their in vitro antifungal activity against six Candida strains: Candida albicans (ATCC 90028 and LM V-42), C. krusei (ATCC 6258 and LM 12 C) and C. tropicalis (ATCC 13803 and LM 14). The Candida strains were found to be sensitive to some of the compounds, which inhibited the growth by 50-90%, with minimum inhibitory concentration (MIC) in the range of 64-512 µg mL-1. The compounds' structures were fully confirmed and characterized by Fourier transform infrared spectroscopy (FTIR), ¹H and 13C nuclear magnetic resonance (NMR) and mass spectrometry (MS).

O objetivo deste estudo foi observar a eficácia do óleo essencial de O. vulgare L. e O. majorana L. na inibição do crescimento e sobrevivência de cepas de fungos potencialmente patogênicas, bem como avaliar os possíveis mecanismos envolvidos no estabelecimento da propriedade antifúngica dos óleos essenciais testados através do ensaio de estabilidade osmótica e morfogênese. As cepas fúngicas utilizadas neste estudo foram Candida albicans ATCC 7645, C. tropicalis LM-14, C. krusei LM-09, Cryptococcus neoformans FGF-5, Aspergillus flavus LM-02, A. fumigatus IPP-21, T. rubrum ATCC 28184, T. mentagrophytes LM-64, Microsporum gypseum ATCC 184, M. canis LM-36 e Cladosporium herbarium ATCC 26362. O óleo essencial de O. vulgare apresentou valor de CIM de 80 µL/mL, enquanto o óleo essencial de O. majorana apresentou valor de CIM de 160 µL/mL. C. krusei LM-09 apresentou-se como a única cepa resistente a todas as concentrações ensaiadas de ambos os óleos essenciais. Os óleos essenciais testados quando ensaiadas em seu valor de CIM causaram um efeito fungicida contra C. albicans ATCC 7645 após 4 h de exposição. O óleo essencial de O. vulgare na concentração de 80 µL/mL exibiu uma total inibição do crescimento micelial radial de T. rubrum ATCC 28184 e M. canis LM-36 ao longo de 14 dias. As cepas fúngicas ensaiadas quando tratadas com sorbitol (agente osmo-protetor) foram capazes de crescer em meio adicionado de mais altas concentrações dos óleos essenciais quando comparados ao meio não adicionado de sorbitol, sugerindo especificidade destes produtos a parede celular como alvo na célula fúngica. As principais alterações causadas pelo óleo essencial de O. vulgare sobre a morfologia de A. flavus LM-02 foram diminuída conidiação, perda de citoplasma, perda de pigmentação e ruptura da estrutura celular indicando degeneração da parede celular fúngica. Estes resultados sugerem que óleos essenciais de espécies de Origanum poderiam ser considerados como potenciais antifúngicos para o controle de fungos patógenos e ocorrência de micoses.

This study aimed to assess the efficacy of O. vulgare L. and O. majorana L. essential oil in inhibiting the growth and survival of potentially pathogenic fungal strains and also sought to evaluate the possible mechanisms involved in the establishment of the antifungal property of the tested essential oils through assays of osmotic stability and morphogenesis. Test strains included in this study were Candida albicans ATCC 7645, C. tropicalis LM-14, C. krusei LM-09, Cryptococcus neoformans FGF-5, Aspergillus flavus LM-02, A. fumigatus IPP-21, T. rubrum ATCC 28184, T. mentagrophytes LM-64, Microsporum gypseum ATCC 184, M. canis LM-36 and Cladosporium herbarium ATCC 26362. O. vulgare essential oil presented a MIC value of 80 µL/mL, while for O. majorana this was 160 µL/mL. C. krusei LM-09 was the only strain resistant to all assayed concentrations of both essential oils. O. vulgare and O. majorana essential oil at their MIC values provided a cidal effect against C. albicans ATCC 7645 after 4 h of exposure. O. vulgare essential oil at 80 µL/mL exhibited 100 % inhibition of the radial mycelia growth of T. rubrum ATCC 28184 and M. canis LM-36 for 14 days. Assayed fungus strain protected by sorbitol (osmo-protectant agent) grew in media containing higher concentrations of O. vulgare and O. majorana essential oil in comparison to media without sorbitol, suggesting some specificity of these essential oils for targeting cell wall in the fungi cell. Main morphological changes observed under light microscopy provided by the essential oil of O. vulgare in A. flavus LM-02 were decreased conidiation, leakage of cytoplasm, loss of pigmentation and disrupted cell structure indicating fungal wall degeneration. These results suggest that essential oils from Origanum could be regarded as a potential antifungal compound for controlling the growth of pathogen fungi and the occurrence of mycoses.

O óleo essencial de Origanum vulgare L. tem sido reconhecido como uma interessante fonte de compostos antimicrobianos para ser aplicado na conservação de alimentos. Neste estudo, avaliou-se o efeito do óleo essencial de O. vulgare sobre o crescimento de A. flavus, A. parasiticus, A. fumigatus, A. terreus e A. ochraceus. O óleo essencial apresentou um significante efeito inibitório sobre todos os fungos ensaiados. A CIM foi 0,6 µL.mL-1 para todos os fungos, enquanto a CFM variou entre 1,25-2,5 µL.mL-1. O crescimento micelial radial de A. flavus e A. parasiticus foi fortemente inibido ao longo de 14 dias pelo óleo essencial nas concentrações de 0,6; 1,25; e 2,5 µL.mL-1 em meio sólido. O óleo essencial a 0,6 e 0,3 µL.mL-1 inibiu o aumento da massa micelial de todos os fungos em valores superiores a 90% em meio líquido, enquanto a 1,25 µL.mL-1, a inibição foi de 100%. O óleo essencial em variadas concentrações (0,6-2,5 µL.mL-1) inibiu a viabilidade e germinação dos esporos fúngicos em um curto tempo de exposição. As principais alterações morfológicas provocadas pelo óleo essencial em A. parasiticus, observadas sob microscopia óptica, foram ausência de conidiação, perda de citoplasma, perda de pigmentação e ruptura de estrutura celular. Estes resultados demonstraram que o óleo essencial de O. vulgare exerce um significante efeito fungitóxico, suportando seu uso racional como agente antifúngico na conservação de alimentos.

Origanum vulgare L. essential oil has been known as an interesting source of antimicrobial compounds to be applied in food conservation. In this study, the effect of O. vulgare essential on the growth of A. flavus, A. parasiticus, A. fumigatus, A. terreus and A. ochraceus was assessed. The essential oil had a significant inhibitory effect on all assayed fungi. MIC was 0.6 µL.mL-1 for all fungi, while MFC was in the range of 1.25-2.5 µL.mL-1. The radial mycelial growth of A. flavus and A. parasiticus was strongly inhibited over 14 days at 0.6, 1.25 and 2.5 µL.mL-1 of oil in solid medium. The mycelial mass of all fungi was inhibited over 90% at 0.6 and 0.3 µL.mL-1 in liquid medium, while it was 100% at 1.25 µL.mL-1. The oil in a range of concentrations (0.6 to 2.5 µL.mL-1) was effective in inhibiting the viability and spores germination in a short time of exposure. The main morphological changes caused by the essential oil in A. parasiticus observed under light microscopy were absence of conidiation, leakage of cytoplasm, loss of pigmentation, and disrupted cell structure. These results demonstrated that O. vulgare essential oil produced a significant fungitoxic effect supporting its possible rational use as anti-mould compound in food conservation.