Evaluation of antifungal activity, mechanisms of action and toxicological profile of the synthetic amide 2-chloro-N-phenylacetamide.

Aspergillus niger causes infections such as otitis and pulmonary aspergillosis in immunocompromised individuals. Treatment involves voriconazole or amphotericin B, and due to the increase in fungal resistance, the search for new compounds with antifungal activity has intensified. In the development of new drugs, cytotoxicity and genotoxicity assays are important, as they allow predicting possible damage that a molecule can cause, and in silico studies predict the pharmacokinetic properties. The aim of this study was to verify the antifungal activity and the mechanism of action of the synthetic amide 2-chloro-N-phenylacetamide against Aspergillus niger strains and toxicity. 2-Chloro-N-phenylacetamide showed antifungal activity against different strains of Aspergillus niger with minimum inhibitory concentrations between 32 and 256 µg/mL and minimum fungicides between 64 and 1024 µg/mL. The minimum inhibitory concentration of 2-chloro-N-phenylacetamide also inhibited conidia germination. When associated with amphotericin B or voriconazole, 2-chloro-N-phenylacetamide had antagonistic effects. Interaction with ergosterol in the plasma membrane is the probable mechanism of action.2-Chloro-N-phenylacetamide has favorable physicochemical parameters, good oral bioavailability and absorption in the gastrointestinal tract, crosses the blood-brain barrier and inhibits CYP1A2. At concentrations of 50 to 500 µg/mL, it has little hemolytic effect and a protective effect for type A and O red blood cells, and in the cells of the oral mucosa it promotes little genotoxic change. It is concluded that 2-chloro-N-phenylacetamide has promising antifungal potential, favorable pharmacokinetic profile for oral administration and low cytotoxic and genotoxic potential, being a promising candidate for in vivo toxicity studies.

Antifungal activity of citronellal against Trichophyton rubrum and its predictive mechanism of action by CYP51 inhibition through molecular docking.

The present study aimed to investigate the antifungal activity of citronellal (CIT) against clinical isolates of T. rubrum and to show the possible mechanism of action involved. The antifungal potential of CIT was evaluated from the Minimum Inhibitory Concentration (MIC), Minimum Fungicide Concentration (MFC) and assays with ergosterol and sorbitol, to elucidate the possible mechanisms of action, and molecular docking. MIC and MFC values ranged from 4 to 512 µg/mL. Regarding the mechanism of action, the monoterpene demonstrated interaction with fungal ergosterol. In addition, it is possible to observe that CIT acts on crucial enzymes for the biosynthesis and maintenance of the fungal cell membrane, due to the ability of the monoterpene to bind to CYP51. The results obtained in this research demonstrate that CIT has the potential to become, in the future, a product for the treatment of dermatophytosis.

Antibacterial effect of isoeugenol against Pseudomonas aeruginosa

Abatsract Pseudomonas aeruginosa is an important nosocomial pathogen and its clinical importance is mainly related to nosocomial infections. Increased rates of bacterial resistance in recent years has led WHO to publish a global priority list to guide research and discovery of new antibiotics, where P. aeruginosa is among the group of bacteria for which there is a critical level of priority for new drugs to be discovered. In this context, isoeugenol appears as an interesting alternative and the objective of this study was to investigate its action against P. aeruginosa. Isoeugenol presented significant antibacterial activity, with minimum inhibitory concentration (MIC) of 64µg/mL and minimum bactericidal concentration (MBC) of 128µg/mL, and was considered bactericidal against this species. Molecular docking revealed interactions that suggest that isoeugenol may bind to the enzyme Penicillin-Binding Protein 3 and interfere with the bacterial cell wall synthesis process. This study reinforces the antibacterial potential of this compound and emphasizes that more studies are needed in order to better investigate its mechanism of antibacterial action.

Antifungal action of α-pinene against Candida spp. isolated from patients with otomycosis and effects of its association with boric acid.

The genus Candida is one of the main causes of otomycosis. The growing index of fungal strains resistant to antifungals makes necessary the search for new agents and α-pinene is a phytoconstituent present in plants with remarkable antimicrobial activity, which becomes an interesting object of study. Thus, the objective of this research was to evaluate the antifungal activity of α-pinene against Candida species isolated from otomycosis, determining the Minimum Inhibitory and Fungicide Concentrations, micromorphological analysis and verifying the effects of the association with boric acid. α-pinene showed significant antifungal activity, with greater inhibitory activity against C. parapsilosis, fungicidal action and proved to be effective in inhibiting fungal structures, such as pseudo-hyphae and promoting a marked decrease in blastoconidia. The combination of α-pinene with boric acid produced additive effects that may be interesting for use in clinical practice.

The impact that ß-citronellol isomers have on the biofilm formation of Candida yeasts.

Infections associated with biofilms developed by Candida spp. are becoming a great problem due to its resistance against the immune response of the host and the action of antifungal agents. Hence, finding substances that can inhibit the development of biofilms increases the likelihood that these compounds one day can become good antifungals applied in the clinic. The aim of this study was to evaluate the effect of ß-citronellol enantiomers on the biofilm formation by Candida albicans and Candida tropicalis isolated from bloodstream infections. Inhibition was evaluated by reading microplates treated with different concentrations of R-(+)-ß-citronellol, S-(-)-ß-citronellol and amphotericin B, compared to negative control, in spectrophotometer at 590 nm. All tested concentrations of ß-citronellol enantiomers inhibited the biofilm formation of Candida. However, it is still necessary to evaluate the behavior of these isomers on mature biofilms, so that they can become more viable as antifungal therapeutical agents.

Antifungal Activity of Essential Oils against Candida albicans Strains Isolated from Users of Dental Prostheses.

OBJECTIVE: The objective of this study was to analyze the antifungal activity of citral, selected by screening natural products, against Candida albicans isolates from subjects who use dental prostheses. METHODOLOGY: Screening of essential oils, including those from Mentha piperita L. (Briq), Origanum vulgare, and Zingiber officinale L., and the phytoconstituents citral and limonene, to select an appropriate natural product. Citral, which mediated the best antifungal response, was selected for biological assays. The minimum inhibitory concentrations (MICs) and minimum fungicidal concentrations (MFCs) for citral and nystatin were determined by the microdilution method. Micromorphological analyses, time-kill curve, and modulation tests were performed. RESULTS: The MIC and MFC of citral were established as 32 µg/mL, consistent with fungicidal activity. The clinical strains were resistant to nystatin. Citral caused micromorphological alteration in the strains. In the time-kill curve, the growth of the clinical strain was reduction in growth equal to 3 log10 colony-forming units per milliliter after exposure to the MIC and MIC × 2 of citral for 2 h. Citral did not modulate the resistance of the studied strains to nystatin. CONCLUSION: This study revealed the potential of citral as a fungicidal agent and highlighted the resistance of clinical strains of C. albicans to nystatin.

Study of the antifungal potential of (r)-(+)-citronellal and its association with therapeutic agents used in the treatment of vulvovaginal candidiasis / Estudo do potencial antifúngico do (r)-(+)-citronelal e sua associação com agentes terapêuticos utilizados no tratamento da candidíase vulvovaginal

Vulvovaginal candidiasis (VVC) is a common fungal infection that affects healthy women of all ages. At least 75% of women will develop one or more infections once during their lifetime, with 6 to 9% of those individuals developing recurrent infections. In view of this context, this study sought to evaluate the antifungal potential of the isolated (R)-(+)-citronellal [(R)-(+)-CT] and associated to therapeutic agents of clinical importance. The enantiomer was solubilized in tween 80 and dimethylsulfoxide (DMSO). Posteriorly diluted in sterile distilled water up to the concentration of 2048µg/mL. The minimum inhibitory concentration (MIC) of the product was determined by microdilution in RPMI-1640 obtaining dilutions of 1024-4µg/mL. The minimum fungicidal concentration (MFC) was determined by the Sabouraud dextrose agar (SDA) depletion technique from aliquots of 1µL of the MIC, MIC × 2 and MIC × 4. The MIC and the MFC values of (R)-(+)-CT for 90% of the C. albicans strains were 16 and 32µg/mL respectively. In the susceptibility test, C. albicans presented a high resistance to fluconazole and to itraconazole, 12 (92.30%) of the strains. However, for ketoconazole and miconazole the resistance was of 4 (30.76%) and 3 (23.07%) of the strains respectively. In the combination testing of the (R)-(+)-CT with ketoconazole and miconazole, the resistance was completely reverted. For fluconazole and itraconazole, the resistance was reverted in 9 (75%) and 7 (58.33%) of the strains respectively. The (R)-(+)-CT presented fungicide activity with MFC of MIC × 2. When in combination with ketoconazole, fluconazole, itraconazole and miconazole increased the inhibition zones of these antifungal drugs, reducing the resistance against C. albicans.

Candidíase vulvovaginal (CVV) é uma infecção fúngica comum que afeta mulheres saudáveis de todas as idades. Pelo menos 75% das mulheres irão desenvolver uma ou mais infecções uma vez durante a vida, com 6 a 9% dos indivíduos desenvolvendo infecções recorrentes. Diante deste contexto, buscou-se avaliar neste estudo o potencial antifúngico do (R)-(+)-citronelal [(R)-(+)-CT] isolado e associado a agentes terapêuticos de importância clínica. O enantiômero foi solubilizado em tween 80 e dimetilsulfóxido (DMSO). Posteriormente diluiu-se em água destilada estéril até a concentração de 2048µg/mL. A concentração inibitória mínima (CIM) do produto foi determinada por microdiluição em meio RPMI-1640 obtendo diluições de 4-1024µg/mL. A concentração fungicida mínima (CFM) foi determinada pela técnica de esgotamento em agar Sabouraud dextrose (ASD) a partir de alíquotas de 1mL da CIM, CIM × 2 e CIM × 4. A CIM e a CFM do (R)-(+)-CT para 90% das cepas de C. albicans foram 16 e 32µg/mL respectivamente. No ensaio de suscetibilidade, C. albicans apresentou alta resistência ao fluconazol e ao itraconazol, 12 (92.30%) das cepas. No em tanto, para o cetoconazol e o miconazol a resistência foi de 4 (30.76%) e 3 (23.07%) das cepas respectivamente. No ensaio de combinação do (R)-(+)-CT com cetoconazol e miconazol, a resistência foi completamente revertida. Para o fluconazol e o itraconazol, a resistências foi revertida em 9 (75%) e 7 (58.33%) das cepas respectivamente. O (R)-(+)-CT apresentou atividade fungicida com CFM igual à CIM × 2. Quando em combinação com cetoconazol, fluconazol, itraconazol e miconazol ampliou as zonas de inibição desses antifúngicos, diminuindo a resistência contra C. albicans.