RESUMO
Onychomycosis is a nail infection caused by dermatophytes, non-dermatophyte fungi, and yeasts, especially Candida species. The present study evaluated the combinatorial effect of different cultured extracts of Candida parapsilosis and Trichophyton mentagrophytes and Trichophyton rubrum with fluconazole, itraconazole, and terbinafine against clinical isolates of Trichophyton rubrum. In addition, investigation of the action of the extracts on the wall or membrane was performed. Pure and mixed cultures of Candida parapsilosis and dermatophytes were filtered through a 0.2-µm membrane and submitted to liquid-liquid extraction using ethyl acetate. After a checkerboard, trial with drugs was performed to evaluate the synergistic interaction with the extract. The results obtained for the minimum inhibitory concentration (MIC) of extracts against the T. rubrum strain in isolation were 500-8000 µg/mL. The MIC range for fluconazole, itraconazole, and terbinafine were 2-32 µg/mL, 0.25-0.5 µg/mL, 0.03-64 µg/mL, respectively. However, when the extract was combined with drugs, the MIC values decreased: extracts 1.9-1000 µg/mL, fluconazole 0.25-4, itraconazole 0.03-0.06 µg/mL, and terbinafine 0.001-0.02 µg/mL. The MIC values of the extracts in the Roswell Park Memorial Institute 1640 medium (RPMI) supplemented with sorbitol did not change, suggesting any action on the cell wall. However, in the presence of RPMI supplemented with ergosterol, MIC values of the extracts increased by up to 2×, indicating action on the fungal cell membrane. A synergistic action was observed between products and drugs, detecting a decrease in MIC values. There is potential and a new therapeutic perspective for fungal control.
RESUMO
Isobavachalcone (IBC) is a natural prenylated chalcone with a broad spectrum of pharmacological properties. In this work, we newly synthesized and investigated the antibacterial activity of IBC against Gram-positive, Gram-negative and mycobacterial species. IBC was active against Gram-positive bacteria, mainly against Methicillin-Susceptible Staphylococcus aureus (MSSA) and Methicillin-Resistant Staphylococcus aureus (MRSA), with minimum inhibitory concentration (MIC) values of 1.56 and 3.12 µg/mL, respectively. On the other hand, IBC was not able to act against Gram-negative species (MIC > 400 µg/mL). IBC displayed activity against mycobacterial species (MIC = 64 µg/mL), including Mycobacterium tuberculosis, Mycobacterium avium and Mycobacterium kansasii. IBC was able to inhibit more than 50% of MSSA and MRSA biofilm formation at 0.78 µg/mL. Its antibiofilm activity was similar to vancomycin, which was active at 0.74 µg/mL. In order to study the mechanism of the action by fluorescence microscopy, the propidium iodide (PI) and SYTO9 fluorophores indicated that IBC disrupted the membrane of Bacillus subtilis. Toxicity assays using human keratinocytes (HaCaT cell line) showed that IBC did not have the capacity to reduce the cell viability. These results suggested that IBC is a promising antibacterial agent with an elucidated mode of action and potential applications as an antibacterial drug and a medical device coating.
