Modelo alternativo utilizando meio simulado do fluído espinhal cerebral (FES) para avaliação da atividade antifúngica de ácidos graxos frente à Cryptococcus spp

Abstract

The research of new methods to evaluate the growth capacity of Cryptococcus fungi species is of fundamental importance for the evaluation of new bioactive compounds, e.g; including; such as aliphatic fatty acids. A model that has already been proposed to mimic the conditions of the CSF was the simulated spinal fluid (SSF) that emerges as an interesting alternative. The objective of this study was to evaluate the antifungal activity of aliphatic fatty acid against Cryptococcus species using the simulated spinal fluid model (SSF). The antioxidant activity of aliphatic fatty acid was evaluated using FRAP assay. MIC and MFC of each acid were determined environmental isolates and strains of C. neoformans, C. grubii and C. gattii. Antifungal activity was also evaluated in vitro in SSF inoculated with fungi. Acids activities were monitored by fungal growth curve and determination of glucose and protein levels. Fatty acids display a better antioxidant activity than vitamin C. MIC and MFC values evaluated in the different fungi were: capric acid 0.19 - 0.80 and 0.75 - 3.04, lauric acid 0.09 - 0.80 and 0.19 - 0.80, caprylic acid 1.50 - 6.04 and 0.19 - 0.80 and undecylenic acid 0.38 - 2.94 and 0.38 - 5.89 μg μL-1, for each fatty acid, respectively. The growth of Cryptococcus species in SSF was satisfactory being observed significantly increased the log CFU mL-1 number in the 72 hour culture period. Only lauric acid was able to inhibit the growth of the three different species of Cryptococcus at the tested concentrations. Levels of glucose for C. neoformans significantly reduced in lauric acid treatment. At 2x MIC glucose levels were significantly reduced for C. grubii, in lauric acid treatment at 2x MIC in 24 hour and capric acid at 48 hour at this concentration. For C. gattii, glucose levels were significantly reduced a period of 48 hours in lauric acid treatment, capric acid at 1⁄2 MIC, MIC and 2x MIC and undecylenic acid at the concentration of 2x MIC at all time of 48 hours, but it did no show significant reduction of protein levels at the times tested. The results observed with the application of the SSF model inoculated with Cryptococcus species were able to demonstrate the in vitro antifungal activity of aliphatic fatty acids. Therefore, the SSF model can be considered an interesting alternative for the study of CSF-like bioactive compounds.