Atividade biológica de óleos essenciais em leveduras do complexo Cryptococcus neoformans

Abstract

Species of the complex Cryptococcus neoformans can cause infection in both healthy individuals and immunocompromissed patients, especially in AIDS patients, in which meningoencephalitis is the main clinical manifestation. There are few available antifungals for cryptococcosis treatment and all of them present high toxicity, besides the reports of resistance. In this context, the natural products are important source in the search for new antifungal compounds. In this study, it was evaluated the biological activity of the essential oils (EO) of Pelargonium graveolensis, Syzygium aromaticum and Cymbopogon flexuosus. The antifungal activity against Cryptococcus isolates was determined by minimum inhibitory concentration (MIC) by microdilution broth. Once the antifungal activity was measured, its cytotoxic activity were evaluated in L929 fibroblastic cell line in an in vitro assay. The mechanism of action of the EOs was analyzed by flow cytometry, using propidium iodide as fluorescent marker for lesions in the cell membrane, and FUN-1 ([2-chloro-4-(2,3-dihydro-3-methyl- (benzo-1,3-thiazol-2-yl)-methylidene)-1-phenylquinolinium iodide]), to analyze alterations of the cellular metabolism. Furthermore, the amount of ergosterol in the fungal membrane was evaluated to ascertain if there were modifications on its synthesis due to the exposition to the EOs. All the EOs presented antifungal activity, P. graveolensis and S. aromaticum with MICs between 128 and 256 µg/mL, while C. flexuosus obtained MICs from 8 to 32 µg/mL, whereas for these values, none EO has shown cytotoxicity in L929 fibroblastic cell line. The metabolic inhibition of fungal cells and membrane lesion were observed as the mechanism of action of all the evaluated EOs, however, only the EO of S. aromaticum was able to decrease the ergosterol amount in the fungal membrane. This study reveals the antifungal potential of the EOs of P. graveolens, S. aromaticum e C. flexuosus, due to their activity in isolated samples of Cryptococcus and relative toxicological safety.