Aims: The aim of this study was to investigate the mechanisms of action of fisetin, a flavonol with antifungal activity previously evaluated against the Cryptococcus neoformans species complex.
Methods and results: Ergosterol content and flow cytometry analysis were determined for the C. neoformans species complex in the presence of fisetin and ultrastructural analysis of morphology was performed on Cryptococcus gattii and C. neoformans. Decrease in the total cellular ergosterol content after exposure to fisetin ranged from 25·4% after exposure to 128 μg ml(-1) to 21·6% after exposure to 64 μg ml(-1) of fisetin compared with the control (without fisetin). The fisetin effects obtained with flow cytometry showed metabolic impairment, and alterations in its normal morphology caused by fisetin in C. neoformans cells were verified using scanning electron microscopy.
Conclusions: Fisetin is a compound that acts in the biosynthesis of ergosterol. Flow cytometry showed that fisetin reduced viability of the metabolically active cells of C. gattii, while morphological changes explain the action of fisetin in inhibiting growth of these fungi.
Significance and impact of the study: This study supports the idea that fisetin may represent a good starting point for the development of future therapeutic substances for cryptococcosis.
Keywords: Cryptococcus neoformans; antifungal activity; fisetin; mechanisms of action; scanning electron microscopy.
© 2016 The Society for Applied Microbiology.