Cryptococcosis is a fungal infection caused mainly by the pathogenic yeasts
Cryptococcus neoformans
and
Cryptococcus gattii
. The infection initiates with the inhalation of propagules that are then deposited in the lungs. If not properly treated, cryptococci cells can disseminate and reach the central nervous system. The current recommended treatment for cryptococcosis employs a three-stage regimen, with the administration of amphotericin B, flucytosine and fluconazole. Although effective, these drugs are often unavailable worldwide, can lead to resistance development, and may display toxic effects on the patients. Thus, new drugs for cryptococcosis treatment are needed. Recently, an iridoid named plumieridine was found in
Allamanda polyantha
seed extract; it exhibited antifungal activity against
C. neoformans
with a MIC of 250 μg/mL. To address the mode of action of plumieridine, several
in silico
and
in vitro
experiments were performed. Through a ligand-based a virtual screening approach, chitinases were identified as potential targets. Confirmatory
in vitro
assays showed that
C. neoformans
cell-free supernatant incubated with plumieridine displayed reduced chitinase activity, while chitinolytic activity was not inhibited in the insoluble cell fraction. Additionally, confocal microscopy revealed changes in the distribution of chitooligomers in the cryptococcal cell wall, from a polarized to a diffuse cell pattern state. Remarkably, further assays have shown that plumieridine can also inhibit the chitinolytic activity from the supernatant and cell-free extracts of bacteria, insect and mouse-derived macrophage cells (J774.A1). Together, our results suggest that plumieridine can be a broad-spectrum chitinase inhibitor.