New Organic Compounds Against Scedosporium and Mucorales: Antifungal Activity and Mechanisms of Cell Wall and Membrane Disruption

The emergence of infections caused by Scedosporium/Lomentospora and Mucorales species poses a major clinical challenge due to their intrinsic resistance to multiple antifungal drugs and the limited number of therapeutic options available. In this study, we evaluated the antifungal activity of synthetic organic compounds and characterized the mechanisms of antifungal activity. Eight compounds were initially screened against Scedosporium aurantiacum and Rhizopus oryzae. Compounds 2, 3, and 4 inhibited more than 60% of fungal growth and were selected for further characterization. Antifungal susceptibility assays revealed that compound 2 exhibited the strongest activity, with minimum inhibitory concentrations ranging from 12.5 to 25 μg/mL, whereas compounds 3 and 4 showed MIC values between 50 and 100 μg/mL. All compounds displayed fungistatic activity and significantly impaired fungal germination and biofilm development. Drug interaction analyses demonstrated additive or synergistic effects when the compounds were combined with clinically used antifungals. Investigations revealed that the compounds induced alterations in the fungal cell surface, including reductions in neutral lipids and chitin, increased membrane permeability, disruption of sterol-enriched membrane microdomains, and ultrastructural abnormalities. Exogenous ergosterol partially reversed the activity of compounds 2 and 3, suggesting interactions with membrane sterols. In silico toxicity prediction indicated generally favorable safety profiles. In summary, these findings identify synthetic organic compounds as promising scaffolds for antifungal drug discovery and highlight their potential to target fungal membrane and cell wall integrity in resistant filamentous pathogens.