Original Synthesis and Preclinical Evaluation of Fluorinated Quinolone-Chalcone Hybrids as Broad-Spectrum Antifungal Agents Against Azole-Resistant Candida and Aspergillus Species

Invasive fungal infections caused by azole-resistant Candida and Aspergillus species are an emerging clinical problem in Nigerian immunocompromised patient populations, where antifungal treatment options are critically limited by drug availability and cost. Fluorinated quinolones and chalcones individually carry antifungal pharmacophoric features, and their hybridisation through covalent linkage represents an original approach to multi-target antifungal drug discovery. This study designed and synthesised twenty-four fluorinated quinolone-chalcone hybrid molecules and conducted preclinical pharmacological evaluation for antifungal activity. Synthesis employed a convergent route combining fluorinated quinolonecarboxaldehyde intermediates with acetophenone Claisen-Schmidt condensation. All compounds were characterised by 1H-NMR, 19F-NMR, 13C-NMR, and HRMS. In vitro antifungal activity was determined by CLSI broth microdilution against C. albicans, azole-resistant C. glabrata, C. auris, and A. fumigatus clinical isolates from Nigerian hospitals. Mechanism of action studies evaluated ergosterol biosynthesis inhibition, membrane integrity disruption, and biofilm inhibition. In vivo efficacy was assessed in a neutropenic mouse model of disseminated candidiasis. Six hybrid compounds showed MIC50 values below 1 microgram per millilitre against azole-resistant C. glabrata and C. auris, organisms not effectively treated by fluconazole. The lead compound demonstrated dual mechanism of action with ERG11 binding and membrane disruption confirmed by computational and biophysical studies. In vivo fungal burden in kidneys was reduced by 2.5 log10 CFU at 20 mg/kg compared to vehicle control. This study provides an original synthetic antifungal scaffold series with activity against clinically challenging azole-resistant fungal pathogens. Keywords: antifungal, quinolone-chalcone hybrids, azole resistance, Candida auris, synthesis.