Antifungal activity of essential oils and their potential synergistic effect with amphotericin B

Candida albicans is a common opportunistic pathogen, causing infections ranging from superficial to bloodstream infections. The limited antifungal options and rising drug resistance challenge clinical treatment. We screened 98 essential oils and identified 48 with antifungal activity against Candida albicans at 1% concentration, determining their minimum inhibitory concentrations (MIC). Of these, 14 maintained fungicidal activity at lower concentrations (0.25% and 0.125%). 5 essential oils (Cinnamon, Satureja montana, Palmarosa, Lemon eucalyptus, and Honey myrtle) showed the highest inhibitory effects on stationary-phase Candida albicans and inhibited hyphae elongation. Synergistic effects were observed when combining Palmarosa with amphotericin B (AmB) against growing-phase Candida albicans, while Cinnamon and Satureja montana with AmB showed superior efficacy against stationary-phase infections. We identified the active components of 5 essential oils using gas chromatography-mass spectrometry (GC-MS) and found the following main constituents: Cinnamon primarily contains benzyl benzoate and eugenol, Satureja montana is dominated by carvacrol and cymene, Palmarosa features geraniol and geranyl acetate, Lemon eucalyptus includes dl-Isopulegol and citronellal, and Honey myrtle is characterized by citral and neral. Our results may aid in developing more effective antifungal treatments.