The Antifungal Effects of Equol Against Candida albicans Involve Mitochondrial Dysfunction

Novel antifungal agents are urgently needed because of the increasing number of drug-resistant <i>Candida</i> strains encountered in clinical practice and the limited variety of available antifungal drugs. Equol, a metabolite of soy isoflavone glycosides, exhibits antifungal activities. In this study, Equol had good inhibitory activity against <i>Candida</i> species. The lowest inhibitory concentration of 125-500 μg/mL was confirmed by the gradient dilution method. In addition, transmission electron microscopy and the relative content assay showed that Equol altered the cell wall and membrane of <i>Candida albicans</i>. Further studies found that Equol treatment increased the intracellular levels of reactive oxygen species and Ca²⁺. Subsequent experiments suggested that Equol treatment depolarized the membrane potential of <i>C. albicans</i> and up-regulated the expression of the apoptosis-inducing factor gene. These results confirmed that Equol damaged the cell wall and membrane, dysregulated the intracellular components, induced oxidative stress and Ca²⁺ accumulation, and ultimately resulted in mitochondrial dysfunction. Collectively, these findings demonstrated that Equol is a potential antifungal agent.