Apigenin induces cell shrinkage in Candida albicans by membrane perturbation

Apigenin, a natural flavone, has been well characterized for its their anticarcinogenic property; however, its bioactivity against pathogenic fungi has not been investigated in detail. In this study, we examined the antifungal activity and mode of action of apigenin. Apigenin inhibited the growth of fungal pathogens, which induced superficial infection and reduced biofilm mass. Three-dimensional flow cytometric analysis demonstrated that apigenin induced morphological changes, especially cell shrinkage, in Candida albicans. We investigated the cause of cell shrinkage using the cyanine dye 3,3΄-dipropylthiacarbocyanine iodide. Results revealed that apigenin altered the cell membrane potential. Apigenin also induced membrane dysfunction, and increased cell permeability to 1,6-diphenyl-1,3,5-hexatriene and propidium iodide. We observed the influx and efflux of fluorescent molecules of varying molecular weights and radii across large unilamellar vesicles and live cells that had been treated with apigenin. Membrane disruption facilitates the release of small intracellular constituents such as ions and sugars, but not proteins. These findings suggested that apigenin exerted an antifungal activity by inducing membrane disturbances, which led to cell shrinkage and leakage of intracellular components.