Microbial Cell Biology Antifungal Property of Dihydrodehydrodiconiferyl Alcohol 9'-O-β-D-glucoside and its Pore-forming Action in Plasma Membrane of Candida albicans

We investigated the antifungal effect of dihydrodehydrodiconiferyl alcohol 9'-O-β-D-glucoside (DDDC9G) and its mechanism(s). Antifungal susceptibility testing showed that DDDC9G exhibted potent antifungal activities with almost no hemolytic effect. To understand the antifungal mechanism(s) of DDDC9G, we conducted the following experiments in this study using Candida albicans. Fluorescence experiments using the probes, 1, 6-diphenyl-1, 3, 5-hexatriene and propidium iodide suggested that DDDC9G perturbed the fungal plasma membrane. The analysis of the transmembrane electrical potential indicated that DDDC9G induced membrane-depolarization. Furthermore, model membrane studies were performed with rhodamine-labeled giant unilamellar vesicles and large unilamellar vesicles containing calcein or FITC-dextran. These results demonstrated that the antifungal effects of DDDC9G upon the fungal plasma membrane were through the formation of pores with the radii between 0.74 nm and 1.4 nm. Finally, in three dimensional flow cytometric contour plots, a reduced cell size was observed as a result of DDDC9G-induced membrane damages. Therefore, the present study suggests that DDDC9G exerts its antifungal effect by damaging the membrane through pore formation in the fungal plasma membrane.