Aucklandia lappa Causes Cell Wall Damage in Candida albicans by Reducing Chitin and (1,3)-β-D-Glucan

The fungal cell wall is a major target of antifungals. In this study, we report the antifungal activity of an ethanol extract from Aucklandia lappa against Candida albicans. We found that the extract caused cell wall injury by decreasing chitin synthesis or assembly and (1,3)-β-D-glucan synthesis. A sorbitol protection assay demonstrated that the minimum inhibitory concentration (MIC) of the A. lappa extract against C. albicans cells increased eight-fold from 0.78 to 6.24 mg/ml in 72 h. Cell aggregates, which indicate damage to the cell wall or membrane, were commonly observed in the A. lappatreated C. albicans cells through microscopic analysis. In addition, the relative fluorescence intensities of the C. albicans cells incubated with the A. lappa extract for 3, 5, and 6 h were 92.1, 84.6, and 79.8%, respectively, compared to the controls, estimated by Calcofluor White binding assay. This result indicates that chitin content was reduced by the A. lappa treatment. Furthermore, synthesis of (1,3)-β-D-glucan polymers was inhibited to 84.3, 79.7, and 70.2% of that of the control treatment following incubation of C. albicans microsomes with the A. lappa extract at a final concentration equal to its MIC, 2× MIC, and 4× MIC, respectively. These findings suggest that the A. lappa ethanol extract may aid the development of a new antifungal to successfully control Candida-associated disease.