In vitro antimicrobial activity and the mode of action of indole-3-carbinol against human pathogenic microorganisms

Indole-3-carbinol (13C) is a naturally occurring constituent of cruciferous vegetables. The aim of this study was to assess the in vitro antimicrobial activity of 13C and its mode of action. By using an NCCLS broth microdilution assay, the activity of 13C was evaluated against human pathogenic microorganisms including clinically isolated antibiotic-resistant bacterial strains. The results indicated that 13C exhibited broad spectrum antimicrobial activities. To elucidate the physiological changes of the fungal cells induced by 13C, we performed a flow cytometric analysis for a cell cycle. The results showed that 13C arrested the cell cycle at the G(2)/M phase in Candida albicans. To understand the antifungal mode of action of 13C, the change in the membrane dynamics was monitored by using fluorescence changing experiments against C. albicans. The results suggest that 13C may exert antifungal activity by disrupting the structure of the cell membrane. The present study indicates that 13C has considerable antimicrobial activity, deserving further investigation for clinical applications.