Effects of Licochalcone and Glabridin on Candida Albicans Virulence Properties

Objectives: Candida albicans distinguishing features such as dimorphism and biofilm formation are thought to play an important role in oral candidosis. Although licorice (Glycyrrhiza glabra) has been used for centuries in Chinese medicine, few studies exist on its effect on C. albicans. In this study, we investigated the effects of two licorice compounds, licochalcone and glabridin, on growth, killing, biofilm formation and adherence of C. albicans. The possible synergistic effect of the licorice compounds with the antifungal Nystatin was also evaluated. Methods: Serial dilutions of licochalcone and glabridin in YNB medium were prepared in microplates to determine for two strains of C. albicans minimal inhibitory concentrations (MIC), minimal fungicidal concentrations (MFC), synergistic effect with Nystatin and biofilm formation. The effects of licorice compounds on hyphal formation was determined by microscopic observation while ¹⁴C-labelled cells of C. albicans were used for performing adherence assays to denture acrylic disks and oral epithelial cells. Results: For both licorice compounds, MIC were 6.25-12.5µg/mL while MFC was 12.5µg/mL for glabridin and 100 µg/mL for licochalcone. The licorice compounds were found to act in synergy with Nystatin to inhibit growth of C. albicans. Biofilm formation was inhibited by 30-60% with licochalcone at 0.2µg/mL while an inhibition of 75-80% was obtained at 2µg/mL. Glabridin had no effect on biofilm formation. A strong inhibitory effect (60-100%) on the transition blastospore-hyphal form was observed with either licochalcone or glabridin at 100µg/mL. None of the licorice compounds inhibited the adherence of C. albicans to denture acrylic and oral epithelial cells. Conclusion: Licorice-derived licochalcone and glabridin are potent antifungal agents for C. albicans and can act in synergy with Nystatin. They may also inhibit two important pathogenic properties of C. albicans. These data suggest that licochalcone and glabridin have a therapeutic potential for C. albicans oral infections.