The effects of tyrosol on yeasts: an overview of current knowledge

Quorum sensing is a cell density-dependent microbial communication form, which can regulate several microbial properties, including virulence, biofilm formation and cell-cell competence. The phenomenon of fungal quorum sensing was first uncovered nearly 25 years ago, following the identification of farnesol and tyrosol as two key signalling molecules. Although the major roles of these regulatory molecules were elucidated, several questions primarily regarding tyrosol-mediated effects remain to be addressed, particularly with regard to molecular events influenced by tyrosol. Based on available literature data, tyrosol possesses potential antifungal activity, especially at supraphysiological concentrations. Moreover, its simultaneous usage with traditional antifungals shows potent synergistic activity against planktonic and sessile Candida cells, including both Candida albicans and certain non-albicans species. Currently, the deep molecular tyrosol-based investigations are still in their infancy compared with farnesol research. However, several promising findings were published in the past 10 years in terms of the potential usage of this compound as an alternative therapeutic treatment. Hence, this mini review summarizes the major functions of tyrosol as a signaling regulator compound in Candida morphogenesis. Furthermore, we discussed the most promising tyrosol-based in vitro data, which may be a foundation for the future development of in vivo models and ultimately innovative therapeutic strategies against fungal infections. KEY POINTS: • Tyrosol is a major quorum-sensing molecule in Candida species, promoting yeast-to-hyphae transition and biofilm formation • Tyrosol has been shown to potentiate the efficacy of conventional antifungal agents, representing a promising adjunctive strategy for the treatment of fungal biofilms • At supraphysiological concentrations, tyrosol induces oxidative stress, negatively influences the intracellular metal homeostasis and alters the fungal metabolism.