Tyrosol as antifungal agent: effect on biomass and metabolic activity of Candida biofilms formed on acrylic surfaces

Objectives: The objective of this study was to evaluate the antifungal effect of tyrosol on pre-formed biofilms of Candida albicans ATCC 10231 and Candida glabrata ATCC 90030.
Methods: Candida biofilms were grown on the surface of acrylic specimens in 24-well plates. The inoculum of each yeast (10⁷ cells/mL in artificial saliva) was added to wells, and the plates were incubated at 37 °C for 24 h. After, pre-formed Candida biofilms (24-h old) were treated with tyrosol (diluted in artificial saliva) at 100 and 200 mM twice a day for 1 min, during 3 days, totaling 6 treatments. The effectiveness of tyrosol was determined by total biomass quantification (using crystal violet staining) and evaluation of metabolic activity (XTT reduction assay). Chlorhexidine gluconate (CHG; 0.37mM) was used as positive control. Statistical analysis was conducted with one-way ANOVA followed by Holm-Sidak post-hoc test (α = 0.05).
Results: For both species tested, tyrosol at 200 mM and CHG promoted significant reductions in total biomass ranging from 51.6 % to 60 %. Regarding biofilm activity, tyrosol at 200 mM was effective against C. albicans and C. glabrata biofilms, achieving reductions in metabolic activity around 35 % and 53 %, respectively. Moreover, the higher reductions (~86 %) in biofilm activity were observed for the groups exposed to CHG.
Conclusions: In conclusion, tyrosol was able to reduce the biomass and metabolic activity of Candida biofilms. Therefore, this compound has potential as antifungal agent to be used in the control of oral diseases such as denture stomatitis.