Multifunctional Activity of Syzygium aromaticum Extracts Against Candida albicans: Free Radicals, Membrane Permeabilization and Cdr1p Localization

Eugenol is a compound with promising antimicrobial properties. The rising phenomenon of multidrug resistance of <i>Candida albicans</i> is driving researchers to search for new, alternative therapeutics that would synergize with conventional antifungal drugs. The aim of the present study is to investigate how eugenol and eugenol-based extracts impair <i>C. albicans</i> growth by generation of reactive oxygen species (ROS) and plasma membrane (PM) disruption. The methods that we applied involve structural analysis of eugenol extracts by HPLC, ATR-FTIR, and polyphenol detection. Additionally, determination of ROS level in <i>C. albicans</i> was performed using microscopic and flow cytometry studies and analysis of PM integrity (PI-staining, observation of PM transporter-Cdr1p-localization) and fluidity (fluorometric study). The results indicate that eugenol impacts fungal growth, and this corresponds with increased ROS levels and diminished PM fluidity in the <i>C. albicans</i> WT strain. <i>C. albicans</i> strains deprived of ergosterol (<i>erg11Δ/Δ</i>) exhibited lowered ROS level and no change in PM fluidity in response to the tested eugenol extracts, but they affected its growth and caused PM permeabilization and Cdr1p delocalization. These conclusions indicate that mode of action of eugenol can be related to disruption of PM structure by both ergosterol-dependent and -independent mechanisms. Ergosterol can play a crucial role in maintaining the PM integrity during treatment with lower concentrations of eugenol.