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Candida albicans is the most common human fungal pathogen, and with the increase in resistance rates worldwide, it is necessary to search for new pharmacological alternatives. Lavandula dentata L. essential oil is recognized as having antimicrobial properties. However, its effect against fungal biofilms has been poorly described. C. albicans-related infections involve the development of biofilms, which are highly resistant to conventional antifungals. In this work, we evaluated the antibiofilm effect of L. dentata L. essential oil against C. albicans. First, we characterized the essential oil by gas chromatography-mass spectrometry. The antifungal effect on C. albicans reference strains was evaluated by a disk diffusion assay and the minimal inhibitory concentration was obtained through a microdilution assay. The effect of the essential oil on the adhesion ability of C. albicans was determined through a crystal violet assay, and morphogenesis inhibition was assessed by light microscopy. The effect of the essential oil on the microarchitecture of biofilms was evaluated through scanning electron microscopy. Finally, the antibiofilm effect was evaluated through an adapted biofilm scratch assay and XTT viability assay. The main constituent of the essential oil was the monoterpenoid eucalyptol (60%). The essential oil presented minimal inhibitory concentrations of 156 and 130 µg/mL against two strains assayed. This minimal inhibitory concentration inhibited adhesion, morphogenesis, biofilm formation, altered microarchitecture, and decreased the viability of established biofilms formed on abiotic surfaces for both strains assayed. This study demonstrates that the essential oil from L. dentata could be a promising treatment against C. albicans biofilms.

Glutathione S-transferases (GSTs) are isoenzymes occurring in the cytoplasm and as integral membrane proteins. In addition to their role in drug metabolism by conjugating electrophilic and lipophilic compounds with glutathione (GSH), these enzymes display multiple functions in cells, including antioxidant action. It has been generalized that reactive oxygen species (ROS) inhibit cytosolic GSTs and activate microsomal GSTs; some evidence shows, however, that different ROS-generating systems can inhibit microsomal GST activity. We therefore tested the effect of Fe3+/ascorbate, another ROS-generating system, on cytosolic and microsomal GST activities from rat liver cytosol and microsomes, respectively, and compared it to that of hydrogen peroxide (H2O2). We found that, while both agents displayed similar inhibitory effects on cytosolic GST activity, they promoted opposite effects on microsomal GST activity. Using specific antioxidant enzymes, we corroborated that the effect of Fe3+/ascorbate involves generation of O2(.-) without dismutation into H2O2. Since these ROS have physicochemical properties and redox potentials that are very distinct, their reactivity is different, and their oxidative action is likely to have different targets. We discuss how these properties are related with the oxidative potency of ROS, especially those of O2(.-) and H2O2.