Nanoemulsion of Gomortega keule Essential Oil: Characterization, Chemical Composition, and Anti-Yeast Activity Against Candida spp.

<b>Background/Objectives:</b> Candidiasis, an opportunistic fungal infection caused by Candida species, is a major health problem, particularly in immunocompromised individuals. Increasing resistance of yeasts such as <i>Candida</i> spp. to pharmacological antifungal agents makes it necessary to explore alternative treatments. The aim of this study was to evaluate the antifungal potential of <i>Gomortega keule</i> essential oil (GKEO) against <i>Candida</i> spp. by assessing growth and development at 24 and 48 h. Encapsulation and characterization of a stable nanoemulsion were carried out to enhance efficacy. <b>Methods</b>: The anti-yeast activity of both free GKEO and the nanoemulsion against <i>Candida albicans</i>, <i>C. glabrata</i>, and <i>C. guilliermondii</i> was evaluated using a microdilution method to determine the minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) at 24 and 48 h. <b>Results</b>: GC-MS/MS analysis identified forty-one components in GKEO, the main ones being eucalyptol (21.41%), 4-terpineol (19.62%), and α-terpinyl acetate (13.89%). Antifungal assays revealed that both free and nanoemulsion-formulated GKEO inhibited the growth of all tested <i>Candida</i> strains. At 48 h, the nanoformulated GKEO achieved a MIC value of 32 µg/mL and an MFC of 64 µg/mL for <i>C. albicans</i> and <i>C. glabrata</i> and showed higher antifungal activity compared to the free oil, in particular against <i>C. albicans</i>, exhibiting a four-fold lower MFC value. The activity of the nanoformulation was comparable to or better than fluconazole against <i>C. glabrata</i> and <i>C. guilliermondii</i>. <b>Conclusions</b>: The GKEO nanoemulsion potentiated anti-yeast activity against <i>Candida</i> spp. The formulation improved the efficacy of GKEO, suggesting its potential as an alternative or adjunctive treatment for candidiasis.