Synergism Effect of the Essential Oil fromOcimum basilicumvar. Maria Bonita and Its Major Components with Fluconazole and Its Influence on Ergosterol Biosynthesis

Abstract

The aim of this study was to evaluate the activity of the EO and its major components ofOcimum basilicumvar. Maria Bonita, a genetically improved cultivar, against the fluconazole sensitive and resistant strains ofCandida albicansandCryptococcus neoformans. Geraniol presented better results than the EO, with a low MIC (76 μg/mL againstC. neoformansand 152 μg/mL against bothCandidastrains). The combination of EO, linalool, or geraniol with fluconazole enhanced their antifungal activity, especially against the resistant strain (MIC reduced to 156, 197, and 38 μg/mL, resp.). The ergosterol assay showed that subinhibitory concentrations of the substances were able to reduce the amount of sterol extracted. The substances tested were able to reduce the capsule size which suggests they have an important mechanism of action. Transmission electron microscopy demonstrated cell wall destruction ofC. neoformansafter treatment with subinhibitory concentrations. InC. albicansultrastructure alterations such as irregularities in the membrane, presence of vesicles, and cell wall thickening were observed. The biofilm formation was inhibited in bothC. albicansstrains at MIC and twice MIC. These results provide further support for the use ofO. basilicumEO and its major components as a potential source of antifungal agents.