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 of Ocimum basilicum var. Maria Bonita, a genetically improved cultivar, against the fluconazole sensitive and resistant strains of Candida albicans and Cryptococcus neoformans. Geraniol presented better results than the EO, with a low MIC (76 μg/mL against C. neoformans and 152 μg/mL against both Candida strains). 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 of C. neoformans after treatment with subinhibitory concentrations. In C. albicans ultrastructure alterations such as irregularities in the membrane, presence of vesicles, and cell wall thickening were observed. The biofilm formation was inhibited in both C. albicans strains at MIC and twice MIC. These results provide further support for the use of O. basilicum EO and its major components as a potential source of antifungal agents.

Inibitory effects of linalool on fungal pathogenicity of clinical isolates of Microsporum canis and Microsporum gypseum

“…The antifungal activity of Ocimum sanctum essential oil (and its major components) including linalool against Candida albicans , and results were found by Cardoso et al., in which Ocimum basilicum essential oil and linalool also inhibited C. albicans . Linalool has also shown antifungal activity against Cryptococcus neoformans by reducing its capsule size . Our findings suggest the potential utility of linalool, a plant active monoterpene, as an anti‐ Microsporum drug as well.…”

“…The plasma membrane plays a vital role in maintaining a homeostatic environment to keep cells healthy and maintain fungal cell viability. Studies have shown that linalool interacts with fungal cell membranes by disrupting ergosterol biosynthesis in Candida albicans . In fact, ergosterol is an important structural component of fungal cell membranes for maintenance of the cell membrane structure and fluidity.…”

Antifungal mechanism of action ofSchinus lentiscifoliusMarchand essential oil and its synergistic effectin vitrowith terbinafine and ciclopirox against dermatophytes

“…Several studies have demonstrated the chemosensitization of pathogens and the synergistic interactions of essential oils and their active compounds with conventional antifungal drugs . The present study evaluated the antifungal effect of S. lentiscifolius essential oil and its combination with commercial antifungals.…”

“…Terbinafine acts by inhibiting squalene epoxidase, an enzyme involved in ergosterol biosynthesis, whereas ciclopirox, through its high affinity for trivalent cations such as Fe 3+ , inhibits metal‐dependent enzymes and affects energy production in the electron transport chains in the mitochondria, nutrient uptake and synthesis of proteins and nucleic acids . The fungal cell wall and membrane are considered as the target sites for the oils and their isolated compounds . An effect on the cell wall of the microorganism caused by the action of these substances can be related to an increase in the amount of the drug available inside the cell to exert its effect, thereby causing rapid death of the cell .…”

“…The use of chemosensitizer agents to a pathogen has been shown as a promising alternative to the lack of new antimicrobials and to the increasing resistance to conventional antifungal therapy, although without adding toxic or adverse effects . In this context, studies have demonstrated that chemosensitization of microorganisms by essential oils or their isolated compounds improved the efficacy of commercial antifungal agents . Essential oils are an important group of plant secondary metabolites used on a large scale in the cosmetic, food and pharmaceutical industries due to their related biological effects .…”