Evaluation of the Synergistic Interaction between Satureja hortensis and Carum carvi Essential Oils and Fluconazole against Candida albicans: In Vitro

Nowadays, excessive use of fungal drugs has led to the development of drug-resistant fungi, making it necessary to find natural and herbal antifungal agents. This in-vitro study aimed to evaluate the interactions of Satureja hortensis and Carum carvi essential oils together and each essential oil with fluconazole against Candida albicans ATCC-10231.

In this study, antifungal properties of different concentrations of S. hortensis (0.0244-1.56 μL/mL) and C. carvi (0.39-25 μL/mL) were investigated by broth-microdilution method based on CLSI M27-A3 and M27-S4 standard documents. The interactions of essential oils together and each essential oil with fluconazole were evaluated by checkerboard assay. Then using the ΣFIC index, the interaction results were interpreted.

S. hortensis essential oil showed higher antifungal activity than C. carvi essential oil. (MIC/MFC: S. hortensis: 1.56/3.12 μL/mL and C. carvi: 12.5/25 μL/mL). The interaction between S. hortensis essential oil and fluconazole was on the synergic and additive borderline (FICI=0.508), the interaction between C. carvi essential oil and fluconazole was additive (FICI=0.62), and C. carvi and S. hortensis essential oils showed no interaction together (FICI=2.015).

The essential oils of S. hortensis and C. carvi separately exhibited powerful antifungal activities. The use of S. hortensis essential oil at a very low concentration along with fluconazole caused an interaction very close to synergy and increased fluconazole antifungal activity. Therefore, S. hortensis is a potential candidate for combined use with fluconazole to treat C. albicans related diseases.