Abstract
Increasing resistance of microbes to available antifungals has necessitated a search for alternative natural products with antifungal properties. Combinations of essential oils (EOs) with known antifungal activities may increase antimicrobial activity, reduce side effects, and overcome resistance. This study determined the antifungal activity of basil, marjoram, clove, cumin and caraway EOs, both individually and in combination. The EOs and the major constituents of clove, cumin and caraway were screened against Candida albicans (C. albicans), and Aspergillus niger (A. niger) using a broth dilution method. Fluconazole was used as a positive control. The MICs of the mixtures of EOs were better than those of the single oils (except in the case of clove oil) especially against C. albicans (1 mg/ml) suggesting a synergistic effect against both C. albicans and A. niger (2 mg/ml) when increasing the concentration of one oil over the other two. Single active components (eugenol, carvone and cuminaldehyde) have better activity than single total oils against both organisms and showed synergistic effects when combined. In summary, mixtures of EOs or their active components had similar/better antifungal activities compared to the single oils or ingredients suggesting a synergistic effect against both C. albicans and A. niger. Clove oil was the best against both organisms while eugenol was the best against A. niger. In conclusion, the synergistic effect of the combinations of the EOs and their active components against C. albicans and A. niger could lead to decreased side effects and consequently they can be used to treat various fungal infections caused by these organisms.