Clinical infections with the Candida albicans represent a significant health problem as it is a pathogen causing high and increasing morbidity and mortality worldwide. As the resistance of fungal infections to available antifungal drugs is also increasing, it is worthwhile to research new potential therapeutic compounds. Essential oils derived from aromatic plants, which have been recognized for their broad-spectrum antimicrobial and antifungal properties for many years, can serve as an alternative to existing drugs. The aim of this study was to investigate the inhibitory efficacy of 35 essential oils (EOs) and their components on Candida albicans, for which the antifungal activity is yet not well-known, and compare the results with the antifungal effectiveness of five essential oils, known to be highly effective based on previously published data. The inhibitory efficacy of the essential oils was evaluated using different methods: diffusion, dilution and fluorescence. Based on the results obtained from these methods, the essential oil of lemon balm (Melissa officinalis) exhibited the most potent fungistatic activity. Consequently, the composition of lemon balm EO was analyzed using GC-MS method to identify and quantify the compounds present in the essential oil. The composition of lemon balm EO was compared to the composition of oregano EO (Origanum vulgare), which is considered the most effective fungicide according to the available literature. To investigate the synergy among the compounds present in the selected essential oil that demonstrated the highest inhibitory activity against Candida albicans, we evaluated the inhibitory effects of individual compounds, whose concentration in the EO exceeded 1 % (anethole, 6-methyl-5-heptene, beta-caryophyllene, geranial, neral, citronellal, caryophyllene oxide and citronellol) using the fluorescence method. It was found that the compounds citronellol and citral, which is a mixture of two isomeric compounds geranial and neral, contributed the most to the excellent antifungal efficacy of lemon balm EO. The results of our research confirm that essential oils from aromatic plants can be a good alternative to existing antimicrobial drugs and that it would be reasonable to further investigate lemon balm EO as a natural means of controlling Candida albicans infections.
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