Activity of Selected Essential Oils against Candida spp. strains. Evaluation of New Aspects of their Specific Pharmacological Properties, with Special Reference to Lemon Balm

Abstract

The aim was\rto investigate the antifungal effectiveness and some of pharmacological\rproperties of essential oils (EOs), which had not yet been thoroughly studied in the planned scope. We first evaluated MIC/MFC of\rsixteen EOs against C. albicans ATCC\r10231. Then, five most active EOs were tested, using 50 clinical Candida spp. strains and additional\rreference C. albicans ATCC 90028\rstrain. The time-kill curve, carryover, post-antifungal effects (PAFE), mutant prevention\rconcentrations, the susceptibility of reference strains to the cell wall\rdisrupting agents and tolerance to oxidative stress, were evaluated. For these\rdetailed studies, we chose the following four essential oils. Clove oil,\rGeranium oil, Lemon balm and Citronella oil, with MICs of 0.097% (v/v),\rresulted concentration- and time-dependent killing and may be therapeutically safe, because they\rdo not generate resistance. The best one was Lemon balm, which caused most extended\rPAFE, significantly reduced tolerance to oxidative stress and increased\rsusceptibility to Calcofluor White, Congo Red and SDS. Phytochemical analysis\rof these four EOs has been performed and compared; looking for the reason that Lemon balm\rwas the best.