THE IN VITRO ANTIFUNGAL AND SYNERGISTIC ACTIVITY OF SELECTED PLANT EXTRACTS AND ESSENTIAL OILS AGAINST CANDIDA SPP.

This study aimed to evaluate the antifungal activity and the potential synergistic activity of ten plant extracts (EXs) and ten essential oils (EOs) obtained from the same plant species, namely Agrimonia eupatoria L., Arctium lappa L., Arnica montana L., Bidens cernua L., Corylus avellana L., Echinacea purpurea L. (Moench), Menta piperita L., Trifolium pratense L., Syzygium aromaticum L., and Angelica sinensis (Oliv.) Diels were used. Three species of the genus Candida, namely C. albicans, C. glabrata, and C. tropicalis, isolated from polluted estuarine water, were used in this study. The chemical composition of all EOs was evaluated by gas chromatography coupled with mass spectrometry (GC-MS) and gas chromatography with flame ionization detector (GC-FID) analysis. Firstly, the susceptibility of Candida spp. strains to EXs and EOs was screened by the agar disc diffusion method. Then the minimum inhibitory concentration (MIC) of the tested EXs and EOs was determined in a concentration range from 256 to 0.125 mu L/mL. Following that, the effective EXs and EOs were divided into two groups (strong effect and weak effect) and tested in combination (strong + weak) at various concentrations depending on the tested strain to determine their potential synergistic effect using the chessboard pattern. The most sensitive strain to treatments with EXs and EOs tested alone and in mixtures was C. albicans. The most potent combinations with other EXs/EOs were observed with Syzygium aromaticum L., for both plant extract and essential oil, respectively. In this study the EOs and EXs tested in combination were much more effective than when acting on the growth of Candida spp. separately. So, the synergistic effect of the combinations of the EXs and EOs can lead to a reduction in the doses of commercial antifungals and can provide an effective way to reduce the infections caused by yeasts of the genus Candida.