Chemical Composition and Anticandidal Effect of Three Thymus Species Essential Oils from Southwest of Morocco against the Emerging Nosocomial Fluconazole-Resistant Strains

Abstract

The purpose of this present work is to study the essential oils composition of three endemic Thymus species from southwest of Morocco: Thymus satureioides Coss., Thymus pallidus Batt. and Thymus leptobotrys Murb., as well as their antifungal activity towards nineteen strains of emerging nosocomial Fluconazole-resistant Candida species. The chemical composition of the essential oils was determined by capillary gas chromatographic-mass spectrometry analysis. The results reveal qualitative and quantitative variation in composition of Thymus species. Seventy-three different compounds, 56 for T. satureioides accounting for 99.97% of the total essential oil, 52 for T. pallidus, accounting for 98.94% of the total essential oil, and 40 for T. leptobotrys accounting for 99.20%, were determined. The results obtained for the anticandidal disc-diffusion assay shows that the 19 strains of Candida species tested were inhibited by the Moroccan Thymus essential oils to a varying degree, with the diameters of the inhibition zone ranging from 49±1.00 to 85±1.15 mm. There were significant differences (p ? 0.05) in the antifungal activities of the essential oils on all species tested who showed larger inhibition zones than the positive control fluconazole and amphotericine B. Candida albicans showed a high sensitivity to essential oils of Thymus pallidus and Thymus leptobotrys compared with essential oil of Thymus satureioides and controls. While non- albicans Candida species showed less sensitivity to essential oils of Thymus pallidus and Thymus leptobotrys and are more sensitive to essential oils of Thymus satureioides than Candida albicans. Interestingly C. krusei, C. dubliniensis and C. glabrata were found to be resistant to conventional antifungal (fluconazole and amphotericine B), while our essential oils tested were able to inhibit the growth of Candida strains resistant to antifungal agents. The value of Minimal inhibitory concentration (MIC) and Minimal Fungicidal Concentration (MFC) of the Thymus essential oils studied ranges from 0.33 mg/mL to 0.91 mg/mL. All the essential oils possessed higher antifungal potential than classical fungicide.

Keywords: Thymus species, essential oils, anticandidal activity, Nosocomial fluconazole-resistant strains.