Evaluation of phytochemical, antibacterial, and antifungal properties of Thymus daenensis and Thymus fedtschenkoi from west of Iran

In this study, the essential oils of Thymus daenensis and Thymus fedtschenkoi were investigated in terms of phytochemical, antibacterial, and antifungal properties. After identifying the essential compounds of these two species of thyme, their antimicrobial properties against Gram-positive bacteria (Bacillus cereus, Staphylococcus aureus, and Enterococcus faecium), Gram-negative bacteria (Escherichia coli, Salmonella enteritidis), and fungus (Candida albicans) were investigated. For this purpose, the flowering branches of T. daenensis and T. fedtschenkoi were collected at full flowering stage from west of Iran (Arak and Hamedan, respectively) in June. Then, the constituents of the essential oils were identified by gas chromatography-mass spectrometry (GC/MS). To determine the sensitivity of microbial agents to the essential oil of these plants, disk diffusion and microdilution methods were used. The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) of the essential oils of both plants were determined against bacteria and fungi. Based on the results, the essential oil content of T. daenensis (3.4%) was more than that of T. fedtschenkoi (2.9%). The main compositions of the essential oils of T. fedtschenkoi ​​ and T. daenensis were linalool (83.1%) and thymol (73.9%), respectively. The essential oils of both species had significant antibacterial and antifungal effects albeit with different levels. In general, the antibacterial activity of T. fedtschenkoi essential oil was higher than that of T. daenensis, especially in the case of gram-positive bacteria. On the other hand, the antibacterial activity of T. daenensis essential oil against E. coli (gram negative) was more than that of T. fedtschenkoi. Antifungal activity of T. daenensis essential oil was higher than that of T. fedtschenkoi against C. albicans. The essential oil of T. fedtschenkoi was rich in linalool, and the higher antimicrobial activity of this species could be attributed to the high percentage of this compound in comparison with T. daenensis.