Antimicrobial Potential and Phytochemical Profile of Wild and Cultivated Populations of Thyme (Thymus sp.) Growing in Western Romania

The purpose of this study was to analyze the chemical composition and antimicrobial activity of some thymus populations collected from five different locations in Western Romania. The chemical compositions of the essential oils (EOs) were studied through GC–MS, and the biological activities were evaluated using the microdilution method. The EO yield ranged between 0.44% and 0.81%. Overall, 60 chemical compounds were identified belonging to three chemotypes: thymol (three populations), geraniol (one population) and carvacrol (one population). Thymus vulgaris L. is distinguished by a high content of thymol, while species of spontaneous flora (Th. odoratissimus and Th. pulegioides) contain, in addition to thymol, appreciable amounts of carvacrol and geraniol. The antimicrobial activity of each the five oils was tested on Staphylococcus aureus (ATCC 25923), Streptococcus pyogenes (ATCC 19615), Esherichia coli (ATCC 25922), Pseudomonas aeruginosa (ATCC 27853), Shigella flexneri (ATCC 12022), Salmonella typhimurium (ATCC 14028), Haemophilus influenzae type B (ATCC 10211), Candida albicans (ATCC 10231) and Candida parapsilopsis (ATCC 22019). The EOs showed biological activity on Gram-positive/Gram-negative/fungal pathogens, the most sensitive strains proving to be S. pyogenes, S. flexneri, S. typhimurium and C. parapsilopsis with an MIC starting at 2 µL EO/100 µL. The species sensitive to the action of Thymus sp. from culture or spontaneous flora are generally the same, but it should be noted that T. odoratissimus has a positive inhibition rate higher than other investigated EOs, regardless of the administered oil concentration. To date, there is no research work presenting the chemical and antimicrobial profiling of T. odoratissimus and the correlations between the antimicrobial potential and chemical composition of wild and cultivated populations of thyme (Thymus sp.) growing in Western Romania.