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Thyme belongs to a genus encompassing over 215 species of hardy perennial herbaceous plants and sub-shrubs, which are native to Europe, particularly around the Mediterranean. Thymus vulgaris L., or garden thyme, with narrow small leaves and clusters of tubular mauve flowers, is used mainly in cookery. Dried herb yields 1% and more essential oil, which is a pale yellowish-red liquid with a sweet, very aromatic odour. Thyme is widely used in the pharmaceutical industry and is a source of substances of antimicrobial effect upon antibiotic-resistant strains of microorganisms. The purpose of our work was to identify the biochemical and antimicrobial peculiarities of Th. vulgaris essential oil against clinical isolates of opportunistic microorganisms. The analysis of thyme essential oil was carried out using GC/MS analysis. The clinical isolates were isolated with the use of differentially diagnostic nutrient media. The antibiotic susceptibility was identified with the help of the disc-diffusion test. The sensitivity of microorganisms to plant extracts was determined by the agar diffusion test. The antibiofilm activity of the extracts was tested in standard 96-well microtitration plates. The GC/MS results confirm the earlier reports that the major volatile constituents obtained from the aerial parts of thyme species were thymol, γ-terpinene, p-cymene, 3-carene and carvacrol. After subjecting the selected essential oil to effective steam distillation, substantial contents of phenolic monoterpenoids were obtained – thymol (67.7%) and γ-terpinene (8.2%). The European Pharmacopoeia set quality standards for thyme essential oil, which dealt mainly with the % content (w/w) of the volatile phenols (expressed as thymol: 36.0–55.0%). Garden thyme essential oil has been found to show a high antimicrobial activity against antibiotic-resistant microorganism strains. The obtained results proved the wide spectrum of antibiotic activity of thyme essential oil. The highest antimicrobial activity was registered against the typical and clinic strains of S. aureus and microscopic Candida genus fungi. Garden thyme essential oil was ascertained to show high antibiofilm-forming activity against S. aureus. The antimicrobial and antibiofilm-forming activities of thyme essential oil against both bacterial pathogens of opportunistic infections and microscopic fungi have proven the good prospects for development of a broad-spectrum agent against opportunistic microbial associations based on this oil.

Keywords: essential oil content, chemical analysis, constituents, large-scale distillation, antimicrobial activity GC-FID analysesThe analysis of EOs was carried out using a gas chromatograph Varian 3090, connected to MS Saturn 2100T integrator. The following operating conditions were used: capillary column: RX-5MS, 30 m x 0.250 mm i.d., film thickness: Essential oils (EOs) are complex mixtures of several components that show a wide range of biological activities. The objective of the present work was to investigate the composition of the essential oils from industrial large-scale distillation, and evaluate their antimicrobial activity on typical and clinic isolates strains. The qualitative compositions of essential oils of several aromatic plants were determined by GC-FID after their industrial large-scale distillation (Calendula Co., Nova Lubovna, Slovakia). GC-FID analysis revealed that essential oils from large-scale show different qualitative and quantitative content in comparison with literature data. Eleven essential oils, namely, Rosmarinus officinalis L., Thymus vulgaris L., Menta ×piperita L., Matricaria recutita L., Hyssopus officinalis L., Salvia officinalis L., Pimpinella anisum L., Juniperus communis L., Abies alba L., Pinus silvestris L., and Coriandrum sativum L. were tested for their antimicrobial activities using disk diffusion method. Thymus vulgaris L. essential oil shows the most potent antimicrobial activity. On other hand, the essential oil of Hyssopus officinalis L., Mentha × piperita L., Rosmarinus officinalis L., and Coriandrum sativum L.. The essential oil show medium antimicrobial activity. There was no antimicrobial activity observed for Matricaria recutita L. ARTICLE INFO

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The study of the R&D in this paper is to determine the range of essential oils (EOs) in the raw materials of species of the genus Thymus of the natural flora in the Carpathian region and their antimicrobial activity. It was found that the component range of EO in species of the genus Thymus depends on the microclimatic conditions of the population. The range of essential oils in the raw material of Th. Serpyllum and Th. Pulegoides is 7–9 mL and Th. Marschallianus is 3.5 mL. The research found that the plants Th. Serpyllum and Th. Pulegoides that grow in sunny habitats have an aromatic mono- and bicyclic monoterpenoid chemotype (K/α-T-neol/ G/p-C/B), with total dominance of carvacrol and p-cymene. The populations of Th. Serpyllum, which grow on the edges of sparse pine forests, and populations of Th. Pullegioide, with denser plant cover and which grow in meadows, have an acyclic and bicyclic monoterpene chemotype (G/α-T-neol/B/K). Plants that grow in the communities of meadow-steppe vegetation have the following chemotypes: Th. Serpyllum—L/K/G with 63% of linalool, Th. Pullegioides—G/α-T-neol/L/B, and Th. Marschallianus—α-T-neol/K/L/α-T-nen/G/B. Of these, the dominant chemotypes are α-terpineol and carvacrol (28:6.5%). A wide spectrum of antimicrobial activity was registered in samples of Th. Pullegoides and Th. Serpyllum that have an aromatic-monoterpenoid chemotype. Essential oils of Th. Pullegoides were dominated by carvacrol, and p-cymene had the highest fungicidal action (41.00 ± 1.0%). Plant populations of Th. Pullegoides and Th. Serpyllum with the aromatic-monoterpenoid chemotype are suggested by R&D to be of use in the pharmaceutical industry. They have high contents of natural components, which are effective in a wide spectrum of antimicrobial activity. The EO of Th. Marschallianus had the lowest influence on the inhibition of bacterial and fungal reproduction.