Study of the antimicrobial and fungicidal activity of the essential oil

The main problem of modern phytotherapy is the medicinal plants that have a sufficient raw material base and contain a large number of biologically active substances. Treatment of diseases with synthetic drugs leads to the development of resistance to pathogenic microflora and the appearance of allergic reactions. Therefore, to solve this problem, it is necessary to find new plant-based antimicrobials that are safe for long-term use and have a wide spectrum of action.

Актуальные вопросы фармацевтической и медицинской науки и практики. 2021. Т. 14, № 2(36). С. 211-214 The study of antibacterial activity is relevant to the scienti fic community. Resistance to antibiotics affects the disease incidence, as well as the development of allergic reactions. Today, the main goal of the pharmaceutical industry is to find herbal medicines that would inhibit the growth and spread of antibiotic-resistant microorganisms to the maximum possible degree. Scientific data analysis indicates that essential oils of plants and their components have an antibacterial effect. They are low-toxic, mild, and safe to use. The essential oil can be a highly effective supplement to the treatment of infectious diseases. It should be noted that the production of essential oil does not require massive expenses and is safe for people. The little-studied species with high concentrations of essential oil and thymol have viable research potential.
The family Lamiaceae is one of the most numerous and widespread in the modern flora. It has up to 200 genera and 7.000 species of grasses, shrubs, and semi-shrubs, cultivated hybrids of various species. Plants are used in modern medicine, as ornamental plants in horticulture, and as industrial crops.
The genus Thymus L. (Thyme), one of the most famous in this family, contains about 400 species, of which up to 50 are identified in the modern flora of Ukraine. Essential oils and extracts are part of phytopreparations with pronounced antimicrobial, anti-inflammatory, and antioxidant effects.
Comprehensive phytochemical study of species of the genus Thymus L. for further study and development of phytoprepa rations based on them is of great practical importance in medicine. Thymus x citriodorus (Pers.) Schreb. var. "Silver Queen" is a natural interspecific hybrid of broad-leaved Thymus pulegoides L. and common Thymus vulgaris L., which are widespread in the wild nature. Information on the accumulation of biologically active substances for this species in the scientific literature is limited. The genus has a large raw material base, a long growing season, which contributes to the accumulation of essential oil and thymol in its composition [1][2][3][4][5].

Aim
The aim of the work was to study the antibacterial activity of the essential oil of Thymus x citriodorus (Pers.) Schreb. var. "Silver Queen" by the method of in vitro against opportunistic pathogens of bacterial and fungal microorganisms cultures.

Materials and methods
The first step of our work was to obtain the essential oil of Thymus x citriodorus (Pers.) Schreb. var. "Silver Queen", the herb of the plant was used. Plant raw materials were har The experiments used 24h cultures of bacteria, from which NS suspensions were prepared with a density of 0.5 according to McFarland, which corresponded to 5 × 106 CFU/ml for Candida albicans and 1.5 × 108 CFU/ml for all other micro organisms. Also, disks soaked with essential oil were used for experiments. For this purpose, ready-made paper disks with a diameter of 6 mm were used, which in laboratory practice were normally used for impregnation with antibiotics.
The disk was immersed in essential oil for a few seconds, after which it was dried and used in research. The day-old culture of the test strain was seeded on the surface of Muel ler-Hinton agar, dried for 5-10 min, then impregnated discs were placed on the agar surface. Plates were incubated at 35 + 1 °C for 18 h in studies with Escherichia coli, Pseudomonad, and Staphylococcus and for 48 h in experiments with Candida. Sensitivity/ resistance to the essential oil was determined by the presence/absence of growth inhibition zones around the oil disk. The diameter of the growth inhi bition was measured in millimeters to an accuracy of 1 mm. The study was performed in triplicate.
It was calculated using the standard statistical package of the licensed program Statistica for Windows 13 (StatSoft Inc., № JPZ804I382130ARCN10-J), as well as SPSS 16.0 and Microsoft Office Excel 2003).

Results
Microbiological studies have shown that the essential oil has a significant antibacterial effect against S. aureus ATCC 25923, E. coli ATCC 259220 and fungicidal activity Candida albicans ATCC 885/6530 ( Table 1).
The essential oil has been represented by a wider range of bactericidal action. The activity against S. aureus was analyzed (growth retardation diameters amounted to 14.60 ± 1.52), as well as for E. coli (19.60 ± 1.85), and Candida albicans (29.30 ± 2.82). It was experimentally proven that the essential oil had no bactericidal effect on the test strain of P. aeruginosa.

Discussion
Upon analysis of the study results, we can state that in our in vitro antibacterial studies we obtained data confirming that the essential oil has an antibacterial effect against the reference test strains of S. aureus, C. albicans and E. coli. The obtained results were indicated the prospect of further research and studied of the essential oil of the littlestudied hybrid species of Thymus x citriodorus (Pers.) Schreb. var. "Silver Queen" as a main antibacterial component for phy topreparations [6][7][8][9][10][11].

Conclusions
1. Upon analysis of the study results, it was found that the essential oil of Thymus x citriodorus (Pers.) Schreb. var. "Silver Queen" has a pronounced antibacterial effect against the reference test strains of S. aureus ATCC 25923, C. albicans and E. coli ATCC 259220.
2. The data obtained were indicated that further study of the hybrid species had a promising medicinal perspective as a source of herbal antibacterial drugs.