Morphological Characterization, Essential Oil Composition and Antibacterial Activity of Some Cultivars from the Genera Monarda, Satureja, Thymus, Ocimum and Hyssopus Grown in the Central Forest-Steppe Zone of Ukraine

Representatives of five genera of the Lamiaceae family, such as Thymus, Satureja, Monarda, Ocimum, and Hyssopus, are especially appreciated for their valuable decorative features and the beneficial biological properties of their essential oils and extracts. In this study, the key morphological features of eight new cultivars (Monarda didyma L., Monarda bradburiana L. C. Beck, Satureja hortensis L., Satureja coerulea L., Thymus vulgaris L., Ocimum basilicum var. citriodorum L., and Hyssopus officinalis L.), cultivated firstly under the conditions of the central forest-steppe of Ukraine, as well as the chemical composition and antibacterial activity of their essential oils, were studied. The chemical composition of the essential oils obtained from the fresh aerial parts of the studied plants via hydrodistillation was evaluated by GC-MS. In addition, the screening tests of antibacterial activity against Staphylococcus aureus (ATCC 25923), Staphylococcus epidermidis (ATCC 12228), Pseudomonas aeruginosa (ATCC 27853), Klebsiella pneumoniae (clinical isolate), and Escherichia coli (ATCC 25922) were performed using the disk diffusion method. Two essential oils, T. vulgaris and M. didyma, were rich in thymol (49.9% and 58.5%, respectively), and four essential oils (M. didyma, M. bradburiana, S. hortensis, and S. coerulea) were rich in carvacrol (49.4–69.9%). The essential oil of O. basilicum contained linalool, citral, and neral (38.7%, 12.6%, and 9.4%), whereas the essential oil of H. officinalis contained pinanone (51.3%) and pinocarvone (18.5%). All the tested essential oils exhibited strong antibacterial activity against S. aureus and S. epidermidis. The essential oils of M. didyma, M. bradburiana, S. hortensis, S. coerulea, T. vulgaris, and O. basilicum had strong antibacterial activity against E. coli as well. Our findings demonstrated that the studied essential oils are rich in characteristic terpenes and terpenoids, which are likely to induce their antimicrobial activity. The revealed morphological features, chemical composition and antibacterial activity of the essential oils highlight the need for further studies to assess the repeatability of results for these cultivars bred across other years on the same plots. Additionally, the studied plants have great potential for further research on the development of medicinal and cosmetic products with various biological properties.