The two aims of this study were to obtain stable thyme-oil loaded nanoemulsions using the statistical design of experiment method (DOE) and to confirm their antimicrobial and disinfecting properties. Thyme oil was used as the oil phase, ECO Tween ® 80 acted as an emulsifier, and the rest of the formulation was deionized water. Ultrasonication was chosen as the method of obtaining the nanoemulsions. It was checked whether the input parameters (oil concentration, emulsifier concentration, amplitude, and sonication time) had a significant impact on the output parameters (nanoemulsion particle size, polydispersity index, viscosity, and stability over time). For the formulations selected on the basis of the statistical data analysis, the values of minimum inhibitory concentrations (MIC) and minimum biocidal concentrations (MBC/MFC) were determined in relation to 10 bacterial strains and 10 strains fungi (filamentous fungi, yeast-like fungi). The results obtained from the statistical analysis showed that the optimal concentration of the thyme oil in nanoemulsion should amount up to 2%. Biological studies proved that the obtained formulation had stronger antibacterial and antifungal activity compared to pure oil. Moreover, it was shown that the nanoemulsion caused the required for disinfectants reduction of > 5 log of bacterial strains ( S. aureus, P. aeruginosa) and > 4 log of fungal strains ( C. albicans) after 30 minutes.

The chemical composition of commercial thyme oils, freshly hydrodistilled EO (essetntial oil) from dried thyme herb and thymol, the main thyme oil constituent, were analyzed in the aspect of possible cytotoxic effect against MCF-7 breast cancer and normal L929 mouse fibroblast cell lines. Based on the GC-MS analysis, it was found that the commercial essential oils revealed similarities in their chemical composition. The content of main components such as thymol, linalool and α-pinene was almost equal. Interestingly, the EO obtained by hydrodistillation from Thymi herba showed considerable differences in the percentage content of some main constituents. The reason for the differences may be caused by the intraspecific chemical variability of T. vulgaris L. Four types of tested EOs can be classified as a ‘thymol’ chemotype, with thymol as the predominant compound. The thymol alone and the freshly hydrodistilled EO demonstrated the highest cytotoxic effect against used cell lines. The difference in IC50 values suggests more sensitive L929 cells are more sensitive in both the CCK-8 assay (except EOs Kawon) and the NRU assay.