The aim of this study was to assess the chemical composition, antioxidant, antimicrobial and antibiofilm activity of the Coriandrum sativum essential oil. Changes in the biofilm profile of Stenotropomonas maltophilia and Bacillus subtilis were studied using MALDI-TOF MS Biotyper on glass and wooden surfaces. The molecular differences of biofilms in different days were observed as well. The major volatile compounds of the coriander essential oil in the present study were β-linalool 66.07%. Coriander essential oil radical scavenging activity was 51.05% of inhibition. Coriander essential oil expressed the strongest antibacterial activity against B. subtilis followed by S. maltophilia and Penicillium expansum. The strongest antibiofilm activity of the coriander essential oil was found against S. maltophilia. A clearly differentiated branch was obtained for early growth variants of S. maltophilia in case of planktonic cells and all experimental groups and time span can be reported for the grouping pattern of B. subtilis preferentially when comparing to the media matrix, but without clear differences among variants. The results indicate that coriander was effective against the tested Penicillium expansum in the vapor phase after 14 days with MID₅₀ 367.19 and MID₉₀ 445.92 µL/L of air.

Eucalyptus globulus essential oil (EGEO) is considered as a potential source of bioactive compounds with significant biological activity. The aim of this study was to analyze the chemical composition of EGEO, in vitro and in situ antimicrobial activity, antibiofilm activity, antioxidant activity, and insecticidal activity. The chemical composition was identified using gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS). The main components of EGEO were 1,8-cineole (63.1%), p-cimene (7.7%), a-pinene (7.3%), and a-limonene (6.9%). Up to 99.2% of monoterpenes were present. The antioxidant potential of essential oil and results indicate that 10 μL of this sample can neutralize 55.44 ± 0.99% of ABTS^•+, which is equivalent to 3.22 ± 0.01 TEAC. Antimicrobial activity was determined via two methods: disk diffusion and minimum inhibitory concentration. The best antimicrobial activity was shown against C. albicans (14.00 ± 1.00 mm) and microscopic fungi (11.00 ± 0.00 mm–12.33 ± 0.58 mm). The minimum inhibitory concentration showed the best results against C. tropicalis (MIC 50 2.93 µL/mL, MIC 90 3.17 µL/mL). The antibiofilm activity of EGEO against biofilm-forming P. flourescens was also confirmed in this study. The antimicrobial activity in situ, i.e., in the vapor phase, was significantly stronger than in the contact application. Insecticidal activity was also tested and at concentrations of 100%, 50%, and 25%; the EGEO killed 100% of O. lavaterae individuals. EGEO was comprehensively investigated in this study and information regarding the biological activities and chemical composition of the essential oil of Eucalyptus globulus was expanded.

Thymus vulgaris essential oil has potential good biological activity. The aim of the research was to evaluate the biological activity of the T. vulgaris essential oil from the Slovak company. The main components of T. vulgaris essential oil were thymol (48.1%), p-cymene (11.7%), 1,8-cineole (6.7), γ-terpinene (6.1%), and carvacrol (5.5%). The antioxidant activity was 85.2 ± 0.2%, which corresponds to 479.34 ± 1.1 TEAC. The antimicrobial activity was moderate or very strong with inhibition zones from 9.89 to 22.44 mm. The lowest values of MIC were determined against B. subtilis, E. faecalis, and S. aureus. In situ antifungal analysis on bread shows that the vapor phase of T. vulgaris essential oil can inhibit the growth of the microscopic filamentous fungi of the genus Penicillium. The antimicrobial activity against S. marcescens showed 46.78–87.80% inhibition at concentrations 62.5–500 µL/mL. The MALDI TOF MS analyses suggest changes in the protein profile of biofilm forming bacteria P. fluorescens and S. enteritidis after the fifth and the ninth day, respectively. Due to the properties of the T. vulgaris essential oil, it can be used in the food industry as a natural supplement to extend the shelf life of the foods.

The essential oil of Melaleuca alternifolia, commonly known as tea tree oil, has many beneficial properties due to its bioactive compounds. The aim of this research was to characterize the tea tree essential oil (TTEO) from Slovakia and its biological properties, which are specific to the chemical composition of essential oil. Gas chromatography/mass spectroscopy revealed that terpinen-4-ol was dominant with a content of 40.3%. γ-Terpinene, 1,8-cineole, and p-cymene were identified in contents of 11.7%, 7.0%, and 6.2%, respectively. Antioxidant activity was determined at 41.6% radical inhibition, which was equivalent to 447 μg Trolox to 1 mL sample. Antimicrobial activity was observed by the disk diffusion method against Gram-positive (G⁺), Gram-negative (G⁻) bacteria and against yeasts, where the best antimicrobial activity was against Enterococcus faecalis and Candida albicans with an inhibition zone of 10.67 mm. The minimum inhibitory concentration showed better susceptibility by G⁺ and G⁻ planktonic cells, while yeast species and biofilm-forming bacteria strains were more resistant. Antibiofilm activity was observed against Pseudomonas fluorescens and Salmonella enterica by MALDI-TOF, where degradation of the protein spectra after the addition of essential oil was obtained. Good biological properties of tea tree essential oil allow its use in the food industry or in medicine as an antioxidant and antimicrobial agent.

The aim of this study was to test the antimicrobial activity of propolis, bee pollen loads and beeswax samples collected in the year 2009 from two locations in Slovakia to pathogenic bacteria, microscopic fungi and yeasts. The antimicrobial effect of the bee product samples were tested using the agar well diffusion method. For extraction, 99.9% and 70% methanol (aqueous, v/v) and 96% and 70% ethanol (aqueous, v/v) were used. Five different strains of bacteria, i.e. Listeria monocytogenes ccM 4699, Pseudomonas aeruginosa ccM 1960; Staphylococcus aureus ccM 3953; Salmonella enterica ccM 4420, Escherichia coli ccM 3988, three different strains of microscopic fungi, Aspergillus fumigatus, Aspergillus flavus, Aspergillus niger, and seven different strains of yeasts Candida krusei, Candida albicans, Candida glabrata, Candida parapsilosis, Candida tropicalis, Geotrichum candidum, Rhodotorula mucilaginosa, were tested. After 48 hours S. aureus was the bacterium most sensitive to the 70% ethanol extract of pollen, A. fumigatus was the most sensitive microscopic fungus (70% ethanol) and C. glabrata the most sensitive yeast (70% methanol). Microorganisms most sensitive to propolis extracts were L. monocytogenes, A. fumigatus (70% ethanol) and G. candidum (70% methanol). Most sensitive to beeswax extracts were E. coli, A. niger and C. tropicalis.