Bioherbicidal Effects of Essential Oils Isolated from Thymus fallax F., Mentha dumetorum Schult. and Origanum vulgare L

Antimicrobial and Anti-Biofilm Activities of Thymus fallax Essential Oil against Oral Pathogens

Aim. Oral infections associated with a wide diversity of microorganisms, including bacteria and yeasts, occur frequently in humans, affecting the whole oral cavity and well-being. Oral pathogens easily grow and propagate in the oral cavity, leading to the formation of dental plaque on both soft and hard tissue. The oral cavity contains up to 700 different species of microorganisms, which Candida and Streptococci are the most common organisms. Oral diseases continue to increase despite the best efforts of the medical and scientific communities. During the past decades, drug resistance to common antibiotics used in the treatment of oral infections has been raised to high levels worldwide. To overcome such resistance, there is a growing tendency to use herbal medicine as alternative. This study was conducted to find out the chemical constitution of Thymus fallax (T. fallax) essential oil and to determine its antimicrobial and anti-biofilm efficacy against common oral pathogens. Materials and Methods. The chemical compositions of the essential oil distilled from T. fallax plants were analyzed using gas chromatography/mass spectrometry (GC/MS). Antimicrobial susceptibility testing against common Streptococcus, Enterococcus, Staphylococcus, and Candida strains was assessed by broth microdilution in 96-well plates as suggested by the Clinical and Laboratory Standards Institute (CLSI) methods. Biofilm growth and development were assessed using XTT reduction assay. Results. Based on the GC/MS test results, thymol (67.75%) followed by caryophyllene (E-) (7.27%) was the main component of this essential oil. T. fallax inhibited the growth of examined microbial pathogens at concentrations of 0.031-16 μL/mL. Also, the essential oil showed biofilm inhibition of greater than 95% in the concentration of 8 μL/mL against all tested bacterial strains as well as Candida albicans ( $p$ value < 0.05). Conclusions. Considering the significant antimicrobial activities of T. fallax, this essential oil has the potential to be used as further antimicrobial and anti-biofilm pharmaceutical products in the control and treatment of oral infections.

Chemical Composition and Antimicrobial Activity of the Essential Oil From Euphorbia helioscopia L

The chemical composition and antimicrobial activity of the essential oil from the aerial parts of Euphorbia helioscopia L. were investigated by gas chromatography-mass spectrometry (GC-MS), GC, and microdilution methods. Thirty-five compounds, representing 83.51% of the total oil, were identified. 1,6-Dihydrocarveol (31.39%), carvone (16.79%), menthol (8.23%), and trans-dihydrocarvone (5.53%) were the principal constituents of the oil. The essential oil exhibited strong antimicrobial activity against strains of the bacteria, Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, Shigella dysenteriae, and a strain of the fungus Candida albicans with a minimal inhibitory concentration value of 31.25 μg/mL and minimum bactericidal concentration values of 31.25 μg/mL ( S. aureus), 62.50 μg/mL ( E. faecalis), >62.50 μg/mL ( E. coli), >62.50 μg/mL ( S. dysenteriae), and >62.50 μg/mL ( C. albicans). These results indicated that the essential oil from the aerial parts of E. helioscopia could be used to control diseases caused by these microbes.

Chemical Diversity of Volatile Compounds of Mints from Southern Part of Pannonian Plain and Balkan Peninsula - New Data

Mints are the most popular economic and traditional herbs. The aim of this article was chemical characterization of volatile compounds from wild populations of Mentha aquatica, M. arvensis, M. longifolia, M. microphylla, M. pulegium, M. spicata, M.×dumetorum, M.×gentillis and M.×verticillata, as well as cultivated samples of M. spicata, M.×piperita 'Alba' and M.×piperita 'Crispa'. Analyses were performed directly from dried aerial parts (herb) of collected samples by headspace gas chromatography-mass spectrometry. In total 54 compounds were detected, representing from 89.99 % to 99.66 % of volatile fractions of all investigated samples. The recorded volatiles were primarily monoterpene hydrocarbons and oxygenated monoterpenes, while oxygenated aromatic monoterpenes, sesquiterpene hydrocarbons and aliphatic compounds were present in lower concentrations in analyzed samples. The major components were linalool, limonene, 1,8-cineol, α-terpinyl acetate, pulegone, β-pinene and menthol. The cluster analysis revealed five main groups or chemotypes according to qualitative and quantitative content of volatiles, as well as similarities among samples. These results contribute to the knowledge on the mints chemistry in Pannonian Plain and Balkan Peninsula.

Cytotoxic Activity of Origanum Vulgare L. on Hepatocellular Carcinoma cell Line HepG2 and Evaluation of its Biological Activity

The potential of plant essential oils (EOs) in anticancer treatment has recently received many research efforts to overcome the development of multidrug resistance and their negative side effects. The aims of the current research are to study (i) the cytotoxic effect of the crude EO extracted from Origanum vulgare subsp hirtum and its main constituents (carvacrol, thymol, citral and limonene) on hepatocarcinoma HepG2 and healthy human renal cells HEK293; (ii) the antibacterial and phytotoxic activities of the above EO and its main constituents. Results showed that cell viability percentage of treated HepG2 by EO and its main constituents was significantly decreased when compared to untreated cells. The calculated inhibition concentration (IC₅₀) values for HepG2 were lower than healthy renal cells, indicating the sort of selectivity of the studied substances. Citral is not potentially recommended as an anticancer therapeutic agent, since there are no significant differences between IC₅₀ values against both tested cell lines. Results showed also that oregano EO and its main constituents have a significant antibacterial activity and a moderate phytotoxic effect. The current research verified that oregano EO and its main constituents could be potentially utilized as anticancer therapeutic agents.

The Essential Oil of Monarda didyma L. (Lamiaceae) Exerts Phytotoxic Activity in Vitro against Various Weed Seed

The chemical composition of the essential oil of the flowering aerial parts of Monarda didyma L. cultivated in central Italy was analyzed by Gas Chromatography/Mass Spectrometry (GC/MS). The major compounds of the oil were thymol (59.3%), p-cymene (10.3%), terpinolene (9.2%), δ-3-carene (4.4%), myrcene (3.7%), and camphene (3.4%). The essential oil was tested in vitro for its anti-germination activity against Papaver rhoeas L., Taraxacum officinale F. H. Wigg., Avena fatua L., Raphanus sativus L. and Lepidium sativum L. seeds, demonstrating good inhibitory activity in a dose-dependent way. The exposure of the employed weed seeds to M. didyma essential oil and thymol solution (59.3%) increased the level of hydrogen peroxide (H₂O₂) and malondialdehyde (MDA), markers of oxidative stress, in emerging 5-day-old rootlets.