Investigation of Antibacterial Activity and Interaction Types of Essential Oils and Their Volatile Components Against Respiratory Tract Bacteria

Respiratory tract infections (RTIs), which mostly occur from autumn to spring, affects people of all ages. Based on pathogenicity, bacteria, viruses, and fungi are the most common cause of these diseases. Therefore, their proper treatment requires complex therapy which can be influenced by secondary bacterial infections. The excessive use of antimicrobials leads to the growing appearance of antibiotic resistant pathogens producing serious problems in medicinal health care nowadays. As a result, efficacy of classic antibiotics is decreasing, they are becoming totally ineffective against these pathogens several times. Therefore, discovery of new alternative treatments, which could support the medical therapy of RTIs, is an important challenge nowadays. Essential oils (EOs) are hydrophobic, natural extracts with complex composition whose antimicrobial effects have been known and used in medicine from ancient times. The application of EOs via inhalation is becoming more frequent nowadays, especially in the case of bacterial infections. Volatile components can easily reach the respiratory tract, the direct contact of fragrances and the infected surface is an advantage of this form of treatment. Multicomponent composition of EOs also gives them benefit against antibiotic-resistant strains. The increasing interest about herbal medicines and their application by the patients requires updated and evidence based knowledge from health care professionals. We must note that the administration of EOs is mostly based on their tradicional use, in several cases more experiments are needed for the determination of their mode of action, dosage and toxicity. In the last decade, the antimicrobial potentials of EOs were studied by several in vitro techniques, but the results mostly focused on the antimicrobial activity of the EOs in liquid media. In the treatment of RTIs, the patients inhale the volatile components through their nose or mouth, hence investigation of the antibacterial activity of EOs’ vapor would be highly important. For the detection of antimicrobial activity of EO volatiles, several in vitro vapor phase techniques exist, however, respiratory tract pathogens are used only in a few studies. Besides, the discovery of new therapeutic alternatives and combination of the effective techniques are another possible solutions. Based on this possibility, in the last decade, several studies focused on the interaction of EOs, volatiles and antibiotics in combination

Antibacterial activity evaluation of selected essential oils in liquid and vapor phase on respiratory tract pathogens.

BACKGROUND: The increasing number of multidrug-resistant bacteria and the fact of antibiotic resistance is leading to a continuous need for discovering alternative treatments against infections, e.g. in the case of respiratory tract diseases. Essential oils (EOs), because of their volatility, can easily reach both the upper and lower parts of the respiratory tract via inhalation. Therefore, the aim of the present study was the antibacterial evaluation of clove, cinnamon bark, eucalyptus, thyme, scots pine, peppermint, and citronella EOs against respiratory tract pathogens such as Streptococcus pneumoniae, S. mutans, S. pyogenes, Haemophilus influenzae, H. parainfluenzae, and Moraxella catarrhalis. Furthermore, we wanted to compare the antibacterial effect of these EOs in two different test systems to provide data for the development of an appropriate product formulation. METHODS: Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined with in vitro vapor phase test (VPT) and broth macrodilution test (BDT). The chemical and percentage compositions of the EOs were determined by GC-MS and GC-FID analysis. RESULTS: Among the EOs, thyme was the most effective against S. mutans (MIC: 0.04 mg/mL in BDT, but cinnamon bark and clove oils also presented high inhibition in liquid medium with MIC values of 0.06 mg/mL and 0.1 mg/mL against S. pneumoniae and S. pyogenes, respectively. M. catarrhalis was the most sensitive to thyme EO (MIC: 0.09 mg/mL). Cinnamon bark EO was the most effective against Haemophilus spp. (MIC: 0.06 mg/mL). In the VPT, cinnamon bark was the most effective oil against all investigated pathogens with MIC values in the range of 15.62-90 mul/L. Surprisingly, the eucalyptus and scots pine showed weak activity against the test bacteria in both test systems. CONCLUSIONS: The EO of thyme, clove and cinnamon bark may provide promising antibacterial activity against respiratory tract pathogens either in liquid medium or in vapor phase. However, their effect is lower than that of the reference antibiotics. The combination of EOs and antibiotics may be beneficial in the alternative treatment of respiratory tract diseases. In vivo studies are necessary to calculate the effective dose of EOs in patients and determine their possible side effects and toxicity

Essential-oil component combinations: possibilities against respiratory tract pathogens

Nowadays, the excessive use of antimicrobials leads to the growing appearance of resistant pathogens in the case of respiratory tract infections (RTIs). Therefore, the discovery of new alternatives, which could support their therapy is an important challenge. Combination of the effective substances is one of the possible solutions. Based on this possibility, several studies focused on the interaction between essential oils (EOs) and their volatiles in the last decade.                Therefore, the aim of the present study was to evaluate the most effective EO components of cinnamon bark, thyme, clove, peppermint, and citronella oils. Direct bioautography (DB) was used in the detection of interaction profiles of trans-cinnamaldehyde, eugenol, thymol, menthol, geraniol, citronellal, and citral against methicillin-resistant Staphylococcus aureus (MRSA, 4262), resistant Pseudomonas aeruginosa (RPA, 34205), and P. aeruginosa (ATCC 27853). First, the minimal detectable dose (MDD) of individual components was determined. According to the MDD values, the combined, as well as the individual compounds, were applied to the TLC plates. The diameters of the inhibition zones were measured with the Motic Images Plus 2.0 program. The statistical analysis was performed with the Mann-Whitney-Wilcoxon test of the R Studio 1.1.383 program.                In the case of P. aeruginosa, a combination of thymol and menthol was active; against RPA, trans-cinnamaldehyde combined with thymol was found to be effective. Against MRSA, menthol combined with trans-cinnamaldehyde, and eugenol also showed enhanced activity.                According to our knowledge, we applied for the first time the DB for the detection of antimicrobially effective combinations of EO compounds. It could be regarded as a cost-effective and quick screening method. In the future, we would like to focus on the combinations of EOs and their main components with antibiotics as well

Treatment of Benign Prostatic Hyperplasia by Natural Drugs

Benign prostatic hyperplasia (BPH) is one of the most common urinary diseases affecting men, generally after the age of 50. The prevalence of this multifactorial disease increases with age. With aging, the plasma level of testosterone decreases, as well as the testosterone/estrogen ratio, resulting in increased estrogen activity, which may facilitate the hyperplasia of the prostate cells. Another theory focuses on dihydrotestosterone (DHT) and the activity of the enzyme 5α-reductase, which converts testosterone to DHT. In older men, the activity of this enzyme increases, leading to a decreased testosterone/DHT ratio. DHT may promote prostate cell growth, resulting in hyperplasia. Some medicinal plants and their compounds act by modulating this enzyme, and have the above-mentioned targets. This review focuses on herbal drugs that are most widely used in the treatment of BPH, including pumpkin seed, willow herb, tomato, maritime pine bark, Pygeum africanum bark, rye pollen, saw palmetto fruit, and nettle root, highlighting the latest results of preclinical and clinical studies, as well as safety issues. In addition, the pharmaceutical care and other therapeutic options of BPH, including pharmacotherapy and surgical options, are discussed, summarizing and comparing the advantages and disadvantages of each therapy

The nanotechnological formulation and anti-biofilm activity of thyme essential oil against Streptococcus pneumoniae

Bacterial biofilm is a structured community of bacterial cells enclosed in a self-produced polymeric matrix and adherent to an inert or living surface, which allows a protected mode of growth and survival in a hostile environment. Infections associated with biofilm growth usually are challenging to eradicate. It is mostly due to the fact that mature biofilms display tolerance towards antibiotics and the immune response. For example, bacterial biofilms can be formed in the human respiratory tract. The essential oil of thyme (Thymus vulgaris L., Lamiaceae) is well-known in the therapy of respiratory tract infections, but there is no information about the anti-biofilm activity of its hydrophilic formulation against respiratory tract pathogens.                The aim of the study was to investigate the anti-biofilm effect of a thyme oil (Aromax Ltd., Hungary) formulated with nanotechnology against Streptococcus pneumoniae (DSM 20566). The oil was analyzed by GC-FID/MS. The Pickering emulsion of the oil was produced via the Stöber synthesis and stabilized with silica-nanoparticles. The bacterial biofilm (108 CFU/mL) was created in 96-well microtiter plates. After incubation (4 h, 37 °C), the Pickering emulsion and the Tween 80 solution of the thyme oil were added to the biofilm in MIC/2 concentration (0.05 mg/mL). After a second incubation (24 h), the adherent cells were fixed with methanol and stained with 0.1% crystal violet and dissolved in 33% acetic acid. The absorbance (A) was measured at 590 nm with a plate reader (BMG Labtech).                Our results showed that the thyme oil had anti-biofilm activity against S. pneumoniae, because it reduced the biomass of the biofilms. It is important to highlight that the Pickering emulsion of the oil was more effective (A = 0.53) than the Tween 80 solution (A = 0.84) compared to the control (A = 3.71). This confirms that the Pickering emulsion of thyme oil can prevent the S. pneumoniae biofilm formation more effectively than the Tween 80 solution

Applicability of cinnamon bark essential oil in respiratory tract diseases – from in vitro to in vivo experiments

Introduction: Because respiratory tract diseases affect every age group and antibiotic resistance is an increasing problem in healthcare, there is a need for additional therapies. Essential oils (EOs) are used via inhalation for the treatment of respiratory tract diseases for a long time. Similarly to other plant extracts, their efficacy should also be proved in several test systems. Therefore, our aim was to study the antibacterial and antiinflammatory effects of cinnamon bark oil in in vitro and in vivo models.                Methods: The chemical composition of cinnamon EO was determined by GC-FID/MS and SPME-GC-MS methods. The antibacterial effect of the EO was tested by macrodilution and vapor-phase methods against respiratory tract pathogens. The emulsion of the EO prepared by nanotechnology was also used for the examination of the biofilm inhibitory effect. The antiinflammatory effect was studied in an LPS-induced acute airway inflammation mouse model.                Results and conclusion: The main component of the EO was trans-cinnamaldehyde (74.0%, 46.0%) in both analytical systems. In the liquid medium, cinnamon EO exhibited antibacterial activity against Streptococcus pyogenes, S. pneumoniae, S. mutans, Haemophilus influenzae and H. parainfluenzae (MIC: 0.06 mg/mL). In the vapor-phase test, the EO was the most effective against Haemophilus strains (MIC: 15.6 μL/L). The biofilm formation of S. mutans was more effectively reduced by the emulsion of cinnamon oil prepared by nanotechnology compared to the emulsions prepared with Tween80 or alcohol. In the animal model, cinnamon oil inhalation reduced airway hyperreactivity, macrophage accumulation in histological images, but did not affect MPO activity. Therefore, cinnamon oil may be a potential antibacterial and antiinflammatory agent for the treatment of respiratory tract diseases

Anti-Haemophilus Activity of Selected Essential Oils Detected by TLC-Direct Bioautography and Biofilm Inhibition

Essential oils (EOs) are becoming increasingly popular in medical applications because of their antimicrobial effect. Direct bioautography (DB) combined with thin layer chromatography (TLC) is a screening method for the detection of antimicrobial compounds in plant extracts, for example, in EOs. Due to their lipophilic character, the common microbiological assays (etc. disk diffusion) could not provide reliable results. The aim of this study was the evaluation of antibacterial and anti-biofilm properties of the EO of cinnamon bark, clove, peppermint, thyme, and their main components against Haemophilus influenzae and H. parainfluenzae. Oil in water (O/W) type Pickering nano-emulsions stabilized with silica nanoparticles from each oil were prepared to increase their water-solubility. Samples with Tween80 surfactant and absolute ethanol were also used. Results showed that H. influenzae was more sensitive to the EOs than H. parainfluenzae (except for cinnamon bark oil). In thin layer chromatography-direct bioautography (TLC-DB) the ethanolic solutions of thyme oil presented the best activity against H. influenzae, while cinnamon oil was the most active against H. parainfluenzae. Pickering nano-emulsion of cinnamon oil inhibited the biofilm formation of H. parainfluenzae (76.35%) more efficiently than samples with Tween80 surfactant or absolute ethanol. In conclusion, Pickering nano-emulsion of EOs could inhibit the biofilm production effectively

Treatment of Benign Prostatic Hyperplasia by Natural Drugs

Benign prostatic hyperplasia (BPH) is one of the most common urinary diseases affecting men, generally after the age of 50. The prevalence of this multifactorial disease increases with age. With aging, the plasma level of testosterone decreases, as well as the testosterone/estrogen ratio, resulting in increased estrogen activity, which may facilitate the hyperplasia of the prostate cells. Another theory focuses on dihydrotestosterone (DHT) and the activity of the enzyme 5α-reductase, which converts testosterone to DHT. In older men, the activity of this enzyme increases, leading to a decreased testosterone/DHT ratio. DHT may promote prostate cell growth, resulting in hyperplasia. Some medicinal plants and their compounds act by modulating this enzyme, and have the above-mentioned targets. This review focuses on herbal drugs that are most widely used in the treatment of BPH, including pumpkin seed, willow herb, tomato, maritime pine bark, Pygeum africanum bark, rye pollen, saw palmetto fruit, and nettle root, highlighting the latest results of preclinical and clinical studies, as well as safety issues. In addition, the pharmaceutical care and other therapeutic options of BPH, including pharmacotherapy and surgical options, are discussed, summarizing and comparing the advantages and disadvantages of each therapy