Antibacterial Properties of Eucalyptus globulus Essential Oil against MRSA: A Systematic Review

Antibacterial and Antibiofilm Activity of Croton urticifolius Lam. Essential Oil Via Membrane Disruption

Antimicrobial resistance is a global health issue, in which microorganisms develop resistance to antimicrobial drugs, making infections more difficult to treat. This threatens the effectiveness of standard medical treatments and necessitates the urgent development of new strategies to combat resistant microbes. Studies have increasingly explored natural sources of new antimicrobial agents that harness the rich diversity of compounds found in plant species. This pursuit holds promise for the discovery of novel treatments for combating antimicrobial resistance. In this context, the chemical composition, antibacterial, and antibiofilm activities of the essential oil from Croton urticifolius Lam. leaves (CuEO) were evaluated. CuEO was extracted via hydrodistillation, and its chemical constituents were identified via gas chromatography-mass spectrometry (GC/MS). The antibacterial activity of CuEO was evaluated in a 96-well plate via the microdilution method, and the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values were determined. The effect of CuEO on biofilm formation was assessed by quantifying the biomass using crystal violet staining and viable cell counting. In addition, alterations in the cellular morphology of biofilms treated with CuEO were examined using scanning electron microscopy (SEM) and laser confocal microscopy. GC/MS analysis identified 26 compounds, with elemicine (39.72%); eucalyptol (19.03%), E-caryophyllene (5.36%), and methyleugenol (4.12%) as the major compounds. In terms of antibacterial activity, CuEO showed bacteriostatic effects against Staphylococcus aureus ATCC 700698, S. aureus ATCC 25923, Staphylococcus epidermidis ATCC 12228, and Escherichia coli ATCC 11303, and bactericidal activity against S. aureus ATCC 700698. In addition, CuEO significantly inhibited bacterial biofilm formation. Microscopic analysis showed that CuEO damaged the bacterial membrane by leaching out the cytoplasmic content. Therefore, the results of this study show that the essential oil of C. urticifolius may be a promising natural alternative for preventing infections caused by bacterial biofilms. This study is the first to report the antibiofilm activity of C. urticifolius essential oil.

Silicon attenuates nutritional disorder of phosphorus in seedlings of Eucalyptus grandis × Eucalyptus urophylla

BACKGROUND

Nutritional disorders of phosphorus (P), due to deficiency or toxicity, reduce the development of Eucalyptus spp. seedlings. Phosphorus deficiency often results in stunted growth and reduced vigor, while phosphorus toxicity can lead to nutrient imbalances and decreased physiological function. These sensitivities highlight the need for precise management of P levels in cultivation practices. The use of the beneficial element silicon (Si) has shown promising results under nutritional stress; nevertheless, comprehensive studies on its effects on Eucalyptus spp. seedlings are still emerging. To further elucidate the role of Si under varying P conditions, an experiment was conducted with clonal seedlings of a hybrid Eucalyptus spp. (Eucalyptus grandis × Eucalyptus urophylla, A207) in a soilless cultivation system. Seedlings were propagated using the minicutting method in vermiculite-filled tubes, followed by treatment with a nutrient solution at three P concentrations: a deficient dose (0.1 mM), an adequate dose (1.0 mM) and an excessive dose (10 mM), with and without the addition of Si (2mM). This study assessed P and Si concentration, nutritional efficiency, oxidative metabolism, photosynthetic parameters, and dry matter production.

RESULTS

Si supply increased phenolic compounds production and reduced electrolyte leakage in seedlings provided with 0.1 mM of P. On the other hand, Si favored quantum efficiency of photosystem II as well as chlorophyll a content in seedlings supplemented with 10 mM of P. In general, Si attenuates P nutritional disorder by reducing the oxidative stress, favoring the non-enzymatic antioxidant system and photosynthetic parameters in seedlings of Eucalyptus grandis × Eucalyptus urophylla.

CONCLUSION

The results of this study indicate that Eucalyptus grandis × Eucalyptus urophylla seedlings are sensitive to P deficiency and toxicity and Si has shown a beneficial effect, attenuating P nutritional disorder by reducing the oxidative stress, favoring the non-enzymatic antioxidant system and photosynthetic parameters.

Redox profile of silver catfish challenged with Aeromonas hydrophila and treated with hexane extract of Hesperozygis ringens (Benth.) Epling through immersion bath

The growing increase in the fish farming sector has favored the establishment of bacterial outbreaks caused by Aeromonas hydrophila in several species. The hexane extract of Hesperozygis ringens (HEHR) (Lamiaceae) leaves increased the survival rate of silver catfish (Rhamdia quelen) experimentally infected by A. hydrophila. However, it is noteworthy that no reports have been found on the possible mechanisms of action of this extract in infected fish. This study aimed to evaluate the effect of the HEHR, administered through single immersion bath, on lipid peroxidation and antioxidant defenses in muscle and liver tissue of silver catfish challenged with A. hydrophila. The results showed that the oxidative status of silver catfish was altered, although oxidative stress was not triggered during the experiment. HEHR at 30 mg/L (HEHR30) was not characterized as a pro-oxidant agent in the presence of infection, unlike florfenicol and HEHR at 15 mg/L treatments in some cases. In short, HEHR30 provided an important increase in hepatic catalase activity, characterizing one of the possible mechanisms involved in the greater survival of fish experimentally infected by A. hydrophila. Additionally, HEHR30 did not induce lipid peroxidation, nor reduced antioxidant defenses of silver catfish infected or not by A. hydrophila.

Production of natural flavor compounds using Bacillus subtilis-fermented soybean meal extract and their biological potential: a comprehensive in vitro study

This study aims to investigate the production of natural flavor compounds through the utilization of Bacillus subtilis-fermented soybean meal extract and evaluate their biological potential. The experiment involved a comprehensive in vitro investigation to assess the capabilities and effects of the produced flavor compounds. The resulting flavor compounds were subjected to various in vitro tests to assess their properties, including cytotoxicity, antioxidant activity, anticancer potential, antiviral activity, and antimicrobial activity. To enhance the fermentation process, soybean meal extract was fortified with a combination of L-Lysine and L-Threonine. Gas chromatography-mass spectrometry (GC/MS) analysis was conducted on the fermented soybean meal using two strains of Bacillus subtilis, namely NRCH123 and NRCZ144. This analysis revealed the presence of various volatile compounds in all extracts, including Butylated hydroxytoluene. The fermented soybean extract with bacillus subtilis NRCZ144 (B2) fortified with a combination of 2.5% (w/w) L-Lysine and 2.5% w/w L-threonine (SLT2) exhibited a rich profile of flavor compounds, with Eucalyptol being identified as the predominant compound. The antioxidant activity of the SLT2 extract was found to be 72.04% at a concentration of 100 μg/mL, indicating significant antioxidant potential. Furthermore, when tested against the human liver cancer cell line HepG2, the extract demonstrated anticancer activity with an IC50 value of 2.26 μg/mL. The extract exhibited potent cytotoxicity, with an IC50 value of 1.02 μg/mL. Importantly, the SLT2 extract displayed strong antibacterial and antifungal activity, even at very low concentrations. The extract's antimicrobial properties indicate its potential for inhibiting the growth of bacteria and fungi.

Short- and long-term effects of essential oils on swine spermatozoa during liquid phase refrigeration

The application of essential oils as potential alternatives to antibiotics in swine semen storage is promising, due to their antioxidant and antibacterial properties. However, detrimental effects on spermatozoa should be clarified first. The aim of this study was to evaluate 9 essential oils (EOs; Satureja montana, Pelargonium graveolens, Cymbopogon nardus, Melaleuca leucadendron, Eucaliptus globulus, Citrus limon, Lavandula angustifolia, Lavandula hybrida, Mentha piperita) and a blend (GL mix) on key morpho-functional parameters of swine spermatozoa. Test compounds were firstly chemo-characterized and experimental doses were prepared by suspending a fixed number of spermatozoa with 3 different concentrations (0.1, 0.5, 1 mg/mL) of EOs. Experimental doses were stored at 16 °C and sampled after 3 and 120 h for analysis. Overall, S. montana, P. graveolens and L. angustifolia EOs induced the strongest alterations, with C. nardus and E. globulus EOs being the best tolerated. Swine spermatozoa represent a good preliminary testing platform to screen toxicity and its different patterns. The comprehensive overview on the potential mechanisms of action of some of the most common EOs, despite of the direct aim of the study being swine reproduction, may be exploited in other fields of research within both veterinary and human medicine.

Antibacterial and Antibiofilm Effects of Different Samples of Five Commercially Available Essential Oils

Essential oils (EOs) have gained economic importance due to their biological activities, and increasing amounts are demanded everywhere. However, substantial differences between the same essential oil samples from different suppliers are reported-concerning their chemical composition and bioactivities-due to numerous companies involved in EOs production and the continuous development of online sales. The present study investigates the antibacterial and antibiofilm activities of two to four samples of five commercially available essential oils (Oregano, Eucalyptus, Rosemary, Clove, and Peppermint oils) produced by autochthonous companies. The manufacturers provided all EOs' chemical compositions determined through GC-MS. The EOs' bioactivities were investigated in vitro against Gram-positive (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa). The antibacterial and antibiofilm effects (ABE% and, respectively, ABfE%) were evaluated spectrophotometrically at 562 and 570 nm using microplate cultivation techniques. The essential oils' calculated parameters were compared with those of three standard broad-spectrum antibiotics: Amoxicillin/Clavulanic acid, Gentamycin, and Streptomycin. The results showed that at the first dilution (D1 = 25 mg/mL), all EOs exhibited antibacterial and antibiofilm activity against all Gram-positive and Gram-negative bacteria tested, and MIC value > 25 mg/mL. Generally, both effects progressively decreased from D1 to D3. Only EOs with a considerable content of highly active metabolites revealed insignificant differences. E. coli showed the lowest susceptibility to all commercially available essential oils-15 EO samples had undetected antibacterial and antibiofilm effects at D2 and D3. Peppermint and Clove oils recorded the most significant differences regarding chemical composition and antibacterial/antibiofilm activities. All registered differences could be due to different places for harvesting the raw plant material, various technological processes through which these essential oils were obtained, the preservation conditions, and complex interactions between constituents.

Modes of Action of 1,8-Cineol in Infections and Inflammation

The monoterpene 1,8-Cineol is a natural plant-based therapeutic agent that is commonly applied to treat different inflammatory diseases due to its mucolytic, anti-microbial and anti-inflammatory properties. It has become increasingly clear in the recent years that 1,8-Cineol spreads almost everywhere in the human body after its oral administration, from the gut to the blood to the brain. Its anti-microbial potential and even its anti-viral effects have been observed to include numerous bacteria and fungi species. Many recent studies help to better understand the cellular and molecular immunological consequences of 1,8-Cineol treatment in inflammatory diseases and further provide information concerning the mechanistic modes of action in the regulation of distinct inflammatory biosynthetic pathways. This review aims to present a holistic and understandable overview of the different aspects of 1,8-Cineol in infections and inflammation.

Synergistic Inhibition of Methicillin-Resistant Staphylococcus aureus (MRSA) by Melaleuca alternifolia Chell (Tea Tree) and Eucalyptus globulus Labill. Essential Oils in Association with Oxacillin

The presence of antibiotic-resistant bacteria has become a major therapeutic priority. This trend indicates the need for alternative agents to antibiotics, such as natural compounds of plant origin. By assessing membrane permeability, we investigated the antimicrobial activity of Melaleuca alternifolia and Eucalyptus globulus essential oils (EOs) against three strains of methicillin-resistant Staphylococcus aureus (MRSA). Using the checkerboard method, the efficacy of single EOs, in association with each other or in combination with oxacillin, was quantified by calculating the fractional inhibitory concentrations (FIC Index). All EOs showed a reduction in bacterial load, an alteration of membrane permeability which leads to an increase in its function, resulting in the release of nucleic acids and proteins. The treatment with EO-oxacillin combinations and associated EO-EO resulted in a synergistic effect in most of the tests performed. EO-EO association showed a high activity in the alteration of the membrane, increasing the permeability to about 80% in all the MRSA strains treated. In conclusion, the combination of EOs and antibiotics represents a valid therapeutic support against MRSA bacteria, allowing for a decrease in the antibiotic concentration needed for therapeutic use.