Essential Oil as Antimicrobial (original) (raw)
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Membrane Toxicity of Antimicrobial Compounds from Essential Oils
Journal of Agricultural and Food Chemistry, 2007
Natural antimicrobial compounds perform their action mainly against cell membranes. The aim of this work was to evaluate the interaction, meant as a mechanism of action, of essential oil antimicrobial compounds with the microbial cell envelope. The lipid profiles of Escherichia coli O157:H7, Staphylococcus aureus, Salmonella enterica serovar Typhimurium, Pseudomonas fluorescens, and Brochothrix thermosphacta cells treated with thymol, carvacrol, limonene, eugenol, and cinnamaldehyde have been analyzed by gas chromatography. In line with the fatty acids analysis, the treated cells were also observed by scanning electron microscopy (SEM) to evaluate structural alterations. The overall results showed a strong decrease of the unsaturated fatty acids (UFAs) for the treated cells; in particular, the C18:2trans and C18:3cis underwent a notable reduction contributing to the total UFA decreases, while the saturated fatty acid C17:0 raised the highest concentration in cinnamaldehyde-treated cells. SEM images showed that the used antimicrobial compounds quickly exerted their antimicrobial activities, determining structural alterations of the cell envelope.
Membranes, 2021
The biological activity of essential oils and their major components is well documented. Essential oils such as oregano and cinnamon are known for their effect against bacteria, fungi, and even viruses. The mechanism of action is proposed to be related to membrane and external cell structures, including cell walls. This study aimed to evaluate the biological activity of seven essential oils and eight of their major components against Gram-negative and Gram-positive bacteria, filamentous fungi, and protozoans. The antimicrobial activity was evaluated by determination of the Minimal Inhibitory Concentration for Bacillus cereus, Staphylococcus aureus, Listeria monocytogenes, Escherichia coli, Salmonella Typhimurium, Shigella sonnei, Aspergillus niger, Aspergillus ochraceus, Alternaria alternata, and Fusarium oxysporium, the half-maximal inhibitory concentration (IC50) for Trypanosoma cruzi and Leishmania mexicana, and the median lethal dose (LD50) for Giardia lamblia. Results showed that oregano essential oil showed the best antibacterial activity (66-100 µg/mL), while cinnamon essential oil had the best fungicidal activity (66-116 µg/mL), and both showed excellent antiprotozoal activity (22-108 µg/mL). Regarding the major components, thymol and carvacrol were also good antimicrobials (23-200 µg/mL), and cinnamaldehyde was an antifungal compound (41-75 µg/mL). The major components were grouped according to their chemical structure as phenylpropanoids, terpenoids, and terpinenes. The statistical analysis of the grouped data demonstrated that protozoans were more susceptible to the essential oils, followed by fungi, Grampositive bacteria, and Gram-negative bacteria. The analysis for the major components showed that the most resistant microbial group was fungi, which was followed by bacteria, and protozoans were also more susceptible. Principal Component Analysis for the essential oils demonstrated the relationship between the biological activity and the microbial group tested, with the first three components explaining 94.3% of the data variability. The chemical structure of the major components was also related to the biological activity presented against the microbial groups tested, where the three first principal components accounted for 91.9% of the variability. The external structures and the characteristics of the cell membranes in the different microbial groups are determinant for their susceptibility to essential oils and their major components.
Essential Oils, a Possible Solution to Overcome Antimicrobial Resistance Crisis
Romanian Medical Journal, 2015
Having emerged as an ideal solution against pathogenic microorganisms, antimicrobial medication seems to have lost the battle today. The ability of the living world to survive and adapt exceeds the synthetic products power of action, leading us today to a real crisis of microbial resistance to antibiotics. An unexpected solution may come also from the bosom of nature, by reconsidering the role and place of the essential oils as antimicrobial combat weapons. Defensive mechanisms created by nature, the essential oils demonstrate extraordinary antibacterial, antiviral and antifungal activity. They also help the synthetic antibiotics in their battle. Among the essential oils and the antibiotics, often intervene synergistic or additive interactions. The essential oils favor the antibiotics to penetrate through the cell wall and to extend their action spectrum. Undoubtedly, essential oils can be of crucial help in the current medical practice, through their complex antibacterial, antivira...
An Overview of the Potential Therapeutic Applications of Essential Oils
Molecules, 2021
The emergence of antimicrobial resistance (AMR) has urged researchers to explore therapeutic alternatives, one of which includes the use of natural plant products such as essential oils (EO). In fact, EO obtained from clove, oregano, thymus, cinnamon bark, rosemary, eucalyptus, and lavender have been shown to present significant inhibitory effects on bacteria, fungi, and viruses; many studies have been done to measure EO efficacy against microorganisms. The strategy of combinatory effects via conventional and non-conventional methods revealed that the combined effects of EO–EO or EO–antibiotic exhibit enhanced efficacy. This paper aims to review the antimicrobial effects of EO, modes of EO action (membrane disruption, efflux inhibition, increase membrane permeability, and decrease in intracellular ATP), and their compounds’ potential as effective agents against bacteria, fungi, and viruses. It is hoped that the integration of EO applications in this work can be used to consider EO f...
Antibacterial Activity of Terpenes and Terpenoids Present in Essential Oils
Molecules
Background: The antimicrobial activity of essential oils has been reported in hundreds of studies, however, the great majority of these studies attribute the activity to the most prevalent compounds without analyzing them independently. Therefore, the aim was to investigate the antibacterial activity of 33 free terpenes commonly found in essential oils and evaluate the cellular ultrastructure to verify possible damage to the cellular membrane. Methods: Screening was performed to select substances with possible antimicrobial activity, then the minimal inhibitory concentrations, bactericidal activity and 24-h time-kill curve studies were evaluated by standard protocols. In addition, the ultrastructure of control and death bacteria were evaluated by scanning electron microscopy. Results: Only 16 of the 33 compounds had antimicrobial activity at the initial screening. Eugenol exhibited rapid bactericidal action against Salmonella enterica serovar Typhimurium (2 h). Terpineol showed exce...
The mode of antibacterial action of essential oils
The antimicrobial activity of essential oils and their components has been recognized for a very long time. Essential oils (EOs) are made from a very complex mixture of volatile molecules that are produced by the secondary metabolism of aromatic and medicinal plants and can be obtained by distillation of different parts of plants. The large number of studies on the antimicrobial activity of EOs has allowed the scientific recognition of these compounds on the control of a wide range of microbial pathogens. The progresses made on the investigation of the mode of action of EOs against bacterial cell targets give us new perspectives to combat persistent and antimicrobial resistant bacterial pathogens. The recent investigation on the activity of EOs disruption of quorum sensing process is an excellent example. On the other hand proteomic analysis show that bacterial pathogens respond to EO sublethal doses using known mechanisms of adaptation to several environmental stress conditions.
Effect of Essential Oils on Pathogenic Bacteria
Pharmaceuticals, 2013
The increasing resistance of microorganisms to conventional chemicals and drugs is a serious and evident worldwide problem that has prompted research into the identification of new biocides with broad activity. Plants and their derivatives, such as essential oils, are often used in folk medicine. In nature, essential oils play an important role in the protection of plants. Essential oils contain a wide variety of secondary metabolites that are capable of inhibiting or slowing the growth of bacteria, yeasts and moulds. Essential oils and their components have activity against a variety of targets, particularly the membrane and cytoplasm, and in some cases, they completely change the morphology of the cells. This brief review describes the activity of essential oils against pathogenic bacteria.
Recent Advances in the Application of Antibacterial Complexes Using Essential Oils
Molecules, 2020
Although antibacterial spectrum of essential oils (EOs) has been analyzed along with consumers’ needs on natural biocides, singular treatments generally require high concentration of EOs and long-term exposures to eliminate target bacteria. To overcome these limitations, antibacterial complex has been developed and this review analyzed previous reports regarding the combined antibacterial effects of EOs. Since unexpectable combined effects (synergism or antagonism) can be derived from the treatment of antibacterial complex, synergistic and antagonistic combinations have been identified to improve the treatment efficiency and to avoid the overestimation of bactericidal efficacy, respectively. Although antibacterial mechanism of EOs is not yet clearly revealed, mode of action regarding synergistic effects especially for the elimination of pathogens by using low quantity of EOs with short-term exposure was reported. Whereas comprehensive analysis on previous literatures for EO-based di...
Microbial Pathogenesis, 2017
The pervasive of bacterial resistance earnestly threaten the prevention and the treatment of infectious diseases. Therefore, scientific communities take precedence over development of new antimicrobial agents. The aim of the study was to determine antimicrobial potency of three North-African essential oils Pituranthos chloranthus, Teucruim ramosissimum and Pistacia lentiscus individually, and in combination with antibiotics, to inhibit the growth of highly resistant clinical pathogen. Bacteria clinically isolated from patients, subsequently, challenged to a panel of drugs to determine the antibiotic-resistance profiles. Drugs displaying clinically irrelevant CMI were subjected to further studies in order to rescue antibiotic actions. Singular activity of essential oils and activity when combined with an antibiotic was hence elucidated. The results obtained highlighted the occurrence of strong antibacterial potential of essential oils when administrated alone. In the interactive experiment essential oils were found highly effective in reducing the resistance of Methicillinresistant Staphylococcus aureus to amoxicillin, tetracycline, piperacillin, ofloxacin and oxacillin and resistance of Acinetobacter baumannii to amoxicillin and to ofloxacin in interactive manner. Furthermore, the results proved synergism among essential oils and both antibiotics ofloxacin and novobiocin against the Extended-Spectrum Beta-Lactamase producing E.coli (ESBL). Time kill kinetics was performed with a combination of subinhibitory concentrations to confirm the efficiency and killing rate of the combination over time. Further, the hypothetical toxicity of essential oils against human keratinocytes HaCat and murine spleenocytes were examined. The chemical composition of essential oils was assessed by GC/MS analysis and the major constituents found were sabinene, limonene, terpinen-4-ol, and β-eudesmol.
Synergy between essential oil components and antibiotics: a review
Critical Reviews in Microbiology, 2014
With the increase in antibiotic-resistant bacteria and the lack of new antibiotics being brought onto the market, alternative strategies need to be found to cope with infections resulting from drug-resistant bacteria. A possible solution may be to combine existing antibiotics with phytochemicals to enhance the efficacy of antibiotics. A group of phytochemicals that is said to have such effects, according to in vitro studies, is essential oils (EOs) and their components. Amongst others, EOs containing carvacrol, cinnamaldehyde, cinnamic acid, eugenol and thymol can have a synergistic effect in combination with antibiotics. Several modes of action have been put forward by which antibiotics and the essential oil components may act synergistically, such as by affecting multiple targets; by physicochemical interactions and inhibiting antibacterial-resistance mechanisms. Many reported assays show additivity or moderate synergism, indicating that EOs may offer possibilities for reducing antibiotic use.