However, there is limited detailed information about how these compounds achieve this antimicrobial activity, and at the same time, additional information is required on the antimicrobial potential of pure compounds present in EOs. It has been observed that the mode of action of EOs is based on their ability to disrupt cell wall and cytoplasmic membrane, leading to lysis and leakage of intracellular compounds. ĮOs exhibit antimicrobial potential against a large number of Gram-negative and Gram-positive bacteria. The biological activities are related with EOs bioactive compounds, as well as the functional groups and structure arrangement from these molecules. A large number of biological activities have been reported for EOs such as antimicrobial, antiviral, antimycotic, antiparasitic, insecticidal, antidiabetic, antioxidant, and anticancer. In addition, these natural compounds are generally recognized as safe by FDA (Food and Drug Administration, US). Nowadays, more than 3000 EOs have been identified and only 10% are approved for use in diverse areas (pharmaceutical, food, and cosmetic). The second group present in EOs (less predominance) are aromatics compounds, derived from phenylpropane (mixtures of aldehydes, alcohols, phenols, methoxy derivatives, and methylenedioxy compounds). They are classified as monoterpenes and sesquiterpenes, according to the number of isoprene units, monoterpenes being the most abundant in EOs components. ĮOs are a complex mixture of natural, volatile, and aromatic compounds synthesized by aromatic plants that have been often used in traditional medicine. The principal phytochemicals present in plants are essential oils (EOs), phenolic compounds, alkaloids, lectins/polypeptides, and polyacetylenes. The majority of these compounds are used by plants as a defense mechanism against other microorganisms, herbivores, and competitors. Plants produce an enormous array of functional relevant secondary metabolites (phytochemicals) that exhibit a diversity of medicinal properties.
Therefore, it is necessary to develop new alternative compounds to decrease the problem of the microbial resistance. It is also estimated that antimicrobial resistance causes more than 2,049,442 illnesses and 23,000 deaths per year in the United States and these cases are increasing every year. According to the World Health Organization (WHO) infectious diseases are the second cause of death around the world. Consequently, the therapeutic options for the treatment of infections have become limited or even unavailable. Due to this growing increase of resistance, many antimicrobial agents are losing their efficacy. During the last decades, rapid evolution and spread of resistance among clinically important bacterial species have been observed. IntroductionĪntimicrobial resistance is one of the most serious public health threats that results mostly from the selective pressure exerted by antibiotic use and abuse. Moreover, these molecules are interesting alternatives to conventional antimicrobials for the control of microbial infections. This study demonstrates that the selected EOs have significant antimicrobial activity against the bacteria tested, acting on the cell surface and causing the disruption of the bacterial membrane. aureus were observed after exposure to EOs. Changes in the hydrophobicity, surface charge, and membrane integrity with the subsequent leakage from E. Citronellol was the most effective molecule against both pathogens, followed by citronellal, carveol, and carvone. Moreover, physicochemical bacterial surface characterization, bacterial surface charge, membrane integrity, and leakage assays were carried out to investigate the antimicrobial mode of action of EOs components. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were assessed for the selected EOs components. The objective of this study was to determine the antibacterial effect and mode of action of selected essential oils (EOs) components: carveol, carvone, citronellol, and citronellal, against Escherichia coli and Staphylococcus aureus. Natural-based products, including plant secondary metabolites (phytochemicals), may be used to surpass or reduce this problem. Bacterial resistance has been increasingly reported worldwide and is one of the major causes of failure in the treatment of infectious diseases.
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