Evaluation of the Antimicrobial Activity and Cytotoxicity of Different Components of Natural Origin Present in Essential Oils

Abstract

Even though essential oils (EOs) have been used for therapeutic purposes, there is now a renewed interest in the antimicrobial properties of phytochemicals and EOs in particular. Their demonstrated low levels of induction of antimicrobial resistance make them interesting for bactericidal applications, though their complex composition makes it necessary to focus on the study of their main components to identify the most effective ones. Herein, the evaluation of the antimicrobial action of different molecules present in EOs against planktonic and biofilm-forming Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria was assessed. The bactericidal mechanisms of the different molecules, as well as their cytocompatibility, were also studied. Carvacrol, cinnamaldehyde, and thymol exhibit the highest in vitro antimicrobial activities against E. coli and S. aureus, with membrane disruption the bactericidal mechanism identified. The addition of those compounds (≥0.5 mg/mL) hampers S. aureus biofilm formation and partially eliminates preformed biofilms. The subcytotoxic values of the tested EO molecules (0.015–0.090 mg/mL) are lower than the minimum inhibitory and bactericidal concentrations obtained for bacteria (0.2–0.5 mg/mL) but are higher than that obtained for chlorhexidine (0.004 mg/mL), indicating the reduced cytotoxicity of EOs. Therefore, carvacrol, cinnamaldehyde, and thymol are molecules contained in EOs that could be used against E. coli– and S. aureus–mediated infections without a potential induction of bactericidal resistance and with lower cell toxicity than the conventional widely used chlorhexidine.

Volatile Antimicrobial Agents and In Vitro Methods for Evaluating Their Activity in the Vapour Phase: A Review

“…As they often possess a broad spectrum of biological effects [13], EOs have potential in various applications for human, animal, and plant health, as well as food quality. Besides antimicrobial activity [14][15][16], EOs and their constituents have been observed to exhibit anaesthetic [17], antiparasitic [18], anti-inflammatory [19], antioxidant [20], antiulcer [21], antiviral [22], cytotoxic [23], immunomodulatory [24], insecticidal [25], and molluscicidal [26] properties. Despite their historical record as medicinal agents, European and American health authorities such as the European Pharmacopoeia and the United States Pharmacopoeia National Formulary list only a small number of EO-bearing plants and their preparations as medicinal [3].…”

Antimicrobial effects of cinnamon essential oil and cinnamaldehyde combined with EDTA against canine otitis externa pathogens

“…; Garcia‐Salinas et al . ). Our findings suggest the potential use of both cinnamon oil and cinnamaldehyde for the topical treatment of infections in dogs, but the latter as a more promising bactericidal compound.…”

“…; Garcia‐Salinas et al . ). The anti‐inflammatory properties and wound healing application of cinnamon oil for soothing the pain resulted from microbial infection and inflammation have been identified (Han and Parker ).…”

The Effect of Ten Essential Oils on Several Cutaneous Drug-Resistant Microorganisms and Their Cyto/Genotoxic and Antioxidant Properties

“…Thymol, eugenol, and carvacrol have an antimicrobial effect against a broad spectrum of bacteria, namely Escherichia coli, Bacillus cereus, Listeria monocytogenes, Salmonella enterica, Clostridium jejuni, Lactobacillus sake, Staphylococcus aureus, and Helicobacter pyroli [15,22,23,26]. García-Salinas et al [46] found that the carvacrol, cinnamaldehyde, and thymol molecules contained in EOs could be used against E. coliand S. aureus-mediated infections, without a potential induction of bactericidal resistance and with lower cell toxicity. Other families of EO compounds also show antimicrobial properties: certain alcohols, aldehydes, ketones, monoterpene (geraniol, linalol, menthol, terpineol, thujanol, thujone, camphor etc.…”