Antimicrobial activity of essential oils: the possibilities of TLC–bioautography

Abstract

Essential oils are well-known for their antimicrobial activity against different plant and human pathogenic microorganisms. The results of the most commonly used antimicrobial assays are very different; sometimes their reliability is questionable, therefore standardized methods need to be used to solve this problem. The present study aims at the phytochemical characterization of some essential oils (thyme, lavender, eucalyptus, spearmint and cinnamon) that are important from the therapeutic and economic aspects and the optimized microbiological investigation of the effect of essential oils on human and plant pathogenic microorganisms. The chemical composition of the essential oils was analysed with thin-layer chromatography (TLC) and their composition was controlled by gas chromatography (GC). The antibacterial effect was investigated using the TLC-bioautographic method. The solvents applied in TLC developing systems were also tested. Our results showed that toluene, ethyl acetate, ethanol and chloroform as solvents used in the assay had no inhibiting effect on the test bacteria. The antibacterial activity of thyme, lavender and cinnamon oils and their main components (thymol, carvacrol, linalool, eugenol) was observed in the case of two plant pathogenic bacteria (Xanthomonas campestris pv. vesicatoria and Pseudomonas syringae pv. phaseolicola) and some human pathogens (Staphylococcus epidermidis, S. saprophyticus and two strains of S. aureus, including one methicillin-resistant strain). On the whole, the antibacterial activity of essential oils can be related to their most abundant components, but the effect of the minor components should also be taken into consideration. Direct bioautography is more cost-effective and compares better with traditional microbiological laboratory methods (e.g. disc-diffusion, agar-plate technique).

Antioxidant and Antimicrobial Properties of the Essential Oil and Extracts of Zanthoxylum alatum Grown in North‐Western Himalaya

“…They were further isolated using repeated preparative TLC and identified by GC/MS analysis. Bioautography procedure enables the evaluation of plant extracts and EOs against human and plant pathogens [36]. For isolation of antibacterial compounds bioautography was performed using B. subtilis as test organism.…”

Chemical composition, antimicrobial activity against Staphylococcus aureus and a pro-apoptotic effect in SGC-7901 of the essential oil from Toona sinensis (A. Juss.) Roem. leaves

“…Essential oils (EOs), volatile secondary metabolites from aromatic plants, have recently gained wild popularity and scientific interests (Yang et al, 2010a). There is mounting evidence showing that EOs possess significant antimicrobial activity against different plant and human pathogenic micro-organisms (Horváth et al, 2010), and they have wide applications in the food flavoring and preservation industries (Bajpai et al, 2012). Additionally, they have been shown to exhibit various interesting bioactivities including antifungal, antiviral, antiparasitic, insecticidal, antispasmodic (Pavlović et al, 2012) and anticancer activities (Yu et al, 2011).…”

Detection of the antibacterial effect of essential oils on outer membrane proteins of Pseudomonas aeruginosa by lab‐on‐a‐chip and MALDI‐TOF/MS

“…The fact of antibiotic resistance has led to research on new antimicrobial agents from medicinal plants. The number of studies has recently increased focusing on the antimicrobial activity of essential oils, as well as their application as a new potential antimicrobial agents against plant and human microorganisms . Unfortunately, the specific target(s) of the antibacterial action of essential oils and their components has not yet been fully understood.…”