Minimum Inhibitory Concentration Of Essential Oils Research Articles

Chemical Composition and Antimicrobial Activity of Plinia rivularis Essential Oil Against Multidrug-Resistant Bacteria

IntroductionThe increasingly common occurrences of multidrug-resistant bacteria represent a global health threat and the discovery of new alternative remedies is necessary. The use of essential oils (EOs) in the treatment of many pathogenic bacteria is promising and several examples have already been highlighted regarding their inhibitory action. Among the botanical families, Myrtaceae stands out for presenting important species that supply bioactive products. MethodsIn this work we investigate the chemical composition of Plinia rivularis (Myrtaceae) leaf EO and its antibacterial activity against resistant and non-resistant bacteria. The EO was obtained by two methods, hydrodistillation and steam distillation. Gas chromatography-flame ionization detector (GC-FID), gas chromatograph-mass spectrometry (GC-MS), nuclear magnetic resonance spectroscopy (NMR) and Fourier transform infrared spectroscopy (FTIR) were the techniques used in the EO chemical characterization. ResultsThe EOs were obtained with yields of 0.37 and 0.16% by hydrodistillation and steam distillation methods, respectively. The analyzes revealed the EOs chemical profile showing the compounds 2H-benzocyclohepten-2-one,3,4,4a,5,6,7,8,9-octahydro-4a-methyl (synonym: 4a-methyl-3,4,4a,5,6,7,8,9-octahydro-2H-benzo[7]annulen-2-one), rosifoliol, β-eudesmol and the diterpene kaurene as main constituents. Through preparative thin-layer chromatography (PTLC), it was possible to obtain the diterpene kaurene with a content of 91%, which was also characterized by NMR. The minimum inhibitory concentrations of EO against bacteria ranged from 0.56 to 2.25 mg.mL-1 and 2.25 to 36 mg.mL-1 for sensitive and resistant bacteria, respectively. Also, EO showed synergistic activity with amikacin and cefotaxime against carbapenem-resistant Pseudomonas aeruginosa (KPC). ConclusionsThis is the first report on the chemical composition of Plinia rivularis EO. Comparison of extraction methods showed variation in yields and small changes in component content. The EO demonstrated activity against resistant and non-resistant bacteria. In addition, the synergistic effect of EO against resistant bacteria may be explored in future studies.

Antimicrobial Efficacy of Blended Essential Oil and Chlorhexidine against Periodontal Pathogen (P.gingivalis)-An In Vitro Study.

Essential oils (EOs) have a considerable amount of therapeutic and preventive effect in treating dental diseases due to their wider potential as antibacterial and anti-inflammatory agents. EOs like virgin coconut oil, eucalyptus oil, peppermint oil thyme oil, and clove oil, when used in combination, may further have enhanced antimicrobial effects. However, limited information exists on the synergistic effect of these oils when used in combination, especially on the primary periodontal pathogen Porphyromonas gingivalis. The current study aims to compare the antimicrobial efficacy of commercially available EO on the periodontal pathogen, P. gingivalis, in comparison to chlorhexidine (CHX). Antimicrobial efficacy of EO and CHX was assessed at various concentrations against the periodontal pathogen P. gingivalis, by evaluating the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). P. gingivalis was seen to be sensitive at a MIC of 100 μg/ml and 50 μg/ml concentration of the EO, which is regarded as the MIC of EO against P. gingivalis and CHX effectively inhibited microbial growth at 0.4 μg/ml. A combination of EOs possesses a potent antibacterial activity against P. gingivalis, and the antibacterial efficacy increases with increasing concentration of EOs.

Antifungal Activity of Essential Oil From Zanthoxylum armatum DC. on Aspergillus flavus and Aflatoxins in Stored Platycladi Semen.

The major objective of this study was to evaluate the inhibitory effect of essential oil (EO) from Zanthoxylum armatum DC. on Aspergillus flavus. The chemical composition of the EO was identified by gas chromatography–mass spectrometer. The minimum inhibitory concentration (MIC) of EO was investigated by liquid fermentation. The morphology, colony number, and aflatoxin content of A. flavus in platycladi semen were investigated by stereomicroscopy, scanning electron microscopy, plate counting, and high-performance liquid chromatography. The results indicated that the MIC of EO was 0.8 μL⋅mL–1, and the main components were β-phellandrene (7.53%), D-limonene (13.24%), linalool (41.73%), terpinen-4-ol (5.33%), and trans-nerolidol (6.30%). After the EO fumigated the platycladi semen, the growth of A. flavus slowed, and the mycelium shrank considerably. The number of colonies after EO treatment at room temperature and cold storage was significantly reduced, the inhibition effect was better under cold storage, and the aflatoxin B1 content did not exceed the standard within 100 days. Therefore, this study demonstrated the good potential of A. flavus growth inhibition during the storage of platycladi semen.

Melaleuca armillaris Essential Oil in Combination With Rifaximin Against Staphylococcus aureus Isolated of Dairy Cows.

Staphylococcus aureus is the major subclinical mastitis-causing pathogen in dairy cows. In some European and Latin American countries, rifaximin (RIF) is a commonly used therapy at drying off. Phytotherapeutics are alternatives for the treatment of infectious diseases. Melaleuca armillaris essential oil (EO) has been reported as a good antimicrobial against S. aureus. The aim of this work was to investigate, in vitro, the combined effect of EO and RIF to identify a synergic interaction against S. aureus in order to obtain enough information for subsequent pharmacokinetic/pharmacodynamic studies. The minimum inhibitory concentrations (MIC) for RIF, EO, and combinations of these against S. aureus strains were determined at pH 7.4, 6.5, and 5.0, representing intracellular conditions where S. aureus is usually located. The fractional inhibitory concentration index (FIC) and the index of antibacterial activity (E) were evaluated. The MIC of EO at pH 7.4 was 25–12.5 μL/mL and decreased with the acidity of the medium. RIF presented a high antimicrobial activity (0.032 μg/mL) against S. aureus regardless of the pH conditions. Combining RIF with EO, we found a synergic effect. A mix of 0.004 μg/mL of RIF and 12.5 μL/mL of EO led to a virtual eradication effect against wild-type strains at pH 7.4. Media acidification improves the EO/RIF activity, so EO would be a good adjuvant for RIF to treat staphylococcal infections and decrease antimicrobial resistance.

Investigating the Potential of the Essential Oil Nanoemulsion of Zataria multiflora Boiss. on the Gene Expression of stx1A and stx2A in Escherichia coli as a Foodborne Pathogen

Background: Several occurrences of infections and intoxications have been globally announced as a result of the Escherichia coli contamination of foodstuffs. In addition, the emergence of antibiotic resistance in different geneses of bacteria is becoming a major concern for public/medical health authorities and researchers. Objective: Accordingly, this study determined the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the essential oil (EO) nanoemulsion (NEO) of Zataria multiflora Boiss against E. coli. Finally, different sub-MIC concentrations of the NEO of zataria EO on the growth rate and the gene expression of stx1A and stx2A were investigated as well. Materials and Methods: Oil in water NEO was formed by the phase inversion technique. The mean diameter of droplets and the zeta potential of NEO were determined, and then the MIC and MBC of EO and NEO were estimated using the broth microdilution method. Eventually, the growth rate and expressions of the stx1A and stx2A genes of E. coli were evaluated after exposure to various sub-MICs. Results: Based on the results, carvacrol was the main constituent of the EO, and NEO droplets had an average size of 61.5 nm and a zeta potential of -27 mV. Further, the MIC values of EO and NEO were 0.45 ± 0.17 and 0.25 ± 0.10 mg/mL, and their MBCs were found 0.55 ± 0.20 and 0.30 ± 0.05 mg/mL, respectively. Furthermore, NEO expressed a stronger inhibitory effect against E. coli growth compared to pure EO. At 75% MIC of EO, the transcriptional rate of stx1A and stx2A decreased 2.24 and 2.66 times at the end of the 72-hour period compared with the control, respectively. After 72 hours, treatment with 75% MIC of NEO resulted in the down-regulation of stx1A and stx2A as 4.75 and 4.80 fold, respectively. Conclusion: The greater activity of the NEO of Z. multiflora Boiss. in comparison with pure EO for slowing down the growth of E. coli and Shiga toxin production shows its potential as a novel ‘green’ food-grade preservative.

Preparation, characterization and antidermatophytic activity of free- and microencapsulated cinnamon essential oil

Essential oils (EO) are effective natural antimicrobials but are susceptible to oxidation. Microencapsulation improves EO stability, reduces toxicity, and controls release. The aim of this study was preparation, characterization and antidermatophytic activity of free and microencapsulated cinnamon essential oil (MP). MP were prepared by the spray drying method and the success of MP encapsulation was confirmed by UV-vis spectroscopy, dynamic light scattering (DLS), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and Fourier transform infrared (FT-IR) spectroscopy. The antifungal effect of EO and MP was evaluated by the broth microdilution method against Microsporum gypseum and Trichophyton mentagrophytes. The checkerboard method was used to assess synergistic interactions. Fluorescence microscopy and scanning electron microscopy were used to investigate the inhibition of hyphal growth by EO and MP. A cytotoxic assay was performed using the VERO cell line. Microencapsulated cinnamon essential oil was found to be micrometric, with a round, regular structure. The minimum inhibitory concentration of EO was found to be between 125–250μg/mL, while that of MP was 220.5–440.5μg/mL. EO was synergistic with fluconazole while microencapsulated oil was less cytotoxic than EO.

Antifungal, Antiaflatoxin and Antioxidant Activity of Plant Essential Oils and Their In Vivo Efficacy in Protection of Chickpea Seeds

AbstractThis study presents the efficacy of six essential oils (EOs), viz. Carum carvi, Myristica fragrans, Melaleuca leucadendra, Cinnamomum camphora, Pelargonium odoratissimum and Cymbopogon citratus, as food preservatives based on antifungal, antiaflatoxin and antioxidant activity. The minimum inhibitory concentration of EOs against aflatoxigenic strain of Aspergillus flavus (LHP‐10) and 13 other storage molds ranged between 1.25 and 6.0 μL/mL, while aflatoxin inhibition was observed at 1.0–5.0 μL/mL. EOs also exhibited free‐radical scavenging activity through DPPH (2,2‐diphenyl‐1‐picrylhydrazil) assay as IC50 value ranged between 3.96 and 96.63 μL/mL. The antifungal action of EOs was observed in terms of reduction in ergosterol content of the plasma membrane of A. flavus. The EOs provided >50% protection of chickpea samples against fungal association without affecting their germination during in vivo testing in storage containers. Based on antifungal, antiaflatoxigenic, antioxidant potential and in vivo efficacy, the tested EOs may be recommended as plant‐based food preservatives.Practical ApplicationsSome safer alternatives are urgently required to replace prevalent synthetic preservatives that have adverse effects on consumer's health and environment. In that respect, some essential oils (EOs) have shown potency in the formulation of plant‐based preservatives against food deterioration from fungi. Based on the results of the present investigation, some EOs may be recommended as plant‐based preservatives in view of their antifungal potency against foodborne molds, aflatoxin secretion and as antioxidant. The EOs also showed efficacy in protecting chickpea seeds from fungal contamination during storage without affecting their viability, strengthening their formulation for practical application.

Antibacterial Properties of Lemongrass (Cymbopogon flexuosus Steud) Wats Essential Oils in Single form and Combination of Honey Against Drug Resistant Pathogenic Bacteria

Antibacterial potential of four lemongrass essential oils (EOs) and their major oil constituent, citral in single form and in combination of honey were evaluated against multi drug resistant (MDR) bacteria Acinetobacter baumannii, Pseudomonas aeruginosa, and Staphylococcus aureus. The antibacterial potentials determined using agar well diffusion method has revealed that Krishna EOs exhibited most potent bactericidal effects than other Eos against all MDR bacteria used. The diameter of zone of inhibition of Krishna EOs ranged from 44-50 mm/50 µL of EOs. However, EOs of Pragati and Suvarna were selectively effective against S. aureus while that of Nima against A. baumannii and P. aeruginosa. Citral expressed better antibacterial potential against all the MDR bacteria with zone of inhibition 38-45 mm/50 µl. The combination of all four different EOs with honey showed pronounced antibacterial activity exclusively against S. aureus. The combination of Suvarna EOs and honey showed 22 % increase in antibacterial activity against A. baumannii than the EOs alone. The combination of citral and honey showed significantly lower antibacterial activity as compared to citral alone against all MDR bacteria used. The minimum inhibitory concentrations of EOs determined were 4.5 µg/ml. Thus, the study revealed enhanced antibacterial potential of lemongrass EO when they are used with honey against drug resistant S. aureus.

Comparative Antimicrobial Activity of Essential oils of Cuminum cyminum L. and Foeniculum vulgare Mill. seeds against Salmonella typhimurium and Escherichia coli

The composition of essential oils obtained from the seeds of Foeniculum vulgare Mill. and Cuminum cyminum L. were analysed using GC and GC-MS. The antimicrobial activities of the essential oils were conducted by disc diffusion method and minimum inhibitory concentration (MIC) by agar dilution method. The essential oils of the seeds of F. vulgare showed maximum zone of inhibition 33 mm against S. typhimurium and 28 mm against E. coli respectively, while C. cyminum showed zone of inhibition 22 mm and 17 mm against S. typhimurium and E. coli respectively. MICs of essential oils were tested at concentration ranging from 2.0 to 0.0075 % (v/v). The F. vulgare essential oil showed lowest MIC values 0.031 and 0.062 % (v/v) against S. typhimurium and E. coli respectively, while C. cyminum showed MIC vaules 0.125 and 0.250 % (v/v) against S. typhimurium and E. coli respectively. The results showed that essential oil of F..vulgare is more effective than C. cyminum and S. typhimurium is more susceptible for the tested spices as compared to E.coli .The GC-MS data showed the main component found in F. vulgare Mill essential oil was identified as trans-anethole (50.4 %), methylchavicol (22.4 %), limonene (11.4 %) and fenchone (11.1 %) whereas γ-terpin-7-al (22.9 %), γ-terpinene (22.6 %), β-pinene (22.2 %) and cuminaldehyde (13.1 %) were the major compounds in C. cyminum L.

Effects of Zataria multifloraBoiss., Rosmarinus officinalisL. and Mentha longifoliaL. Essential Oils on Growth and Gene Expression of Enterotoxins C and E in Staphylococcus aureusATCC 29213

AbstractGiven the side effects associated with the use of synthetic preservatives, an attractive alternative may reside in the evaluation of the antimicrobial effects of herbal essential oils (EOs) for use in the food industry. This study was conducted to determine the minimum inhibitory concentration (MIC) of Zataria multiflora Boiss., Rosmarinus officinalis L and Mentha longifolia L. EOs for Staphylococcus aureus and the effect of subMICs of EOs on growth and production of enterotoxins C and E. MIC of EOs were 0.03, 0.4 and 1.4% (v/v) for Z. multiflora Boiss., R. officinalis L. and M. longifolia L., respectively. Seventy‐five percent MIC decreased the growth rate significantly; after 180 and 360 min of EO treatment, optical density600 values were 48.3 and 47.2% with respect to the control for Z. multiflora Boiss., 61.9 and 66.5% for R. officinalis L. and 71.4 and 80.69% for M. longifolia L. SubMICs of EOs decreased the gene expression of staphylococcal enterotoxins and the effectiveness of EOs was as follows: Z. multiflora Boiss. > R. officinalis L. > M. longifolia L.Practical ApplicationStaphylococcal food poisoning is considered to be one of the most medically and economically important diseases worldwide, thus preservatives are used in food products to inhibit the growth of this microorganism. Concerns over the safety of some chemical preservatives and negative consumer reaction to those perceived as being of chemical and/or artificial origin have prompted increased interest in more natural or “green” alternatives for the maintenance or extension of product shelf life. Many spices and herbs exert antimicrobial activity conferred by phenolic compounds present in their essential oil (EO) fractions, some of which are classified as Generally Recognized as Safe substances. These compounds, or even their originating EOs, could therefore be of considerable interest for use in the food industry as naturally occurring inhibitors of the postharvest growth of native and contaminating bacteria.

Antibacterial activity of eugenol and peppermint oil in model food systems

Food borne illness caused by microorganisms is a large and growing public health concern worldwide. Due to increased concerns of food safety and consumer demand for safer additives there is growing interests in use of natural antimicrobial compounds, and essential oils are being explored for food uses. In the present study, we have evaluated the antibacterial activity of eugenol and peppermint oil against two Gram-positive and two Gram-negative bacteria, and both the oils inhibited growth of tested bacteria with minimum inhibitory concentration (MIC) of 0.25% or below. The efficacy of these oils was also tested in model food systems (cabbage and barley) and real food (papaya pulp) during storage. At MIC, the growth of bacteria was similar to control in model foods, however double of MIC was effective in reducing the bacterial growth in both the model systems. For similar reduction in bacterial count in papaya pulp, five-fold MIC of essential oils was required. Due to high inhibitory concentration of essential oils in papaya, their effect on sensory and textural properties of foods needs a deeper study.

Assessment of some essential oils as food preservatives based on antifungal, antiaflatoxin, antioxidant activities and in vivo efficacy in food system

The present study strengthens the food preservative potential of plant essential oils (EOs) viz. Origanum majorana L., Coriandrum sativum L., Hedychium spicatum Ham. ex Smith, Commiphora myrrha (Nees) Engl., and Cananga odorata Hook.f. & Thomson based on their antifungal, antiaflatoxin, and antioxidant efficacy. The essential oils were found more efficacious than some prevalent organic preservatives viz. salicylic acid, BHT, ascorbic acid and gallic acid as they inhibited the growth and aflatoxin secretion of the aflatoxigenic strain Aspergillus flavus (LHP-6) at lower concentrations. The minimum inhibitory concentration of EOs against the toxigenic strain of A. flavus ranged between 2.0μl/ml and 3.0μl/ml. In addition, the EOs exhibited broad fungitoxic spectrum against nine food borne molds and strong antioxidant activity. The IC50 value of the oils ranged between 1.3 and 21.67μl/ml while their total phenolic content ranged between 2.90 and 33.33μg/mg. All the EOs except C. odorata showed non-phytotoxic nature on germination of chickpea seeds. During in vivo investigations in food system all the five essential oils showed above 50% protection of chickpea seed from A. flavus infestation showing their potential as plant based preservatives for enhancement of shelf life of food items.

Antibacterial activity, chemical composition, and cytotoxicity of leaf's essential oil from brazilian pepper tree (schinus terebinthifolius, raddi).

The antibacterial potential of leaf’s essential oil (EO) from Brazilian pepper tree (Schinus terebinthifolius Raddi) against staphylococcal isolates from dogs with otitis externa was evaluated. The minimum inhibitory concentration of EO ranged from 78.1 to 1,250 μg/mL. The oil was analyzed by GC and GC/MS and cytotoxicity tests were carried out with laboratory animals.

In vitroandin vivoantifungal activity of essential oils ofCymbopogon martiniandChenopodium ambrosioidesand their synergism against dermatophytes

The present study was carried out to evaluate the antifungal efficacy of essential oils (EO) of Cymbopogon martini, Chenopodium ambrosioides and of their combination against dermatophytes and some filamentous fungi in vitro as well as in vivo using a guinea pig model. The minimum inhibitory concentrations of EOs and of their combination were found between 150 and 500 ppm, while those of known antifungal drugs ranged from 1000 to 5500 ppm. EO ointments were prepared and applied against induced ringworm in guinea pig model and disease removal was observed in 7-21 days, and the hair samples showed negative results for fungal culture in a time-dependent manner after the application of EO ointments. Chemical constituents of EOs were determined by GC-MS. Both the EOs and their combination displayed strong antifungal effects. The results provide a scientific validation for the use of these EOs in the treatment of dermatophyte infections and may be recommended as an alternative to synthetic drug for topical application.