Essential Oil Microemulsion Research Articles

Drug loaded essential oil microemulsions enhance photostability and evaluation of in vitro efficacy.

Loss of stability of pharmaceutical APIs (Active Pharmaceutical Ingredient) due to photolytic activity has been a major concern in the pharmaceutical industry as it leads to loss of activity of API and excipients, the formation of toxic by-products, change in color and flavor. Itraconazole (ITZ) bulk drug was exposed to UVC (254 nm) irradiation in an environmental chamber (37 °C, 75 %RH) and its photoprotection by cinnamon, clove, eugenol, and oregano based microemulsion was analyzed. No significant change in the spectra was observed at various time points, confirming the photo-protective activity of microemulsions, unlike the bulk drug. FTIR spectra illustrate the fundamental peaks of the functional groups of ITZ and ITZ loaded MEs. The overlaid spectra showed that there was a minor change in peaks of UV exposed ITZ bulk drug but the ITZ loaded microemulsions were able to protect all the major functional groups. The in vitro anti-microbial assay against C. albicans demonstrated no significant change in the activity of ITZ loaded microemulsion between untreated, 7th day and 15th day while the activity of bulk drug was reduced drastically in the UVC exposed sample. It was concluded that microemulsions can be used as an effective photo-protective drug delivery vehicle for light-sensitive compounds.

Antimicrobial and antibiofilm activity of Cymbopogon flexuosus essential oil microemulsions

ABSTRACT The objective of the study was to determine the antimicrobial activity antibiofilm and to identify the main components of the essential oil (EO) obtained from the leaves of Cymbopogon flexuosus. The antibacterial and antibiofilm activity was determined against Staphylococcus aureus ATCC 29213, Pseudomonas aeruginosa ATCC 27853, Salmonella Typhimurium ATCC 14028 and Listeria monocytogenes ATCC 19117. The effect of EO on biofilm was evaluated by quantifying viable cell number (CFU) and biomass by crystal violet (CV) analysis. The composition of the essential oils was determined by GC / FID and GC / MS. The results showed action against L. monocytogenes, S. aureus and S. Typhimurium with MIC and MBC values ​​of 3.9 μL mL-1, thus showing satisfactory antimicrobial activity, given this was the lowest concentration tested. For the antibiofilm activity, a significant reduction (P < 0.05) was observed for S. typhimurium and S. aureus. Biofilm biomass significantly reduced only for S. aureus and P. aeruginosa. EO presented the geranial and neral isomers as major components.

Evaluation of the Mosquito Repellent Activity of Nano-sized Microemulsion of Eucalyptus globulus Essential Oil Against Culicinae

Background: The mosquitoes of Culicidae family are serious vectors of several tropical diseases, such as malaria, filariasis, encephalitis, and nuisance. Control of mosquitoes and protection of people from their bites are of the most important ways to prevent transmitted diseases. Although the efficacy of N, N-diethyl-m-toluamide (DEET) is high and generally used as mosquito repellent, yet a number of biting diptera are tolerant to DEET. Furthermore, there are concerns about the safety of DEET and its allergic and toxic effects. Therefore, it is necessary to use other repellents like plant essential oils. Objectives: The aim of this work was to develop a safe repellent with a long-lasting protection based on micro-emulsion of eucalyptus essential oil. Methods: Eucalyptus globulus essential oil was obtained by water distillation in a Clevenger apparatus. The larvae of Culicidae were collected and adult mosquitoes reared for the repellency test. Preparation of micro-emulsions of Eucalyptus globulus essential oil was made by mixing the specified surfactant (Tween 80 and Span 20) and the appropriate amount of co-surfactant (propylene glycol) under the water titration method. The laboratory method, arm in cage, was used to estimate the time of protection of essential oil micro-emulsion against mosquitoes and DEET used as a standard repellent. Results: Physicochemical properties of formulated micro-emulsions were appropriate and suitable for topical application. Particle size of eucalyptus oil 15% w/w micro-emulsion was lowest. When applying eucalyptus oil micro-emulsion at concentrations of 5, 10, and 15% w/w, time of protection against mosquitoes were 82 ± 15.8, 135.7 ± 26.4, and 170.7 ± 26 minutes, respectively. These times of protection were similar to DEET at same concentrations and significantly more than eucalyptus essential oil. Conclusions: The formulated micro-emulsion of eucalyptus oil at a concentration of 15% w/w has potential repellency to the extent of DEET. It seems that nano-sized microemulsion is stable in terms of thermodynamics and kinetics. In conclusion, preparation of nano-sized microemulsion could delay the volatility of eucalyptus essential oil and volatile oil release from formulations and consequently increase protection time against mosquitoes.

The use of orange peel essential oil microemulsion and nanoemulsion in pectin‐based coating to extend the shelf life of fresh‐cut orange

This study was conducted to evaluate the effect of pectin-based edible coatings containing orange peel essential oil (OPEO) at 0.5 and 1.0% concentrations on quality parameters of orange slices stored at 4 °C for 17 days. The variations of pH and titratable acidity in coated samples containing microemulsion and nanoemulsion were significantly higher than the controls and pectin-coated slices. The highest and lowest increases of the total soluble solids were observed in controls and 1% OPEO nanoemulsion samples, respectively. The weight and ascorbic acid losses of all coated samples were significantly lower than the controls. Higher antibacterial and antifungal effects were observed in the nanoemulsion-coated samples. In sensory evaluation, no significant differences were observed in the samples coated with microemulsion and nanoemulsion. The results showed that the nanoemulsion-based edible coatings containing OPEO can extend the shelf life of orange slices without any undesirable impacts on sensory attributes. Practical applications It is recommended to use edible coatings incorporated with essential oils to overcome the concerns of minimally processed fruit. Microemulsion and nanoemulsion of orange peel essential oil in pectin-based coatings reduced the quality loss. Also, higher antimicrobial effects were observed in nanoemulsion-coated orange slices.

Preparation of Essential Oil-Based Microemulsions for Improving the Solubility, pH Stability, Photostability, and Skin Permeation of Quercetin.

Quercetin can bring many benefits to skin based on its various bioactivities. However, the therapeutic effect of quercetin is limited due to the poor water solubility, pH instability, light instability, and skin permeation. The aim of the present work was applying essential oil-based microemulsions to improve the solubility, pH stability, photostability, and skin permeation of quercetin for topical application. Peppermint oil (PO-ME), clove oil (CO-ME), and rosemary oil (RMO-ME) were selected as model essential oils. Microemulsions composed of Cremophor EL/1,2-propanediol/essential oils (47:23:30, w/w) were selected as model formulations, based on the pseudo-ternary phase diagram and the characterizations. In the solubility study, the solubility of quercetin was improved dozens of times by microemulsions. Quercetin was found instable under alkaline condition, with 50% degraded in the solution of pH 13. However, PO-ME, CO-ME, and RMO-ME could protect quercetin from the hydroxide ions, with 47, 9, and 12% of quercetin degraded. In the photostability study, the essential oil-based microemulsions showed the capability of protecting quercetin from degradation under UV radiation. Where more than 67% of quercetin was degraded in aqueous solution, while less than 7% of quercetin degraded in microemulsions. At last, the in vitro skin permeation study showed that the essential oil-based microemulsions could enhance the permeation capacity of quercetin by 2.5-3 times compared to the aqueous solution. Hence, the prepared essential oil microemulsions could improve the solubility, pH stability, photostability, and skin permeation of quercetin, which will be beneficial for its topical application.

Effect of the lemon essential oils on the safety and sensory quality of salted sardines (Sardina pilchardus Walbaum 1792)

The main aim of this research was to investigate the biopreservative effects of lemon essential oil (EO) micro-emulsions on salted sardines. The experimental design included two experimental trials, SR1 and SR2 carried out with 25 ml of lemon EO micro-emulsion at 0.3 and 1.0% (v/v), respectively, and a control trial performed without EO addition. Chemical analyses on salted sardines inoculated with the EOs clearly showed a substantial persistence of several volatile organic compounds (VOCs) belonging to groups of monoterpene hydrocarbons, oxygenated monoterpenes and sesquiterpene hydrocarbons derived from EOs during the entire period of ripening. In particular, the molecules mostly represented were limonene, p-cymene and β-pinene. Immediately after the addition of EOs, the concentrations of all microbial groups decreased. The presence of Enterobacteriaceae, staphylococci and rod lactic acid bacteria (LAB) observed in the trials SR1 and SR2 was significantly lower than that registered for the control trial during the entire period of monitoring. Furthermore, the addition of EOs determined a lower accumulation of histamine in sardines compared to those of the control trial. The highest scores of sensory evaluation were registered for flavour and overall acceptability of the experimental trials in presence of EOs. On the basis of the increasing interest toward novel food preservatives, we conclude that the use of EOs to produce salted fishes represents a valid strategy to improve safety and sensory characteristics of salted sardines. This work has also economic implications, since the flavour improvement due to the addition of lemon EOs might increase the consumption of sardines by regular and new consumers.

Betel leaf (Piper betle L.) essential oil microemulsion: Characterization and antifungal activity on growth, and apparent lag time of Aspergillus flavus in tomato paste

The present study aimed at characterization of betel leaf (Piper betle L.) essential oil based microemulsion (BLEO-ME) and modelling its effect on growth of Aspergillus flavus in tomato paste. The microemulsion was formulated using betel leaf essential oil, Tween 20 and water by low energy emulsification method. The average droplet size of formulated emulsions having different concentration of surfactant (5%, 10% and 15%) and BLEO (2.5%, 5% and 10%) was evaluated. The formulated BLEO-ME was observed to be kinetically and thermodynamically stable for at least 90 days at 4 °C. Primary modelling estimated maximum growth rate (μmax) and apparent lag time (λ) of the selected mould in tomato paste. Secondary modelling was performed to evaluate the effect of different concentration of BLEO on estimated growth parameters. Estimated Emax (minimum concentration of oil at which mould growth was inhibited) and MIC (minimum inhibitory concentration of BLEO at which lag time is infinite) value against A. flavus was estimated to be 2.01 ppm and 3.55 ppm in tomato paste, respectively. Accuracy and bias factor of the fitted secondary models suggested good similarity between observed and estimated values of μmax and λ. The formulated BLEO-ME exhibited antifungal efficacy in tomato paste, which suggests its potential as natural preservative.

Antibacterial activity of plant essential oil microemulsion against wound isolate Macrococcus caseolyticus

Antibacterial activity of plant essential oil microemulsion against wound isolate Macrococcus caseolyticus

Incorporation of soybean oil improves the dilutability of essential oil microemulsions

Plant essential oils (EOs) have strong antimicrobial and antioxidant activities. However, their water insolubility and volatility limit their practical application. Microemulsions are thermodynamically stable delivery systems for hydrophobic bioactive compounds but can be destabilized after dilution by the polar phase. In the present study, soybean oil (SBO) was studied for the impacts on formation and dilutability of EO microemulsions comprised of polysorbate 80 (Tween™ 80) as a surfactant and equal mass of water and propylene glycol as the polar phase. The oil phase contained EO (cinnamon bark oil, eugenol, or thymol) and SBO at 1:0, 2:1 or 4:1 mass ratios. Pseudo-ternary phase diagrams were constructed after titrating the polar phase into Tween™ 80–oil mixture at 1:1 to 9:1 mass ratios. Blending SBO with EO expanded the regimes of microemulsions and reduced the droplet dimensions that were stable over 90days. Viscosity and electrical conductivity data indicated the transition from W/O to O/W microemulsions as the content of polar phase increased from 10% to 90% w/w. The enhanced dilutability of microemulsions after blending with SBO can broaden the application of EOs.

Analysis and antibacterial activity of Nigella sativa essential oil formulated in microemulsion system.

The Essential oil (EO) of Nigella sativa (black cumin) was extracted from the crude oil and the volatile constituents were characterized using gas chromatographic analysis. The EO was formulated in water-based microemulsion system and its antibacterial activity against six pathogenic bacteria was evaluated using the agar well diffusion method. This activity was compared with two other well known biologically active natural and synthetic antimicrobials namely eugenol and Ceftriaxone(®). Results showed that N. sativa EO microemulsion was highly effective against S. aureus, B. cereus and S. typhimurium even at the lowest tested concentration of that EO in the microemulsion (100.0 μg/well). Interestingly, the EO microemulsion showed higher antibacterial activity than Ceftriaxone solution against S. typhimurium at 400.0 μg/well and almost comparable activity against E. coli at 500.0 μg/well. No activity was detected for the EO microemulsion against L. monocytogenes and P. aeruginosa. Eugenol which was also formulated in microemulsion was less effective than N. sativa EO microemulsion except against P. aeruginosa. The synthetic antibiotic (Ceftriaxone) was effective against most of the six tested bacterial strains. This work is the first report revealing the formulation of N. sativa EO in microemulsion system and investigating its antibacterial activity. The results may offer potential application of that water-based microemulsion in controlling the prevalence of some pathogenic bacteria.

Formulating essential oil microemulsions as washing solutions for organic fresh produce production

Applications of plant-derived organic essential oils (EOs) as antimicrobials for post-harvest produce operations are limited by their low water solubility. To dissolve EOs in water, microemulsions were studied using two surfactants permitted for organic production, sucrose octanoate ester (SOE) and soy lecithin that were mixed at various mass ratios before dilution with water to 40% w/w. EOs were then mixed with the surfactant solution by hand shaking. Based on visual transparency, intermediate lecithin:SOE mass ratios favoured the formation of microemulsions, e.g., up to 4.0% clove bud oil at ratios of 2:8 and 3:7, and 4.0% cinnamon bark oil and 3.0% thyme oil at ratios of 2:8 and 1:9, respectively. Microemulsions with intermediate lecithin:SOE mass ratios had a relatively low viscosity and better ability to wet fresh produce surfaces. The microemulsions established in this work may be used as washing solutions to enhance the microbial safety of organic fresh produce.

Evaluation of cinnamon essential oil microemulsion and its vapor phase for controlling postharvest gray mold of pears (Pyrus pyrifolia)

Essential oil of cinnamon (CM) is a potential alternative to chemical fungicides. Thus this work aimed to investigate the possible effects of CM microemulsions on decay developments and qualitative properties of pears. The decay incidence of samples treated with 500 µg L⁻¹ microemulsion was significantly reduced by 18.7% in comparison to that of 500 µg L⁻¹ non-microemulsion after 4 days' storage at 20 °C. In the vapor phase, the CM microemulsion with the lowest concentration had the best control for decay incidence and lesion diameter. The interval between inoculations also influenced decay development. Pears treated with Botrytis cinerea and immediately followed by CM microemulsion showed the lowest decay incidence. Moreover, in the natural decay experiment, the percentage of rotted pears was 3.8% in the CM microemulsion treatment and 5.8% in the control. CM microemulsion delayed the loss of ascorbic acid, yet it had no significant influence on pear qualities such as firmness and color. CM microemulsion may be an alternative way to control the gray mold of pears without a negative influence on its qualities.