Peppermint Essential Oil Research Articles

Co-partition and stabilization of polyphenols with low partition coefficient (Log P＜3) in emulsified oil droplets mediated by peppermint essential oil

Emulsion-based carriers have been widely studied for the co-encapsulation of active ingredients with different partition coefficient (Log P). However, it is challenging to encapsulate active ingredients with low Log P values in emulsified oil droplets. In this study, (-)-epigallocatechin gallate (EGCG, 160 µg/g*emulsion, Log P 2.38) and resveratrol (Res, 320 µg/g*emulsion, Log P 2.57), as models with low Log P, were co-encapsulated in emulsified oil droplets for the first time by peppermint essential oil (PEO) mediation. During storage process, EGCG and Res consistently remain co-located inside the emulsified oil droplets. However, both EGCG and Res migrated towards the inner layer of the interface of emulsified oil droplets along with PEO. Res exhibited better stability compared to EGCG, while the degradation of EGCG occurred within the emulsified oil droplets. Furthermore, when co-localized with Res, the degradation rate of EGCG slowed down. PEO did not degrade during storage, and over 98 % of PEO was encapsulated within the emulsified oil droplets. This is the crucial reason for maintaining the stability of SC-stabilized emulsion and achieving high encapsulation efficiency of active ingredients. This provides a green and simple strategy for co-encapsulation of active ingredients with Log P lower than 3.0 within emulsified oil droplets.

Antimicrobial Efficacy of Saline, Chlorhexidine, and Zataria Multiflora and Mentha Piperita Essential Oils in Root Canal Irrigation of Primary Molars.

Objectives: This study aimed to compare the antimicrobial efficacy of saline, 0.5% and 2% Zataria multiflora (Z. multiflora) essential oil, 0.5% and 2% Mentha piperita (M. piperita) essential oil, and 0.2% chlorhexidine (CHX) as root canal irrigants for primary molar teeth. Materials and Methods: A total of 64 primary molars were used in this in vitro study. The teeth were randomly assigned to six groups (N=10). The root canals were prepared up to file #35, and all teeth were sterilized before contamination with Enterococcus faecalis (E. faecalis; ATCC 29212) suspension. After 48 hours of incubation, the root canals in each group were irrigated with the respective irrigants. Sterile paper points were then used to collect microbial samples from the root canals. A colony counter was used to count the number of colony-forming units (CFUs). Data were analyzed by SPSS version 20 (alpha=0.05). Results: The colony count was significantly different among the groups (P<0.001), and 2% M. piperita (P=0.009), 0.5% Z. multiflora (P=0.021), and 0.2% CHX (P=0.002) were significantly more effective than saline in elimination of E. faecalis. The ascending order of microbial count after irrigation was as follows: saline > 0.5% M. piperita > 0.2% CHX > 2% M. piperita > 0.5% Z. multiflora. Conclusion: The current study showed the optimal antibacterial activity of 0.5% Z. multiflora essential oil and 2% M. piperita essential oil against E. faecalis, and indicated their possible efficacy for use as an irrigant for root canal irrigation of primary molars.

Field effectiveness of some essential oil emulsions against the whitefly Bemisia tabaci (GENN.) that infest potato plants in Egypt

AbstractWhitefly, Bemisia tabaci, nymphs and sucking sap adults, is one of the most damaging pests of potato, Solanum tuberosum. Excessive use of pesticides causes environmental pollution and the death of beneficial insects, so it is necessary to search for safer controlling alternatives. An experiment was carried out during seasons 2020–2021 and 2021–2022, under field conditions in Egypt. The objective of this study was to identify the main constituent compounds of peppermint and eucalyptus essential oils prepare coarse emulsion (CE) and nanoemulsion (NE) of both peppermint and eucalyptus essential oils and evaluate their efficiency against the whitefly, B. tabaci, in potato cultivars and the effect of these emulsions on the chemical components of potato leaves. The results revealed that the toxicity of the emulsions decreased with increasing time after spraying. The second spray which took place at a 10-day interval was more effective than the first spray. During the season of 2021, three days following the second spray, the tested emulsions' toxicity was highly effective. The reduction percentages of nymph for peppermint coarse emulsion (PCE), peppermint nanoemulsion (PNE), eucalyptus coarse emulsion (ECE), eucalyptus nanoemulsion (ENE) and imidacloprid were 82.64, 84.14, 73.26, 72.72 and 89.03, but they were 78.58, 83.27, 77.85, 69.97 and 89.26 compared with 2022. A moderately positive correlation was identified between temperature, specific humidity, wind speed and the effectiveness of the emulsions. This indicates that higher levels of temperature, humidity and wind speed were associated with increased efficacy of the emulsions. The study of the phytochemicals (total soluble protein, total carbohydrate, total phenolic contents and peroxidase activity). PCE and ECE achieved a slight decrease in protein levels. Also, ECE increased total plant carbohydrates. All treatments did not affect the phenolic compounds of potato leaf plants except ENE, which caused an increase in phenolic compounds. All treatments decreased the nitrogen plants' contents, while PCE, PNE, and ENE increased the potassium content. All treatments increase the activity of peroxidase (POX) compared with untreated plants. The formulations PNE and ENE might be an interesting alternative for integrated pest management of B. tabaci nymphs.

Peppermint essential oil enhances the vase life of Dendrobium orchids

To extend the vase life of cut flowers, there is now a trend of using plant essential oils in place of synthetic chemicals, as they are fully biodegradable, more eco-friendly, and safer. The objective of this study was to examine the possible application and postharvest quality effects of three plant essential oils namely, ginger (Zingiber officinale Roscoe), peppermint (Mentha piperita L.), and citronella (Cymbopogon nardus Rendle), as natural vase solution for cut Dendrobium flowers. Peppermint essential oil showed promise as a holding solution for extending the vase life of Dendrobium orchids. To confirm vase life extension, emulsions containing peppermint essential oil at concentrations of 50 and 100 μg mL−1 combined with 4 % glucose to formulate holding solutions applied to Dendrobium orchids. Vase life, some biochemical changes, electrolyte leakage, total microbial count in the holding solution, and physical condition via scanning electron microscopy (SEM) were evaluated over a period of 25 days. The three major compounds in peppermint essential oil were identified as menthol (33.24 %), 1-menthone (18.91 %) and menthofuran (14.85 %). The essential oil was applied in emulsion form as a holding solution. Treatment with 4 % glucose and either 50 or 100 μg mL−1 peppermint essential oil prolonged the vase life of Dendrobium orchids to up to 28 days. Scanning electron microscopy on Day 7 showed that the xylem vessels of treated orchids remained clear, suggesting reduced microbial plugging at the stalk end. Similarly, on Day 20, a reduced microbial cell count was observed for treated orchids (<1 log CFU mL−1) in comparison with controls (7.20 ± 0.04 log CFU mL−1). Finally, the essential oil improved flower quality by helping preserve petal membrane stability and petal anthocyanin content. Our results suggest the application of peppermint essential oil as a novel alternative to chemicals used in holding solutions for extending the vase life of Dendrobium orchids.

Clove and Peppermint Essential Oils Effect on Pathogenic Gut Micro-Biota in Chronic Hepatic Disease Patients

Multidrug-resistant bacteria infections in cirrhotic patients are currently increasing and associated with greater morbidity and mortality. The aim of this study was to decrease complications and bacterial infections that probably occurred after a patient undergoes liver transplantation surgery in Egypt using natural edible nontoxic peppermint and clove essential oils. All patients undergo clinical, laboratory, and microbiological testing. The recorded results showed that administered minimum inhibitory concentration (MIC) of clove and peppermint essential oils significantly reduced the total colony forming unit (CFU) count of multidrug-resistant pathogenic bacteria isolated from patients with chronic hepatic disease. The gas chromatography-mass spectrometry (GC-MS) analysis of clove and peppermint oil revealed the presence of active constituents with antibacterial activities as indicated in previous reviews.

The mechanistic insights of essential oil of Mentha piperita to control Botrytis cinerea and the prospection of lipid nanoparticles to its application

Botrytis cinerea is the phytopathogenic fungus responsible for the gray mold disease that affects crops worldwide. Essential oils (EOs) have emerged as a sustainable tool to reduce the adverse impact of synthetic fungicides. Nevertheless, the scarce information about the physiological mechanism action and the limitations to applying EOs has restricted its use. This study focused on elucidating the physiological action mechanisms and prospection of lipid nanoparticles to apply EO of Mentha piperita. The results showed that the EO of M. piperita at 500, 700, and 900 μL L−1 inhibited the mycelial growth at 100 %. The inhibition of spore germination of B. cinerea reached 31.43 % at 900 μL L−1. The EO of M. piperita decreased the dry weight and increased pH, electrical conductivity, and cellular material absorbing OD260 nm of cultures of B. cinerea. The fluorescence technique revealed that EO reduced hyphae width, mitochondrial activity, and viability, and increased ROS production. The formulation of EO of M. piperita loaded- solid lipid nanoparticles (SLN) at 500, 700, and 900 μL L−1 had particle size ∼ 200 nm, polydispersity index < 0.2, and stability. Also, the thermogravimetric analysis indicated that the EO of M. piperita-loaded SLN has great thermal stability at 50 °C. EO of M. piperita-loaded SLN reduced the mycelial growth of B. cinerea by 70 %, while SLN formulation (without EO) reached 42 % inhibition. These results supported that EO of M. piperita-loaded SLN is a sustainable tool for reducing the disease produced by B. cinerea.

A Comprehensive Study on Peppermint Oil and Cinnamon Oil as Nanoemulsion: Preparation, Stability, Cytotoxicity, Antimicrobial, Antifungal, and Antioxidant Activity.

Recent studies have shown that nanoemulsions prepared with essential oils have significant antimicrobial potential against multidrug-resistant pathogens due to increased chemical stability. Nanoemulsion also promotes controlled and sustained release, which increases their bioavailability and efficacy against multidrug-resistant bacteria. This study aimed to investigate the antimicrobial, antifungal, antioxidant, and cytotoxicity properties of cinnamon essential oil and peppermint essential oil as nanoemulsions compared to pure forms. For this purpose, analyses of the selected stable nanoemulsions were carried out. The droplet sizes and zeta potentials of peppermint essential oil nanoemulsions and cinnamon essential oil nanoemulsions were found to be 154.6±1.42 nm and -17.1±0.68 mV and 200.3±4.71 nm and -20.0±0.81 mV, respectively. Although the amount of essential oil used in nanoemulsions was 25% w/w, antioxidant and antimicrobial activities were found to be more effective compared to pure essential oils. In cytotoxicity studies on the 3T3 cell line, both essential oil nanoemulsions showed higher cell viability than pure essential oils. At the same time, cinnamon essential oil nanoemulsions exhibited a higher antioxidant property than peppermint essential oil nanoemulsions and showed superiority in the antimicrobial susceptibility test conducted against four bacteria and two fungi. Cell viability tests determined that cinnamon essential oil nanoemulsions showed considerably higher cell viability compared to pure cinnamon essential oil. These findings indicated that the prepared nanoemulsions in the current study might positively influence the dosing regimen and clinical outcomes of antibiotic therapy.

Improving antifungal effect of peppermint essential oil

Nanoencapsulation of essential oils is a promising strategy for extending their antifungal activity and addressing evaporation and decomposition in unfavorable environmental conditions. This research aimed to synthesize and compare the physical properties of solid lipid nanoparticles (SLNs) containing peppermint essential oil (PE) during 12 months of storage at various temperatures (4°C, 25°C, 27°C with 60% relative humidity, 37°C, and 40°C with 75% relative humidity), and to investigate their antifungal activity compared to free PE. The SLN formulations were prepared using high-shear homogenization and ultrasound techniques and were analyzed using a particle size analyzer, differential scanning calorimetry, transmission electron microscopy, and microscopic images of fungal mycelium to assess encapsulation efficacy. The results showed that the PE-SLNs had a size of 164.2 ±5.8 nm, a PDI value of 0.176 ±0.01, a zeta potential value of –11.3 mV, and an encapsulation percentage of approximately 75 ±0.5%. Overall, the physical properties of the formulations showed a slight and acceptable increase over the 12-month storage period at all investigated temperatures. Furthermore, the in vitro inhibition percentage of free PE at a concentration of 2000 μL L–1 against Penicillium italicum and P. digitatum was 66.7% ±2.6 and 66.8% ±0.8, respectively, while for PE-SLNs it was 88.8% ±0.9 and 89.9% ±1.4. These results demonstrate the potential of SLNs as an effective carrier for sustained delivery of PE with improved antifungal activity during storage.

Production and composition of peppermint essential oil in seasons after summer and winter transplantations

Production and composition of peppermint essential oil in seasons after summer and winter transplantations

Effects of peppermint essential oil and artifier on growth performance, carcass characteristics and nutrient digestibilities in broiler chickens fed with low energy diets

The aim of this experiment was to investigate the effects of peppermint essential oil (PEO) and an emulsifier called artifier on growth performance, carcass characteristics, and nutrient digestibility of broiler chickens fed low-energy diets. A total of 240 one-day-old male Ross 308 broiler chickens were divided into five treatments: control, low-energy diet, low-energy diet + 150 ppm PEO, low-energy diet + 300 ppm artifier, and low-energy diet + 150 ppm PEO + 300 ppm artifier. Each treatment was replicated four times in a completely randomized design. The chickens were fed these treatments during the starter, grower, and finisher periods for a total of 42 days. The results indicated that broiler chickens receiving the low-energy diet supplemented with PEO + artifier had similar body weight gain, feed conversion ratio, and breast percentage, but exhibited significantly lower abdominal fat percentage compared to those fed the control diet (P < 0.05). Furthermore, birds receiving PEO and artifier in low-energy diets, either individually or in combination, demonstrated higher digestibility of dry matter and fat during the starter and grower periods in comparison to those receiving the low-energy diet without any additives (P < 0.05). Over the entire rearing period, the simultaneous inclusion of 150 ppm PEO and 300 ppm artifier in the low-energy diet resulted in comparable growth performance to the control diet. Additionally, the concurrent use of PEO and artifier in the low-energy diet for broiler chickens led to a decrease in abdominal fat, increased digestibility of fat and dry matter, and enhanced nutrient utilization compared to the control diet.

Peppermint essential oil and ZnO nanoparticles: A green and effective combination for a cooling bilayer patch with antibacterial activity

Nowadays, comprehensive research has been done all over the world regarding the biomedical, pharmaceutical, and environmental applications of hydrogels. Hydrogel patches are widely used for wound healing due to their biocompatibility, biodegradability, and hydration capability. In this study, a bilayer hydrogel patch was developed, which consists of a back layer of polyvinyl alcohol (PVA) and a front layer of sodium alginate (SA) containing peppermint essential oil (PEO) and zinc oxide nanoparticles (ZnO NPs). A thermal camera showed the cooling effect of PEO on the hydrogel patch. PEO contains a high concentration of menthol, which is a compound that activates transient receptor potential melastatin 8 (TRPM8) channels in the skin, which leads to a feeling of skin coolness. The results showed that the antibacterial, antioxidant, and hemostatic properties of hydrogel patches were increased by PEO and ZnO NPs. The wound healing performance of hydrogel patches on rats was also evaluated for 14 days. Wound closure was accelerated by the hydrogel patch containing PEO and ZnO NPs, inflammation was reduced, collagen synthesis was increased, and skin structure and function were restored. Therefore, it was concluded that the hydrogel patch containing PEO and ZnO NPs is a promising candidate for wound healing applications.

Peppermint oil‐infused polylactic acid films: A novel approach for antimicrobial and biodegradable food packaging

AbstractExtensive research is currently dedicated to creating biodegradable packaging materials that match the qualities of traditional synthetic packaging materials. Among these options, polylactic acid (PLA) is noteworthy. PLA is a renewable‐source‐derived thermoplastic polymer with excellent barrier properties, mechanical strength, and a strong safety profile. To enhance food product shelf life, active packaging materials, incorporating functional ingredients like antimicrobials, have gained prominence. Peppermint essential oil is one such active ingredient, offering potential improvements in preserving food freshness and safety. This study's objective is to craft antimicrobial, biodegradable food packaging materials by blending peppermint oil into PLA films. Various peppermint oil concentrations (1.25%, 1.875%, and 2.5% w/v) were blended with PLA to assess their impact on opacity, water vapor permeability (WVP), mechanical and thermal properties, and antimicrobial characteristics. Higher peppermint oil concentrations increased opacity, making them advantageous for light‐sensitive food items. These films reduced WVP without affecting PLA's thermal stability. Antimicrobial effectiveness was evaluated against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), showing inhibition with 1.875% and 2.5% w/v peppermint oil concentrations. Compared to control, PLA films with peppermint oil extended the shelf life of packaged chicken breast meats from 3 to 8 days. As a result, incorporating peppermint oil into PLA films presents a promising solution for advanced antimicrobial and biodegradable food packaging.Highlights The incorporation of peppermint oil resulted in higher opacity values. Peppermint incorporated PLA films showed antimicrobial activity. Peppermint oil addition decreased water vapor permeability of PLA films. Peppermint oil added PLA films increased the shelf life of chicken meat up to 8 days.

Modulating peppermint oil flavor release properties of emulsion-filled protein gels: Impact of cross-linking method and matrix composition

For some food applications, it is desirable to control the flavor release profiles of volatile flavor compounds. In this study, the effects of crosslinking method and protein composition on the flavor release properties of emulsion-filled protein hydrogels were explored, using peppermint essential oil as a model volatile compound. Emulsion-filled protein gels with different properties were prepared using different crosslinking methods and gelatin concentrations. Flavor release from the emulsion gels was then monitored using an electronic nose, gas chromatography-mass spectrometry (GC–MS), and sensory evaluation. Enzyme-crosslinked gels had greater hardness and storage modulus than heat-crosslinked ones. The hardness and storage modulus of the gels increased with increasing gelatin concentration. For similar gel compositions, flavor release and sensory perception were faster from the heat-crosslinked gels than the enzyme-crosslinked ones. For the same crosslinking method, flavor release and perception decreased with increasing gelatin concentration, which was attributed to retardation of flavor diffusion through the hydrogel matrix. Overall, this study shows that the release of hydrophobic aromatic substances can be modulated by controlling the composition and crosslinking of protein hydrogels, which may be useful for certain food applications.

In vitro Antifungal Activity of Mentha piperita and Thymus vulgaris Essential Oils against Ochratoxigenic Aspergillus carbonarius Isolated from Bozcaada Çavuş Grape

In this study, the antifungal properties of Mentha piperita and Thymus vulgaris essential oils against an isolate of ochratoxin A producer, Aspergillus carbonarius, isolated from Bozcaada Çavuş grape, were evaluated in three steps. By GC-MS of M. piperita and T. vulgaris essential oils, the main components were determined to be menthol (39.911%) and carvacrol (49.042%). Antifungal activity was first evaluated by the agar well diffusion method, and it was determined that the tested essential oils completely inhibited the growth of A. carbonarius and were as effective as fluconazole antifungal. In the second step, the MIC and MFC values of the tested essential oils were determined; both values were 1 µL mL-1. Finally, it was determined that M. piperita and T. vulgaris essential oils completely inhibited the radial growth of A. carbonarius at the MIC value. These results show that M. piperita and T. vulgaris essential oils may be a good strategy to control ochratoxigenic A. carbonarius contamination.

Enhancing (−)-epigallocatechin gallate thermal stability in emulsified oil droplets: Designing a thermal insulation interface for O/W emulsion

In this study, we constructed a thermal insulation interface layer for O/W emulsion using composite nanoparticles formed through the aggregation of CaCO3 particles, which was mediated by sodium casein (SC) and chitosan oligosaccharide (CHO). As a representative of hydrophilic thermo-sensitive active ingredients, the (−)-epigallocatechin gallate (EGCG) was dispersed in a blended oil comprising peppermint essential oil (PEO) and sunflower seed oil (SO). The retention rate of EGCG in the emulsion, which had a thermal insulation protective layer, increased by 34.37% after heating, compared to the control emulsion. Furthermore, our research findings indicate that the thermal degradation process of EGCG in emulsified oil droplets involves initial isomerization into (−)-gallocatechin gallate (GCG), followed by subsequent degradation. Notably, the presence of the thermal insulation interface layer effectively suppresses the thermal degradation of GCG. This can be primarily attributed to the numerous mesopores in SC&CHO&CaCO3 particles and low thermal diffusivity of the thermal insulation interface layer. This study provides a reliable solution for the stable encapsulation of thermo-sensitive active ingredients in emulsified oil droplets of O/W emulsion through the design of a thermal insulation interface layer, thus effectively improving their stability.

Soil Properties and Yield of Peppermint (Mentha Piperita L.) in Response to Different Nitrogen Fertilizers Under Water-Deficit Conditions

ABSTRACT Drought and lack of nutrients (including nitrogen) limit crop production in arid and semi-arid regions, including Iran. In order to investigate the combined effect of nitrogen fertilizer sources (organic and chemical) under low water stress on soil properties, biological yield and peppermint essential oil, a three-year experiment was conducted during the spring and summer of the years (2017–2019) in the semi-arid region of Iran. The experiment was conducted as split plots in the form of randomized complete blocks with three replications. Experimental treatments include three irrigation regimes (irrigation after draining 25, 40 and 55% of usable water in the root zone) as the main factor and six fertilizer treatments based on plant nitrogen requirements (100% Chemical, No fertilizer, 50% Chemical + 50% Azocompost, 100% Vermicompost, 100% Azocompost, 50% Chemical + 50% Vermicompost) as sub-factors. The results showed that water-deficit conditions decreased organic carbon, total nitrogen content, soil phosphorus and potassium and biological yield and increased the percentage of peppermint essential oil. Also, in most of the treatment compositions of irrigation regime, the application of organic fertilizer (especially pure vermicompost and azocompost treatments) or combination with chemical fertilizer the increase organic carbon, macronutrients (nitrogen and phosphorus) and micro (iron and zinc) in soil solution, causing improved biological yield and essential oil content and moderated the effects of water-deficit stress on peppermint. These practical measures can help save water and fertilizer consumption while promoting the production of healthy medicinal products over the course of three years.

Production of zein nanofibers using an electrospinning technique for the encapsulation of peppermint (Mentha piperita L.) essential oil

Peppermint is a perennial herb with high inhibitory power against bacteria because its chemical profile contains menthol and menthone. In this research, peppermint essential oil (PEO) was encapsulated in various levels (0, 2.5, 5, and 10% w/v) in nanofibers (NFs) obtained from zein using an electrospinning technique. SEM, XRD, TGA, and FTIR tests were performed to investigate the characteristics of NFs after producing them. Also, the resultant NFs were evaluated regarding encapsulation efficiency (EE) and antimicrobial properties via disc-diffusion against Escherichia coli, Staphylococcus aureus, Bacillus cereus, and Salmonella enterica. The results indicated that the morphology was tubular, uniform, and free bead. Fiber diameter increased on average by increasing the amount of PEO (p<0.05). XRD results showed that PEO was amorphous in electrospun zein NFs. TGA and FTIR analyses confirmed the presence of PEO in the electrospun fibers. In addition, the FTIR spectrum showed that the zein protein changed its secondary structure because of the PEO. The results of EE showed that an increase in PEO concentration caused a relevant rise in EE (P<0.05). The electrospun NFs containing PEO showed antimicrobial properties against the target bacteria. According to the current research, NFs obtained from zein via electrospinning can be applied suitably as a substrate to encapsulate PEO as a hydrophobic component.

Enhancing functional features of pectin‐based coating by incorporating cellulose nanofibre/peppermint oil

SummaryFruit loss frequently occurs due to physical and microbial deterioration. This study aimed to develop an emulsified coating formulation based on pectin (BP)/cellulose nanofibre (CNF)/(peppermint essential oil) PEO using the Pickering technique with an appropriate level of CNF as a stabiliser and to study its effect on grape quality during storage. The incorporation of 0.4% PEO‐stabilised with various 0.1%–0.325% CNF into 0.5% BP edible coatings was developed. A 0.175% concentration of CNF was found to be appropriate for stabilising the emulsion system. This technique improved the functional performance of BP coatings, including their antifungal activity against Penicillium digitatum by 64.94% on the 7th day of incubation. Moreover, light transmission at UV and visible wavelengths and elongation improved by 23.17% and 71.26% respectively compared to the pure BP‐based coating. Scanning electron microscopy and Fourier‐transform infrared spectroscopy were used to characterise the biocompatibility of each coating formulation. The PEO‐CNF emulsion coating may be an alternative for the active coating of fresh fruit commodities.

Menthacarin treatment attenuates nociception in models of visceral hypersensitivity.

Chronic visceral hypersensitivity is closely associated with irritable bowel syndrome (IBS), a very common disorder which significantly impairs quality of life, characterized by abdominal pain, and distension. Imaging studies have found that IBS patients show higher metabolic activities and functional differences from normal controls in the anterior cingulate cortex (ACC), in response to visceral pain stimulation. Non-clinical data and clinical data suggest that medicinal products containing essential oils such as peppermint or caraway oil exert beneficial effects on IBS symptoms. We assessed acute and long-term treatment effects of a mixture of peppermint and caraway essential oils (Menthacarin) on brain electrophysiological markers of gut pain sensitivity in two rat models of visceral hypersensitivity. Chronic administration of corticosteroids and acute repeated mechanical hyperstimulation under anesthesia induced hyperalgesia and hypersensitivity, characterized by an increase in electrophysiological excitatory responses of ACC neurons to colorectal distension (CRD) and an increase in the proportion of neurons responding to otherwise subthreshold stimulation, respectively. Long-term, but not acute, oral administration of Menthacarin (60 mg kg-1 day-1) significantly reduced the net excitatory response to CRD in normally responsive control animals and counteracted the development of visceral hyperalgesia and hypersensitivity induced by repeated corticosterone administration and acute mechanical stimulation. The present study shows that, using the CRD method, chronic Menthacarin administration at a clinically relevant dose attenuates the neuronal discharge associated with visceral pain stimuli in the rat ACC, particularly in models of hypersensitivity, suggesting a potential for treating exaggerated visceral pain sensitivity.

Two-dimensional correlation infrared spectroscopy elucidated the volatilization process of the microemulsion composed of peppermint essential oil and composite herbal extract

Microemulsion is usually a transparent and isotropic liquid mixture composed of oil phase, water phase, surfactant and cosurfactant. The surfactant-framed nanoscale droplets in the microemulsion can penetrate into the skin surface to reduce its barrier function. This makes microemulsion an ideal preparation for the transdermal drug delivery. The permeability of microemulsion may be further enhanced when botanical essential oils that can dissolve the stratum corneum are used as the oil phase. However, the volatility of essential oils is possible to shorten the retention time of the microemulsion on the skin surface. Therefore, analytical methods are required to understand the volatilization process of the microemulsion composed of essential oils to develop the reasonable topical drug carrier system. In this research, Fourier transform infrared (FTIR) spectroscopy with an attenuated total reflection (ATR) accessory cooperated with two-dimensional correlation spectroscopy (2DCOS) to elucidate the volatilization processes of some microemulsions composed of peppermint essential oil. Principal component analysis (PCA) and moving-window two-dimensional correlation spectroscopy (MW2DCOS) revealed the multiple stages of the volatilization processes of the microemulsions. Synchronous 2D correlation infrared spectra indicated the compositional changes during each stage. It was found that the successive volatilizations of ethanol, water and menthone were the major events during the volatilization process of the microemulsion composed of peppermint essential oil. Ethanol can accelerate the volatilization of water, while the composite herbal extract seemed to not influence the volatilization of the other ingredients. After a 20-min-long volatilization process, the remaining microemulsion still contained considerable peppermint essential oil to affect the skin. The above results showed the feasibility of developing the microemulsion composed of peppermint essential oil for the transdermal drug delivery of composite herbal extract. This research also proved that the combination of ATR-FTIR spectroscopy and 2DCOS was valuable to study the volatilization process of the microemulsion.