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

BACKGROUND

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.

OBJECTIVE

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.

METHOD

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.

RESULTS

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.

CONCLUSION

These findings indicated that the prepared nanoemulsions in the current study might positively influence the dosing regimen and clinical outcomes of antibiotic therapy.

Development and characterization of nanoemulsions loaded with essential oil and β-cypermethrin and their bioefficacy on insect pest of economic and medical importance

BACKGROUND

The development of novel and ecofriendly tools plays an important role in insect pest management. Nanoemulsions (NEs) based on essential oils (EOs) offer a safer alternative for human health and the environment. This study aimed to elaborate and evaluate the toxicological effects of NEs containing peppermint or palmarosa EOs combined with β-cypermethrin (β-CP) using ultrasound technique.

RESULTS

The optimized ratio of active ingredients to surfactant was 1:2. The NEs containing peppermint EO combined with β-CP (NEs peppermint/β-CP) were polydisperse with two peaks at 12.77 nm (33.4% intensity) and 299.1 nm (66.6% intensity). However, the NEs containing palmarosa EO combined with β-CP (NEs palmarosa/β-CP) were monodisperse with a size of 104.5 nm. Both NEs were transparent and stable for 2 months. The insecticidal effect of NEs was evaluated against Tribolium castaneum and Sitophilus oryzae adults, as well as Culex pipiens pipiens larvae. On all these insects, NEs peppermint/β-CP enhanced pyrethroid bioactivity from 4.22- to 16-folds while NEs palmarosa/β-CP, from 3.90- to 10.6-folds. Moreover, both NEs maintained high insecticidal activities against all insects for 2 months, although a slight increase of the particle size was detected.

CONCLUSION

The NEs elaborated in this work can be considered as highly promising formulations for the development of new insecticides. © 2023 Society of Chemical Industry.

The Use of Fibers, Herbal Medicines and Spices in Children with Irritable Bowel Syndrome: A Narrative Review

The pathophysiology of irritable bowel syndrome in children involves multiple factors. Thus, treatment options are variable, targeting both diet and the child's and parents' behavior via pharmacological and psychological interventions or neuromodulation. Parents are increasingly interested in complementary and alternative therapies for children with irritable bowel syndrome, especially when other treatments have been tried without relieving the child's symptoms. This paper examines current evidence for the benefits and side effects of herbal remedies and spices in pediatric patients with IBS. The benefits of peppermint oil, STW5, psyllium fiber, Curcuma, ginger, and other herbal medicines are discussed based on findings in the current literature.

Development and Optimization of a Novel Lozenge Containing a Metronidazole-Peppermint Oil-Tranexamic Acid Self-Nanoemulsified Delivery System to Be Used after Dental Extraction: In Vitro Evaluation and In Vivo Appraisal

In-depth studies on essential oil-based nanoemulsions (NEs) have centered on a variety of oral health issues. NEs improve the delivery of nonpolar active agents to sites and thereby boost the dissolution and distribution of the agents. Metronidazole-peppermint oil-tranexamic acid self-nanoemulsifying drug delivery systems (MZ-PO-TX-SNEDDS) were created and loaded into novel lozenges to act as antifungal, hemostatic, antimicrobial, and analgesic dosage forms after dental extractions. The design-of-experiments approach was used in creating them. To generate the NEs, different concentrations of MZ-PO (240, 180, and 120 mg), 2% TX (600, 450, and 300 mg), and Smix1:1 (600, 400, and 200 mg) were used. The ideal formulation had serum levels of 1530 U/mL of interleukin-6, a minimal inhibitory concentration against bacteria of 1.5 µg/mL, a droplet size of 96 nm, and a blood coagulation time of 16.5 min. Moreover, the produced NE offered better MZ release. The adopted design was used to produce the ideal formulation; it contained 240 mg of MZ-PO, 600 mg of 2% TX, and 600 mg of Smix1:1. It was incorporated into lozenges with acceptable characteristics and an improved capability for drug release. These lozenges had reasonable coagulation times, IL-6 serum levels, and MIC values. All of these characteristics are desirable for managing symptoms following tooth extractions. Therefore, these lozenges loaded with MZ-PO-TX-SNEDDs might be considered a beneficial paradigm for relieving complications encountered after tooth extractions.

The Use of Peppermint Oil in Gastroenterology

BACKGROUND

For decades, mint has been used worldwide for its relieving effects against gastrointestinal disturbances. Peppermint is a perennial herb common in Europe and North America. The active ingredient of peppermint oil is menthol and has various gastroenterological and non-gastroenterological uses, especially in the context of functional gastrointestinal disorders (FGIDs).

METHODS

We conducted a literature search on the main medical databases for original articles, reviews, meta-analyses, randomized clinical trials, and case series using the following keywords and acronyms and their associations: peppermint oil, gastro-intestinal motility, irritable bowel syndrome, functional dyspepsia, gastrointestinal sensitivity and gastrointestinal endoscopy.

RESULTS

Peppermint oil and its constituents exert smooth muscle relaxant and anti-spasmodic effects on the lower esophageal sphincter, stomach, duodenum, and large bowel. Moreover, peppermint oil can modulate visceral and central nervous system sensitivity. Taken together, these effects suggest using peppermint oil both for improved endoscopic performance and for treating functional dyspepsia and irritable bowel syndrome. Importantly, peppermint oil has an attractive safety profile compared to classical pharmacological treatments, especially in FGIDs.

CONCLUSION

Peppermint oil is a safe herbal medicine therapy for application in gastroenterology, with promising scientific perspectives and rapidly expanding use in clinical practice.

Menthacarin for long-term treatment of functional dyspepsia - Results from a clinical trial follow-up

BACKGROUND

Menthacarin was shown to be effective and safe in clinical trials in patients with functional dyspepsia (FD). Long-term treatment results have not been reported yet.

METHODS

An open-label, 11-month follow-up (FU) was offered to FD patients who had undergone treatment with Menthacarin (1 gastro-resistant capsule b.i.d. vs. placebo (PL)) in a 4-week, double-blind, clinical trial. During FU, all patients (former verum and PL) were treated with 1 gastro-resistant capsule Menthacarin b.i.d. Main outcomes were the changes in pain intensity and severity of sensation of pressure, heaviness, and fullness from original baseline and global improvement.

RESULTS

70 patients were included in the analyses (former Menthacarin group: 36, former PL group: 34). At the end of the PL-controlled study phase, all 3 main efficacy variables were statistically significantly improved in the Menthacarin group compared to PL. In the FU phase, former PL patients started to improve under Menthacarin treatment towards the outcomes seen in the former Menthacarin group (alignment at approximately 6 months), while former Menthacarin patients showed sustained or even continuously improved outcomes by month 12. At study end, more than 90% of patients were "much or very much improved" in both groups. Menthacarin treatment was well tolerated.

CONCLUSIONS

The favorable effects seen in the FU period suggest that Menthacarin is a valuable treatment option in FD patients who require symptomatic treatment also in the longer term for up to 12 months.

Self-Medication for the Treatment of Abdominal Cramps and Pain-A Real-Life Comparison of Three Frequently Used Preparations

Functional gastrointestinal disorders (FGIDs), including irritable bowel syndrome (IBS), are frequently handled by self-management with over-the-counter (OTC) products such as hyoscine butylbromide (HBB), alone or in combination with paracetamol, and natural products such as peppermint oil. To obtain real-world information, we have performed an anonymous pharmacy-based patient survey among 1686 users of HBB, HBB + paracetamol, and peppermint oil. Based on the distinct but overlapping indications for the three OTC products, multiple logistic regression was applied to compare them in users reporting gastrointestinal cramps and pain, bloating, flatulence, or IBS as cardinal symptoms. All three treatments reduced symptoms and associated impairments of work/daily chores, leisure activities, and sleep by approximately 50%. Based on the four cardinal symptoms and the four dependent continuous variables of interest (change in intensity of symptoms and of the three impairment domains) a total of 16 logistic regression models were applied. HBB, HBB + paracetamol, and peppermint oil had similar reported overall effectiveness in those models. Gender, age, baseline symptom severity, and impairment in one of three domains had small and inconsistent effects on perceived treatment success. We provide evidence that HBB, HBB + paracetamol, and peppermint oil have comparable effectiveness in their approved indications under real-world conditions in an OTC setting.

Systematic review and meta-analysis: efficacy of peppermint oil in irritable bowel syndrome

BACKGROUND

Irritable bowel syndrome (IBS) is one of the most common disorders of gut-brain interaction, with a complex pathophysiology. Antispasmodics are prescribed as first-line therapy because of their action on gut dysmotility. In this regard, peppermint oil also has antispasmodic properties.

AIM

To update our previous meta-analysis to assess efficacy and safety of peppermint oil, particularly as recent studies have cast doubt on its role in the treatment of IBS METHODS: We searched the medical literature up to 2nd April 2022 to identify randomised controlled trials (RCTs) of peppermint oil in IBS. Efficacy and safety were judged using dichotomous assessments of effect on global IBS symptoms or abdominal pain, and occurrence of any adverse event or of gastro-oesophageal reflux. Data were pooled using a random effects model, with efficacy and safety reported as pooled relative risks (RRs) with 95% confidence intervals (CIs).

RESULTS

We identified 10 eligible RCTs (1030 patients). Peppermint oil was more efficacious than placebo for global IBS symptoms (RR of not improving = 0.65; 95% CI 0.43-0.98, number needed to treat [NNT] = 4; 95% CI 2.5-71), and abdominal pain (RR of abdominal pain not improving = 0.76; 95% CI 0.62-0.93, NNT = 7; 95% CI 4-24). Adverse event rates were significantly higher with peppermint oil (RR of any adverse event = 1.57; 95% CI 1.04-2.37).

CONCLUSIONS

Peppermint oil was superior to placebo for the treatment of IBS, but adverse events were more frequent, and quality of evidence was very low. Adequately powered RCTs of peppermint oil as first-line treatment for IBS are needed.

Active Antioxidant Packaging from Essential Oils Incorporated Polylactic Acid/Poly(butylene adipate-co-terephthalate)/Thermoplastic Starch for Preserving Straw Mushroom

The short-term shelf life of straw mushrooms (Volvariella volvacea) is a major challenge, hampering their wide distribution. Thus, the aim of this work was to develop a novel active packaging composed of essential oils (EOs), particularly clove oil (CO) and peppermint oil (PO), to reduce autolysis of straw mushrooms. The morphological characterizations, mechanical properties, barrier properties, and antioxidant activities of the films were characterized. The suppressive effects of the EOs on straw mushroom autolysis were estimated during storage at 16 ± 1 °C for 96 h. The results indicated that the addition of EOs weakened the mechanical and barrier properties of the films. The radical-scavenging activities of polylactic acid/poly(butylene adipate-co-terephthalate)/thermoplastic starch-peppermint oil (PLA/PBAT/TPS-PO) and polylactic acid/poly(butylene adipate-co-terephthalate)/thermoplastic starch-clove oil (PLA/PBAT/TPS-CO) films for 2,2-diphenyl-1-picrylhydrazyl were 56.0% and 91.3%, respectively. However, the PLA/PBAT/TPS-PO film was more effective in reducing polyphenol oxidase activity and maintaining the total phenol content of straw mushrooms, demonstrating better antioxidative activity. Mushrooms packaged with the PLA/PBAT/TPS-PO film exhibited the lowest autolysis rate (42.29%, p < 0.05) after 96 h of storage. Thus, PO is a good preservative agent for straw mushroom.

Essential oil nebulization in mild COVID-19(EONCO): Early phase exploratory clinical trial

Background

Medications studied for therapeutic benefits in coronavirus disease 2019 (COVID-19) have produced inconclusive efficacy results except for steroids.

Objective

A prospective randomized open-label, parallel-arm Phase I/II clinical trial was planned to compare essential oil (EO) blend versus placebo nebulization in mild COVID-19.

Methods

A Phase I safety evaluation was carried out in a single ascending and multiple ascending dose study designs. We assessed Phase II therapeutic efficacy on COVID-19 and general respiratory symptoms on days 0, 3, 5, 7, 10, and 14 on the predesigned case record form. Viremia was evaluated on day 0, day 5, and day 10.

Results

Dose-limiting toxicities were not reached with the doses, frequencies, and duration studied, thus confirming the formulation's preliminary safety. General respiratory symptoms (p < 0.001), anosmia (p < 0.05), and dysgeusia (p < 0.001) benefited significantly with the use of EO blend nebulization compared to placebo. Symptomatic COVID-19 participants with mild disease did not show treatment benefits in terms of symptomatic relief (p = 1.0) and viremia clearance (p = 0.74) compared to the placebo. EO blend was found to be associated with the reduced evolution of symptoms in previously asymptomatic reverse transcription polymerase chain reaction (RT-PCR)-positive study participants (p = 0.034).

Conclusion

EO nebulization appears to be a safer add-on symptomatic relief approach for mild COVID-19. However, the direct antiviral action of the EO blend needs to be assessed with different concentrations of combinations of individual phytochemicals in the EO blend.

Randomised trial: Peppermint oil (menthol) pharmacokinetics in children and effects on gut motility in children with functional abdominal pain

AIMS

Little is known regarding the pharmacokinetics and pharmacodynamics of menthol, the active ingredient in peppermint oil (PMO). Our aim was to investigate the pharmacokinetics of menthol at 3 dose levels in children and determine their effects on gut motility and transit.

METHODS

Thirty children ages 7-12 years with functional abdominal pain underwent wireless motility capsule (WMC) testing. Approximately 1 week later they were randomized to 180, 360 or 540 mg of enteric coated PMO (10 participants per dose). Menthol pharmacokinetics were determined via blood sampling over 24 hours. They then took their respective dose of PMO (180 mg once, 180 mg twice or 180 mg thrice daily) for 1 week during which time the WMC test was repeated.

RESULTS

Evaluable area under the plasma concentration vs. time curve (AUC_last ) data were available in 29 of 30 participants. A direct linear relationship (apparent dose-proportionality for systemic menthol exposure) was observed between PMO dose and menthol systemic exposure with mean elimination half-life 2.1, 3.5 and 4.6 hours for the 180, 360 and 540 mg doses, respectively. WMC technical issues precluded complete motility data in all participants. Colonic transit time was inversely related to AUC_last (P = .003); transit time in other regions was not affected. In contrast, stomach, small bowel and whole gut (but not colonic) contractility positively correlated with menthol AUC_last (P < .05).

CONCLUSION

Pharmacokinetics and pharmacodynamics of menthol derived from PMO demonstrated apparent dose-proportionality. A higher dose of PMO may be needed to achieve maximal gut response. www.clinicaltrials.gov NCT03295747.

Pain in irritable bowel syndrome: Does anything really help?

Pain relief remains a significant challenge in the management of irritable bowel syndrome (IBS): "Does anything really help relieve the pain in patients with IBS?". Interventions aimed at pain relief in patients with IBS include diet, probiotics or antibiotics, antidepressants, antispasmodics, and drugs targeting specific gastrointestinal receptors such as opioid or histamine receptors. In the systematic review and meta-analysis published in this journal, Lambarth et al. examined the literature on the role of oral and parenteral anti-neuropathic agents in the management of pain in patients with IBS. This review article appraises their assessment of the efficacy of the anti-neuropathic agents amitriptyline, pregabalin, gabapentin, and duloxetine in the relief of abdominal pain or discomfort, and impact on overall IBS severity and quality of life. This commentary provides an update of current evidence on the efficacy of the dietary and pharmacological treatments that are available or in development, as well psychological and cognitive behavioral therapy for pain in IBS. Advances in recent years augur well for efficacious treatments that may expand the therapeutic arsenal for pain in IBS.

[Improving comprehensive retention rate of peppermint oil in freeze-dried preparation based on cyclodextrin inclusion technology]

The freeze-drying technique, characterized by low-temperature processing, is especially suitable for sensitive volatile oils with thermal instability. However, there are few studies focusing on the retention of volatile oils in the processing of freeze-dried preparations. This study evaluated the effects of different addition methods(adsorption, emulsification, solid dispersion, and inclusion) on the retention rate of the main components in peppermint oil, aiming to explore the application feasibility of freeze-dried preparations of volatile oils. Firstly, the addition method was determined based on the retention rates of menthol in four freeze-dried preparations. Secondly, an orthogonal test was designed to optimize the preparation process based on the characteristics of the preferred addition method. The results showed that the most suitable preparation form of peppermint oil was inclusion with beta-cyclodextrin(β-CD), and the retention rate of menthol in freeze-drying was 86.36%. According to the two-step preparation process of inclusion and freeze-drying, we introduced the product of inclusion rate and retention rate, i.e., comprehensive retention rate, to determine the optimum processing parameters. The results showed that β-CD/oil ratio of 7∶1, inclusion temperature of 40 ℃, and inclusion time of 2 h were the optimum processing parameters. The product prepared with these parameter had the comprehensive retention rate of 68.41%, retention rate of 92.53%, and inclusion rate of 73.93%. The inclusion compound was white powder with significantly increased solubility. The pre-paration process based on cyclodextrin inclusion in this study is stable and reliable and provides a new idea for ensuring the efficacy and stability of volatile components in freeze-dried preparations.

Comparative Study on Microencapsulation of Lavender (Lavandula angustifolia Mill.) and Peppermint (Mentha piperita L.) Essential Oils via Spray-Drying Technique

Essential oils have been studied for various applications, including for therapeutic purposes. There is extensive literature regarding their properties; however, their low stability limits their application. Generally, the microencapsulation of essential oils allows enhanced stability and enables the potential incorporation in solid dosage forms. Lavender and peppermint oils were encapsulated in microparticles using a spray-drying technique under optimized conditions: 170 °C temperature, 35 m³/h aspiration volume flow, and 7.5 mL/min feed flow. Arabic gum and maltodextrin were used as coating polymers individually in varying concentrations from 5 to 20% (w/v) and in combination. The microparticles were studied for morphology, particle size, oil content, and flowability. The formulated powder particles showed a high yield of 71 to 84%, mean diameter 2.41 to 5.99 µm, and total oil content of up to 10.80%. The results showed that both the wall material type and concentration, as well as the type of essential oil, significantly affected the encapsulation process and the final particle characteristics. Our study has demonstrated that the encapsulation of lavender and peppermint oils in Arabic gum/maltodextrin microparticles by spray-drying represents a feasible approach for the conversion of liquids into solids regarding their further use in powder technology.

A trial-based economic evaluation of peppermint oil for the treatment of irritable bowel syndrome

Background

Irritable Bowel Syndrome (IBS) is a prevalent, chronic gastrointestinal disorder that imposes a substantial socioeconomic burden. Peppermint oil is a frequently used treatment for IBS, but evidence about cost‐effectiveness is lacking.

Objective

We aimed to assess cost‐effectiveness of small‐intestinal release peppermint oil versus placebo in IBS patients.

Methods

In a multicenter randomized placebo‐controlled trial, cost‐effectiveness was evaluated from a societal perspective. The incremental cost‐effectiveness ratios (ICERs) were expressed as (1) incremental costs per Quality Adjusted Life Years (QALY), and (2) incremental costs per successfully treated patient, that is per abdominal pain responder (according to FDA definitions), both after an eight‐week treatment period with placebo versus peppermint oil. Cost‐utility and uncertainty were estimated using non‐parametric bootstrapping. Sensitivity analyses were performed.

Results

The analysis comprised 126 patients (N = 64 placebo, N = 62 small‐intestinal release peppermint oil). Peppermint oil was a dominant treatment compared to placebo in 46% of bootstrap replications. Peppermint oil was also more effective but at higher cost in 31% of replications. The net‐benefit acceptability curve showed that peppermint oil has a 56% probability of being cost‐effective at a conservative willingness‐to‐pay threshold of €10.000/QALY. Peppermint oil was also a dominant treatment per additional successfully treated patient according to FDA definitions, that is in 51% of replications. In this case, the acceptability curve showed an 89% probability of being cost‐effective.

Conclusions

In patients with IBS, small‐intestinal release peppermint oil appears to be a cost‐effective treatment although there is uncertainty surrounding the ICER. When using abdominal pain responder as outcome measure for the ICER, peppermint oil has a high probability of being cost‐effective. The use of peppermint oil, which is a low‐cost treatment, can be justified by the modest QALY gains and slightly higher proportion of abdominal pain responders. More research and long‐term data are necessary to confirm the cost‐effectiveness of peppermint oil. NCT02716285.

Effect of peppermint oil and its microemulsion on necrotic enteritis in broiler chickens

Background and Aim:

Clostridium perfringens is one of the multiple drug-resistant intestinal pathogens causing necrotic enteritis disease, leading to great economic losses in poultry farms. This study aimed to evaluate the potential use of peppermint oil and its microemulsion (ME) as an alternative to antibiotics to control necrotic enteritis in broiler chickens.

Materials and Methods:

Peppermint oil ME formulation (15% oil/water) was prepared and characterized by zeta potential, Fourier transform infrared, high-resolution transmission electron microscopy, and liquid chromatography–mass spectrometry (LC-MS/MS). The minimal inhibitory concentrations of the peppermint oil and its ME were investigated. A total of 80 commercial one day old Arbor Acres broiler chickens were randomly assigned to four groups of 20 birds each. The four groups were the negative control, positive control, peppermint oil (0.5 mL/mL water/10 days old), and its ME (0.25 mL/mL water/10 days old) groups. C. perfringens was orally provided at concentration of 1×10⁸ CFU/mL on days 14, 15, and 16. Clinical signs and mortality were observed daily. Growth performance, gross lesions and cecal samples were investigated and examined on days 21, 28, and 35.

Results:

Peppermint oil ME formulation has a polydispersity index, zeta potential and droplet size of 0.234, −24 mV±4.19, and 29.96±1.56 nm, respectively. LC–MS/MS analysis of oil and ME revealed common presence of phenolic compounds such as rosmorinic (360.31 g/mol), chlorogenic acid (354.31 g/mol), hesperidin (610.56 g/mol), and luteolin 7-O-β-glucuronide (462.1 g/mol). The treated groups with peppermint oil and ME showed lower lesions, mortality and colony-forming units in addition to higher growth performance (p < 0.05) compared to the positive control group.

Conclusion:

Our study suggests the potential efficacy of peppermint oil and ME in the reduction of necrotic enteritis lesions and C. perfringens count.

Inhalation of Essential Oil from Mentha piperita Ameliorates PM10-Exposed Asthma by Targeting IL-6/JAK2/STAT3 Pathway Based on a Network Pharmacological Analysis

Fine particulate matter (PM) exposure exhibits a crucial risk factor to exacerbate airway epithelial remodeling, fibrosis, and pulmonary destruction in asthma. Based on the use of essential oils from aromatic plants on pain relief and anti-inflammatory properties, we investigated the inhibitory effects of essential oil derived from the Mentha species (MEO) against asthma exposed to PM10. The MEO (0.1 v/v %) was aerosolized by a nebulizer to ovalbumin and PM10-induced asthmatic mice. Histological changes were confirmed in the lung tissues. To define the mode of action of the MEO on asthma, a protein–protein interaction network was constructed using menthol and menthone as the major components of the MEO. Cytokine expression and the JAK2/STAT3 signaling pathway were analyzed in lung epithelial A549 cells co-treated with MEO and PM10. Inhalation of MEO by nebulization inhibited respiratory epithelium hyperplasia, collagen deposition, and goblet cell activation in asthmatic mice. Through a network pharmacological analysis, cytokine–cytokine receptor interaction and JAK/STAT was expected to be underlying mechanisms of MEO on asthma. Treatment with MEO significantly reduced the IL-6 levels with a decrease in pro-inflammatory and T helper 2-specific cytokines. PM10-induced phosphorylation of JAK2 and STAT3 was significantly decreased by MEO. Collectively, MEO may have an inhibitory effect on asthma under the condition of PM10 exposure through the IL-6/JAK2/STAT3 signaling pathway.

Determination of peppermint compounds in breath by needle trap micro-extraction coupled with gas chromatography-tandem mass spectrometry

Breath analysis is an alternative approach for disease diagnosis and for monitoring therapy. The lack of standardized procedures for collecting and analysing breath samples currently limits its use in clinical practice. In order to overcome this limitation, the "Peppermint Consortium" was established within the breath community to carry out breath wash-out experiments and define reference values for a panel of compounds contained in the peppermint oil capsule. Here, we present a needle trap micro-extraction technique coupled with gas chromatography and tandem mass spectrometry for a rapid and accurate determination of alpha-pinene, beta-pinene, limonene, eucalyptol, menthofuran, menthone, menthol and menthyl acetate in mixed breath samples. Detection limits between 1 and 20 pptv were observed when 25 mL of a humidified standard gas mixture were loaded into a needle trap device at a flow rate of 10 mL/min. Inter- and intra-day precisions were lower than 15%, thus confirming the reliability of the assay. Our procedure was used to analyse breath samples taken from a nominally healthy volunteer who were invited to swallow a 200 mg capsule of peppermint oil. Six samples were collected at various times within six hours of ingestion. Analyte concentrations were not affected by the sampling mode (i.e. mixed vs. end-tidal fraction), whereas respiratory rate and exhalation flow rate values slightly influenced the concentration of the target compounds in breath samples.

Smart Data Collection for the Assessment of Treatment Effects in Irritable Bowel Syndrome: Observational Study

BACKGROUND

End-of-day symptom diaries are recommended by drug regulatory authorities to assess treatment response in patients with irritable bowel syndrome. We developed a smartphone app to measure treatment response.

OBJECTIVE

Because the employment of an app to measure treatment response in irritable bowel syndrome is relatively new, we aimed to explore patients' adherence to diary use and characteristics associated with adherence.

METHODS

A smartphone app was developed to serve as a symptom diary. Patients with irritable bowel syndrome (based on Rome IV criteria) were instructed to fill out end-of-day diary questionnaires during an 8-week treatment. Additional online questionnaires assessed demographics, irritable bowel syndrome symptom severity, and psychosocial comorbidities. Adherence rate to the diary was defined as the percentage of days completed out of total days. Adherence to the additional web-based questionnaires was also assessed.

RESULTS

Overall, 189 patients were included (age: mean 34.0 years, SD 13.3 years; female: 147/189, 77.8%; male: 42/189, 22.2%). The mean adherence rate was 87.9% (SD 9.4%). However, adherence to the diary decreased over time (P<.001). No significant association was found between adherence and gender (P=.84), age (P=.22), or education level (lower education level: P=.58, middle education level: P=.46, versus high education level), while higher anxiety scores were associated with lower adherence (P=.03). Adherence to the online questionnaires was also high (>99%). Missing data due to technical issues were limited.

CONCLUSIONS

The use of a smartphone app as a symptom diary to assess treatment response resulted in high patient adherence. The data-collection framework described led to standardized data collection with excellent completeness and can be used for future randomized controlled trials. Due to the slight decrease in adherence to diary use throughout the study, this method might be less suitable for longer trials.

Food supplements and diet as treatment options in irritable bowel syndrome

Irritable bowel syndrome (IBS) is a chronic functional bowel disorder affecting 5.7% of the general population. Most patients relate their symptoms of IBS to foods they consume with diet being the most frequently reported factor impacting their life. However, although some foods may trigger symptoms, others may provide symptom relief. Indeed, several foods and diets have been investigated for their effectiveness in relieving IBS symptoms. In this issue of Neurogastroenterology and Motility, a double-blind randomized placebo-controlled trial in 160 patients with IBS demonstrated Aloe vera not to be effective in improving IBS symptoms. The aim of this review is to discuss the evidence on the effect of food supplements and diets in the management of IBS. Specifically, this review examines the evidence for aloe vera, peppermint oil, probiotics, fiber and prebiotics, healthy eating, the low FODMAP diet, and the gluten-free diet.

Role of Peppermint Oil in Diffuse Esophageal Spasm in the Geriatric Population

Diffuse esophageal spasm, also known as distal esophageal spasm (DES), is a rare motility disorder among the population with symptomatic motility disorders. This disorder is most commonly reported in females, with a median age of 60 years. Multiple therapeutic options have been developed for the treatment of DES. There has been limited research regarding the use of peppermint oil in the treatment of DES. Here, we discuss the interesting case of an elderly female patient who received symptomatic relief from peppermint oil.

Peppermint and caraway oils have muscle inhibitory and pro-secretory activity in the human intestine in vitro

BACKGROUND

Herbal medicinal products with a broad activity spectrum may be promising alternatives to treat functional gastrointestinal disorders (FGD). Menthacarin^® is a drug with a fixed combination of peppermint and caraway oils, which is clinically used to treat FGD-associated symptoms.

MATERIALS

We studied the effects of peppermint and caraway oils on contractile and secretory activity in 255 human small and large intestinal preparations derived from surgical resections (73 patients). Motility was recorded in circular smooth muscle strips and secretion with the Ussing chamber-voltage clamp technique. Electrical field stimulation evoked nerve induced contractile responses. KEY RESULTS: Peppermint and caraway oil concentrations dependently inhibited muscle contractility as indicated by sustained muscle relaxation and decrease in phasic contractility. These effects occurred in small and large intestinal preparations with IC₅₀ values ranging between 17 and 90 µg/mL for peppermint oil and between 7 and 127 µg/mL for caraway oil. Neither peppermint nor caraway oil influenced the nerve evoked contractile response. The inhibition of contractile activity, but not the muscle relaxation, was prevented by the L-type calcium channel activator Bay K8644 but not by the neurotoxin tetrodotoxin. Both peppermint oil and caraway oil increased epithelial secretion, which remained in tetrodotoxin.

CONCLUSION & INTERFERENCE

The findings revealed a strong muscle inhibitory and pro-secretory action of peppermint and caraway oils at clinically relevant concentrations. Both actions were nerve-independent. The inhibition of contractility was mediated by inhibition of L-type calcium channels. The effects on muscle and epithelial activity may contribute to the beneficial effects observed in patients with FGD.

Comparing the Effect of Intranasal Lidocaine 4% with Peppermint Essential Oil Drop 1.5% on Migraine Attacks: A Double-Blind Clinical Trial

Background:

Prevalence of migraine, as a chronic neurovascular disorder, was approximately 10.3 and 23.1% among men and women, respectively, mostly in people younger than 40 years old. Migraine is prevalent in different geographic areas worldwide. The present study was designed to compare the impact of intranasal lidocaine 4% and peppermint essential oil drop 1.5% on migraine attacks.

Methods:

In this double-blind, parallel, randomized controlled trial, 120 adult patients with a diagnosis of migraine based on the International Headache Society criteria were treated with intranasal lidocaine drop 4% or peppermint essential oil drop 1.5% or placebo. Patients expressed their symptoms 5 and 15 min after dripping, and if they still had a headache after 15 min, they were given the second dose. Patients with a second dose of medication, 15 min later recorded their headache rate. All patients recorded their symptoms after 30 min. Symptoms of the patients were followed by a researcher through the phone and in-person after 2 months. Then, the questionnaires were filled.

Results:

In the present study, there was a significant difference among groups in headache intensity after treatment (P < 0.001). In 40% of the patients in the peppermint oil and lidocaine groups, the intensity of headache decreased. In the placebo group, fewer patients responded highly to the treatment, whereas 41.5% of patients in the lidocaine group and 42.1% of patients in the peppermint oil group responded to the treatment considerably.

Conclusions:

Concerning the findings of the present study, nasal application of peppermint oil caused considerable reduction in the intensity and frequency of headache and relieved majority of patients' pain similar to lidocaine. On the basis of findings of this study, it can be concluded that nasal menthol, such as lidocaine, can be used to relieve migraine headaches.

Essential Oils as Antimicrobial Agents-Myth or Real Alternative?

Herbs and the essential oils derived from them have been used from the beginning of human history for different purposes. Their beneficial properties have been applied to mask unpleasant odors, attract the attention of other people, add flavor and aroma properties to prepared dishes, perfumes, and cosmetics, etc. Herbs and essential oils (EOs) have also been used in medicine because of their biological properties, such as larvicidal action, analgesic and anti-inflammatory properties, antioxidant, fungicide, and antitumor activities, and many more. Many EOs exhibit antimicrobial properties, which is extremely important in fields of science and industry, such as medicine, agriculture, or cosmetology. Among the 250 EOs which are commercially available, about a dozen possess high antimicrobial potential. According to available papers and patents, EOs seem to be a potential alternative to synthetic compounds, especially because of the resistance that has been increasingly developed by pathogenic microorganisms. In this review we summarize the latest research studies about the most-active EOs that are known and used because of their antimicrobial properties. Finally, it is noteworthy that the antimicrobial activities of EOs are not preeminent for all strains. Further investigations should, thus, focus on targeting EOs and microorganisms.

Preparation of Peppermint Oil-Based Nanodevices Loaded with Paclitaxel: Cytotoxic and Apoptosis Studies in HeLa Cells

In this work, several normal, oil-in-water (o/w) microemulsions (MEs) were prepared using peppermint essential oil, jojoba oil, trans-anethole, and vitamin E as oil phases to test their capacity to load paclitaxel (PTX). Initially, pseudo-ternary partial phase diagrams were constructed in order to find the normal microemulsion region using d-α-tocopherol polyethylene glycol 1000 succinate (TPGS-1000) as surfactant and isobutanol (iso-BuOH) as co-surfactant. Selected ME formulations were loaded with PTX reaching concentrations of 0.6 mg mL^-1 for the peppermint oil and trans-anethole MEs, while for the vitamin E and jojoba oil MEs, the maximum concentration was 0.3 mg mL^-1. The PTX-loaded MEs were stable according to the results of heating-cooling cycles and mechanical force (centrifugation) test. Particularly, drug release profile for the PTX-loaded peppermint oil ME (MEPP) showed that ∼ 90% of drug was released in the first 48 h. Also, MEPP formulation showed 70% and 90% viability reduction on human cervical cancer (HeLa) cells after 24 and 48 h of exposure, respectively. In addition, HeLa cell apoptosis was confirmed by measuring caspase activity and DNA fragmentation. Results showed that the MEPP sample presented a major pro-apoptotic capability by comparing with the unloaded PTX ME sample.

Controlled Release of Peppermint Oil from Paraffin-Coated Activated Carbon Contained in Sachets to Inhibit Mold Growth During Long Term Storage of Brown Rice

The aim of the study was to control the release of peppermint oil (700 µL/L) by coating activated carbon (AC) contained in sachets with different solutions (tapioca starch, corn starch, gelatine, carnauba, paraffin, and mixed carnauba-paraffin) for inhibiting the growth of Aspergillus flavus on brown rice (BR). Paraffin-coated AC with adsorbed peppermint oil was then applied to extend the shelf life of BR during long-term storage (60 days) at 30 ± 2 °C. The mechanism of peppermint oil vapor release in this system was also studied using GC-MS. The result revealed that paraffin-coated AC with adsorbed peppermint oil present in sachets showed the highest antifungal activity against A. flavus growing on the surface of BR. In addition, paraffin-coated AC with adsorbed peppermint oil could prolong the shelf life of BR from 10 days (control) to at least 60 days under tropical climatic conditions. Moreover, storage of BR in the presence of sachets containing paraffin-coated AC with adsorbed peppermint oil at a concentration of 700 µL/L revealed no significant effects on major rice quality-related factors, such as moisture content, color, water uptake percentage, and gelatinization temperature. Peppermint oil component analysis by GC-MS indicated that paraffin could trap some minor components of peppermint oil and allow the major components such as menthone, menthol, and alpha-pinene, which are compounds that play an important role in mold growth inhibition, to be exposed to air. Thus, this research demonstrated the potential of paraffin-coated AC containing adsorbed peppermint oil for controlling the growth of molds during prolonged rice storage. PRACTICAL APPLICATION: Paraffin-coated activated carbon with adsorbed peppermint oil has the potential to be commercially applied to brown rice grains for facilitating long-term storage. This technique is beneficial for avoiding the occurrence of negative sensorial factors when peppermint oil vapors are used. This process is interesting and easy to apply during large-scale implementation of a rice storage system.

In vitro Simulated Digestion and Microstructure of Peppermint Oil Nanoemulsion

The variations in average particle size, zeta potential, free fatty acids (FFA) release rate, and the bioavailability of menthol under in vitro simulated digestion conditions of peppermint oil nanoemulsion were investigated. 3D confocal laser scanning microscopy and Cryo-scanning electron microscopy were used to observe the microstructure characteristics of peppermint oil nanoemulsion, which indicated that soybean protein was completely adsorbed at the oil-water interface of the nanoemulsion and presented a core shell structure. And the results indicated that FFA release rate and menthol bioavailability of peppermint oil nanoemulsion prepared by using high-pressure homogenization were much higher. In the simulated gastric digestion phase, the average particle size and the zeta potential of the nanoemulsion increased, and droplet polymerization appeared. After the simulated intestinal, the interfacial protein of nanoemulsion was hydrolyzed, and the oil droplets were digested, which resulted in the decreased particle size and increased absolute value of zeta potential.

Determination of metabolites of Geotrichum citri-aurantii treated with peppermint oil using liquid chromatography-mass spectrometry and gas chromatography-mass spectrometry

Sour rot is a leading disease of citrus fruit caused by the postharvest pathogen Geotrichum citri-aurantii. It has been reported that essential oils can be used as substitutes for synthetic fungicides to control the pathogen. In this study, changes in metabolites and antifungal effects of G. citri-aurantii treated with peppermint oil (PO) were investigated. The inhibition rate of the mycelial growth increased as the PO concentration increased, and 6 μl PO/disk resulted in a radial growth inhibition of 79.2%. The electrical conductivity of G. citri-aurantii treated with PO increased compared to the control. By comparing the metabolic profiles of treated and untreated G. citri-aurantii cells, a total of 53 distinct metabolites 9 were up-regulated and 44 were down-regulated were found, including 16 lipid metabolites, 6 carbohydrate metabolites, 2 amino acid metabolites, 5 alcohols, 2 glycoside metabolites, and 3 ketone metabolites, etc, and these metabolites are involved in 25 major metabolic pathways. PRACTICAL APPLICATIONS: Chemical fungicides can effectively control G. citri-aurantii during fruit postharvest period. However, synthetic chemical fungicides have gradually led to buildup of resistance of fungil, which seriously causes the frequent of food-borne diseases. PO extracted from natural plants can be used as natural additive in many foods due to their antioxidant, antibacterial, and antifungal properties. Therefore, PO can be considered as a promising bacteriostatic agent for the defense of G. citri-aurantii during fruit postharvest period.

Review article: the physiological effects and safety of peppermint oil and its efficacy in irritable bowel syndrome and other functional disorders

BACKGROUND

Peppermint oil has been used for centuries as a treatment for gastrointestinal ailments. It has been shown to have several effects on gastrointestinal physiology relevant to clinical care and management.

AIM

To review the literature on peppermint oil regarding its metabolism, effects on gastrointestinal physiology, clinical use and efficacy, and safety.

METHODS

We performed a PubMed literature search using the following terms individually or in combination: peppermint, peppermint oil, pharmacokinetics, menthol, oesophagus, stomach, small intestine, gallbladder, colon, transit, dyspepsia, nausea, abdominal pain, and irritable bowel syndrome. Full manuscripts evaluating peppermint oil that were published through 15 July 2017 were reviewed. When evaluating therapeutic indications, only randomised clinical trials were included. References from selected manuscripts were used if relevant.

RESULTS

It appears that peppermint oil may have several mechanisms of action including: smooth muscle relaxation (via calcium channel blockade or direct enteric nervous system effects); visceral sensitivity modulation (via transient receptor potential cation channels); anti-microbial effects; anti-inflammatory activity; modulation of psychosocial distress. Peppermint oil has been found to affect oesophageal, gastric, small bowel, gall-bladder, and colonic physiology. It has been used to facilitate completion of colonoscopy and endoscopic retrograde cholangiopancreatography. Placebo controlled studies support its use in irritable bowel syndrome, functional dyspepsia, childhood functional abdominal pain, and post-operative nausea. Few adverse effects have been reported in peppermint oil trials.

CONCLUSION

Peppermint oil is a natural product which affects physiology throughout the gastrointestinal tract, has been used successfully for several clinical disorders, and appears to have a good safety profile.

A randomized placebo-controlled trial on the effects of Menthacarin, a proprietary peppermint- and caraway-oil-preparation, on symptoms and quality of life in patients with functional dyspepsia

BACKGROUND

Functional dyspepsia (FD) is a very common condition affecting more than 10% of the population. While there is no cure, a few drugs have been found to be effective for the relief of symptoms, although most are only effective in a subgroup of patients. We assess and compare the efficacy of a fixed peppermint/caraway-oil-combination (Menthacarin) on symptoms and quality of life (QoL) in patients with FD symptoms consistent with epigastric pain syndrome (EPS) and postprandial distress syndrome (PDS).

METHODS

In a prospective, double-blind, multicenter trial, 114 outpatients with chronic or recurrent FD were randomized and treated for 4 weeks with the proprietary peppermint- and caraway-oil-preparation Menthacarin or placebo (2×1 capsule/day). Improvement of abdominal pain and discomfort were used as co-primary efficacy measures (scores measured with the validated Nepean Dyspepsia Index).

KEY RESULTS

After 2 and 4 weeks, active treatment was superior to placebo in alleviating symptoms consistent with PDS and EPS (P all <.001). After 4 weeks of treatment, pain and discomfort scores improved by 7.6±4.8 and 3.6±2.5 points (full analysis set; mean±SD) for Menthacarin and by 3.4±4.3 and 1.3±2.1 points for placebo, respectively. All secondary efficacy measures showed advantages for Menthacarin.

CONCLUSIONS & INFERENCES

Menthacarin is an effective therapy for the relief of pain and discomfort and improvement of disease-specific QoL in patients with FD and significantly improves symptoms consistent with EPS and PDS.

Antispasmodic drugs in colonoscopy: a review of their pharmacology, safety and efficacy in improving polyp detection and related outcomes

Antispasmodic drugs are cheap, effective and generally safe. They may improve outcomes in colonoscopy, however their use has not been consistent or widespread. This manuscript reviews the three most commonly used antispasmodics in colonoscopy, namely, hyoscine butylbromide (and related ammonium compounds), glucagon and peppermint oil. The pharmacology, action and safety of the agents, as well as the evidence for them improving colonoscopic outcomes will be discussed. In addition to polyp detection, other colonoscopic outcome endpoints of interest include cecal and ileal intubation, and patient comfort. The drugs studied were all found to be effective gastrointestinal antispasmodics with good safety profiles. There is insufficient evidence to conclude whether antispasmodics improve cecal intubation rate, predominantly because the baseline rates are already high. Antispasmodics probably have efficacy in reducing cecal intubation time especially in those with marked colonic spasm. Antispasmodics do not offer significant benefit in polyp detection or improving patient comfort during colonoscopy. Future studies should focus on inexperienced colonoscopists as well as those with marked colonic spasm, in whom the greatest benefit seems to lie.

Effectiveness of topical peppermint oil on symptomatic treatment of chronic pruritus

Background

Pruritus is one of the commonest skin complaints. Peppermint oil can be effective in reducing the severity of such a condition.

Aim

The aim of this study was to assess the efficacy of topically applied peppermint oil in the treatment of chronic pruritus.

Subjects and methods

Fifty selected subjects diagnosed with chronic pruritus due to hepatic, renal, or diabetic cause were studied and divided into two groups of 25 patients each. Group I patients were instructed to hydrate the skin and then apply topical peppermint oil, while Group II patients applied petrolatum topically by hand; this application was done on the areas of pruritus, twice daily for 2 weeks. The severity of the itch was assessed and compared before and after the study by the 5-D itch scale (5D-IS). The results were analyzed by SPSS software. Statistical methods such as descriptive analysis, independent samples t-test, paired samples t-test, and chi-square test were employed.

Results

There was a significant improvement regarding all studied individual parameters (5-D IS) for the peppermint oil users with no significance among petrolatum users. A comparison of total score of 5-D IS between patients of Group I and patients of Group II favored the improvement following the use of peppermint oil than using placebo (P-value <0.05).

Conclusion

The topical treatment of chronic pruritus with peppermint oil is effective, easy to use, safe, cheap, and more acceptable for those whose topical and systemic treatments tend to be irritating, contraindicated, or less well tolerated.

Sub-MICs of Mentha piperita essential oil and menthol inhibits AHL mediated quorum sensing and biofilm of Gram-negative bacteria

Bacterial quorum sensing (QS) is a density dependent communication system that regulates the expression of certain genes including production of virulence factors in many pathogens. Bioactive plant extract/compounds inhibiting QS regulated gene expression may be a potential candidate as antipathogenic drug. In this study anti-QS activity of peppermint (Mentha piperita) oil was first tested using the Chromobacterium violaceum CVO26 biosensor. Further, the findings of the present investigation revealed that peppermint oil (PMO) at sub-Minimum Inhibitory Concentrations (sub-MICs) strongly interfered with acyl homoserine lactone (AHL) regulated virulence factors and biofilm formation in Pseudomonas aeruginosa and Aeromonas hydrophila. The result of molecular docking analysis attributed the QS inhibitory activity exhibited by PMO to menthol. Assessment of ability of menthol to interfere with QS systems of various Gram-negative pathogens comprising diverse AHL molecules revealed that it reduced the AHL dependent production of violacein, virulence factors, and biofilm formation indicating broad-spectrum anti-QS activity. Using two Escherichia coli biosensors, MG4/pKDT17 and pEAL08-2, we also confirmed that menthol inhibited both the las and pqs QS systems. Further, findings of the in vivo studies with menthol on nematode model Caenorhabditis elegans showed significantly enhanced survival of the nematode. Our data identified menthol as a novel broad spectrum QS inhibitor.

Microemulsions based on a sunflower lecithin-Tween 20 blend have high capacity for dissolving peppermint oil and stabilizing coenzyme Q10

The objectives of the present study were to improve the capability of microemulsions to dissolve peppermint oil by blending sunflower lecithin with Tween 20 and to study the possibility of codelivering lipophilic bioactive compounds. The oil loading in microemulsions with 20% (w/w) Tween 20 increased from 3% (w/w) to 20% (w/w) upon gradual supplementation of 6% (w/w) lecithin. All microemulsions had particles of <12 nm that did not change over 70 d of storage at 21 °C. They had relatively low Newtonian viscosities and were physically and chemically stable after 50-200-fold dilution in water, resulting from similar hydrophile-lipophile-balance values of the surfactant mixture and peppermint oil. Furthermore, the microemulsions were capable of dissolving coenzyme Q10 and preventing its degradation at UV 302 nm, more significant for the microemulsion with lecithin. Therefore, natural surfactant lecithin can reduce the use of synthetic Tween 20 to dissolve peppermint oil and protect the degradation of dissolved lipophilic bioactive components in transparent products.

Screening of venlafaxine hydrochloride for transdermal delivery: passive diffusion and iontophoresis

The objective of the study was to investigate in vitro transdermal delivery of venlafaxine hydrochloride across the pigskin by passive diffusion and iontophoresis. For passive diffusion, experiments were carried out in Franz diffusion cell whereas for iontophoretic permeation, the diffusion cell was modified to contain both the donor and return electrode on the same side of skin. Anodal iontophoresis was carried out using a current density of 0.5 mA/cm(2). Donor concentrations used were 585.5 mg/ml (saturated solution) and 100 mg/ml. Experiments initially performed to determine the transport efficiency of venlafaxine ions showed promising results. Iontophoresis increased the permeation rate at both concentration levels over their passive counterparts (P < 0.01), but surprisingly higher steady-state flux was obtained from lower donor drug load (P < 0.01). The favorable pH of the unsaturated solutions is suggested to be the cause for this effect. Mild synergistic effect was observed when iontophoresis was carried out incorporating peppermint oil in the donor but the same was not found in passive diffusion. Highest steady-state flux obtained in the experiment was 3.279 mumol/cm(2)/h when peppermint oil (0.1%) was included in the donor. As the maintenance requirement of venlafaxine hydrochloride is approximately 9.956 mumol/h, the results suggested that the drug is a promising candidate for iontophoretic delivery.

Mentha x piperita, Mentha spicata and Effects of Their Essential Oils on Meloidogyne in Soil

Six peppermint (Mentha x piperita) and six spearmint (M. spicata) PI accessions were inoculated with Meloidogyne incognita race 3 and M. arenaria race 2, under greenhouse conditions. No galls formed on roots of any of the plants inoculated with 1,800 eggs/pot. Fewer than two galls per root system formed on three PI accessions of peppermint inoculated with M. incognita at 5,400 eggs/pot. Only one peppermint accession developed galls when inoculated with M. arenaria, whereas none of the spearmint accessions was susceptible to this species. Plant dry weights generally were unaffected by infection with root-knot nematodes at these densities. Growing peppermint and spearmint accessions for 8 or 12 weeks in M. arenaria-infested soil before tomato resulted in 90% reduction of root galls compared with tomato following tomato. Cineole, eugenol, geraniol, linalool, and peppermint oils at 50 and 250 mg oil/kg soil caused no reduction in the number of galls caused by M. arenaria on tomato. At 1,500 mg oil/kg soil, geraniol, eugenol, linalool, and peppermint oils (P =0.05) reduced the number of galls caused by M. arenaria, but the decrease in galling caused by M. incognita was not significant. Geraniol, linalool, and peppermint oil at 1,000 and 1,500 mg were phytotoxic to tomato.