A Phase I Study Evaluating Tolerability, Pharmacokinetics, and Preliminary Efficacy of L-Menthol in Upper Gastrointestinal Endoscopy

Factors affecting gastrointestinal function recovery after cesarean section among Chinese mothers: A cross-sectional study

This study was conducted to explore the influencing factors of gastrointestinal function recovery after cesarean section (CS), which could provide a reference for the enhanced recovery after surgery in obstetrics. This is a cross-sectional survey on Chinese mothers receiving CS. The participants's socio-demographic characteristics, perioperative diet, medical condition and gastrointestinal function after surgery were collected by a self-designed questionnaire. Binary logistic regression analysis was employed to explore the influencing factors of gastrointestinal function recovery after CS. A total of 1501 (94.76%) valid questionnaires were collected. The first borborygmus was 2.21 ± 0.63 hours, and the first anal exhaust was 35.73 ± 14.85 hours after the CS. The incidence of abdominal distension and intestinal obstruction were 15.1% and 0.7%, respectively. The parity, type of CS, 2-hours bleeding after surgery, time of first meal after surgery, whether taking peppermint water after surgery were the independent influencing factors for gastrointestinal function recovery after CS. We should pay more attention to the mothers with scarred uterus, manage the labor process strictly, and reduce 2-hours bleeding after surgery. The mothers with CS should also be encouraged to eat early and take peppermint water to promote intestinal peristalsis actively.

Development of multi-drug resistance to anticancer drugs in HepG2 cells due to MRP2 upregulation on exposure to menthol

BACKGROUND

Menthol exerts relaxing, antibacterial, and anti-inflammatory activities, and is marketed as a functional food and therapeutic drug.

AIM

In the present study, the effects of menthol on the expression of multidrug resistance associated protein 2 (MRP2) and its association with the cytotoxicity of epirubicin (EPI) and cisplatin (CIS) were examined using HepG2 cells.

METHODS

The expression levels of target genes were examined by real-time PCR. The intracellular concentration of incorporated EPI was measured by high-performance liquid chromatography. Cell viability was evaluated by MTT analysis.

RESULTS

The expression of MRP2 mRNA was increased by exposing HepG2 cells to menthol for 24 hr. Consistent with a previous report suggesting an inverse correlation between MRP2 and Akt behavior, increased expression of MRP2 was also observed on suppression of the Akt function. Intracellular accumulation of EPI was significantly decreased by exposure of HepG2 cells to menthol, and a significant decrease in the intracellular concentration of EPI remaining was observed in HepG2 cells exposed to menthol. The decreased intracellular accumulation of EPI was significantly suppressed by treatment with MK-571, but not verapamil. Both EPI and CIS exerted cytocidal effects on HepG2 cells, but the decrease in cell viability was significantly attenuated by 24-hr menthol pre-exposure.

CONCLUSION

These results demonstrate that menthol causes hepatocellular carcinoma to acquire resistance to anticancer drugs such as EPI and CIS by MRP2 induction.

Essential Oils as Multicomponent Mixtures and Their Potential for Human Health and Well-Being

Essential oils (EOs) and their individual volatile organic constituents have been an inherent part of our civilization for thousands of years. They are widely used as fragrances in perfumes and cosmetics and contribute to a healthy diet, but also act as active ingredients of pharmaceutical products. Their antibacterial, antiviral, and anti-inflammatory properties have qualified EOs early on for both, the causal and symptomatic therapy of a number of diseases, but also for prevention. Obtained from natural, mostly plant materials, EOs constitute a typical example of a multicomponent mixture (more than one constituent substances, MOCS) with up to several hundreds of individual compounds, which in a sophisticated composition make up the property of a particular complete EO. The integrative use of EOs as MOCS will play a major role in human and veterinary medicine now and in the future and is already widely used in some cases, e.g., in aromatherapy for the treatment of psychosomatic complaints, for inhalation in the treatment of respiratory diseases, or topically administered to manage adverse skin diseases. The diversity of molecules with different functionalities exhibits a broad range of multiple physical and chemical properties, which are the base of their multi-target activity as opposed to single isolated compounds. Whether and how such a broad-spectrum effect is reflected in natural mixtures and which kind of pharmacological potential they provide will be considered in the context of ONE Health in more detail in this review.

Antiperistaltic effect and safety of L-menthol for esophagogastroduodenoscopy in the elderly with contraindication to hyoscine-N-butylbromide

Hyoscine-N-butylbromide (HBB) is the most used antiperistaltic agent during esophagogastroduodenoscopy (EGD). However, almost half of the elderly have a contraindication to HBB. We aimed to evaluate l-menthol’s antiperistaltic effect and safety for EGD in the elderly with contraindication to HBB. This prospective, randomized, double-blind, placebo-controlled study screened 86 elderly patients (≥ 65 years old) scheduled to undergo EGD, and 52 of them with contraindication to HBB were enrolled. The participants were randomized to receive l-menthol (n = 26) or a placebo (n = 26), which was locally sprayed on the gastric antrum endoscopically. The proportion of patients with no or mild peristalsis after medication and at the end of EGD was significantly higher in the l-menthol group (76.9%) than in the placebo group (11.5%, p < 0.001). l-Menthol administration significantly reduced peristaltic grade, improved contraction parameters, and eased intragastric examination relative to the placebo (p < 0.001, respectively). Hemodynamic changes, adverse events, and discomfort levels of patients were similar between the two groups. l-Menthol is an effective and safe alternative antiperistaltic medication for EGD in elderly patients with contraindication to HBB. Further large, randomized trials are required to clarify whether l-menthol can lead to better detection yield in the elderly.

Clinical trial registration: The study was registered at ClinicalTrials.gov (NCT04593836).

l-Menthol increases extracellular dopamine and c-Fos-like immunoreactivity in the dorsal striatum, and promotes ambulatory activity in mice

Similar to psychostimulants, the peripheral administration of menthol promotes mouse motor activity, and the neurotransmitter dopamine has been suggested to be involved in this effect. The present study aimed to elucidate the effects of l-menthol on parts of the central nervous system that are involved in motor effects. The subcutaneous administration of l-menthol significantly increased the number of c-Fos-like immunoreactive nuclei in the dorsal striatum of the mice, and motor activity was promoted. It also increased the extracellular dopamine level in the dorsal striatum of the mice. These observations indicated that after subcutaneous administration, l-menthol enhances dopamine-mediated neurotransmission, and activates neuronal activity in the dorsal striatum, thereby promoting motor activity in mice.

Antiperistaltic effect and safety of l-menthol oral solution on gastric mucosa for upper gastrointestinal endoscopy in Chinese patients: Phase III, multicenter, randomized, double-blind, placebo-controlled study

OBJECTIVE

The topical antispasmodic agent l-menthol is commonly used for gastric peristalsis suppression during diagnostic upper gastrointestinal (GI) endoscopy. We evaluated the efficacy and safety of a single dose l-menthol solution in suppressing gastric peristalsis during upper GI endoscopy in Chinese patients.

METHODS

In this phase III, multicenter, randomized, double-blind, placebo-controlled study (ClinicalTrials.gov: NCT03263910), 220 patients scheduled to undergo upper GI endoscopy at five Chinese referral centers received a single dose of either 160 mg of l-menthol (n = 109) or placebo (n = 111). Both treatments were sprayed endoscopically on the gastric mucosa. An independent committee evaluated the degree of gastric peristalsis (peristaltic score: grade 1-5).

RESULTS

At baseline, the proportion of patients with grade 1 peristalsis (no peristalsis) did not differ between the groups. The proportion of patients with grade 1 peristalsis post-treatment was significantly higher in the l-menthol group (40.37%, 44/109) versus the placebo group (16.22%, 18/111; P < 0.001); the difference between the groups was 24.15% (95% confidence interval: 12.67%-35.63%; P < 0.001). In the l-menthol group, 61.47% of patients had grade 1 peristalsis after endoscopy versus 24.55% in the placebo group (P < 0.001). The ease of intragastric examination correlated significantly with the grade of peristalsis. The incidence of adverse events was comparable between the groups (P = 0.340).

CONCLUSIONS

During upper GI endoscopy, a single dose of l-menthol solution (160 mg) sprayed on the gastric mucosa significantly attenuated gastric peristalsis versus placebo, thereby improving the visual stability without any safety concerns.

Modifying effects of menthol against benzo(a)pyrene-induced forestomach carcinogenesis in female Swiss mice

Benzo(a)pyrene (BaP) is a polycyclic aromatic hydrocarbon widespread in the environment and closely associated to tobacco use, which is an important risk factor for highly incident stomach cancer. Menthol, a monoterpene extracted from Mentha genus species, has multiple biological properties, including anti-inflammatory and gastroprotective properties, but its effects on carcinogenesis are still to be fully understood. Thus, we evaluated the modifying effects of Ment against BaP-induced forestomach carcinogenesis. Female Swiss mice received BaP by intragastrical (i.g.) administration (50 mg/kg of body weight [b wt], 2×/week), from weeks 1-5 weeks. Concomitantly, mice received Menthol at 25 (Ment25) or 50 (Ment50) mg/kg b wt (i.g, 3×/week). Animals were euthanized at weeks 5 (n = 5 mice/group) or 30 (n = 10 mice/group). At week 5, both Ment doses reduced peripheral leukocyte blood genotoxicity 4 h after the last BaP administration, but only Ment50 attenuated this biomarker 8 h after the last BaP administration. In accordance to these findings, both Ment interventions attenuated BaP-induced increase in the percentage of H2A.X-positive forestomach epithelial cells. Moreover, Ment50 reduced cell proliferation and apoptosis (i.e., Ki-67 and caspase-3, respectively) in forestomach epithelium but exerted no significant effects on NFκB, and Nrf2 protein levels. At week 30, Ment50 reduced by ~55% the incidence of BaP-induced forestomach diffuse hyperplasia and multiplicity of forestomach tumors (squamous cell papillomas and carcinomas). Our findings indicate that Ment50, administered during initiation phase, attenuates forestomach carcinogenesis by reducing early genotoxicity, cell proliferation, and apoptosis induced by BaP.

Breath-Taking Perspectives and Preliminary Data toward Early Detection of Chronic Liver Diseases

The gold standard method for chronic liver diseases diagnosis and staging remains liver biopsy, despite the spread of less invasive surrogate modalities based on imaging and blood biomarkers. Still, more than 50% of chronic liver disease cases are detected at later stages when patients exhibit episodes of liver decompensation. Breath analysis represents an attractive means for the development of non-invasive tests for several pathologies, including chronic liver diseases. In this perspective review, we summarize the main findings of studies that compared the breath of patients with chronic liver diseases against that of control subjects and found candidate biomarkers for a potential breath test. Interestingly, identified compounds with best classification performance are of exogenous origin and used as flavoring agents in food. Therefore, random dietary exposure of the general population to these compounds prevents the establishment of threshold levels for the identification of disease subjects. To overcome this limitation, we propose the exogenous volatile organic compounds (EVOCs) probe approach, where one or multiple of these flavoring agent(s) are administered at a standard dose and liver dysfunction associated with chronic liver diseases is evaluated as a washout of ingested compound(s). We report preliminary results in healthy subjects in support of the potential of the EVOC Probe approach.

Monoterpenes: current knowledge on food source, metabolism, and health effects

Monoterpenes, volatile metabolites produced by plants, are involved in the taste and aroma perception of fruits and vegetables and have been used for centuries in gastronomy, as food preservatives and for therapeutic purposes. Biological activities such as antimicrobial, analgesic and anti-inflammatory are well-established for some of these molecules. More recently, the ability of monoterpenes to regulate energy metabolism, and exert antidiabetic, anti-obesity and gut microbiota modulation activities have been described. Despite their promising health effects, the lack of reliable quantification of monoterpenes in food, hindered the investigation of their role as dietary bioactive compounds in epidemiological studies. Moreover, only few studies have documented the biotransformation of these compounds and identified the monoterpene metabolites with biological activity. This review presents up-to-date knowledge about the occurrence of monoterpenes in food, their bioavailability and potential role in the modulation of intermediate metabolism and inflammation, focusing on novel findings of molecular mechanisms, underlining research gaps and new avenues to be explored.

L-Menthol for Gastrointestinal Endoscopy: A Systematic Review and Meta-Analysis

In randomized controlled trials, L-menthol inhibits gastrointestinal peristalsis during endoscopy. Our goal was to quantitatively synthesize the available evidence to evaluate the efficacy and safety of L-menthol for gastrointestinal endoscopy.

Effect of spraying l-menthol on peristalsis resumption during endoscopic submucosal dissection of gastric tumors

Background and Aim

l‐Menthol has smooth muscle‐relaxing and antiperistaltic effects. We examined its effectiveness against peristalsis resumption during endoscopic submucosal dissection (ESD) of gastric tumors.

Methods

We retrospectively examined clinical data of 485 patients (501 lesions) who underwent ESD for upper gastrointestinal tumors in 2017. We included 119 patients (127 lesions) in whom peristaltic movement resumed during ESD and l‐menthol was applied; 366 patients (374 lesions) without l‐menthol application were used as controls. Video recordings were reviewed to determine whether l‐menthol suppressed peristalsis resumption.

Results

In cases with l‐menthol application, 2 (2.9%), 36 (14.3%), and 89 (71.2%) lesions were found in the upper (U), middle (M), and lower (L) regions, respectively. In the control group, the corresponding values were 66 (17.6%), 215 (57.5%), and 93 (24.9%), respectively. l‐Menthol efficacy was observed in 116 of the 127 treated lesions (91.3%), over 90% of which were in the posterior wall of the U region, anterior wall and greater curvature of the M region, and anterior wall and lesser curvature of the L region. The most and least effective areas for l‐menthol application were the anterior wall of gastric antrum and posterior wall of the M region, respectively. The mean time from application to peristalsis inhibition was 8.7 s. No adverse effects were observed; perforation and secondary hemorrhage were not significantly different between the groups.

Conclusion

Direct l‐menthol application to the submucosal layer during mucosal resection affects smooth muscles and rapidly inhibits peristalsis resumption. Clinically, l‐Menthol can be used to suppress peristalsis recurrence during ESD, without adverse effects.

Current Knowledge on the Vascular Effects of Menthol

Menthol is a monoterpene alcohol, widely used in several food and healthcare products for its particular odor and flavor. For some decades, menthol has been known to act on the vasculature directly in the endothelium and vascular smooth muscle, with recent studies showing that it also evokes an indirect vascular response via sensory fibers. The mechanisms underlying menthol's vascular action are complex due to the diversity of cellular targets, to the interplay between signaling pathways and to the variability in terms of response. Menthol can evoke either a perfusion increase or decrease in vivo in different vascular territories, an observation that warrants a critical discussion. Menthol vascular actions in vivo seem to depend on whether the vascular territory under analysis has been directly provoked with menthol or is located deep/distant to the application site. Menthol increases perfusion of directly provoked skin regions due to a complex interplay of increased nitric oxide (NO), endothelium-derived hyperpolarization factors (EDHFs) and sensory nerve responses. In non-provoked vascular beds menthol decreases perfusion which might be attributed to heat-conservation sympathetically-mediated vasoconstriction, although an increase in tissue evaporative heat loss due the formulation ethanol may also play a role. There is increasing evidence that several of menthol's cellular targets are involved in cardiovascular diseases, such as hypertension. Thus menthol and pharmacologically-similar drugs can play important preventive and therapeutic roles, which merits further investigation.

FEMA GRAS assessment of natural flavor complexes: Mint, buchu, dill and caraway derived flavoring ingredients

In 2015, the Expert Panel of the Flavor and Extract Manufacturers Association (FEMA) initiated a re-evaluation of the safety of over 250 natural flavor complexes (NFCs) used as flavor ingredients. NFC flavor materials include a variety of essential oils and botanical extracts. The re-evaluation of NFCs is conducted based on a constituent-based procedure outlined in 2005 and updated in 2018 that evaluates the safety of NFCs for their intended use as flavor ingredients. This procedure is applied in the re-evaluation of the generally recognized as safe (GRAS) status of NFCs with constituent profiles that are dominated by alicyclic ketones such as menthone and carvone, secondary alcohols such as menthol and carveol, and related compounds. The FEMA Expert Panel affirmed the GRAS status of Peppermint Oil (FEMA 2848), Spearmint Oil (FEMA 3032), Spearmint Extract (FEMA 3031), Cornmint Oil (FEMA 4219), Erospicata Oil (FEMA 4777), Curly Mint Oil (FEMA 4778), Pennyroyal Oil (FEMA 2839), Buchu Leaves Oil (FEMA 2169), Caraway Oil (FEMA 2238) and Dill Oil (FEMA 2383) and determined FEMA GRAS status for Buchu Leaves Extract (FEMA 4923), Peppermint Oil, Terpeneless (FEMA 4924) and Spearmint Oil, Terpeneless (FEMA 4925).

Preclinical disposition of MGS0274 besylate, a prodrug of a potent group II metabotropic glutamate receptor agonist MGS0008 for the treatment of schizophrenia

MGS0274 besylate is an ester-based lipophilic prodrug of a metabotropic glutamate (mGlu) 2 and mGlu3 receptor agonist MGS0008 and being developed for the treatment of schizophrenia. We investigated the disposition of these compounds in rats and monkeys and in vitro metabolism in humans to evaluate whether MGS0274 besylate could be useful as a prodrug in humans. After the oral administration of MGS0274 besylate to monkeys (2.89 mg/kg), MGS0008 was immediately found in plasma, reached a maximum concentration at 4 hours postdose, and decreased with a terminal half-life of 16.7 hours; MGS0274 was barely detectable. The oral bioavailability as MGS0008 was 83.7%, which was approximately 20-fold greater than that after oral dosing of MGS0008 (3.8%). In rats, MGS0008 penetrated the cerebrospinal fluid and was eliminated slower than from plasma. The in vitro metabolism study indicated that MGS0274 was rapidly hydrolyzed to MGS0008, which was not further metabolized. After the intravenous administration of MGS0008 to rats and monkeys, almost all the dose was excreted unchanged in urine. These results suggested that MGS0274 was, as expected, presystemically hydrolyzed to MGS0008 after gastrointestinal absorption and that MGS0008 was distributed throughout the body without further metabolism and ultimately excreted in urine in the animals. Furthermore, the hydrolytic activity against MGS0274 in the human liver S9 fraction was comparable to that in monkeys, suggesting the possibility of the rapid presystemic hydrolysis of MGS0274 to MGS0008 in humans, as it is in monkeys. Consequently, MGS0274 besylate is expected to function as a preferable prodrug in humans.

An in silico investigation of menthol metabolism

Prevalence of mentholated products for consumption has brought great importance to studies on menthol’s metabolic pathways to ensure safety, design more potent derivatives, and identify therapeutic benefits. Proposed pathways of (-)-menthol metabolism based on metabolites found experimentally in previous works by Yamaguchi, Caldwell & Farmer, Madyastha & Srivatsan and Hiki et al. were not in agreement. This in silico approach is based on the three in vivo studies and aims to resolve the discrepancies. Reactions in the pathways are conjugation with glucuronic acid/sulfate, oxidation to alcohol, aldehyde & carboxylic acid, and formation of a four-membered/five-membered ring. Gas-phase structures, standard Gibbs energies and SMD solvation energies at B3LYP/6-311++G(d,p) level were obtained for 102 compounds in the pathways. This study provides a more complete picture of menthol metabolism by combining information from three experimental studies and filling missing links in previously published pathways.

Herbs and Spices- Biomarkers of Intake Based on Human Intervention Studies - A Systematic Review

Culinary herbs and spices have been used as both food flavoring and food preservative agents for centuries. Moreover, due to their known and presumptive health benefits, herbs and spices have also been used in medical practices since ancient times. Some of the health effects attributed to herbs and spices include antioxidant, anti-microbial, and anti-inflammatory effects as well as potential protection against cardiovascular disease, neurodegeneration, type 2 diabetes, and cancer. While interest in herbs and spices as medicinal agents remains high and their use in foods continues to grow, there have been remarkably few studies that have attempted to track the dietary intake of herbs and spices and even fewer that have tried to find potential biomarkers of food intake (BFIs). The aim of the present review is to systematically survey the global literature on herbs and spices in an effort to identify and evaluate specific intake biomarkers for a representative set of common herbs and spices in humans. A total of 25 herbs and spices were initially chosen, including anise, basil, black pepper, caraway, chili pepper, cinnamon, clove, cumin, curcumin, dill, fennel, fenugreek, ginger, lemongrass, marjoram, nutmeg, oregano, parsley, peppermint and spearmint, rosemary, saffron, sage, tarragon, and thyme. However, only 17 of these herbs and spices had published, peer-reviewed studies describing potential biomarkers of intake. In many studies, the herb or spice of interest was administrated in the form of a capsule or extract and very few studies were performed with actual foods. A systematic assessment of the candidate biomarkers was also performed. Given the limitations in the experimental designs for many of the published studies, further work is needed to better evaluate the identified set of BFIs. Although the daily intake of herbs and spices is very low compared to most other foods, this important set of food seasoning agents should not be underestimated, especially given their potential benefits to human health.

Enhanced anti-cancer activity by menthol in HepG2 cells exposed to paclitaxel and vincristine: possible involvement of CYP3A4 downregulation

Background Menthol is widely used as a constituent of functional foods and chemical drugs. In the present study, we investigated changes in the expression of cytochrome P450 isoform CYP3A4mRNA after treating human hepatocellular carcinoma HepG2 cells with menthol. We also examined the effects of pretreatment with menthol on the cytotoxic activity of paclitaxel (PAC) and vincristine (VIN), which are substrates of CYP3A4, in the cells. Methods HepG2 cells were maintained in Dulbecco's Modified Eagle's Medium. Expression of CYP3A4 was examined by the real-time polymerase chain reaction. Survival rate of HepG2 cells was evaluated by the MTT assay. Results The gene expression level of CYP3A4 in HepG2 cells was significantly reduced by treatment with menthol for 1 day. The viability of HepG2 cells was not affected by treatment with menthol alone once a day for two consecutive days. The degree of reduction in cell viability by PAC or VIN in HepG2 cells was significantly increased by menthol treatment for 24 h prior to exposure to these anti-cancer drugs. Conclusions These results demonstrate that menthol enhanced the anti-tumor effects of PAC and VIN through the downregulation of CYP3A4 in HepG2 cells without exerting cytotoxic activity.

A Novel Ileocolonic Release Peppermint Oil Capsule for Treatment of Irritable Bowel Syndrome: A Phase I Study in Healthy Volunteers

INTRODUCTION

Peppermint oil (PO) has been shown to reduce abdominal pain in patients with irritable bowel syndrome (IBS). PO is assumed to induce intestinal smooth muscle relaxation and desensitization of nociceptive nerve afferents. To increase colonic PO concentration, an ileocolonic release peppermint oil (IC-PO) capsule has been developed. The aim of this study was to compare pharmacokinetic parameters of the currently available small intestinal release PO (SI-PO) and the novel IC-PO.

METHODS

In this randomized, double-blind, crossover study, subjects received 182 mg of either SI-PO or IC-PO in a crossover design with a washout period of more than 14 days. Blood samples were collected to determine menthol glucuronide concentrations.

RESULTS

Eight healthy volunteers (50% female, median age 22) were included. The time to reach the maximum concentration (T_max) of IC-PO was significantly longer compared to SI-PO with a median (IQR) of 360 (360-405) versus 180 (120-180) min. The lag time (T_lag) was significantly longer with a median (IQR) of 225 (204-284) for IC-PO compared to 37 (6-65) min for SI-PO. The areas under the menthol glucuronide plasma concentration-time curves were significantly smaller with a median (IQR) of 2331 μg h/L (2006-2510) for IC-PO compared to 2623 μg h/L (2471-2920) for SI-PO. No significant differences were found in peak concentrations and elimination half-lives.

CONCLUSION

IC-PO has a significantly delayed peak menthol glucuronide concentration and T_lag, both pointing to the release of PO in the more distal part of the intestine. This may enhance therapeutic efficacy as it results in increased exposure of colonic mucosal afferents to the PO. A randomized controlled trial investigating the efficacy of SI and IC-PO in IBS is currently ongoing.

TRIAL REGISTRATION

ClinicalTrials.gov identifier, NCT02291445, EudraCT database 2014-004195-32.

The safety evaluation of food flavouring substances: the role of metabolic studies

The safety assessment of a flavour substance examines several factors, including metabolic and physiological disposition data. The present article provides an overview of the metabolism and disposition of flavour substances by identifying general applicable principles of metabolism to illustrate how information on metabolic fate is taken into account in their safety evaluation. The metabolism of the majority of flavour substances involves a series both of enzymatic and non-enzymatic biotransformation that often results in products that are more hydrophilic and more readily excretable than their precursors. Flavours can undergo metabolic reactions, such as oxidation, reduction, or hydrolysis that alter a functional group relative to the parent compound. The altered functional group may serve as a reaction site for a subsequent metabolic transformation. Metabolic intermediates undergo conjugation with an endogenous agent such as glucuronic acid, sulphate, glutathione, amino acids, or acetate. Such conjugates are typically readily excreted through the kidneys and liver. This paper summarizes the types of metabolic reactions that have been documented for flavour substances that are added to the human food chain, the methodologies available for metabolic studies, and the factors that affect the metabolic fate of a flavour substance.

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.

Menthol Smokers: Metabolomic Profiling and Smoking Behavior

BACKGROUND

The use of menthol in cigarettes and marketing is under consideration for regulation by the FDA. However, the effects of menthol on smoking behavior and carcinogen exposure have been inconclusive. We previously reported metabolomic profiling for cigarette smokers, and novelly identified a menthol-glucuronide (MG) as the most significant metabolite directly related to smoking. Here, MG is studied in relation to smoking behavior and metabolomic profiles.

METHODS

This is a cross-sectional study of 105 smokers who smoked two cigarettes in the laboratory one hour apart. Blood nicotine, MG, and exhaled carbon monoxide (CO) boosts were determined (the difference before and after smoking). Spearman correlation, χ2, and ANCOVA adjusted for gender, race, and cotinine levels for menthol smokers assessed the relationship of MG boost, smoking behavior, and metabolic profiles. Multivariate metabolite characterization using supervised partial least squares-discriminant analysis (PLS-DA) was carried out for the classification of metabolomics profiles.

RESULTS

MG boost was positively correlated with CO boost, nicotine boost, average puff volume, puff duration, and total smoke exposure. Classification using PLS-DA, MG was the top metabolite discriminating metabolome of menthol versus nonmenthol smokers. Among menthol smokers, 42 metabolites were significantly correlated with MG boost, which linked to cellular functions, such as of cell death, survival, and movement.

CONCLUSIONS

Plasma MG boost is a new smoking behavior biomarker that may provide novel information over self-reported use of menthol cigarettes by integrating different smoking measures for understanding smoking behavior and harm of menthol cigarettes.

IMPACT

These results provide insight into the biological effect of menthol smoking. Cancer Epidemiol Biomarkers Prev; 26(1); 51-60. ©2016 AACR.

Encapsulation of l-menthol in hydroxypropyl-β-cyclodextrin and release characteristics of the inclusion complex

l-menthol has been widely used in flavour, food and pharmaceuticals. Because of its high volatility and whisker growth, l-menthol-hydroxypropyl-β-cyclodextrin inclusion complex was produced to improve shelf-life, provide protection, and enhance the stability of l-menthol. The inclusion complex was characterized by Fourier transform infrared spectroscopy, X-ray diffraction. The results show that l-menthol was successfully encapsulated in hydroxypropyl-β-cyclodextrin. l-menthol loading capacity is about 8.44%. Geometries and binding energies of l-menthol-hydroxypropyl-β-cyclodextrin inclusion complexes were investigated using molecular mechanics calculations. The shape and orientation of the most stable complex, and the minimum binding energy were determined. L-menthol release from complex was determined by thermogravimetric analysis. Two l-menthol release rate peaks were observed at 69.3 and 279.1°C. The l-menthol release reaction order, release activation energy and the preexponential factor were obtained.

Evaluation of mint efficacy regarding dysmenorrhea in comparison with mefenamic acid: A double blinded randomized crossover study

BACKGROUND

Menthol is the most important active material in mint and different mechanisms have been suggested for the way mint functions, most of which emphasize its analgesic effect owing to the presence of a group of temporary protein receptors. This study investigates the efficacy of peppermint capsule in the treatment of primary dysmenorrhea, in comparison with Mefenamic Acid and placebo.

MATERIALS AND METHODS

This was a prospective, double-blinded, crossover study and was conducted on 127 girl students studying in Hamadan University of Medical Sciences who had experienced primary dysmenorrhea. Each participant was asked to take one of the drugs including Mefenamic Acid and Mint, starting from the first menstruation for 3 days. At the end of each period, a questionnaire was used to gather information; through the volunteer herself, pain intensity was recorded according to visual analog scale (VAS), duration of pain according to COX questionnaire, and bleeding amount according to pictorial blood loss assessment chart (PBAC) chart (Hygham).

RESULTS

Average pain intensity and duration of pain were significantly lower after intake of Mefenamic Acid and Mint (P < 0.05). Average bleeding was significantly lower in those taking Mefenamic Acid capsule than in those taking peppermint extract (P < 0.05). Nausea and diarrhea were lower in the mint group than in Mefenamic Acid group. But analgesic usage was lower in Mefenamic Acid group than in peppermint group (P < 0.05).

CONCLUSIONS

While the bleeding amount did not significantly change, pain and its severity and all the clinical signs and symptoms decreased after taking peppermint extract. Because the side effect of herbal drugs is lower than other medicinal drugs, using mint is advised for treating dysmenorrhea symptoms.

The absorption and metabolism of a single L-menthol oral versus skin administration: Effects on thermogenesis and metabolic rate

We investigated the absorption and metabolism pharmacokinetics of a single L-menthol oral versus skin administration and the effects on human thermogenesis and metabolic rate. Twenty healthy adults were randomly distributed into oral (capsule) and skin (gel) groups and treated with 10 mg kg(-1) L-menthol (ORALMENT; SKINMENT) or control (lactose capsule: ORALCON; water application: SKINCON) in a random order on two different days. Levels of serum L-menthol increased similarly in ORALMENT and SKINMENT (p > 0.05). L-menthol glucuronidation was greater in ORALMENT than SKINMENT (p < 0.05). Cutaneous vasoconstriction, rectal temperature and body heat storage showed greater increase following SKINMENT compared to ORALMENT and control conditions (p < 0.05). Metabolic rate increased from baseline by 18% in SKINMENT and 10% in ORALMENT and respiratory exchange ratio decreased more in ORALMENT (5.4%) than SKINMENT (4.8%) compared to control conditions (p < 0.05). Levels of plasma adiponectin and leptin as well as heart rate variability were similar to control following either treatment (p > 0.05). Participants reported no cold, shivering, discomfort, stress or skin irritation. We conclude that a single L-menthol skin administration increased thermogenesis and metabolic rate in humans. These effects are minor following L-menthol oral administration probably due to faster glucuronidation and greater blood menthol glucuronide levels.

Systemic exposure to menthol following administration of peppermint oil to paediatric patients

OBJECTIVE

Peppermint oil (PMO) has been used to treat abdominal ailments dating to ancient Egypt, Greece and Rome. Despite its increasing paediatric use, as in irritable bowel syndrome (IBS) treatment, the pharmacokinetics (PK) of menthol in children given PMO has not been explored.

DESIGN AND SETTING

Single-site, exploratory pilot study of menthol PK following a single 187 mg dose of PMO. Subjects with paediatric Rome II defined (IBS; n=6, male and female, 7-15 years of age) were enrolled. Blood samples were obtained before PMO administration and at 10 discrete time points over a 12 h postdose period. Menthol was quantitated from plasma using a validated gas chromatography mass spectrometry technique. Menthol PK parameters were determined using a standard non-compartmental approach.

RESULTS

Following a dose of PMO, a substantial lag time (range 1-4 h) was seen in all subjects for the appearance of menthol which in turn, produced a delayed time of peak (Tmax=5.3 ± 2.4 h) plasma concentration (Cmax=698.2 ± 245.4 ng/mL). Tmax and Tlag were significantly more variable than the two exposure parameters; Cmax, mean residence time and total area under the curve (AUC=4039.7 ± 583.8 ng/mL × h) which had a coefficient of variation of <20%.

CONCLUSIONS

Delayed appearance of menthol in plasma after oral PMO administration in children is likely a formulation-specific event which, in IBS, could increase intestinal residence time of the active ingredient. Our data also demonstrate the feasibility of using menthol PK in children with IBS to support definitive studies of PMO dose-effect relationships.

Change in pharmacokinetic behavior of intravenously administered midazolam due to increased CYP3A2 expression in rats treated with menthol

Menthol is used widely as a constituent of functional foods and chemical drugs. The present study investigated changes in the pharmacokinetic behavior of intravenously administered midazolam (MDZ), a probe for CYP3A, when rats were treated with menthol. The study also examined which isoforms of CYP3A1 and 3A2 were menthol-inducible and contributed to the altered disposition of midazolam. Menthol was administered intraperitoneally to rats once daily for 3 days at a dose of 10 mg/kg, while the control rats received vehicle alone. The pharmacokinetic examination of i.v. administered midazolam revealed that serum midazolam concentrations at each sampling point were lower in the menthol-treated rats than in the control rats. Regarding the pharmacokinetic parameters of the menthol-treated group, the area under the curve (AUC) was decreased significantly and, correspondingly, the elimination rate constant at terminal phase (ke) was increased significantly without significant changes in the volume of distribution at steady state (Vdss). The metabolic production of the 1'-hydroxylated and 4'-hydroxylated forms of MDZ by hepatic microsomes was significantly greater in the menthol-treated rats than in the control rats. The expression levels of mRNA and protein for hepatic CYP3A2 were more than 2.5-fold higher than the control levels when the rats were treated with menthol, whereas no changes were observed in the expression levels of CYP3A1. These results indicate that menthol enhanced the elimination clearance of midazolam by inducing hepatic CYP3A2 and that careful attention should be paid when menthol is ingested in combination with drugs that act as substrates for CYP3A.

Simultaneous quantification of multiple volatile active components in rat plasma using a headspace-solid phase dynamic extraction method coupled to gas chromatography-tandem mass spectroscopy: application in a pharmacokinetic study of Longhu Rendan pills

A HS-SPDE-GC-MS/MS method for investigating pharmacokinetics of l-menthol, borneol, isoborneol, and camphor in rat plasma after oral administration of LRPs.

Efficacy of spraying l-menthol solution during endoscopic treatment of early gastric cancer: a phase III, multicenter, randomized, double-blind, placebo-controlled study

BACKGROUND

The topical antispasmodic agent l-menthol is useful for inhibiting gastric peristalsis during diagnostic upper gastrointestinal endoscopy. However, it remains unclear whether l-menthol is similarly effective during therapeutic endoscopy, thereby improving treatment outcomes in a clinical setting.

METHODS

A total of 83 patients scheduled to undergo endoscopic treatment at 8 Japanese referral centers were randomly assigned to receive l-menthol or placebo. The degree of gastric peristalsis (peristaltic score: grade 1-5) was assessed by an independent committee. The primary outcome was the proportion of subjects in whom no or mild peristalsis (grade 1 or 2) was maintained throughout endoscopic treatment. Secondary outcomes were the duration of sustained response and the incidence of adverse drug reactions.

RESULTS

The proportion of patients with no or mild peristalsis was significantly higher in the l-menthol group (85.4 %, 95 % confidence intervals 70.8-94.4: 35/41 subjects) than in the placebo group (39.0 %, 24.2-55: 16/41; P < 0.001). The sustained response rates in the l-menthol and the placebo were, respectively, 90.0 and 39.6 % 30 min post-dose, and 79.9 and 35.7 % at the completion of the resection. The sustained response rates were significantly higher in the l-menthol group than in the placebo group (P < 0.001, log-rank test). The incidence of adverse drug reactions did not differ significantly between the two groups (P = 1.000).

CONCLUSIONS

During gastric endoscopic submucosal dissection, spraying l-menthol on the gastric mucosa significantly suppressed peristalsis, with minimal adverse drug reactions as compared with placebo. l-menthol solution might be useful for therapeutic endoscopy.