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PubMed1999

[Peppermint oil-caraway oil fixed combination in non-ulcer dyspepsia--comparison of the effects of enteric preparations].

223 patients with non-ulcer dyspepsia (dysmotility type dyspepsia or essential/idiopathic dyspepsia, also in combination with irritable bowel syndrome) were included in a prospective, randomised, reference- and double-blind controlled multicentre trial to compare two different preparations of a fixed combination of peppermint oil and caraway oil. The aim of the trial was to evaluate the equivalence of the efficacy and tolerability of these two preparations. The test formulation consisted of the drug combination in an enteric coated capsule containing 90 mg peppermint oil and 50 mg caraway oil, while an enteric soluble formulation containing 36 mg peppermint oil and 20 mg caraway oil was used as the reference. The main target item defined was the "difference in pain intensity between the beginning and the end of therapy", measured by the patient on a visual analogue scale (0 = no pain, 10 = extremely strong pain). In 213 patients (n = 108 on the test preparation, n = 105 on the reference preparation) with mean pain intensity baseline measurements of 6.1 points in the test preparation group and 5.9 points in the reference group a statistically significant decline in pain intensity was observed in the two groups (-3.6 resP. -3.3 points; p < 0.001; two-sided one-sample t-test). Equivalent efficacy of both preparations was demonstrated (p < 0.001; one-sided t-test for equivalence). With respect to concomitant variables, the results in both groups were also similar. Regarding "pain frequency", the efficacy of the test preparation was significantly better (p = 0.04; two-sided t-test for difference). Both preparations were well tolerated. Despite the higher dose, the adverse event "eructation with peppermint taste" was less frequent in the group treated with the test formulation, due to the enteric coated capsule preparation.

Adult↗
PubMed2000

Effects of peppermint oil and caraway oil on gastroduodenal motility.

The effect of enteric-coated (Enteroplant) and non-enteric-coated preparations containing a peppermint-caraway oil combination with 90 mg peppermint oil and 50 mg caraway oil was studied on gastroduodenal motility with stationary manometry in six healthy volunteers. The results showed that: (1) both enteric-coated and non-enteric-coated preparations have effects on the migrating motor complex (MMC); (2) mainly a decrease in the number of contractions and contraction amplitudes is seen during the various phases of the MMC; (3) non-enteric-coated preparations have their effects mainly during the first MMC after administration; (4) enteric-coated preparations have their effects temporally delayed during the second MMC after administration. In conclusion, enteric-coated and non-enteric-coated peppermint-caraway oil combinations are safe preparations, acting locally to cause smooth muscle relaxation.

Adult↗
PubMed2005

Genetic engineering of peppermint for improved essential oil composition and yield.

The biochemistry, organization, and regulation of essential oil metabolism in the epidermal oil glands of peppermint have been defined, and most of the genes encoding enzymes of the eight-step pathway to the principal monoterpene component (-)-menthol have been isolated. Using these tools for pathway engineering, two genes and two expression strategies have been employed to create transgenic peppermint plants with improved oil composition and yield. These experiments, along with related studies on other pathway genes, have led to a systematic, stepwise approach for the creation of a 'super' peppermint.

Crops, Agricultural↗
PubMed1986

Metabolism of monoterpenes: demonstration that (+)-cis-isopulegone, not piperitenone, is the key intermediate in the conversion of (-)-isopiperitenone to (+)-pulegone in peppermint (Mentha piperita).

Piperitenone is commonly considered to be the key intermediate in the conversion of (-)-isopiperitenone to (+)-pulegone in peppermint; however, [3H]piperitenone gave rise only to the inert metabolite (+)-piperitone when incubated with peppermint leaf discs. Under identical conditions, (-)-[3H]isopiperitenone was efficiently incorporated into (+)-pulegone, (-)-menthone, and (+)-isomenthone in leaf discs, and yielded an additional metabolite identified as (+)-cis-isopulegone; piperitenone was poorly labeled. Moreover, (+)-cis-[3H]isopulegone was rapidly converted to (+)-pulegone, (-)-menthone, and (+)-isomenthone in leaf discs, and the reduction of (+)-[3H]pulegone to (-)-menthone and (+)-isomenthone was similarly documented. Each step of the pathway was demonstrated in a crude soluble preparation from peppermint leaf epidermis and each of the relevant enzymes was partially purified in order to compare relative rates of catalysis. The results of these studies indicate that the endocyclic double bond of (-)-isopiperitenone is reduced to yield (+)-cis-isopulegone, which is isomerized to (+)-pulegone as the immediate precursor of (-)-menthone and (+)-isomenthone, and they rule out piperitenone as an intermediate of the pathway.

Biotransformation↗
PubMed2005

Pharmacology and preclinical pharmacokinetics of peppermint oil.

The principal pharmacodynamic effect of peppermint oil relevant to the gastrointestinal tract is a dose-related antispasmodic effect on the smooth musculature due to the interference of menthol with the movement of calcium across the cell membrane. The choleretic and antifoaming effects of peppermint oil may play an additional role in medicinal use. Peppermint oil is relatively rapidly absorbed after oral administration and eliminated mainly via the bile. The major biliary metabolite is menthol glucuronide, which undergoes enterohepatic circulation. The urinary metabolites result from hydroxylation at the C-7 methyl group at C-8 and C-9 of the isopropyl moiety, forming a series of mono- and dihydroxymenthols and carboxylic acids, some of which are excreted in part as glucuronic acid conjugates. Studies with tritiated I-menthol in rats indicated about equal excretion in feces and urine. The main metabolite indentified was menthol-glucuronide. Additional metabolites are mono- or di-hydroxylated menthol derivatives.

Administration, Oral↗
PubMed2005

Effect of harvest time and drying method on biomass production, essential oil yield, and quality of peppermint (Mentha x piperita L.).

In the period from 2000 to 2002, studies on peppermint (Mentha x piperita) herb and essential oil (EO) production have been conducted at Planteforsk, Apelsvoll Research Centre Div. Kise in Norway. The trials were aimed at finding the optimal harvest date and suitable drying methods to maximize EO yield and to obtain a desirable oil quality. Peppermint plants from the first production year (2000 and 2001) and the second production year (2002) were harvested during flowering at three developmental stages (early, full, and late bloom). Biomass and leaf production were recorded, and the water content of the plant material was detected after the application of different drying methods: instantaneous drying at 30, 50, and 70 degrees C and prewilting (ground drying) for 1 or 5 days followed by final drying at 30 degrees C. Finally, plant samples were transferred to The Plant Biocentre at NTNU, Trondheim, Norway, for hydrodistillation and gas chromatography-mass spectrometry (GC-MS) analyses of the EOs. Peppermint oil yield increased from early to full bloom and late bloom (average of all years and drying methods except for 50 and 70 degrees C: 2.95, 4.13 and 4.20 L/daa, respectively) as an effect of biomass production and leaf growth. The flavor-impact compounds, menthol and menthone, reached their optimum at full bloom (43-54 and 12-30%, respectively). Prewilting led to slight decreased EO levels after 1 day (7.7%) and 5 days of ground drying (1.5%) and no EO quality changes, compared to direct drying at 30 degrees C. The plant weight (H2O content) was drastically decreased to the average under 80 and 45% in all years, thus reducing the energy supply and costs for the necessary final drying step.

Agriculture↗
PubMed1994

Effect of peppermint and eucalyptus oil preparations on neurophysiological and experimental algesimetric headache parameters.

The effects of peppermint oil and eucalyptus oil preparations on neurophysiological, psychological and experimental algesimetric parameters were investigated in 32 healthy subjects in a double-blind, placebo-controlled, randomized cross-over design. Four different test preparations were applied to large areas of the forehead and temples using a small sponge and their effect was evaluated by comparing baseline and treatment measure. The combination of peppermint oil, eucalyptus oil and ethanol increased cognitive performance and had a muscle-relaxing and mentally relaxing effect, but had little influence on pain sensitivity. A significant analgesic effect with a reduction in sensitivity to headache was produced by a combination of peppermint oil and ethanol. The essential plant oil preparations often used in empiric medicine can thus be shown by laboratory tests to exert significant effects on mechanisms associated with the pathophysiology of headache.

Administration, Topical↗
PubMed2003

Menthofuran regulates essential oil biosynthesis in peppermint by controlling a downstream monoterpene reductase.

(+)-Pulegone is a central intermediate in the biosynthesis of (-)-menthol, the most significant component of peppermint essential oil. Depending on environmental conditions, this branch point metabolite may be reduced to (-)-menthone en route to menthol, by pulegone reductase (PR), or oxidized to (+)-menthofuran, by menthofuran synthase (MFS). To elucidate regulation of pulegone metabolism, we modified the expression of mfs under control of the CaMV 35S promoter in transformed peppermint plants. Overexpression and cosuppression of mfs resulted in the respective increase or decrease in the production of menthofuran, indicating that the control of MFS resides primarily at the level of transcription. Significantly, in both WT peppermint as well as in all transformed plants, the flux of (+)-pulegone through PR correlated negatively with the essential oil content of menthofuran, such that menthofuran, and pulegone increased, or decreased, in concert. These results suggested that menthofuran itself might influence the reduction of pulegone. Although (+)-menthofuran did not inhibit (+)-PR activity, stem feeding with menthofuran selectively decreased pr transcript levels in immature leaves, thereby accounting for decreased reductase activity and increased pulegone content. These data demonstrate that the metabolic fate of (+)-pulegone is controlled through transcriptional regulation of mfs and that menthofuran, either directly or indirectly, influences this process by down-regulating transcription from pr and/or decreasing pr message stability. The ability to reduce both menthofuran and pulegone levels is of commercial significance in improving essential oil quality; however, the physiological rationale for such complex regulation is presently unclear.

Cyclohexane Monoterpenes↗
PubMed1997

Isolation and bacterial expression of a sesquiterpene synthase cDNA clone from peppermint (Mentha x piperita, L.) that produces the aphid alarm pheromone (E)-beta-farnesene.

(E)-beta-Farnesene is a sesquiterpene semiochemical that is used extensively by both plants and insects for communication. This acyclic olefin is found in the essential oil of peppermint (Mentha x piperita) and can be synthesized from farnesyl diphosphate by a cell-free extract of peppermint secretory gland cells. A cDNA from peppermint encoding (E)-beta-farnesene synthase was cloned by random sequencing of an oil gland library and was expressed in Escherichia coli. The corresponding synthase has a deduced size of 63.8 kDa and requires a divalent cation for catalysis (Km for Mg2+ approximately 150 microM; Km for Mn2+ approximately 7 microM). The sesquiterpenoids produced by the recombinant enzyme, as determined by radio-GC and GC-MS, are (E)-beta-farnesene (85%), (Z)-beta-farnesene (8%), and delta-cadinene (5%) with the native C15 substrate farnesyl diphosphate (Km approximately 0.6 microM; Vrel = 100) and Mg2+ as cofactor, and (E)-beta-farnesene (98%) and (Z)-beta-farnesene (2%) with Mn2+ as cofactor (Vrel = 80). With the C10 analog, GDP, as substrate (Km = 1.5 microM; Vrel = 3 with Mg2+ as cofactor), the monoterpenes limonene (48%), terpinolene (15%), and myrcene (15%) are produced.

Amino Acid Sequence↗
PubMed2000

Regulation of monoterpene accumulation in leaves of peppermint.

Plants synthesize numerous classes of natural products that accumulate during development and are thought to function as constitutive defenses against herbivores and pathogens. However, little information is available about how the levels of such defenses are regulated. We measured the accumulation of monoterpenes, a model group of constitutive defenses, in peppermint (Mentha x piperita L.) leaves and investigated several physiological processes that could regulate their accumulation: the rate of biosynthesis, the rate of metabolic loss, and the rate of volatilization. Monoterpene accumulation was found to be restricted to leaves of 12 to 20 d of age, the period of maximal leaf expansion. The rate of monoterpene biosynthesis determined by (14)CO(2) incorporation was closely correlated with monoterpene accumulation, as determined by gas chromatographic analysis, and appeared to be the principal factor controlling the monoterpene level of peppermint leaves. No significant catabolic losses of monoterpenes were detected throughout leaf development, and monoterpene volatilization was found to occur at a very low rate, which, on a monthly basis, represented less than 1% of the total pool of stored monoterpenes. The composition of volatilized monoterpenes differed significantly from that of the total plant monoterpene pool, suggesting that these volatilized products may arise from a separate secretory system. With the demonstration that the rate of biosynthesis is the chief process that determines monoterpene accumulation in peppermint, efforts to improve production in this species can now focus on the genes, enzymes, and cell differentiation processes that regulate monoterpene biosynthesis.

Chromatography, Gas↗
PubMed2000

Developmental regulation of monoterpene biosynthesis in the glandular trichomes of peppermint.

Monoterpene production in peppermint (Mentha x piperita L.) glandular trichomes is determined by the rate of biosynthesis, as determined by (14)CO(2) incorporation, and is restricted to leaves 12 to 20 d of age. Using oil glands isolated from peppermint leaves of different ages, in vitro assay of the eight sequential enzymes responsible for the biosynthesis of the principal monoterpene (-)-menthol indicated that all but one biosynthetic enzyme had a very similar developmental profile. Activities were highest in leaves 12 to 20 d of age, with a sharp peak centered at 15 d. The exception, (-)-menthone reductase, the last enzyme of the pathway, exhibited a later peak of activity, which was centered at approximately 21 d. The correlation between in vitro enzyme activity and the rate of biosynthesis measured in vivo suggests that monoterpene formation is controlled mainly by the coordinately regulated activity of the relevant biosynthetic enzymes. Developmental immunoblotting of limonene synthase, which catalyzes the committed step of the pathway, demonstrated a direct correlation between enzyme activity and enzyme protein, suggesting that the dynamic time course for the remaining pathway enzyme activities also reflects the corresponding protein levels. RNA-blot analyses indicated that the genes encoding enzymes of the early pathway steps are transcriptionally activated in a coordinated fashion, with a time course superimpossible with activity measurements and immunoblot data. These results demonstrating coincidental temporal changes in enzyme activities, enzyme protein level, and steady-state transcript abundances indicate that most of the monoterpene biosynthetic enzymes in peppermint are developmentally regulated at the level of gene expression.

Blotting, Northern↗
PubMed1969

Evidence for metabolic turnover of monoterpenes in peppermint.

Two types of experimental evidence are presented which suggest that the monoterpenes of peppermint (Mentha piperita L.) are subject to metabolic turnover. In kinetic studies with (14)CO(2), peppermint cuttings rapidly incorporate label into the monoterpenes and then lose most of the label from the monoterpenes, without corresponding changes in the amount of monoterpenes present. When peppermint plants are grown in a controlled environment (16-hr photoperiod, 24 degrees day, 8 degrees night) and analyzed at intervals leaf pair by leaf pair, there is a steady increase in monoterpenes until the time of floral initiation, followed by a rapid decrease. It is suggested that monoterpenes may serve as substrates for energy metabolism in the secretory cells after other stored substrates have been depleted.

Journal Article↗
PubMed1979

Metabolism of Monoterpenes: Demonstration of (+)-Neomenthyl-beta-d-Glucoside as a Major Metabolite of (-)-Menthone in Peppermint (Mentha Piperita).

(-)-Menthone, the major monoterpene component of the essential oil of maturing peppermint (Mentha piperita L.) leaves (6 micromoles per leaf) is rapidly metabolized at the onset of flowering with a concomitant rise in the level of (-)-menthol (to about 2 micromoles per leaf). Exogenous (-)-[G-(3)H]menthone is converted into (-)-[(3)H]menthol as the major steam-volatile product in leaf discs in flowering peppermint (10% of incorporated tracer); however, the major portion of the incorporated tracer (86%) resided in the nonvolatile metabolites of (-)-[G-(3)H]menthone. Acid hydrolysis of the nonvolatile material released over half of the radioactivity to the steamvolatile fraction, and the major component of this fraction was identified as (+)-neomenthol by radiochromatographic analysis and by synthesis of crystalline derivatives, thus suggesting the presence of a neomenthyl glycoside. Thin layer chromatography, ion exchange chromatography, and gel permeation chromatography on Bio-Gel P-2 allowed the purification of the putative neomenthyl glycoside, and these results suggested that the glycoside contained a single, neutral sugar residue. Hydrolysis of the purified glycoside, followed by reduction of the resulting sugar moiety with NaB(3)H(4), generated a single labeled product that was subsequently identified as glucitol by radio gas-liquid chromatography of both the hexatrimethylsilyl ether and hexaacetate derivative, and by crystallization to constant specific radioactivity of both the alditol and the corresponding hexabenzoate. These results, along with studies on the hydrolysis of the glycoside by specific glycosidases, strongly suggest that (+)-neomenthyl-beta-d-glucoside is a major metabolite of (-)-menthone in flowering peppermint. This is the first report on the occurrence of a neomenthyl glycoside, and the first evidence implicating glycosylation as an early step in monoterpene catabolism.

Journal Article↗
PubMed1982

Metabolism of Monoterpenes: Conversion of l-Menthone to l-Menthol and d-Neomenthol by Stereospecific Dehydrogenases from Peppermint (Mentha piperita) Leaves.

The monoterpene ketone l-menthone is specifically converted to l-menthol and l-menthyl acetate and to d-neomenthol and d-neomenthyl-beta-d-glucoside in mature peppermint (Mentha piperita L. cv. Black Mitcham) leaves. The selectivity of product formation results from compartmentation of the menthol dehydrogenase with the acetyl transferase and that of the neomenthol dehydrogenase with the glucosyl transferase. Soluble enzyme preparations, but not particulate preparations, from mature peppermint leaves catalyzed the NADPH-dependent reduction of l-menthone to both epimeric alcohols, and the two dehydrogenases responsible for these stereospecific transformations were resolved by affinity chromatography on Mātrex Gel Red A. Both enzymes have a molecular weight of approximately 35,000, possess a K(m) for NADPH of about 2 x 10(-5)m, are very sensitive to inhibition by thiol-directed reagents, and are not readily reversible. The menthol dehydrogenase showed a pH optimum at 7.5, exhibited a K(m) for l-menthone of about 2.5 x 10(-4)m, and also reduced d-isomenthone to d-neoisomenthol. The neomenthol dehydrogenase showed a pH optimum at 7.6, exhibited a K(m) for l-menthone of about 2.2 x 10(-5)m, and also reduced d-isomenthone to d-isomenthol. These stereochemically distinct, but otherwise similar, enzymes are of key importance in determining the metabolic fate of menthone in peppermint, and they are probably typical of the class of dehydrogenases thought to be responsible for the metabolism of monoterpene ketones during plant development.

Journal Article↗
PubMed2001

Botanical perspectives on health peppermint: more than just an after-dinner mint.

Throughout history different species of mint have been used across the globe for their varying properties, both medicinal and culinary. Today, the commercial sales of mints are expanding each year--and at the end of a large meal after-dinner mints are frequently served. But why do we take them? Peppermint (Mentha piperita) is usually taken after a meal for its ability to reduce indigestion and colonic spasms by reducing the gastrocolic reflex. It is a naturally occurring hybrid cross between water mint (M. aquatica) and spearmint (M. spicata) and is best known for its role as a popular flavouring agent. Less well recognised is peppermint's potential role in the management of numerous other medical conditions including certain procedures, e.g. colonoscopy. With the growing popularity of herbal remedies, among both the public and medical practitioners, it would seem that now is an opportune time to consider further what peppermint has to offer the world of medicine.

Colonic Diseases, Functional↗
PubMed2005

Acute lung injury after peppermint oil injection.

UNLABELLED: We describe a case of acute lung injury following IV injection of peppermint oil. An 18-yr-old woman injected the oil and developed fulminant pulmonary edema requiring ventilator support. Within 4 h after injection her arterial oxygen tension was 8.1 kPa (60 mm Hg) at an inspired oxygen fraction (F(IO2)) of 0.7 (P/F ratio: 85) despite a positive end expiratory pressure (PEEP) of 20 mbar, therefore meeting criteria for acute respiratory distress syndrome (ARDS). Mean pulmonary artery pressures and pulmonary artery wedge pressures were within normal limits throughout the case (<25 mm Hg and <10 mm Hg, respectively). Ventilation with high PEEP and diuresis resulted in a P/F ratio of 265 after 24 h. The patient was successfully weaned from the ventilator on the 9th day. This report is the first description of the sequelae of IV peppermint oil injection. The injection resulted in pulmonary edema and acute lung injury, presumably due to direct toxicity and a resultant increase in pulmonary vascular permeability. IMPLICATIONS: This report is the first description of IV peppermint oil injection. The patient rapidly developed severe fluid overload of the lung and subsequent lung injury that required intubation, mechanical ventilation, and intensive care therapy for 13 days. The pulmonary edema was presumably caused by direct toxicity and an increase in pulmonary vascular permeability.

Adolescent↗
PubMed1995

Does peppermint oil relieve spasm during barium enema?

The effectiveness of topical peppermint oil added to barium sulphate suspension in relieving colonic muscle spasm during double contrast barium enema examination was assessed in a double blind study. 141 patients were randomized either to a control group (71 patients) examined with standard barium suspension or to the treatment group which received peppermint oil mixed with the barium preparation. No residual spasm was evident in a significant proportion of patients in the treated group (60%) compared with the control group (35%) (p < 0.001). The patients' acceptability of the procedure was good and there were no adverse effects on the overall quality of the examination. In conclusion, the addition of peppermint oil to the barium suspension seems to reduce the incidence of colonic spasm during the examination. The technique is simple, safe, cheap and it may lessen the need for intravenous administration of spasmolytic agents.

Adult↗