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At least 181 records · Page 10Linked to original sources
PubMed1998

Determination of l-menthol in pharmaceutical products by high performance liquid chromatography with polarized photometric detection.

A simple analytical method for l-menthol by high-performance liquid chromatography with a polarized photometric detector was established. The polarized photometric detector was constructed with two polarizers mounted on both sides of the flow cell in a conventional photometric detector and can be easily used for the detection of optically active compound, such as l-menthol. This study was conducted with a newly developed split-cell assembly in order to increase the sensitivity. The characteristic of this method is the ability to determine optically active compounds selectively among the other coexisting materials and the pretreatment of the sample can be very simple or not required at all. The detection of l-menthol by this method is 0.5 microgram. A good agreement was shown between another commonly used GC method and the method described in this paper.

Chromatography, Gas↗
PubMedDate not supplied

Feasibility study of repeated harvesting of menthol from biologically viable Mentha x piperata using ultrasonic extraction.

To potentially replace the conventional destructive extraction process, we have shown the feasibility of devising a novel technique that uses ultrasound to nonlethally and repeatedly extract menthol from biologically viable peppermint plants (Mentha x piperita). Our results show that plants ultrasonicated for 1 h at 22 degrees C in a standard 40 kHz ultrasonic bath could release approximately 17.8 microg of menthol per gram of leaf tissue (2% of total product). The amount of menthol release increases with the time of treatment and is greatly affected by the temperature of the ultrasonic bath water. An increase from 2% to 12% of total product was observed when the temperature was increased from 22 degrees C to 39 degrees C. When the temperature effects were isolated, the mechanism of the product release was found to be that of cavitation. The treated plants remained viable and were ready for the subsequent ultrasound extraction after approximately 4 days of recuperation. However, the amount of product released is reduced in subsequent extractions. Scanning electron micrographs indicate that there are two mechanisms involved in extraction: (1) the diffusion of product through the cuticle of peppermint glandular trichomes and (2) the exudation of the product from broken and damaged trichomes. This study has shown the possibility of using an on-line ultrasonic, nondestructive extraction method to continuously release intracellular plant metabolites from the plants while maintaining the plant's viability.

Equipment Design↗
PubMed2001

Pharmacokinetics of menthol and carvone after administration of an enteric coated formulation containing peppermint oil and caraway oil.

Enteric coating of peppermint oil/caraway oil capsules avoids subjective discomfort to the patient caused by gastroesophageal reflux. In order to confirm bioequivalence of an enteric coated formulation containing peppermint oil and caraway oil (CAS 277309-55-4, Enteroplant) and an immediate release formulation of both oils, the pharmacokinetics of menthol and carvone after oral administration of the two formulations were studied in a randomized, two-period cross-over study in 16 healthy male volunteers. The subjects received 180 mg peppermint oil and 100 mg caraway oil, once as 2 enteric coated capsules of the fixed enteric coated combination preparation containing 90 mg peppermint oil (WS 1340) and 50 mg caraway oil (WS 1520) each (test) and once in the form of 5 capsules of an immediate release formulation (reference) containing 36 mg peppermint (WS 1340) oil and 20 mg caraway oil (WS 1520) each. The capsules were taken with 250 ml water after a 10 h fast. Both substances were determined in plasma by GC/MS after extraction. The limit of quantification was 10 ng/ml for menthol and 0.5 ng/ml for carvone. The mean maximum plasma levels for menthol were 1196 ng/ml after administration of the test medication and 1492 ng/ml after administration of the reference medication. The bioavailability with respect to the AUC was comparable after administration of test and reference preparation, the 90% confidence interval was 97 to 105%. As expected, there were considerable differences for Tmax. After application of the enteric coated form the maximum concentration was reached significantly later (3.0 h vs. 1.7 h) compared to the immediate release capsule. Corresponding data were also calculated for carvone. After application of the test medication the maxima of 14 ng/ml for both formulations were reached later (2.5 h vs. 1.3 h). The 90% confidence interval of the AUC for carvone was 79 to 119% and therefore slightly outside the acceptable range for bioequivalence of 80 to 125%. However, this fact should not be relevant, in particular since the dosage of the enteric coated capsule lies at the upper limit of the model text and positive clinical studies, also on the therapeutic equivalence of the two formulations, are available.

Adult↗
PubMed2005

TRPA1 and TRPM8 activation in humans: effects of cinnamaldehyde and menthol.

The aim of this study was to evaluate the psychophysical effects of both TRPA1 and TRPM8 activation in humans by application of either cinnamaldehyde or menthol. We applied 10% cinnamaldehyde or 40% menthol solutions on the forearm in 10 study participants. Quantitative sensory testing and laser Doppler imaging was performed before and after exposure to the compounds. Cinnamaldehyde evoked significant spontaneous pain and induced heat and mechanical hyperalgesia, cold hypoalgesia and a neurogenic axon reflex erythema. In contrast, TRPM8 activation by menthol produced no axon reflex reaction and resulted in cold hyperalgesia. We conclude that agonists of TRPA1 and TRPM8 channels produce strikingly different psychophysical patterns.

Acrolein↗
PubMed2006

Effects of menthol on the triggering of the swallowing reflex in elderly patients with dysphagia.

AIMS: To investigate the effect of menthol on swallowing reflex sensitivity in elderly patients with dysphagia. METHODS AND RESULTS: The swallowing reflex sensitivity of institutionalized elderly patients was evaluated as a latent time of swallowing reflex (LTSR), induced by the injection of 1 ml solution into the pharynx. LTSR was significantly shortened in a concentration-dependent manner, from 13.8 s [95% confidence interval (CI) 11.1, 16.5] by distilled water to 9.4 s (95% CI 7.1. 11.8) by 10(-2)m menthol. CONCLUSION: Using menthol with elderly patients with dysphagia may improve the sensitivity of their swallowing reflex, resulting in prevention of aspiration pneumonia.

Aged, 80 and over↗
PubMed1988

The effects of menthol isomers on nasal sensation of airflow.

The effects of inhalation of L-menthol, D-isomenthol and D-neomenthol, upon nasal resistance and sensation to airflow were investigated in 40 subjects. L-menthol caused a highly significant enhancement of nasal sensation of airflow but despite their great similarity in structure and a similar peppermint smell the isomers D-isomenthol and D-neomenthol had no effect on nasal sensation of airflow. These findings show that L-menthol has a specific pharmacological action on nasal sensory nerve endings which is not related to its peppermint smell.

Adolescent↗
PubMed1990

The effects of menthol on reaction time and nasal sensation of airflow in subjects suffering from the common cold.

The effects of sucking a lozenge containing 11 mg L-menthol on reaction time and nasal sensation were investigated in a double blind trial on 60 subjects suffering from the common cold. Reaction time was determined by measuring the response time to a stimulus presented on a microcomputer screen and nasal sensation was scored on a visual analogue scale. Menthol ingestion compared to placebo caused a significant increase in nasal sensation of airflow which persisted for up to 30 min. The simple and choice reaction times measured before ingestion of the lozenge were similar to those found in healthy uninfected subjects and there was no change in reaction time after ingestion of menthol.

Adolescent↗
PubMed2006

Ethanol inhibits cold-menthol receptor TRPM8 by modulating its interaction with membrane phosphatidylinositol 4,5-bisphosphate.

Ethanol has opposite effects on two members of the transient receptor potential (TRP) family of ion channels: it inhibits the cold-menthol receptor TRPM8, whereas it potentiates the activity of the heat- and capsaicin-gated vanilloid receptor TRPV1. Both thermosensitive cation channels are critically regulated by the membrane lipid, phosphatidylinositol 4,5-bisphosphate (PIP(2)). The effects of this phospholipid on TRPM8 and TRPV1 are also functionally opposite: PIP(2) is necessary for the activation of TRPM8 but it constitutively inhibits TRPV1. This parallel led us to investigate the possible role of PIP(2) in the ethanol-induced modulation of rat TRPM8, heterologously expressed in HEK293T cells. In this study, we characterize the effects of ethanol (0.1-10%) on whole-cell currents produced by menthol and by low temperature (< 17 degrees C). We show that the inclusion of PIP(2) in the intracellular solution results in a strong reduction in the ethanol-induced inhibition of menthol-evoked responses. Conversely, intracellular dialysis with anti-PIP(2) antibody or with the PIP(2) scavenger, poly L-lysine, enhanced the ethanol-induced inhibition of TRPM8. A 20 min pre-incubation with wortmannin caused a modest decrease in inhibition produced by 1% ethanol, indicating that the ethanol-induced inhibition is not mediated by lipid kinases. These findings suggest that ethanol inhibits TRPM8 by weakening the PIP(2)-TRPM8 channel interaction; a similar mechanism may contribute to the ethanol-mediated modulation of some other PIP(2)-sensitive TRP channels.

Alanine↗
PubMed1980

The risk of jaundice in glucose-6-phosphate dehydrogenase deficient babies exposed to menthol.

A major cause of neonatal morbidity and mortality in Lagos, Nigeria, is severe neonatal jaundice seen in G-6-PD deficient babies. The observation that the jaundice is more severe in outpatient than in inpatient babies suggests that its cause is exogenous. "Mentholated" powder which is commonly used in many clinics and at home to dress umbilical cords was suspected to be the offending agent. A controlled study of the effects of one of these powders was carried out on 60 consecutive G-6-PD deficient babies. In 30 of them the umbilical cords were dressed daily with the powder while the remaining half who were untreated served as controls. The treated babies developed statistically more significant jaundice than the controls. Inability of neonates to conjugate menthol in this power is probably responsible for the jaundice developed by these G-6-PD deficient babies. It is concluded that the use of menthol and/or camphor-containing commerical products on neonates be discontinued, especially in communities where the incidence of G-6-PD deficiency is high as the use of such products may be contributiing to the severity of neonatal jaundice.

Bilirubin↗
PubMed1991

Effect of menthol on the bladder cooling reflex in the cat.

The effect of menthol on the urinary bladder cooling reflex was studied in alpha-chloralose-anaesthetized cats. The cooling reflex was elicited by bladder or urethral instillations of cold saline and monitored by multiunit recordings from efferent and afferent pelvic nerve filaments. The bladder cooling reflex was greatly exaggerated by intraluminal exposure of the bladder or the urethra to a 0.6 mM solution of menthol. The effect occurred without a sensitizing effect on bladder mechanoreceptors. It could be described as a shift of the temperature-response curve for the cooling reflex towards higher temperatures. This change resembles the effect of menthol on cutaneous cold receptors. It is proposed that the bladder cooling reflex originates from cold receptors in the bladder and urethral walls.

Animals↗
PubMed2003

Development of nociceptive synaptic inputs to the neonatal rat dorsal horn: glutamate release by capsaicin and menthol.

To study the postnatal development of nociceptive synaptic inputs in the superficial dorsal horn of the neonatal rat spinal cord, we examined the effect of capsaicin and menthol on glutamatergic mEPSCs in postnatal day (P) 0-1, P5-6 and P9-11 slices of spinal cord. Capsaicin (100 nM to 2 microM) increased the mEPSC frequency in a concentration-dependent manner at all ages tested, with a significant enhancement of the effect between P5 and P10. This effect was sensitive to vanilloid receptor (VR) antagonists. The elevation in mEPSC frequency occurred at concentrations of capsaicin (100 nM) that did not alter the distribution of mEPSC amplitudes and was abolished by a dorsal rhizotomy, demonstrating that capsaicin acts via presynaptic VR1 receptors localized on primary afferents. Menthol significantly increased the mEPSC frequency with a similar developmental pattern to capsaicin without consistently affecting mEPSC amplitude. The increase in mEPSC frequency following capsaicin did not depend on transmembrane calcium influx since it persisted in zero [Ca2+]o. The facilitation of spontaneous glutamate release by capsaicin was sufficient to evoke action potentials in neonatal dorsal horn neurons but was accompanied by a block of EPSCs evoked by electrical stimulation of the dorsal root. These results indicate that VR1-expressing nociceptive primary afferents form functional synaptic connections in the superficial dorsal horn from birth and that activation of the VR1 receptor increases spontaneous glutamate release via an undetermined mechanism. In addition, the data suggest that immature primary afferents express functional menthol receptors that are capable of modulating transmitter release. These results have important functional implications for infant pain processing.

Action Potentials↗
PubMed2005

The role of menthol in skin penetration from topical formulations of ibuprofen 5% in vivo.

In vivo plasma profiles from formulations containing 5% ibuprofen were compared after a single topical application in a randomised, double-blind, cross-over trial. Ibuleve gel (Dermal Laboratories, UK) contained only ibuprofen whilst Deep Relief gel (Mentholatum, UK) also contained 3% menthol. In contrast to results obtained when these products were compared under in vitro conditions, there was no statistically significant difference in vivo between delivery of ibuprofen. Estimated relative bioavailability fraction (Deep Relief gel/Ibuleve gel) from log-transformed AUC((0-24h)) was 0.99 (95% CI: 0.94-1.04), estimated C(max )ratio was 0.96 (95% CI: 0.91-1.00) and estimated t(max) ratio was 1.01 (95% CI: 0.81-1.20). Menthol produces local vasodilation, which reduces skin barrier function, and these data demonstrate that it is inappropriate to extrapolate from in vitro data where formulation components produce biologically-mediated enhancement of permeation which cannot be modelled ex vivo. In clinical use, these products deliver comparable amounts of ibuprofen, but only Deep Reliefgel provides the secondary immediate benefit of the direct analgesic action of menthol.

Administration, Cutaneous↗
PubMed2004

Dermal absorption of camphor, menthol, and methyl salicylate in humans.

Camphor, menthol, and methyl salicylate occur in numerous over-the-counter products. Although extensively used, there have been no estimates of human exposure following administration via dermal application. Furthermore, there is little information about the pharmacokinetics of those compounds. The authors report the plasma concentrations of the intact compounds as a function of dose following dermal patch application. Three groups of 8 subjects (4 male, 4 female) applied a different number of commercial patches (2, 4, or 8) to the skin for 8 hours. Plasma samples were assayed using sensitive and selective gas-chromatographic methods. For the 8-patch group, the average maximum plasma concentrations (Cmax +/- SD) were 41.0 +/- 5.8 ng/mL, 31.9 +/- 8.8 ng/mL, and 29.5 +/- 10.5 ng/mL for camphor, menthol, and methyl salicylate, respectively. The corresponding values for the 4-patch group were 26.8 +/- 7.2 ng/mL, 19.0 +/- 5.4 ng/mL, and 16.8 +/- 6.8 ng/mL. The harmonic mean terminal half-lives were 5.6 +/- 1.3 hours, 4.7 +/- 1.6 hours, and 3.0 +/- 1.2 hours for camphor, menthol, and methyl salicylate, respectively. The 2-patch group had measurable but low plasma concentrations of each compound. Low-dose dermal application for an extended time results in low plasma concentrations of all 3 compounds. Four and 8 patches, when applied for 8 hours, gave measurable and nearly proportional plasma concentrations. Although unable to determine the absolute dermal bioavailability of these compounds, there appears to be relatively low systemic exposure to these potentially toxic compounds, even when an unrealistically large number of patches are applied for an unusually long time.

Administration, Topical↗
PubMed1991

Effects of l-menthol and dl-camphor on the penetration and hydrolysis of methyl salicylate in hairless mouse skin.

Plasters containing methyl salicylate with and without l-menthol and dl-camphor were prepared and topically applied on hairless mouse skin to investigate the effects of l-menthol and dl-camphor on the skin penetration and hydrolysis of methyl salicylate in the skin. The in vitro hydrolysis of methyl salicylate was also investigated using the skin homogenate. It was found that l-menthol with dl-camphor enhanced the skin penetration of methyl salicylate, and they inhibited both the in vivo and in vitro hydrolysis of methyl salicylate to salicylic acid.

Administration, Topical↗
PubMed1996

l-Menthol, oleic acid and lauricidin in absorption enhancement of free and sodium salt of diclofenac using ethanol treated silicone membrane as model for skin.

The mechanism of l-menthol, oleic acid and lauricidin as enhancers on percutaneous absorption was examined using diclofenac (DH) as a hydrophobic drug and sodium diclofenac (DNa) as a hydrophilic drug in in vitro diffusion experiments with two kinds of membranes: ethanol-treated and untreated silicone membranes; these were models for the lipid and pore pathways of skin. A 20% w/w ethanol-aqueous solution decreased the flux of DH but increased the flux of DNa significantly across the treated membrane compared with those fluxes across the untreated membrane, suggesting that DH penetrated by the lipid pathway and DNa by the pore pathway. The permeability of DNa through the pore pathway decreased significantly across the treated membrane with the addition of oleic acid and lauricidin. l-Menthol increased the permeability coefficients of DH and DNa more in a treated membrane than in an untreated one, showing the same tendency as in rat skin. Thus, while oleic acid and lauricidin did not increase the permeation of DNa by the pore pathway, l-menthol appeared to enhance the permeation of the drug by both the lipid and pore pathways.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1998

Anomer-selective glucosylation of l-menthol by yeast alpha-glucosidase.

l-Menthol was glucosylated by the alpha-glucosidase (EC 3.2.1.20) of Saccharomyces cerevisiae using maltose as the glucosyl donor. When 50 mg of l-menthol and 1.6 M maltose in 10 mM citrate-phosphate buffer (pH 5.5) were incubated at 45 degrees C, l-menthyl alpha-D-glucopyranoside (alpha-MenG) was alpha-anomer-selectively formed as a product. The specificity of the alpha-linkage was confirmed by 13C-NMR analysis. In the reaction mixture after 2 h, alpha-MenG was mainly accumulated in a crystalline form and the concentration of dissolved alpha-MenG was constant at 1.4 mM. The molar conversion yield of alpha-MenG produced based on the supplied l-menthol was maximally 30.7% at 48 h of reaction.

Catalysis↗
PubMedDate not supplied

The effects of camphor, eucalyptus and menthol vapour on nasal resistance to airflow and nasal sensation.

The effects of five minutes exposure to camphor, eucalyptus or menthol vapour on nasal resistance to airflow and nasal sensation of airflow were compared with the effects of exercise on the nose. Inhalation of camphor, eucalyptus or menthol had no effect on nasal resistance to airflow but the majority of subjects reported a cold sensation in the nose with the sensation of improved airflow. Exercise caused a decrease in nasal resistance but did not induce any nasal sensation of cold or improved airflow. The results indicate that camphor, eucalyptus and menthol stimulate cold receptors in the nose. The clinical significance of nasal sensation of airflow is discussed.

Adult↗
PubMedDate not supplied

Validation of a method for simultaneous determination of menthol and methyl salicylate in pharmaceuticals by capillary gas chromatography with cool on-column injection.

The conditions for the identification and quantitative determination of menthol and methyl salicylate in ointment Balsamum Mentholi Compositum on a hydrocarbon-ester base (vaseline-lanolin), have been established by using capillary gas chromatography with cool on-column injection and flame ionization detection (FID). The good separation of menthol (tR = 7.2 min), methyl salicylate (tR = 8.7 min) and thymol (tR = 12.3 min) and camphor (tR = 6.0 min), used as alternative internal standards, beside vehiculum constituents (peak of tR = 15.8 min) was obtained. The method features a high sensitivity - detection limit for menthol and methyl salicylate was 0.1 ng and 5.0 ng, respectively, high accuracy, precision and recovery for active substances: 100.0% +/- 2.2%, when camphor was used as an internal standard.

Chromatography, Gas↗