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Age-related effects on the threshold, psychophysical function, and pleasantness of menthol.

Participants were 20 persons half of whom were 18 to 26 years of age (M = 21) and half of whom were over 65 years (M = 75). All were ambulatory, noninstitutionalized, and reported good to excellent health. The stimulus was menthol delivered in air to the nostrils. Threshold was measured using the up-down staircase method. Intensity and pleasantness were measured by magnitude estimation. The average threshold for the elderly participants was significantly higher than for young participants. The median slope of the intensity function was steeper by a factor of two for younger adults. The average pleasantness functions were steeper for the younger persons. Finally, although the younger adults found menthol less pleasant with repeated exposure, the elderly persons showed no effect of exposure. The results suggest that the average, healthy elderly person's odor/trigeminal world differs from that of the young adult. Further experiments are exploring the relative contributions of olfactory, trigeminal, and cognitive factors in producing this change.

Adolescent↗

Capsaicin and menthol in the treatment of itch and pain: recently cloned receptors provide the key.

Topical capsaicin is reported to be an effective treatment for idiopathic intractable pruritus ani. While both capsaicin and menthol application produce a transient perianal burning sensation, only capsaicin relieves itching. Classical observations on functional desensitisation of nociceptors by capsaicin may explain the beneficial effects but the recent discovery of a range of receptors which respond to capsaicin, menthol, and temperature, and their expression in subsets of sensory nerve fibres, provides an exciting prospect towards advancing our understanding and treatment of sensory dysfunction.

Administration, Topical↗

In vitro/in vivo difference in enhanced skin permeation of nicardipine hydrochloride by the 1-menthol-ethanol system.

The in vitro/in vivo difference in enhanced skin permeation of nicardipine hydrochloride (NC) by simultaneous use of 1-menthol and ethanol (MEW system, 1-menthol:ethanol:water = 5:40:55) was investigated in hairless rats. First, the cutaneous blood flow clearance (clearance from skin to blood flow) of NC per unit area of skin (CLCB/A), which was comparable to the permeability coefficient across skin (PC), was calculated from intracutaneous and intravenous injection data using the deconvolution method; the value was 1.67 microliters/h/cm2. Two formulations containing NC and the MEW system, solution (SOL) and 15% hydroxypropyl cellulose gel (GEL), were used for in vitro and in vivo permeation experiments. The in vitro PC of NC via excised skin from SOL (23.3 microliters/h/cm2) was significantly higher than CLCB/A, and that from GEL (1.48 microliters/h/cm2) was similar to CLCB/A. Consequently, the steady-state concentration of NC in skin during in vivo application of SOL was 6.6 times higher than corresponding in vitro data. In vivo PCs from SOL and GEL were however significantly lower than CLCB/A. These results may be explained by the findings, using a laser Doppler flowmeter, that cutaneous blood flow was decreased by the application of MEW.

Animals↗

Feasibility of use of several cardiovascular agents in transdermal therapeutic systems with l-menthol-ethanol system on hairless rat and human skin.

Effect of the simultaneous use of l-menthol and ethanol on the skin permeation of six potent cardiovascular agents: nicardipine hydrochloride, atenolol, captopril, nifedipine, vinpocetine and nilvadipine (in hydrophilic order) was investigated to evaluate the feasibility of their use in a transdermal therapeutic system (TTS). In vitro diffusion experiments were carried out using excised hairless rat and human skin, and the application area of TTS required for the minimum therapeutic effect was estimated by a simple pharmacokinetic calculation. Marked enhancing effect by the l-menthol-ethanol system was found independent of drug lipophilicity, but the mode of action was dependent on the lipophilicity of the drug. The action of the system on lipophilic drugs (nifedipine, vinpocetine and nilvadipine) was mainly due to their increase in solubility in the system, while that on hydrophilic (or water soluble) drugs (nicardipine hydrochloride, atenolol and captopril) was the result of increase in their skin permeability coefficient. This enhancing effect was adequate to assure their minimum effective concentration (MEC) in human. The area of application of a drug to maintain the MEC was calculated to be 0.15 cm2 for hydrophilic or water soluble drugs and 3.7-13 cm2 for lipophilic drugs.

Administration, Cutaneous↗

Effect of l-menthol-ethanol-water system on the systemic absorption of flurbiprofen after repeated topical applications in rabbits.

The effect of the l-menthol-ethanol-water system (MEW system), a skin penetration enhancer, on the systemic absorption of flurbiprofen (FP) after repeated topical applications was investigated. FP (1%) gel containing ethanol (25%) and l-menthol (3%) as penetration enhancers was applied to rabbit dorsal skin and the in vivo absorption rate of FP was compared with the in vitro penetration rate through excised skin. In vivo absorption rate of FP was initially high and decreased with time to a value approximately equal to the in vitro rate. The remaining FP in the gel 6 h after the application was 60% of the initial loading and the systemic bioavailability over the 6 h application was about 10%, suggesting that the rest (30%) had accumulated in the skin tissues. The gel was applied for 6 h on the same site or on a new site after the first 6 h-application to learn the effect of repeated applications on FP absorption. The maximum FP concentration after the second application on the virgin skin was slightly higher than that after the first application, as expected in a typical pharmacokinetic process. In contrast, the same site application induced remarkably lower plasma concentration and area under the curve (AUC). A drug-free gel was also utilized to evaluate the effects of the enhancer system. Pretreatment of the drug-free gel on the same site also decreased the FP absorption, whereas post-treatment increased the plasma level of FP, in spite of the removal of the drug gel. These phenomena could be explained by ethanol in the MEW system acting a local irritant and a drug carrier.

Administration, Topical↗

Effects of removal of stratum corneum, delipidization and addition of enhancers, ethanol and l-menthol, on skin permeation of benzoic acid and its 4-n-alkyl substituents in excised guinea pig dorsal skin.

Skin penetration of benzoic acid and its 4-alkyl substituents (methyl, ethyl, n-propyl and n-butyl) through excised guinea pig dorsal skin was examined, and effects of removal of stratum corneum, delipidization and addition of the penetration enhancers, ethanol and l-menthol plus ethanol, were observed. Permeability coefficients, which increased with the increase in their alkyl chain lengths, depended on the ratio of undissociated form of the derivatives. Removal of stratum corneum by tape stripping and delipidization by a chloroform-methanol mixture, whose effects on the permeation were similar, increased the permeability coefficients of the derivatives, especially those of relatively hydrophilic derivatives. Addition of 1% l-menthol plus 15% ethanol increased the permeability coefficient of benzoic acid, but decreased those of ethyl-, n-propyl- and n-butyl-substituents, and differences in the permeability coefficients among these acids almost disappeared. A similar though weaker tendency was observed for the effects of 15% ethanol itself. Analysis of transfer free energy of the methylene group from vehicle to skin revealed that tape stripping and delipidization induced the reduction of lipophilic barrier property, although it still remained after these treatments. The analysis also showed that the addition of the enhancers made the skin relatively more hydrophilic compared to the vehicle, which induced an increase in permeability coefficient of benzoic acid and decreases in those of its lipophilic substituents.

Animals↗

(+)-Menthol and its hydroxy derivatives, novel fungal monoterpenols from the fusicoccin-producing fungi, Phomopsis amygdali F6a and Niigata 2.

In our search for new fusicoccins of unique diterpene glucosides from Phomopsis amygdali, we found that a fragrant substance was formed in the early stage of fusicoccin fermentation. This fragrant constituent was isolated and identified as (+)-menthol, which is a novel fungal metabolite as the enantiomer of well-known peppermint (-)-menthol. (+)-7-Hydroxymenthol and new (+)-(6S)-hydroxymenthol were also isolated and identified as fungal metabolites. In addition, p-menthanetriol, which has been reported as the first fungal monoterpene from the fungus, was also isolated. The possible biosynthetic relationship of these metabolites is discussed.

Carbon Isotopes↗

[The effects of menthol, borneolum and moschus on nasal airflow sensation and nasal resistance].

Menthol and borneolum have been used widely in traditional Chinese medicine for the treatment of nasal obstruction, but the mechanism has been still unknown. The effects of inhalation of menthol, borneolum, moschus on nasal resistance and airflow sensation were investigated in 52 subjects. All of these medicines could cause a highly significant enhancement of nasal airflow sensation but had no effect on nasal resistance. Therefore this sort of medicine is regarded as pseudo nasal decongestant.

Adult↗

[Gas chromatographic determination of camphor, menthol, methyl salicylate, thymol in JEIL COOL PAP].

The contents of camphor, menthol, methyl salicylate and thymol in JEIL COOL PAP were determined with gas chromatography by using a stainless steel column (2 m x 3 mm i.d.) packed with 15% DEGS, Chromosorb W (AW-DMCS) 80-100 mesh. Temperature programming was from 70 degrees C to 180 degrees C. The quantitative determination was performed with diphenyl as the internal standard. The internal standard method showed good linearity (r = 0.9995-0.9999). The average recoveries were 99.63% (camphor), 99.83% (menthol), 100.0% (methyl salicylate) and 100.4% (thymol).

Camphor↗

Comparison of acid anhydrides with carboxylic acids in enantioselective enzymatic esterification of racemic menthol.

Optical resolution of racemic menthol has been efficiently achieved by lipase-catalyzed enantioselective esterification in an organic solvent. The performance of the reaction using an acid anhydride as an acyl donor was compared with that using its corresponding free acid. The reactivities of acid anhydrides were found to be higher than their corresponding free acids, but acid anhydrides were also found to be easily hydrolyzed into free acids under the catalysis of the same enzyme. The existence of a too-high concentration of an acid anhydride in a micro-aqueous reaction system will cause dehydration and thus deactivation of the enzyme, and will enhance non-selective esterification of a chiral alcohol, which will reduce the optical purity of the product. All these drawbacks, however, could be effectively overcome in a semi-batch reaction system into which propionic anhydride was continuously fed. This system showed some advantages over a batch reaction system using free propionic acid: the reaction time of dl-menthol was shortened by half, the stability of the enzyme was much enhanced, and the optical purity of the product (l-menthyl ester) was kept at a similarly high level (> 98% ee).

Acids↗

Cool and menthol receptor TRPM8 in human urinary bladder disorders and clinical correlations.

BACKGROUND: The recent identification of the cold-menthol sensory receptor (TRPM8; CMR1), provides us with an opportunity to advance our understanding of its role in the pathophysiology of bladder dysfunction, and its potential mediation of the bladder cooling reflex. In this study, we report the distribution of the cool and menthol receptor TRPM8 in the urinary bladder in patients with overactive and painful bladder syndromes, and its relationship with clinical symptoms. METHODS: Bladder specimens obtained from patients with painful bladder syndrome (PBS, n = 16), idiopathic detrusor overactivity (IDO, n = 14), and asymptomatic microscopic hematuria (controls, n = 17), were immunostained using specific antibodies to TRPM8; nerve fibre and urothelial immunostaining were analysed using fibre counts and computerized image analysis respectively. The results of immunohistochemistry were compared between the groups and correlated with the Pain, Frequency and Urgency scores. RESULTS: TRPM8-immunoreactive staining was observed in the urothelium and nerve fibres scattered in the suburothelium. The nerve fibre staining was seen in fine-calibre axons and thick (myelinated) fibres. There was marked increase of TRPM8-immunoreactive nerve fibres in IDO (P = 0.0249) and PBS (P < 0.0001) specimens, compared with controls. A significantly higher number of TRPM8-immunoreactive axons were also seen in the IDO (P = 0.0246) and PBS (P < 0.0001) groups. Urothelial TRPM8 and TRPM8-immunoreactive thick myelinated fibres appeared unchanged in IDO and PBS. The relative density of TRPM8-immunoreactive nerve fibres significantly correlated with the Frequency (r = 0.5487, P = 0.0004) and Pain (r = 0.6582, P < 0.0001) scores, but not Urgency score. CONCLUSION: This study demonstrates increased TRPM8 in nerve fibres of overactive and painful bladders, and its relationship with clinical symptoms. TRPM8 may play a role in the symptomatology and pathophysiology of these disorders, and may provide an additional target for future overactive and painful bladder pharmacotherapy.

Adult↗

A rapid HPLC method for the quantification of tyrothricin, menthol, and benzocaine in pharmaceutical formulations.

A rapid, sensitive, and accurate reversed-phase HPLC method has been developed for the analysis and quantification of pharmaceutical formulations containing tyrothricin (1), an antibiotic used in antiseptic buccal compressed tablets for local application. The assay has been carried out under isocratic conditions, using a stationary phase of alumina particles coated with polybutadiene and an alkaline mobile phase (pH = 8.2). No HPLC method was reported for the analysis of 1. So, this new technique is an alternative to the slow and tedious microbiological methods. On the other hand, it allows the simultaneous quantification of 1, benzocaine (2), and menthol (3), an aromatic compound not currently analyzed by liquid chromatography.

Benzocaine↗

Simple measurement of gluconeogenesis by direct 2H NMR analysis of menthol glucuronide enrichment from 2H2O.

The contribution of gluconeogenesis to fasting glucose production was determined by a simple measurement of urinary menthol glucuronide (MG) 2H enrichment from 2H2O. Following ingestion of 2H2O (0.5% body water) during an overnight fast and a pharmacological dose (400 mg) of a commercial peppermint oil preparation the next morning, 364 micromol MG was quantitatively recovered from a 2-h urine collection by ether extraction and a 125 micromol portion was directly analyzed by 2H NMR. The glucuronide 2H-signals were fully resolved and their relative intensities matched those of the monoacetone glucose derivative. The pharmacokinetics and yields of urinary MG after ingestion of 400 mg peppermint oil as either gelatin or enteric-coated capsules 1 h before breakfast were quantified in five healthy subjects. Gelatin capsules yielded 197 +/- 81 micromol of MG from the initial 2-h urine collection while enteric-coated capsules gave 238 +/- 84 micromol MG from the 2- to 4-h urine collection.

Adult↗

Immobilization of lipase from Candida cylindraceae and its use in the synthesis of menthol esters by transesterification.

Lipase (EC 3.1.1.3) from Candida cylindraceae has been immobilized by the cellulose-titanium chloride method, and on EP-400 polyethylene, with and without glutaraldehyde crosslinking, to give active preparations when assessed by their ability to catalyse the hydrolysis of tributyrin. In both cases, the use of glutaraldehyde crosslinking was shown to improve the stability of the preparations for repeated use. The lipase immobilized on EP-400 polyethylene was found to be effective in transesterification using tributyrin or triacetin as acyl donors with l-menthol as acceptor. The production of methyl butanoate and of methyl acetate using this immobilized preparation was in each case enhanced in the presence of Amberlite IR 47 Anion exchange resin (OH form).

Candida↗

Development and validation of chromatographic methods (HPLC and GC) for the determination of the active components (benzocaine, tyrothricin and menthol) of a pharmaceutical preparation.

Methods are reported for the determination of tyrothricin and benzocaine by HPLC and menthol by GC in the analysis of throat lozenges (tablets) containing all three compounds. After optimization of the variables involved in both HPLC and GC the methods have been characterized and validated according to the guidelines of the Spanish Pharmacopoeia, and applied to both the monitoring of the manufacturing process and the quality control of the final product.

Anesthetics, Local↗

Ca2+-dependent PKC activation mediates menthol-induced desensitization of transient receptor potential M8.

In 1950, Hensel and Zotterman reported cooling-induced desensitization of cold receptors by extracellular discharge recordings of cold fibers. Since then, however, its intracellular mechanism has remained unresolved. We studied menthol-induced desensitization of cold/menthol receptors (TRPM8, transient receptor potential M8) expressed in HEK cells. TRPM8 desensitization depended on extracellular Ca2+ ions, indicating that Ca2+ influx-induced [Ca2+]i elevation caused the desensitization. We studied whether Ca2+-dependent kinase, PKC, mediated TRPM8 desensitization. PMA, a PKC activator, desensitized TRPM8. Inhibitor of Ca2+-dependent PKC isozymes specifically abolished PMA-induced TRPM8 desensitization. PMA similarly desensitized wild type TRPM8 and mutant TRPM8, in which serine or threonine residues in some putative PKC phosphorylation sites were replaced by alanine. PMA treatment did not induce internalization of TRPM8. As the basis of cooling-induced desensitization of cold receptors, we conclude that cooling-activated TRPM8 causes Ca2+-dependent PKC isozymes to desensitize TRPM8 itself.

Animals↗