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PubMed1999

Antimicrobial activity of the essential oil of Calamintha nepeta and its constituent pulegone against bacteria and fungi.

The chemical composition of the essential oil of Calamintha nepeta and its antimicrobial activity against Listeria monocytogenes, Bacillus cereus, Salmonella veneziana, S. paratyphi B. S. typhimurium, Fusarium moniliforme, Botrytis cinerea, Aspergillus niger and Pyricularia oryzae have been studied. Moreover the main constituents of the oil (limonene, menthone, pulegone, menthol) have been tested against the same microorganisms. Only pulegone showed antimicrobial activity, particularly against all the Salmonella species.

Anti-Bacterial Agents↗

PubMed2004

Transdermal delivery system for zidovudine: in vitro, ex vivo and in vivo evaluation.

The objective of this study was to prepare a transdermal delivery system (TDS) for zidovudine (AZT) with a combination of menthol and oleic acid as penetration enhancers incorporated in hydroxypropyl methylcellulose, and to evaluate ex vivo as well as in vivo permeation across rat skin. It was found that AZT in gel formulation was stable in both refrigerated as well as accelerated stability conditions for 3 months and further, the gel did not significantly retard the permeability of AZT across the skin in comparison with solution formulation. Ex vivo steady state flux of AZT across rat skin from gel was 2.26 mg cm(-2) h(-1), which is sufficient to achieve therapeutic plasma concentrations. Intravenous pharmacokinetic parameters of AZT in rats were determined and used together with ex vivo flux data to generate theoretical plasma profiles of AZT and compared with plasma concentrations achieved after application of TDS. Further, steady state plasma concentrations of drug following multiple applications of TDS were determined and good correlations between ex vivo and in vivo data were observed. In addition, the combination of penetration enhancers used at 2.5% w/w in this study proved efficient in achieving sufficient enhancement in the transdermal permeability of AZT across rat skin with reduced skin irritation potential when compared with individual penetration enhancers at higher concentrations.

Adjuvants, Pharmaceutic↗

PubMed2005

Transdermal delivery of imipramine hydrochloride: development and evaluation (in vitro and in vivo) of reservoir gel formulation.

The in vitro permeation studies of imipramine hydrochloride (IMH) reported earlier from our laboratory showed that a combination of menthol (2.5% w/v) and oleic acid (2.5% w/v) worked well in terms of safety and efficacy. The main objective of this study was to evaluate the in vivo performance of this combination; in order to do that, penetration enhancers were incorporated in a hydro-alcoholic gel of hydroxypropylmethyl cellulose along with IMH and used as the drug matrix in a reservoir transdermal patch. A stability study of IMH gel was performed at 40 degrees C/75% RH for 2 months. The results of this study indicate that gels of IMH stored at 40 degrees C/75% RH turned yellow brown in 2 months and the small change in viscosity of gel at 40 degrees C/75% RH had an insignificant effect on the release rate of IMH from the gel (p>0.05). The in vivo performance of the gel was tested in rats using a reservoir transdermal patch, which consisted of a backing membrane, drug matrix and retaining membrane with an area of 12.5 cm2. Plasma concentrations of 3 microg/ml of IMH were achieved and in a histopathological study 24 h occlusion was found to be safe.

Administration, Cutaneous↗

PubMedDate not supplied

Modulation of calcium-currents by capsaicin in a subpopulation of sensory neurones of guinea pig.

The action of capsaicin (CAP) on the total Ca2+ current was examined in internally perfused voltage-clamped dorsal root ganglion (DRG) neurones of guinea pigs. CAP changed the total Ca2+ current in about 50% of the investigated DRG neurones ("CAP-sensitive" neurones) in the following way: (I) a transient increase of the current amplitude at potentials between -35 mV and about -10 mV was accompanied by a shift of the current-voltage relation towards negative potentials by 5-8 mV; (II) the current inactivation was accelerated at potentials positive to about -35 mV; and (III) the current activation of Ca2+ currents (time to peak values) was also accelerated. Separated low voltage-activated (T-type) currents at potentials negative to about -35 mV were either not affected or reduced. It remains undecided whether CAP increases T-type currents in a particular potential range or activates an N-type current. External application of 50 microM Ni2+ blocks the effect of CAP, but does not affect the acceleration of the high voltage-activated (L-type) current inactivation induced by menthol. This appears to exclude a CAP effect on L-type current inactivation. "CAP sensitive" and "CAP insensitive" neurones could be discriminated by their different Ca2+ currents: the former demonstrate both fast and slow inactivating currents while the latter have only L-type currents. The observed changes of fast-inactivating Ca2+ currents may be related to the specific action of CAP on peptidergic sensory neurones.

Animals↗

PubMed1996

A comparison of topical Emla cream with Bonain's solution for anesthesia of the tympanic membrane during tympanocentesis.

The purpose of this study was to investigate the relative efficacy of Emla cream (a eutectic formulation of lignocaine and prilocaine) and Bonain's solution (equal amounts of cocaine hydrochloride, menthol and phenol) as local anesthetic agents to the tympanic membrane. Fifty patients undergoing bilateral tympanocentesis were included. The patients were used as their own controls. One tympanic membrane was anesthetized with Emla cream and the other with Bonain's solution. The operating microscope was used. After a 30 min analgesic time, tympanocentesis was performed with aspiration of middle ear secretions. Each patient was then asked to fill in a questionnaire that graded the severity of pain experienced: none, very mild, mild, moderate or severe. Findings showed that Bonain's solution was more effective in tympanocentesis. All patients experienced no pain to very mild pain. With Emla cream 15 of 50 patients experienced mild to moderate pain. No significant side effects occurred with either anesthetic agent.

Adolescent↗

PubMed1990

Ampullary electroreceptors in catfish (Teleostei): temperature dependence of stimulus transduction.

The response properties of ampullary electroreceptors have been studied in the catfish Ictalurus nebulosus at skin temperatures between 5 and 35 degrees C. A unimodal relationship between spontaneous activity and temperature was obtained. Mean (+/- SEM) peak discharge rate was 57.3 +/- 1.8 impulses s-1 at 25 degrees C; the receptors were active at 5 degrees C (15.0 impulses s-1) and at 35 degrees C (31.5 impulses s-1). There were no dynamic responses to temperature changes in either the warming or cooling direction. The shape of the frequency characteristic depended on temperature: the peak of the gain curve shifted to low frequencies at low temperatures. There was a concomitant change of the phase characteristic: the intersection at zero degree phase angle shifted to higher frequencies with an increase of temperature, thus increasing the lead at lower frequencies and decreasing the lag at higher frequencies. Latency after combined excitatory and inhibitory impulse stimulation was temperature dependent, ranging from 16.4 ms (5 degrees C) to 5.6 ms (35 degrees C). Application of the specific calcium channel blocker menthol (0.2 mM) suppressed spontaneous activity, the effect becoming more prominent at higher temperatures. Sensitivity to sinusoidal electrical stimulation was also impaired, but to a lesser degree and mainly at lower temperatures. We conclude that the filter properties of the receptor organ can be modelled by a band-pass filter in series with a latency, both of which are temperature dependent. These filter properties might be partially based on the activation kinetics of the transduction channels.

Animals↗

PubMed1989

Is there directional smelling?

The aim of the present study was to establish the crucial precondition for directional smelling, i.e. the ability of humans to discriminate between odorous stimuli perceived either from the right or from the left side. When the 'pure' odorants hydrogen sulphide or vanillin were used as stimulants localization was random. On the other hand stimulation with carbon dioxide or menthol yielded identification rates of more than 96%. These results established the fact that directional orientation, considering single momentary odorous sensations, can only be assumed, when the olfactory stimulants simultaneously excite the trigeminal somatosensory system.

Adult↗

PubMed1984

Inhibition of human lecithin cholesterol acyltransferase by monoterpenes.

The lecithin-cholesterol acyltransferase activity of human plasma was found to be inhibited by Rowachol, a proprietary mixture of pure monoterpenes. Menthol, the major ingredient in Rowachol (32%), and a number of other monoterpenes were found to inhibit the enzyme independently. Concentrations of monoterpenes required to achieve 50% inhibition were of the same order of magnitude as the cholesterol concentration present in the reaction mixture.

Camphor↗

PubMedDate not supplied

Pruritus: a practical approach.

Pruritus is usually caused by a primary disorder of the skin, but can also be caused by a systemic disease (Table 1). Some dermatologic conditions that cause pruritus can be inconspicuous or nonspecific (Table 2), while others are usually apparent on physical examination (Table 3). Classification of pruritus as localized (Fig. 1) vs. generalized (Fig. 3) can be helpful in arriving at a correct diagnosis. The history and physical examination are the most important diagnostic tools, though laboratory testing for systemic disease may be necessary. In refractory cases, one should consider occult systemic disease (such as malignancy), psychiatric disease (especially depression), and HIV infection. Subsequent referral to a dermatologist may be indicted. When treatment of the underlying cause of pruritus is not possible, antihistamines and topical agents (menthol, phenol, and/or pramoxine) can be helpful.

Anal Canal↗

PubMedDate not supplied

Glucuronidation of 7-hydroxy-4-methylcoumarin by human liver microsomes. Inhibition by certain drugs.

Glucuronidation of 7-hydroxy-4-methylcoumarin (7-OH-4-MC) was comparable in three of the four human liver samples studied. In liver sample IV the glucuronidation rate of 7-OH-4-MC was almost 40% of that in the other samples. That might be due to interindividual variation in the capacity to glucuronidate. Glucuronidation rates were not reduced in the one human liver sample which displayed mild centrilobular cholestasis on histopathology. Furosemide (FR), salicylic acid (SA), lorazepam (Z) and menthol (MT) inhibited the glucuronidation of 7-OH-4-MC to varying degrees (30-90%). Paracetamol (PA) and 5-hydroxytryptamine (HT) were not inhibitors of the glucuronidation of 7-OH-4-MC. These findings suggest the presence of other UDP-glucuronosyltransferase (UDPGT) isozymes in the human liver microsomes which are responsible for the glucuronidation of PA and HT than those which glucuronidate 7-OH-4-MC.

Coumarins↗

PubMed2005

ThermoTRP channels and cold sensing: what are they really up to?

Cooling is sensed by peripheral thermoreceptors, the main transduction mechanism of which is probably a cold- and menthol-activated ion channel, transient receptor potential (melastatin)-8 (TRPM8). Stronger cooling also activates another TRP channel, TRP (ankyrin-like)-1, (TRPA1), which has been suggested to underlie cold nociception. This review examines the roles of these two channels and other mechanisms in thermal transduction. TRPM8 is activated directly by gentle cooling and depolarises sensory neurones; its threshold temperature (normally approximately 26-31 degrees C in native neurones) is very flexible and it can adapt to long-term variations in baseline temperature to sensitively detect small temperature changes. This modulation is enabled by TRPM8's low intrinsic thermal sensitivity: it is sensitised to varying degrees by its cellular context. TRPM8 is not the only thermosensitive element in cold receptors and interacts with other ionic currents to shape cold receptor activity. Cold can also cause pain: the transduction mechanism is uncertain, possibly involving TRPM8 in some neurones, but another candidate is TRPA1 which is activated in expression systems by strong cooling. However, native neurones that appear to express TRPA1 respond very slowly to cold, and TRPA1 alone cannot account readily for cold nociceptor activity or cold pain in humans. Other, as yet unknown, mechanisms of cold nociception are likely.

Adaptation, Physiological↗

PubMed2004

Effect of monoterpenes on lipid oxidation in maize.

The monoterpenes 1,8-cineole, thymol, geraniol, menthol and camphor strongly inhibited the root growth of Zea mays L. seedlings. They induced an oxidative stress as measured by the production of malondialdehyde, conjugated dienes and peroxides. This oxidative stress depended on the length of the exposure and on the monoterpene applied. The total fatty acid content was measured and fatty acid composition was analyzed. Unsaturated fatty acids increased in the treated samples. The alcoholic and non-alcoholic monoterpenes appeared to have different modes of action.

Acyclic Monoterpenes↗

PubMed2005

The de novo design of median molecules within a property range of interest.

In this paper an application is presented of the median molecule workflow to the de novo design of novel molecular entities with a property profile of interest. Median molecules are structures that are optimised to be similar to a set of existing molecules of interest as an approach for lead exploration and hopping. An overview of this workflow is provided together with an example of an instance using the similarity to camphor and menthol as objectives. The methodology of the experiments is defined and the workflow is applied to designing novel molecules for two physical property datasets: mean molecular polarisability and aqueous solubility. This paper concludes with a discussion of the characteristics of this method.

Camphor↗

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↗

PubMed1983

Demonstration that limonene is the first cyclic intermediate in the biosynthesis of oxygenated p-menthane monoterpenes in Mentha piperita and other Mentha species.

The volatile oil of mature Mentha piperita (peppermint) leaves contains as major components the oxygenated p-menthane monoterpenes l-menthol (47%) and l-menthone (24%) as well as very low levels of the monoterpene olefins limonene (1%) and terpinolene (0.1%), which are considered to be probable precursors of the oxygenated derivatives. Immature leaves, which are actively synthesizing monoterpenes, produce an oil with comparatively higher levels of limonene (approximately 3%), and isolation of the pure olefin showed this compound to consist of approximately 80% of the l-(4S)-enantiomer and approximately 20% of the d-(4R)-enantiomer. The time course of incorporation of [U-14C]sucrose into the monoterpenes of M. piperita shoot tips was consistent with the initial formation of limonene and its subsequent conversion to menthone via pulegone. d,l-[9-3H]Limonene and [9,10-3H]terpinolene were prepared and tested directly as precursors of oxygenated p-menthane monoterpenes in M. piperita shoot tips. Limonene was readily incorporated into pulegone, menthone, and other oxygenated derivatives, whereas terpinolene was not appreciably incorporated into these compounds. Similarly, d,l-[9-3H]limonene was specifically incorporated into pulegone in Mentha pulegium and into the C-2-oxygenated derivative carvone in Mentha spicata, confirming the role of this olefin as the essential precursor of oxygenated p-menthane monoterpenes. Soluble enzyme preparations from the epidermis of immature M. piperita leaves converted the acyclic terpenoid precursor [1-3H]geranyl pyrophosphate to limonene as the major cyclic product, providing a further indication that this olefin plays a central role in the formation of oxygenated monoterpenes in Mentha. No free intermediates were detected in the cyclization of geranyl pyrophosphate to limonene, suggesting that the olefin is the first cyclic intermediate to arise in the pathway, and resolution of the biosynthetic limonene, by crystallization of the derived d- and l-carvoximes, indicated an enantiomer mixture nearly identical to that isolated from the leaf oil.

Cell-Free System↗

PubMed1986

Inhibitors of ex vivo aggregation of human platelets induced by decompression, during reduced barometric pressure.

It has been shown experimentally ex vivo that human platelet aggregation is induced by decompression (reduced pressure) produced by various means, i.e., reduced barometric pressure, reduced hydrostatic pressure, and reduced hydrodynamic pressure due to Bernoulli's principle. We report here that the spontaneous platelet aggregation induced by reduced barometric pressure (253 torr for three hours) is inhibited by 1:10(7) diluted Japanese herbal plant oil (JHP) and also by two of its major constituents, menthone and menthol with the median inhibitory concentration (IC50) in the millimolar range. These drugs gave essentially similar results when collagen and ADP were used as aggregating agents. Inhibitor concentrations were determined by microscopic examination of platelets in wet preparations when the aggregating stimulus was reduced pressure and by optical aggregometry when collagen and ADP were the aggregating agents. Potential usefulness of these compounds in the prevention of decompression syndrome (DCS) and acute mountain sickness (AMS) are discussed.

Atmospheric Pressure↗

PubMed1992

Antibacterial activity of essential oil components.

Antibacterial activity of fifteen essential oil components towards food borne Staphylococcus sp., Micrococcus sp., Bacillus sp. and Enterobacter sp. was studied by an agar plate technique. Cinnamic aldehyde was the most active compound followed by citral, geraniol, eugenol and menthol. At 500 micrograms/ml, cinnamic aldehyde completely inhibited the bacterial growth for more than 30 days at 30 degrees C that was comparable to 200 micrograms/ml of butylated hydroxy anisole (BHA). At lower temperatures, 25 and 20 degrees C, antibacterial activity of the five essential oil components increased. Addition of sodium chloride at 4% level (w/v) in the medium had no effect on the inhibitory activity of cinnamic aldehyde. In mixtures of cinnamic aldehyde and eugenol or BHA an additive effect was observed.

Acrolein↗

PubMed2005

Headspace solid-phase microextraction gas chromatography-mass spectrometry method for the identification of cosmetic ingredients causing delamination of packagings.

A headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) method using a 75 microm Carboxen polydimethylsiloxane fibre was used to identify volatile compounds of cosmetic formulations responsible for causing loss of adhesion between layers of multilayer packagings. To obtain the sample, the sachet with the product was kept in an oven at 40 degrees C in order to favour the migration of the aggressive compounds to the inner layers. Then the sachet was manually delaminated and the aluminium/polyester and polyethylene layers were analysed. The cosmetic product was also analysed by HS-SPME-GC-MS. Several compounds used in the cosmetic industry such as perfumes or fixing agents were detected in the inner layers of the laminated material, showing the migration of them through the layer in contact with the product (polyethylene). Phenoxy ethanol, beta-linalool, menthol and p-propenylanisole are suspected to be responsible for the loss of adhesion. In order to provide a complete overview of the cause of the aforementioned phenomenon, the packaging material was exposed to the cosmetic products in order to measure the decrease of the adhesion strength with time. It was observed that the product with a higher phenoxy ethanol concentration caused a higher loss of adhesion strength. The results obtained showed that this method is suitable for identifying aggressive compounds in cosmetic products, as well as for giving prior information about which products may be problematic for packaging in sachets.

Absorption↗