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At least 523 records · Page 29Linked to original sources
PubMed2001

Effect of Mentha x piperita essential oil and monoterpenes on cucumber root membrane potential.

Peppermint (Mentha piperita L.) essential oil and its main components were assessed for their ability to interfere with plant plasma membrane potentials. Tests were conducted on root segments isolated from etiolated seedlings of cucumber (Cucumis sativus L.). Increasing the concentration of peppermint essential oil from 5 to 50 ppm caused a decrease in membrane potential (Vm) hyperpolarization of 10-3 mV, whereas concentrations from 100 up to 900 ppm caused an increasing depolarization of Vm (from 5 to 110 mV). When tested at 300 ppm, (+)-menthyl acetate, (-)-limonene and 1,8-cineole did not exert any significant effect on V(m), whereas (+)-menthofuran (73 mV), (+)-pulegone (85 mV), (+)-neomenthol (96 mV), (-)-menthol (105 mV) and (-)-menthone (111 mV) showed increased ability to depolarize V(m). A plot of log of octanol-water partition coefficient (K(ow)) against their depolarizing effect showed a significant negative correlation, suggesting that among all monoterpenoids increased membrane depolarization depends on lower K(ow). However, among monoterpene ketones, alcohols and furans, increased membrane depolarization is associated with a decline in water solubility. The possible effect of monoterpenoids on membrane ion fluxes is also discussed, since changes in the bioelectric potential of cells imply changes in the flux of ions across the plasma membrane

Cucumis sativus↗
PubMed1997

The contribution of cytotoxicity to DNA-effects in the single cell gel test (comet assay).

We evaluated genotoxic and cytotoxic effects of the three non-mutagenic and non-carcinogenic compounds p-nitrophenol, D-menthol and sodium N-lauroyl sarcosine which have previously been shown to induce DNA double strand breaks (DNA dsb) secondary to induced cytotoxicity. We tested whether genotoxic effects in the alkaline single cell gel test (comet assay) may be confounded by cytotoxicity-induced DNA dsb. Cell viability was determined at the end of the treatment using the fluorescein diacetate/ethidium bromide-assay and plating efficiency was used as an indicator of long-term survivability. Experiments with V79 Chinese hamster cells and human white blood cells revealed negative results in the comet assay despite strong cytotoxic effects. However, cells with extremely fragmented DNA ('clouds') occurred but were excluded from the evaluation under the principle that they represent dead cells. We also noticed a significant loss of cells at cytotoxic concentrations that might be attributed to the induction of highly fragmented DNA which is lost during electrophoresis. Since the comet assay allows the determination of DNA effects on the single cell level, a confounding effect of cytotoxicity on test results can be avoided.

Animals↗
PubMed2003

Lessons from peppers and peppermint: the molecular logic of thermosensation.

Sensory neurons report a wide range of temperatures, from noxious heat to noxious cold. Natural products that elicit psychophysical sensations of hot or cold, such as capsaicin or menthol, were instrumental in the discovery of thermal detectors belonging to the transient receptor potential (TRP) family of cation channels. Studies are now beginning to reveal how these channels contribute to thermosensation and how chemical signaling pathways, such as those activated by tissue injury, alter thermal sensitivity through TRP channel modulation. Analysis of TRP channel expression among sensory neurons is also providing insight into how thermal stimuli are encoded by the peripheral nervous system.

Animals↗
PubMed2003

Measurement of long range H,C couplings in natural products in orienting media: a tool for structure elucidation of natural products.

In this paper we show that water insoluble compounds dissolved in poly-gamma-benzyl-glutamate are amenable to the measurement of a number of homo- and heteronuclear dipolar couplings. The sensitivity and experimental precision of dipolar couplings are sufficient to obtain a good match with the structure. In order to achieve the necessary precision for H,C dipolar couplings between protons and carbons that are not directly bound a new method for the measurement of heteronuclear long range couplings is introduced that allows a one-parameter fit to a HSQC-based experiment as reference experiment. The methodology is applied to menthol (1R, 3S, 4R).

Carbon↗
PubMed2003

Effects of C fiber blockade on cardiorespiratory responses to laryngeal stimulation in concious lambs.

The primary aim of the study was to explore cardiorespiratory reflexes originating from laryngeal C fiber endings in the neonatal period. Seventeen lambs were instrumented for recording glottal adductor and diaphragm EMG, heart rate, systemic arterial pressure and respiratory movements. C fiber blockade was induced in eight lambs by 30 mg/kg capsaicin, the remaining nine lambs serving as controls. Cardiorespiratory reflexes were induced in non-sedated lambs by flowing air, menthol or 13% CO2, or by injecting water or 50 microg capsaicin in the laryngeal inlet through an endoscope. Responses to all stimuli but capsaicin were similar between the two groups. While cardiorespiratory responses were induced by capsaicin in control lambs, the responses were significantly inhibited in lambs with C fiber blockade. We conclude that laryngeal C fiber endings are functional and responsible for laryngeal chemoreflexes in newborn lambs.

Analysis of Variance↗
PubMedDate not supplied

Use of Rhodotorula minuta live cells hosted in water-in-oil macroemulsion for biotrasformation reaction.

A lecithin/water/isooctane water-in-oil (w/o) macroemulsion was used as a host system for biotransformation reactions. In particular, the hydrolytic activity of the yeast Rhodotorula minuta toward (+/-)-succinic acid bis-2-isopropyl-5-methylcyclohexyl ester and p-nitrophenyl butyrate is reported. Evidence that R. minuta entrapped in w/o macroemulsion is able to hydrolyze the p-nitrophenyl butyrate ester is presented. By performing the yeast-catalyzed hydrolysis of (+/-)-succinic acid bis-2-isopropyl-5-methylcyclohexyl ester, the synthesis of (-)-menthol was obtained, indicating that R. minuta retains its high stereoselectivity in the macroemulsion system. In addition, no significant differences were observed among the hydrolysis rates and yields obtained using yeast cells hosted into w/o macroemulsions containing different amounts of water. Optical microscopy studies on the distribution of diameters of the dispersed phase indicate that the macroemulsion system is stable in terms of polydispersity. The diameter of the w/o macroemulsion droplets is indeed constant irrespective of the addition of water and/or chemicals (involved in the biotransformation reaction) to the system hosting yeast cells. The reactor devised here might be applied to other interesting bioconversion processes.

Biotransformation↗
PubMed2000

Suppression of the furylfuramide-induced SOS response by monoterpenoids with a p-menthane skeleton using the Salmonella typhimurium TA1535/pSK1002 Umu test.

Suppression of the furylfuramide-induced SOS response by 25 kinds monoterpenoids (hydrocarbons, alcohols, ketones, and aldehydes) with a p-menthane skeleton was studied. Suppression of the SOS-inducing activity by monoterpenoids was determined in the umu test using Salmonella typhimurium TA1535/pSK1002. The terpene alcohols, ketones, and aldehydes had potent suppressive effects, but the hydrocarbons did not. Especially, (+)-menthol, (+)-pulegone, piperitenone, and cuminaldehyde were shown to have the most potent suppressive effects, and the ID(50) (dose for 50% inhibition) was 0.52 micromol/mL.

Alcohols↗
PubMed2002

Essential oil composition of sachalinmint from Norway detected by solid-phase microextraction and gas chromatography-mass spectrometry analysis.

The essential oil of leaves and flowers of sachalinmint [Mentha sachalinensis (Briq.) Kudô] grown in Norway (Trondheim) has been studied by headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry analysis (GC-MS). The essential oil content increased linearly in acropetal direction from 1.08% (0-20 cm plant height) to 1.75% (60-80 cm; young leaves and flowers). The steam-distilled samples showed a minor complex matrix with a very high menthol and a much lower menthone content (87.89 and 4.05%, respectively). From testing of HS-SPME unequilibrated exposure times ranging from 10 s to 5 min, an extraction time of 30 s was found to be sufficient to detect both low- and high-eluting compounds. Comparison of HS-SPME and steam-distilled samples established that the same tendencies of increasing menthol/menthone content in the basipetal/acropetal direction could be detected by both analysis methods. With regard to the extraction efficiency, HS-SPME gave additional detailed information about less important terpenic compounds.

Gas Chromatography-Mass Spectrometry↗
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↗
PubMed1992

Percutaneous absorption enhancement of leuprolide.

Chemical enhancers and vehicles were tested for their ability to improve the percutaneous absorption of leuprolide, a nonapeptide (luteinizing hormone releasing hormone analogue; MW 1209.4). In vitro permeabilities in nude mouse, snake, and cadaver skin were evaluated in either Franz diffusion cells or a Bronaugh flow-through system using an HPLC assay. Skin irritation caused by the formulations was evaluated in the rabbit. The chemical enhancer systems investigated strongly enhanced skin penetration of leuprolide. Maximum permeability enhancement of leuprolide acetate can be achieved with a nonirritating formulation containing ethanol, menthol, camphor, methyl salicylate, urea, and hydrogel. The in vitro permeability in nude mouse skin was 10 or 100 times higher than that obtained in cadaver skin, depending on the type of enhancer that was used in the formulation. Snake skin was at least 10 times less permeable than cadaver skin in this study. However, the effects of chemical enhancers on skin permeability were highly dependent on the skin model. Further, the in vitro permeability of leuprolide in the base form was 10 times higher than in the acetate form with the enhancers.

Acetates↗
PubMed2001

Physiology. Cold current in thermoreceptive neurons.

We sense the temperature of our skin and surroundings using specific thermoreceptors, which are sensitive to cold and warmth, but little is known about how these receptors transduce temperature into electrical activity. We have discovered an inward ionic current that is activated by moderate cooling in a small number of rat sensory neurons. This current has features that are found in intact cold receptors, including sensitization by menthol, adaptation upon sustained cooling, and modulation by calcium, and is likely to be important in cold sensing.

Animals↗
PubMed2004

The principle of temperature-dependent gating in cold- and heat-sensitive TRP channels.

The mammalian sensory system is capable of discriminating thermal stimuli ranging from noxious cold to noxious heat. Principal temperature sensors belong to the TRP cation channel family, but the mechanisms underlying the marked temperature sensitivity of opening and closing ('gating') of these channels are unknown. Here we show that temperature sensing is tightly linked to voltage-dependent gating in the cold-sensitive channel TRPM8 and the heat-sensitive channel TRPV1. Both channels are activated upon depolarization, and changes in temperature result in graded shifts of their voltage-dependent activation curves. The chemical agonists menthol (TRPM8) and capsaicin (TRPV1) function as gating modifiers, shifting activation curves towards physiological membrane potentials. Kinetic analysis of gating at different temperatures indicates that temperature sensitivity in TRPM8 and TRPV1 arises from a tenfold difference in the activation energies associated with voltage-dependent opening and closing. Our results suggest a simple unifying principle that explains both cold and heat sensitivity in TRP channels.

Capsaicin↗
PubMed2000

Purification and characterization of a Baeyer-Villiger mono-oxygenase from Rhodococcus erythropolis DCL14 involved in three different monocyclic monoterpene degradation pathways.

A Baeyer-Villiger mono-oxygenase (BVMO), catalysing the NADPH- and oxygen-dependent oxidation of the monocyclic monoterpene ketones 1-hydroxy-2-oxolimonene, dihydrocarvone and menthone, was purified to homogeneity from Rhodococcus erythropolis DCL14. Monocyclic monoterpene ketone mono-oxygenase (MMKMO) is a monomeric enzyme of molecular mass 60 kDa. It contains 1 mol of FAD/monomer as the prosthetic group. The N-terminal amino acid sequence showed homology with many other NADPH-dependent and FAD-containing (Type 1) BVMOs. Maximal enzyme activity was measured at pH 9 and 35 degrees C. MMKMO has a broad substrate specificity, catalysing the lactonization of a large number of monocyclic monoterpene ketones and substituted cyclohexanones. The natural substrates 1-hydroxy-2-oxolimonene, dihydrocarvone and menthone were converted stoichiometrically into 3-isopropenyl-6-oxoheptanoate (the spontaneous rearrangement product of the lactone formed by MMKMO), 4-isopropenyl-7-methyl-2-oxo-oxepanone and 7-isopropyl-4-methyl-2-oxo-oxepanone respectively. The MMKMO-catalysed conversion of iso-dihydrocarvone showed an opposite regioselectivity to that of dihydrocarvone; in this case, 6-isopropenyl-3-methyl-2-oxo-oxepanone was formed as the product. MMKMO converted all enantiomers of the natural substrates with almost equal efficiency. MMKMO is involved in the conversion of the monocyclic monoterpene ketone intermediates formed in the degradation pathways of all stereoisomers of three different monocyclic monoterpenes, i.e. limonene, (dihydro)carveol and menthol.

Aldehydes↗
PubMedDate not supplied

Transdermal drug delivery systems of a beta blocker: design, in vitro, and in vivo characterization.

The matrix type transdermal drug delivery systems (TDDS) of metoprolol were prepared by film casting technique using a fabricated stainless steel film casting apparatus and characterized in vitro by drug release, skin permeation, skin irritation, and in vivo pharmacodynamic and stability studies. Four formulations were prepared that differed in the ratio of matrix forming polymers. Formulations M-1, M-2, M-3, and M-4 were composed of Eudragit RL-100 and polyvinyl acetate with the following ratios: 2:8, 4:6, 6:4, and 8:2, respectively. All the four formulations carried 10% (w/w) of metoprolol tartrate, 5% (w/w) of dibutylphthalate, and 5% (w/w) of (+/-) menthol in dichloromethane:isopropyl alcohol (80:20 v/v). Cumulative amount of drug released in 48 hr from the four formulations was 79.16%, 81.17%, 85.98%, and 95.04%. The corresponding values for cumulative amount of drug permeated for the said formulations were 59.72%, 66.52%, 77.36%, and 90.38%. On the basis of in vitro drug release and skin permeation performance, formulation M-4 was found to be better than the other three formulations and it was selected as the optimized formulation. The formulation appeared to be stable when stored at 40 degrees C and 75% RH with negligible degradation of the drug. The TDDS was found to be free of any skin irritation as suggested by skin irritation score of 1.16 (<2.00) under Draize score test. Statistically significant reduction in mean blood pressure (p < .01) was achieved in methyl prednisolone-induced hypertensive rats on treatment with the TDDS.

2-Propanol↗
PubMed1999

Nicotine metabolism variability and nicotine addiction.

Individual variation in nicotine metabolism may play a role in a person's level of smoking, as well as in the transition from initiation to maintenance of a smoking behavior pattern. Since there is a paucity of research on nicotine metabolism in youth that smoke, a brief review of salient aspects of nicotine metabolism in adults provides a basis from which to extrapolate. We do know that factors influencing the rate of nicotine metabolism include differences in nicotine intake and absorption, inhalation patterns, genetic polymorphisms of pertinent enzymes, as well as daily activities such as meal consumption. Variability is illustrated with differences in cotinine levels identified in African-American and Caucasian women and in menthol and nonmenthol smokers. There are a number of areas where more information to improve understanding the initiation and maintenance of smoking behavior is needed. Characterization of nicotine metabolism and smoking topography in youth from multiple ethnic groups who are engaged in smoking initiation is currently lacking. Important measures of smoke constituent exposure such as carbon monoxide, nicotine and cotinine, as well as puff volume and duration and respiratory movements should be addressed. While there are numerous factors that impact initiation and maintenance of smoking behavior, nicotine metabolism may represent one important aspect.

Absorption↗
PubMed1976

Effect of inhaling medication vapors from a colds preparation on murine pulmonary bacterial defense systems.

The usefulness of murine pulmonary defense systems as a means for assessing potential toxicity was further confirmed. Recent investigations had indicated that the effects of a chemical agent on mucociliary transport and phagocytic function comprised a sensitive indicator. As one example of such an application, because of the wide usage of proprietary colds preparations containing volatile oils, as well as the use of such oils in various industries, it is important to reassess the potential of such preparations for toxicity when new test systems become available. Mice and rats were exposed to vapors of camphor, menthol, eucalyptol, and turpentine, as contained in a commonly used colds preparation, for 4 and 8 hr prior to challenge with aerosols of radiolabeled Staphylococcus aureus. The exposure system simulated conditions present when the colds preparation is vaporized according to directions for use. Rates of pulmonary bacterial transport and inactivation, as well as of phagocytic ingestion, were determined following exposure to the colds preparation. Each of these rates was unchanged by the treatment. Thus, in this biological system exposure to therapeutic levels of the colds preparation did not impair mucociliary or phagocytic function.

Animals↗
PubMed2001

Pulmonary peptide delivery: effect of taste-masking excipients on leuprolide suspension metered-dose inhalers.

The purpose of this study was to evaluate the effect of taste-masking excipients on in vitro and in vivo performance of a leuprolide metered-dose inhaler (MDI) suspension formulation. Taste-masking excipients (aspartame and menthol) were added to a leuprolide suspension MDI formulation. The leuprolide MDI formulation with the taste-masking excipients was characterized in terms of milling time, particle size distribution, dose delivery and uniformity, and drug absorption in dogs. The data were compared with a formula that did not contain taste-masking excipients. It was found that the longer milling time for the leuprolide suspension with the taste-masking excipients was required to obtain a similar particle size distribution compared with the formula without taste-masking excipients using a fluid energy mill. Although measurable differences in mass median aerodynamic diameter (MMAD) and geometric standard deviation (GSD) were not observed between the two formulations, the percent of particles < or = 5 microns and the actuator retention for the formula with the taste-masking excipients were significantly different from the formula without taste-masking excipients using the Marple-Miller cascade impactor. Taste-masking excipients did not show a significant effect on valve delivery and through-can dose uniformity. However, the mean ex-actuator dose was 150.4 mg for the formula with the taste-masking excipients and 162.2 mg for the reference formula, respectively, indicating a significant difference. In tracheostomized dogs, both formulations showed comparable pharmacokinetic parameters including Cmax, Tmax, AUC0-12 and bioavailability (F%), indicating that the taste-masking excipients do not have an effect on lung absorption of leuprolide acetate. Therefore, inclusion of taste-masking excipients in the leuprolide MDI suspension formulation showed a significant impact on drug micronization, exactuator dose, and particle deposition pattern. Mechanistically, the unfavorable performance of leuprolide MDI in the presence of taste-masking excipients could be due to modification of the properties of the suspension itself and alteration of propellant evaporation following actuation.

Administration, Inhalation↗