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At least 937 records · Page 52Linked to original sources
PubMed1999

In vitro percutaneous absorption enhancement of propranolol hydrochloride through porcine epidermis by terpenes/ethanol.

The purpose of this study was to investigate the mechanism(s) of percutaneous absorption enhancement of propranolol hydrochloride (PHCL) across porcine epidermis by terpenes (e.g. menthone and limonene) in combination with ethanol. The in vitro percutaneous absorption experiments were performed using Franz diffusion cells. The solubility of PHCL in control and enhancer solutions was determined through high-performance liquid chromatography. Partitioning of PHCL to powdered SC from control or enhancer solutions was also determined in order to investigate the binding of PHCL to the SC from the SC/enhancer system. Fourier transform infrared spectroscopy (FT-IR) was employed to study the biophysical changes in stratum corneum (SC) lipids. The in vitro macroscopic barrier properties were investigated by measuring transepidermal water loss (TEWL) using Tewameter. Five percent menthone or limonene in combination with ethanol (EtOH) (menthone/EtOH or limonene/EtOH) significantly increased (P<0.05) the flux of PHCL through porcine epidermis in comparison to the control (EtOH). The partitioning of PHCL to the SC from the SC/enhancer system was also significantly greater than the SC/control system. The above enhancers showed a decrease in the peak heights and areas for both asymmetric and symmetric C-H stretching absorbances in comparison with the untreated SC, indicating the SC lipids extraction. Menthone/EtOH and limonene/EtOH enhanced (P<0.05) the in vitro TEWL through the epidermis in comparison to the control. Thus, an enhancement in the flux of PHCL by menthone/EtOH and limonene/EtOH is due to SC lipid extraction, macroscopic barrier perturbation, and improvement in the partitioning of the drug to the SC.

Animals↗
PubMedDate not supplied

Late effects of local anesthetics on tympanic membrane structure.

With the rat tympanic membrane used as a model, various topical anesthetics in current clinical use (phenol, Bonain's liquid, and Xylocaine spray) were tested. Structural changes were observed for up to five months from the time of anesthetic application. The most protracted changes affect the lamina propria, which exhibits a pronounced thickening. The extent of the changes, however, differs according to the agent used; for example, phenol applied to discrete areas exhibited the least widespread changes. In the tympanic portion of the lamina propria, the connective tissue was loosely packed with less regularly arranged collagen fibers, while a tightly packed fiber bundle existed on the meatal side. It is inferred that the submucosal connective tissue layer is the portion of the connective tissue layer where the remodeling and reconstruction of the fibrous layer occur.

Aerosols↗
PubMed2000

Olfactory experience decreases responsiveness of the olfactory bulb in the adult rat.

We recently reported the existence of dramatic modifications of the olfactory bulb reactivity following a very simple manipulation of the olfactory input as an exposure to an odorant. The present study aimed at testing the possibility that such effects could depend on the nature of the exposure odour. For this purpose, rats were exposed 20 min per day during six consecutive days to cineole, methyl-amyl ketone, isoamyl acetate or with no odour in the control group. On day 7, rats were anaesthetized and the spontaneous activity of mitral/tufted cells was recorded along with their responses to the familiar odour and to four novel odours. Results revealed that: (i) the firing frequencies were not significantly different in the four groups; (ii) the proportion of excitatory responses was considerably decreased in the exposed groups while the number of non-responses was significantly enhanced; (iii) excitatory responses were decreased not only to the familiar odour but also to four other novel odours; (iv) this lower responsiveness was long lasting at least for isoamyl acetate exposure; and (v) increasing concentration of test odours was not enough to allow mitral/tufted cells to recover control responsiveness. All of these effects have a differential importance according to the exposure odour. In particular, the more powerful an odour is in activating control cells, the more non-specific the decrease in mitral/tufted cell reactivity is. Hypotheses on the underlying mechanisms are advanced.

Action Potentials↗
PubMed1998

Lack of histological cerebellar changes in Wistar rats given pulegone for 28 days. Comparison of immersion and perfusion tissue fixation.

Pulegone was given orally by gavage to groups of 28 SPF Wistar rats at dosage levels of 0 or 160 mg/kg body weight per day for 28 days. Clinically treated animals showed slackness, depression, decreased food consumption, and body weight. The loss of body weight was accompanied by a marked decrease in plasma creatinine. In contrast to earlier results, this study did not reveal occurrence of cyst-like spaces in the white matter of cerebellum using either perfusion or immersion tissue fixation techniques. Pulegone increased plasma alkaline phosphatase and relative liver weight indicating an adverse effect on the liver.

Animals↗
PubMed2001

Evaluation and structure-activity relationship of synthesized cyclohexanol derivatives on percutaneous absorption of ketoprofen using artificial neural network.

The effect of 35 newly synthesized O-ethylmenthol (MET) derivatives on percutaneous absorption of ketoprofen was investigated in rats. In order to understand the relationship between the structure of compounds and promoting activity (structure-activity relationship), an artificial neural network (ANN) was employed. In the in vivo percutaneous absorption study, male Wistar rats, weighing 160-180 g, were used. The apparent penetration rate (Rp) was estimated based on a pharmacokinetic model with a constant rate of penetration through the skin after a lag time. As an index of the promoting activity of each compound, an enhancement factor (Ef), defined as follows, was used: Ef=Rp(with enhancer)/Rp(without enhancer). An irritation evoked on rat skin was microscopically judged at the end of the in vivo percutaneous absorption experiment and evaluated as a total irritation score (TIS). Ef and TIS were selected as output variables to determine the ANN structure. Calculated logP, molecular weight, steric energy (SE), van der Waals area, van der Waals volume, dipole moment, highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) were used as factors to determine the structural nature of cyclohexanol derivatives. Among these parameters, logP, SE and LUMO significantly affected the prediction of Ef and TIS. The predicted values of Ef and TIS coincided well with in vivo percutaneous absorption experimental values. However, results observed with a linear regression method were poor compared with the ANN approach. The contribution index of logP was approximately 50% in the prediction of Ef, suggesting that lipophilicity among physicochemical properties contributes most of the promoting activity of these compounds.

Animals↗
PubMed2001

Effect of menthone on the in vitro percutaneous absorption of tamoxifen and skin reversibility.

The effect of penetration enhancer (i.e., 1, 2, 3 and 5% menthone in combination with 50% ethanol (EtOH)) was investigated on the in vitro percutaneous absorption of tamoxifen, and post-recovery epidermal permeability after removal of the above enhancer. The flux of tamoxifen with menthone in combination with 50% EtOH was significantly greater (P<0.05) than the control (50% EtOH). The flux of tamoxifen increased with increasing concentrations of menthone. The post-recovery flux through enhancer exposed epidermis was significantly decreased (P<0.05) as compared to pre-recovery. However, post-recovery flux of tamoxifen through the enhancer-exposed epidermis did not completely recover to the baseline (i.e., post-recovery flux through phosphate buffered saline, pH 7.4 treated epidermis).

Administration, Topical↗
PubMed2003

Enhanced iontophoretic delivery of buspirone hydrochloride across human skin using chemical enhancers.

Buspirone hydrochloride (BH) is a structurally and pharmacologically unique anxiolytic that is used to treat a variety of different anxiety conditions. The marketed product is named BuSpar. The in vitro iontophoretic delivery of BH through human skin was investigated in order to evaluate the feasibility of delivering a therapeutic dose of BH by this route. We also examined the influence of co-formulations of chemical enhancers (Azone, oleic acid, menthone, cineole, and terpineol) on BH permeation, both without iontophoresis and with iontophoresis-to look for possible synergistic effects. By applying iontophoresis at 0.5 mA/cm(2), it was possible to achieve a BH steady state flux of approximately 350 microg/cm(2)h, which would be therapeutically effective if clinically duplicated. Importantly, 24 h of iontophoresis at 0.5 mA/cm(2) did not affect skin morphology and after the current was switched off, the skin's permeability to BH rapidly reverted to its pre-iontophoretic level. Without iontophoreis, BH transdermal flux was significantly enhanced by the application of 2.5% (v/v) concentrations of Azone, oleic acid, or menthone but not cineole or terpineol. Furthermore, this paper identified a synergistic transport enhancement effect developing when very low current (0.025 mA/cm(2)) iontophoresis was applied in conjunction with Azone treatment.

Adjuvants, Pharmaceutic↗
PubMed2000

Zinc modulates the electro-olfactogram of the frog.

OBJECTIVE: Zinc is considered an important element in olfaction, however, its exact role is still unclear. A large amount of zinc is contained in the olfactory mucosa, so Zn(2+) may behave as a neuromodulator, as in the hippocampus. To reveal the acute effects of Zn(2+) on olfactory mucosa, electro-olfactograms (EOG) were recorded with or without Zn(2+). METHODS: The isolated olfactory mucosa of a bullfrog (Rana catesbiana) was set in an EOG recording chamber and bathed in Ringer's solution. Effects of ZnSO(4) (25 microM) on EOGs were examined. Four types of stimulants, n-amyl acetate (200 microM), menthone (10 microM), forskolin (2 microM), and 3-isobutil-methylxisanthine (IBMX, 100 microM) were tested. RESULTS: Zn(2+) (25 microM) charged with the ciliated surface of the olfactory mucosa attenuates EOGs which were produced not only by odorants but also by forskolin and IBMX. The attenuating ratios of EOGs for stimulants were as follows; n-amyl acetate (0.51+/-0.18, n=4), menthone (0.48+/-0.28, n=4), forskolin (0.61+/-0.16, n=4), and IBMX (0.68+/-0.19, n=4); (mean+/-S.D.). These attenuations were reversible. The results indicate that Zn(2+) may block the c-AMP dependent transduction channels of the olfactory cells. CONCLUSION: Micro molar Zn(2+) attenuates EOG of the frog. Zn(2+) may be thought to behave as one of the modulators in olfactory reception.

1-Methyl-3-isobutylxanthine↗
PubMed2000

Excitatory actions of propofol and ketamine in the snail Lymnaea stagnalis.

This study compares the actions of the intravenous anaesthetics propofol and ketamine on animal behaviour and neuronal activity in the snail Lymnaea stagnalis, particularly in relation to excitatory effects observed clinically. When injected into the whole animal, neither agent induced total anaesthesia. Rather, behavioural activity was enhanced by propofol (10(-5) M) and ketamine (10(-7) M), indicating excitatory effects. When superfused over the isolated central nervous system (CNS), differential effects were produced in two identified neurons, right pedal dorsal 1 (RPeD1) and visceral dorsal 4 (VD4). Resting membrane properties were largely unaffected. However, spike after hyperpolarisation was significantly reduced in RPeD1, but not VD4, with some evidence of increased excitability. In addition, an intrinsic bursting property (post-stimulus burst) in VD4 was altered by propofol (10(-7) M). The results suggest significant excitatory components in the actions of some intravenous anaesthetics, as well as a potential role in modifying excitation and bursting mechanisms in the CNS.

Anesthetics, Dissociative↗
PubMed2000

Characterisation of tolbutamide hydroxylase activity in the common brushtail possum, (Trichosurus vulpecula) and koala (Phascolarctos cinereus): inhibition by the eucalyptus terpene 1,8-cineole.

Plant constituents such as terpenes are major constituents of the essential oil in Eucalyptus sp. 1,8-Cineole and p-cymene (Terpenes present in high amounts in Eucalyptus leaves) are potential substrates for the CYP family of enzymes. We have investigated tolbutamide hydroxylase as a probe substrate reaction in both koala and terpene pretreated and control brushtail possum liver microsomes and examined inhibition of this reaction by Eucalyptus terpenes. The specific activity determined for tolbutamide hydroxylase in the terpene treated brushtails was significantly higher than that for the control animals (1865+/-334 nmol/mg microsomal protein per min versus 895+/-27 nmol/mg microsomal protein per min). The activity determined in koala microsomes was 8159+/-370 nmol/mg microsomal protein per min. Vmax values and Km values for the terpene treated possum, control, possum and koala were 1932-2225 nmol/mg microsomal protein per min and 0.80 0.81 mM; 1406-1484 nmol/mg microsomal protein per min and 0.87-0.92 mM and 5895-6403 nmol/mg microsomal protein per min and 0.067-0.071 mM, respectively. Terpenes were examined as potential inhibitors of tolbutamide hydroxylase activity. 1,8-Cineole was found to be a competitive inhibitor for the enzyme responsible for tolbutamide hydroxylation (Ki 15 microM) in the possum. In koala liver microsomes stimulation of tolbutamide hydroxylase activity was observed when concentrations of cineole were increased. Therefore, although inhibition was observed, the type of inhibition could not be determined.

Animals↗
PubMed2001

Fullerene modified supported lipid membrane as sensitive element of sensor for odorants.

A supported lipid bilayer membrane (s-BLMs) formed on a freshly cleaved metallic surface by the Tien method was applied for the design of an electrochemical sensor for detection of neutral odorant molecules. The lipid bilayer was modified by saturation with fullerene C(60), which possesses electron mediator properties and facilitates a redox reaction occurring at the border of the lipid membrane and metal surface. I(2)/I(-) and ferrocenyl trimethyl bromide were used as electroactive marker ions. The smell compounds adsorb on the surface of the lipid layer and change its structure. As a consequence the ratio of marker ion penetration to the lipid membrane is altered. The magnitude of these changes depends on the amount and chemical structure of adsorbed molecules. The research presented was carried out by cyclic voltammetry. The magnitude of the electrochemical signal generated by smell compounds was correlated with other parameters describing their molecular properties such as: octanol/water partition coefficients and dipole moments.

1-Octanol↗
PubMed1997

Comparison of conventional and ultrasonically assisted extractions of pharmaceutically active compounds from Salvia officinalis.

Conventional as well as ultrasonically assisted extractions of biologically active compounds from Salvia officinalis using 65% ethanol have been studied. Cineole, Thujone and Borneol were used as standards for the GLC-MS evaluation of the extracts. The effect of temperature, stirring and mode of sonication (ultrasonic bath or horn system) have been studied. The results indicate that ultrasonically assisted extraction with mechanical stirring at room temperature in a period of 12 h produces a substantial improvement over conventional methodology.

Bicyclic Monoterpenes↗
PubMed2001

Metabolites of dietary 1,8-cineole in the male koala (Phascolarctos cinereus).

The in vivo metabolic fate of 1,8-cineole was investigated in six male koalas. Koalas were fed ad lib a diet of Eucalyptus cephalocarpa leaf with a 1,8-cineole concentration of 2.53+/-0.70% dry mass of leaf, corresponding to a 1,8-cineole intake of 2.4+/-1.1 mmol/kg (3.1+/-1.3 g). Urine and faeces were collected for 24 h and metabolites identified by GC-MS and LC-MS. Metabolites were quantified before and after hydrolysis with beta-glucuronidase to give free and total levels, respectively. Fractional recovery of ingested 1,8-cineole was 1.3+/-0.4 and 1.4+/-0.4 (mean+/-S.D.) for free and total measurements, respectively. Seven metabolites were identified and quantified: 9- and 7-hydroxycineole, 9- and 7-cineolic acid, 7-hydroxy-9-cineolic acid, 9-hydroxy-7-cineolic acid and 7,9-dicineolic acid. The hydroxycineolic acids dominated the metabolite profile (85%). 7,9-Dicineolic acid, a novel metabolite of 1,8-cineole, accounted for almost 10% of the recovered dose making it the second most abundant metabolite after 7-hydroxy-9-cineolic acid (77%). Together, the less oxidised metabolites, the hydroxycineoles and cineolic acid, accounted for only 5% of the cineole consumed. Significant conjugation only occurred with four minor, less oxidised, alcohol and carboxylic acid metabolites. We have shown that the koala detoxifies and eliminates 1,8-cineole primarily by extensive oxidation without utilising conjugation pathways.

Animals↗
PubMed2004

p-Menthane-3-carboxaldehyde: a useful chiral auxiliary for the synthesis of chiral quaternary carbons of high enantiomeric purity.

(+)- or (-)-p-Menthane-3-carboxaldehyde is made in two easy steps from (+)- or (-)-menthone, respectively. This auxiliary allows for the synthesis of carbonyl compounds bearing a alpha-chiral quaternary carbon. The flexibility, efficiency, and ease of use of the method are demonstrated in a series of examples, which include the total synthesis of (+)-cuparenone as well as a partial synthesis of (-)-cassiol.

Aldehydes↗
PubMed2006

Metallophosphite-catalyzed asymmetric acylation of alpha,beta-unsaturated amides.

The l-menthone-derived TADDOL phosphite 6b catalyzes highly enantioselective conjugate additions of acyl silanes to alpha,beta-unsaturated amides. p-Methoxybenzoyl cyclohexyldimethylsilane adds to a variety of N,N-dimethyl acrylamide derivatives in the presence of the lithium salt of 6b. In many instances the alpha-silyl-gamma-ketoamide product undergoes facile enantioenrichment (to 97-99% ee) upon recrystallization. Desilylation with HF.pyr affords the formal Stetter addition products. Baeyer-Villiger oxidation of the desilylated gamma-ketoamides affords useful ester products. An X-ray diffraction study of 6b reveals that the isopropyl group of the menthone ketal influences the position of the syn-pseudoaxial phenyl group in the TADDOL structure. Through a crossover experiment, the silicon migration step in the reaction mechanism is shown to be strictly intramolecular.

Acylation↗