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PubMed2005

Assessment of losses in honey yield due to the chalkbrood disease, with reference to the determination of its economic injury levels in Egypt.

In Egypt, the chalk brood (CHB) disease caused by the fungus, Ascosphaera apis Maassen started again infesting the honeybee, Apis melifera L (Hymenoptera: Apidae) colonies after a cessation pause of seven to nine years. For the first time, an attempt has been made to look into the problem of the CHB disease from the view point of assessing losses in both clover (Trifolium alexandrinum) and chinus (Chinus molus) honey yields. In this regard, two techniques were adopted. Under the natural conditions of the experimental apiary (first technique), loss in clover honey was 18.412 +/- 0.663%, on average, whereas the average loss in chinus honey was 18.332 +/- 1.536%. In the second technique of loss appraisal (artificial infection). The tested honeybee colonies were artificially infected with four sources of A. apis infection, I.e. black mummies, white mummies, pollen grains and water, in addition to controls to create the so-called "different levels of infection". The mean percentages of losses in clover honey were 30.06 +/- 1.807, 27.95 +/- 1.062; 21.13 +/- 0.987; 16.96 +/- 0.672 and 0.00 +/- 0.00 for black mummies, white mummies, pollen grains, water and control, respectively. Taking into account the relationship between number of resulted mummies in each source of infection and % loss in clover honey, it could be concluded that as the resulted mummies increased, the corresponding clover honey yield decreased in each source of infection. It was noticed that the % loss in clover honey differed as the used technique differed. For example, the percentage loss in clover honey produced from colonies exposed to the natural conditions was relatively less than that of the artificially infected ones. This has been discussed in the text. However, the causative pathogen of CHB disease resulted in serious decrease in honey production. Loss appraisal is a perquisite step for the determination of the economic injury levels (EILs). By regressing % loss in clover honey yield against the total number of fallen mummies, the linear equation was worked out to be: Y = 0.242 + 0.040 x (r2 = 0.99, F = 62408.865). Depending on the total costs of controlling CHB disease, the EIL values were 31.875 and 11.250 mummies/colony for cedar oil and thymol granules, subsequently. As to the chinus honey the corresponding EILs were 18.940 and 6.683 mummies/colony for cedar oil and thymol granules, in respect, as a result of adopting the regression formula: Y = -6.762 + 0.101 X. As for the clover honey (artificial infection) the EIL values were 39.844 and 14.063 mummies/ colony in case of using cedar oil and thymol grains, subsequently. These values were worked out using the formula Y = 5.871 + 0.032 X. From the practical point of view, apiarists should not use thymol or cedar oil as fallen mummies don't reach the suggested EILs values to minimize control costs as much as possible.

Animals↗
PubMed2005

The effects of thyme volatiles on the induction of DNA damage by the heterocyclic amine IQ and mitomycin C.

The leafy parts of thyme and its essential oil have been used in foods for its flavour, aroma and preservation for many years. In the present study the genotoxic potential of major compounds of thyme oil, i.e. thymol, carvacrol, and gamma-terpinene and of the methanolic extracts of thyme, were investigated in human lymphocytes by single-cell gel electrophoresis. Also, the effects of these substances on the induction of DNA damage by 2-amino-3-methylimidazo[4,5-f]-quinoline (IQ) and mitomycin C (MMC) were evaluated. No increase in DNA strand breakage was observed at thymol and gamma-terpinene concentrations below 0.1 mM, but at the higher concentration of 0.2 mM significant increases in DNA damage were seen. Thymol and gamma-terpinene significantly reduced the DNA strand breakage induced by IQ and MMC at the lower concentrations studied. Carvacrol, which is an isomer of thymol, seemed to protect lymphocytes from the genotoxic effects of IQ and MMC at non-toxic concentrations below 0.05 mM, but at the higher concentration of 0.1 mM carvacrol itself induced DNA damage. Also the constituents of the n-hexane and ethyl acetate fractions prepared from the concentrated aqueous methanolic extracts of Thymus spicata protected lymphocytes against IQ- and MMC-induced DNA damage in a concentration-dependent manner.

Alkylating Agents↗
PubMed1992

Localization of the biosynthesis and accumulation of monoterpenoids in glandular trichomes of thyme.

Quantitative analyses of the essential oils in intact glandular trichomes isolated from thyme cotyledons by the use of an adhesive tape and a glass capillary tube showed that the content of thymol per cotyledon was approximately equal to the sum total of thymol in peltate glandular trichomes (PGTs) and capitate glandular trichomes (CGTs). The amounts of thymol and gamma-terpinene in PGTs increased with time until 9 days after germination, when these monoterpenes were exclusively found in PGTs. The radioactivity of [U- (14)C]-sucrose administered to cotyledonal segments was incorporated into gamma-terpinene and thymol most actively by the peripheral part abundant in PGTs, whereas the incorporation was markedly decreased by a partial removal of PGTs from cotyledons. The cell-free extract of isolated PGTs was capable of cyclizing [ (14)C]-geranyl pyrophosphate into gamma-terpinene, but this enzymatic reaction failed when PGTs were removed from cotyledons. These results indicate that the biosynthesis and accumulation of monoterpenes in thyme seedlings take place primarily in PGTs.

Journal Article↗
PubMed2004

Eugenol stimulates lactate accumulation yet inhibits volatile fatty acid production and eliminates coliform bacteria in cattle and swine waste.

AIM: To determine how eugenol affects fermentation parameters and faecal coliforms in cattle and swine waste slurries stored anaerobically. METHODS AND RESULTS: Waste slurries (faeces:urine:water, 50:35:15) were blended with and without additives and aliquoted to triplicate 1-l flasks. Faecal coliforms were eliminated in cattle and swine waste slurries within 1 or 2 days with additions of eugenol at 10.05 mm (0.15%) and 16.75 mm (0.25%). At these concentrations volatile fatty acids (VFA) were reduced ca 70 and 50% in cattle and swine waste, respectively, over 6-8 weeks. Additionally, in cattle waste, eugenol stimulated the accumulation of lactate (>180 mm) when compared with thymol treatment (20 mm lactate). In swine waste, lactate accumulation did not occur without additives; eugenol and thymol stimulated lactate accumulation to concentrations of 22 and 32 mm, respectively. CONCLUSIONS: Eugenol added to cattle waste may be more beneficial than thymol because not only does it effectively control faecal coliforms and odour (VFA production), it also stimulates lactate accumulation. This in turn, causes the pH to drop more rapidly, further inhibiting microbial activity and nutrient emissions. SIGNIFICANCE AND IMPACT OF THE STUDY: Plant essential oils have the potential to solve some of the environmental problems associated with consolidated animal feeding operations. Thymol and eugenol reduce fermentative activity, thus, have the potential to reduce emissions of greenhouse gases and odour, and curtail transmission of pathogens in cattle and swine wastes.

Animals↗
PubMed2000

Laboratory evaluation of miticides to control Varroa jacobsoni (Acari: Varroidae), a honey bee (Hymenoptera: Apidae) parasite.

A laboratory bioassay was developed to evaluate miticides to control Varroa jacobsoni (Oudemans), an important parasite of the honey bee, Apis mellifera L. Bees and mites were exposed to applications of essential oil constituents in petri dishes (60 by 20 mm). The registered mite control agents tau-fluvalinate (Apistan) and formic acid also were evaluated as positive controls. Treatments that caused high mite mortality (> 70%) at doses that produced low bee mortality (< 30%) were considered mite selective. The six most selective of the 22 treatments tested (clove oil, benzyl acetate, thymol, carvacrol, methyl salicylate, and Magic3) were further evaluated to estimate LD50 values and selectivity ratios (A. mellifera LD50/V. jacobsoni LD50) at 24, 43, and 67 h after exposure. Tau-fluvalinate was the most selective treatment, but thymol, clove oil, Magic3, and methyl salicylate demonstrated selectivity equal to or greater than formic acid. The effect of mode of application (complete exposure versus vapor only) on bee and mite mortality was assessed for thymol, clove oil, and Magic3 by using a 2-chambered dish design. Estimated V. jacobsoni LD50 values were significantly lower for complete exposure applications of thymol and Magic3, suggesting that both vapor and topical exposure influenced mite mortality, whereas estimated values for clove oil suggested that topical exposure had little or no influence on mite mortality. These results indicate that essential oil constituents alone may not be selective enough to control Varroa under all conditions, but could be a useful component of an integrated pest management approach to parasitic mite management in honey bee colonies.

Animals↗
PubMed2002

Bactericidal activities of plant essential oils and some of their isolated constituents against Campylobacter jejuni, Escherichia coli, Listeria monocytogenes, and Salmonella enterica.

An improved method of sample preparation was used in a microplate assay to evaluate the bactericidal activity levels of 96 essential oils and 23 oil compounds against Campylobacter jejuni, Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella enterica obtained from food and clinical sources. Bactericidal activity (BA50) was defined as the percentage of the sample in the assay mixture that resulted in a 50% decrease in CFU relative to a buffer control. Twenty-seven oils and 12 compounds were active against all four species of bacteria. The oils that were most active against C. jejuni (with BA50 values ranging from 0.003 to 0.009) were marigold, ginger root, jasmine, patchouli, gardenia, cedarwood, carrot seed, celery seed, mugwort, spikenard, and orange bitter oils; those that were most active against E. coli (with BA50 values ranging from 0.046 to 0.14) were oregano, thyme, cinnamon, palmarosa, bay leaf, clove bud, lemon grass, and allspice oils; those that were most active against L monocytogenes (with BA50 values ranging from 0.057 to 0.092) were gardenia, cedarwood, bay leaf, clove bud, oregano, cinnamon, allspice, thyme, and patchouli oils; and those that were most active against S. enterica (with BA50 values ranging from 0.045 to 0.14) were thyme, oregano, cinnamon, clove bud, allspice, bay leaf, palmarosa, and marjoram oils. The oil compounds that were most active against C. jejuni (with BA50 values ranging from 0.003 to 0.034) were cinnamaldehyde, estragole, carvacrol, benzaldehyde, citral, thymol, eugenol, perillaldehyde, carvone R, and geranyl acetate; those that were most active against E. coli (with BA50 values ranging from 0.057 to 0.28) were carvacrol, cinnamaldehyde, thymol, eugenol, salicylaldehyde, geraniol, isoeugenol, citral, perillaldehyde, and estragole; those that were most active against L monocytogenes (with BA50 values ranging from 0.019 to 0.43) were cinnamaldehyde, eugenol, thymol, carvacrol, citral, geraniol, perillaldehyde, carvone S, estragole, and salicylaldehyde; and those that were most active against S. enterica (with BA50 values ranging from 0.034 to 0.21) were thymol, cinnamaldehyde, carvacrol, eugenol, salicylaldehyde, geraniol, isoeugenol, terpineol, perillaldehyde, and estragole. The possible significance of these results with regard to food microbiology is discussed.

Bacteria↗
PubMed2000

Botanical biocides. 4. Mosquitocidal activity of certain Thymus capitatus constituents.

Successive extraction of Thyme plant, Thymus capitatus (L.) Hoffm. and Link (Lamiaceae), by different solvents of increasing polarity, showed that potency was highly attributed to the non-polar fraction (e.g., petroleum ether) when tests were carried out against the larvae and adults of Culex pipiens (L). Of special concern to the mosquitocidal activity, the following fractions and isolates were recognized: the volatile oil, unsaponifiable portion, and certain compounds isolated from the unsaponifiable portion (e.g., Thymol, alpha-Amyrin, Carvacrol + beta-Caryophyllene). The volatile oil, Thymol, and the unsaponifiable portion proved high larvicidal potency against the tested insect (LC50 = 49.0, 58.0, and 100.0 ppm, respectively). Non-lethal concentrations of these substances synergized the toxicity of Malathion, while induced additive or antagonistic effects when mixed with Permethrin or Pirimiphos-methyl. The unsaponifiable portion and volatile oil showed the highest adulticidal potency (LC50 = 0.0070 and 0.0076 mg/cm2, respectively). The efficacy of the tested candidates as repellent agents was found in the following order: unsaponifiable portion > alpha-Amyrin > Thymol > volatile oil > Carvacrol + beta-Caryophyllene. Thymol as well as volatile oil affected egg hatchability, causing Sterility Indices accounting for 0.70 and 0.74, respectively, while the unsaponifiable portion showed lower degree of sterility (0.81). The results obtained in this study may shed light on the importance of T. capitatus as a probable source of some biologically active agents for mosquito control in the future.

Animals↗
PubMed1999

Effect of active molluscicidal component of spices on different enzyme activities and biogenic amine levels in the nervous tissue of Lymnaea acuminata.

In vivo exposure of Lymnaea acuminata to thymol and [6]-gingerol (active molluscicidal components of Trachyspermum ammi and Zingiber officinale, respectively) indicates that they significantly alter acetylcholinesterase, lactic dehydrogenase, succinic dehydrogenase and cyto-oxidase activity in the nervous -tissue of snails. In vitro exposure showed that, except for acetylcholinesterase and lactic dehydrogenase, no significant changes were observed in cyto-oxidase and succinic dehydrogenase activity in the nervous tissue of L. acuminata. Sublethal exposure to thymol and [6]-gingerol reduced the levels of 5-hydroxytryptamine (5-HT) and dopamine (DA) in the nervous tissue of L. acuminata. There was, however, no significant change in the level of 5-hydroxy indol acetic acid (5-HIAA). Thymol and [6]-gingerol thus affects all the known neurotransmission mechanisms in the snail either separately or through a complex interaction between the different neurotransmitters. This may account for their toxicity to snails.

Acetylcholinesterase↗
PubMed2006

Effect of oregano (Origanum vulgare L.) and thyme (Thymus vulgaris L.) essential oils on Trypanosoma cruzi (Protozoa: Kinetoplastida) growth and ultrastructure.

In the present work, we have investigated the effect of essential oils obtained from Origanum vulgare L. (oregano) and Thymus vulgaris L. (thyme) on growth and ultrastructure of diverse evolutive forms of Trypanosoma cruzi. Culture epimastigotes and bloodstream trypomastigotes were incubated for 24 h with different concentrations of oregano or thyme essential oils and with thymol (the main constituent of thyme), and the inhibitory concentration (IC)(50) was determined by cell counting. Crude extract of oregano essential oil inhibited epimastigote growth (IC(50)/24 h = 175 microg/ml) and also induced trypomastigote lysis (IC(50)/24 h = 115 microg/ml). Thyme essential oil presented IC(50)/24 h values of 77 microg/ml for epimastigotes and 38 mug/ml for trypomastigotes, while treatment with thymol resulted in an IC(50)/24 h of 62 microg/ml for epimastigotes and 53 microg/ml for trypomastigotes. Scanning electron microscopy of treated cells showed few morphological alterations at the plasma membrane. Observation by transmission electron microscopy showed cytoplasmic swelling with occasional morphological alterations in plasma and flagellar membrane. Our data indicate that oregano and thyme essential oils are effective against T. cruzi, with higher activity of thyme, and that thymol may be the main component responsible for the trypanocidal activity.

Animals↗
PubMed1981

The distribution of lipid in the cell structure: an improved method for the electron microscope.

An improved partition method for visualizing lipid consists in fixing tissues in paraformaldehyde-glutaraldehyde followed by osmium tetroxide. Three progressive grades of lipid staining are then obtained: (i) by renewed osmium tetroxide alone, (ii) by partition in myrcene or farnesol solutions followed by renewed osmium, (iii) by saturated thymol in sucrose followed by partition and renewed osmium. No additional metallic stains are used. The thymol treatment in (iii) renders 'masked' lipid accessible to partition--the effect being regulated as required by time and temperature. Thymol used before the first osmium facilitates lipid extraction which provides a complementary test for lipid. The possibilities of the method have been demonstrated on sections of familiar tissues of insect (mainly Rhodnius, Hemiptera) and mammal (mouse). By and large the results support what is known already about the distribution of lipid in cells, but observations on lipid in muscle fibres, in the nucleolus and chromatin, in the cells of the adrenal cortex, in the lung and intestine suggest that the method might prove a source of new information.

Acyclic Monoterpenes↗
PubMed2001

Acute, sublethal, antifeedant, and synergistic effects of monoterpenoid essential oil compounds on the tobacco cutworm, Spodoptera litura (Lep., Noctuidae).

Monoterpenoids (terpenes and biogenically related phenols) commonly found in plant essential oils were tested for acute toxicity via topical application to tobacco cutworms (Spodoptera litura Fab.). The most toxic among 10 such compounds was thymol (LD(50) = 25.4 microg/larva) from garden thyme, Thymus vulgaris. The compounds were then tested for sublethal effects, specifically inhibition of larval growth after topical application of low doses. Among 6 compounds tested, an LD(10) dose reduced growth by 20% on average 3 days after administration. Feeding deterrence was determined using a cabbage leaf disk choice test. The most deterrent compound was thymol, with a DC(50) of 85.6 microg/cm(2) leaf disk area. Because minor constituents in complex essential oils have been suggested to act as synergists, binary mixtures of the compounds were tested for synergy vis à vis acute toxicity and feeding deterrence. trans-Anethole acted synergistically with thymol, citronellal, and alpha-terpineol, in terms of both acute toxicity and feeding deterrence. On the basis of these findings, several complex mixtures were developed and tested as leads for effective control agents. Candidate mixtures demonstrated good synergistic effects. The observed LD(50) of mixture 3 was 40.6 microg/larvae compared to an expected value of 74.6 microg/larvae. The result of this research is a proprietary product suitable for commercial production.

Animals↗
PubMed2003

Antimicrobial and antioxidant activity of the essential oil and methanol extracts of Thymus pectinatus Fisch. et Mey. Var. pectinatus (Lamiaceae).

The essential oil, obtained by using a Clevenger distillation apparatus, and water-soluble (polar) and water-insoluble (nonpolar) subfractions of the methanol extract of Thymus pectinatus Fisch. et Mey. var. pectinatus were assayed for their antimicrobial and antioxidant properties. No (or slight) antimicrobial activity was observed when the subfractions were tested, whereas the essential oil showed strong antimicrobial activity against all microorganisms tested. Antioxidant activities of the polar subfraction and the essential oil were evaluated using 2,2-diphenyl-1-picrylhydrazyl, hydroxyl radical, superoxide radical scavenging, and lipid peroxidation assays. The essential oil, in particular, and the polar subfraction of the methanol extract showed antioxidant activity. The essential oil was analyzed by GC/MS, and 24 compounds, representing 99.6% of the essential oil, were identified: thymol, gamma-terpinene, p-cymene, carvacrol, and borneol were the main components. An antimicrobial activity test carried out with fractions of the essential oil showed that the activity was mainly observed in those fractions containing thymol, in particular, and carvacrol. The activity was, therefore, attributed to the presence of these compounds. Other constituents of the essential oil, such as borneol, gamma-terpinene, and p-cymene, could be also taken into account for their possible synergistic or antagonistic effects. On the other hand, thymol and carvacrol were individually found to possess weaker antioxidant activity than the crude oil itself, indicating that other constituents of the essential oil may contribute to the antioxidant activity observed. In conclusion, the results presented here show that T. pectinatus essential oil could be considered as a natural antimicrobial and antioxidant source.

Anti-Bacterial Agents↗
PubMed2003

Watering level effect on Thymus hyemalis Lange essential oil yield and composition.

Thymus hyemalis Lange (chemotype thymol) was cultivated as an experimental crop under different watering level conditions in order to achieve 80, 60, 40, and 20% of the local potential evapotranspiration (Eto). Two harvesting periods were considered, winter and spring. As a consequence of the great variability among plants, essential oil yield percentages did not show statistically significant differences among seasons and different levels of water supply. Capillary GC-MS analysis of the essential oils permitted the detection of 84 volatile components. Among them, 54 are described for the first time as volatile constituents of the chromatographic profile of this Thymus species. Winter harvesting showed high concentrations in thymol percentage (25.92 +/- 4.39), the 40% Eto watering level being the best with respect to obtaining the optimum quality of this essential oil. However, in spring this thyme species needs a greater water supply (80% Eto) to achieve the same amount of thymol in the essential oil (29.20 +/- 2.83). From this, it was concluded that winter harvesting could be used for the extraction of the essential oil, with a low level of water supply, whereas spring harvesting could be employed for collection of leaves as a food condiment.

Gas Chromatography-Mass Spectrometry↗
PubMed2004

Investigation of the Origanum onites L. essential oil using the chorioallantoic membrane (CAM) assay.

The in vivo test on the chorioallantoic membrane of the fertilized hen's egg (CAM assay) is a current method to determine antiangiogenic, antiinflammatory activity and toxic effects of individual compounds or complex plant extracts. The method is used for testing natural compounds in small amounts for revealing various modes of action and the complex mechanisms related to angiogenesis and inflammation. Furthermore, possible side effects such as membrane irritation, toxic, and anticoagulant properties of the investigated material in question can be detected. For the evaluation, the essential oil obtained by hydrodistillation of the aerial parts of Origanum onites L., a common spice and medicinal plant, was tested for its effect in the chorioallantoic membrane (CAM) assay. The essential oil composition was revealed by means of gas chromatography-mass spectrometry (GC-MS). Eighty three components were identified, representing 99.1% of the total oil. Carvacrol, thymol, p-cymene, and gamma-terpinene were found as major components and were also individually tested in the CAM assay. Along with the monoterpenes carvacrol and thymol, their methyl ether derivatives were also examined for comparison of their physiological action. Neither the essential oil nor its components showed any pronounced antiinflammatory or antiangiogenic property in the CAM assay, at 10-250 microg/pellet. However, the irritant effect of the essential oil was linked to thymol in a dose-response fashion, up to 10 microg/pellet, where it was still showing irritation.

Allantois↗
PubMed2005

Modulating effects of thyme and its major ingredients on oxidative DNA damage in human lymphocytes.

The present study was carried out to investigate the modulating effects of thyme and its major components against the oxidative DNA damage induced by H(2)O(2). The human lymphocytes with thymol, carvacrol, and gamma-terpinene incubated with or without 0.1 mM H(2)O(2) for 30 min at 37 degrees C and the DNA damage were evaluated by singe cell gel electropheresis (comet assay). Concentrations above 0.1 mM thymol and gamma-terpinene and 0.05 mM carvacrol significantly induced DNA damage in human lymphocytes, but at the smaller concentrations no additional DNA strand breakage has been observed. At the all concentrations studied, gamma-terpinene did not show any protective effect against H(2)O(2) induced oxidative DNA damage, but the phenolic compounds thymol and carvacrol at concentrations below 0.2 and 0.1 mM, respectively, significantly reduced the oxidative DNA damage (p < 0.001). The n-hexane and ethyl acetate fractions prepared from the methanolic extracts of Thymus spicata also were found to inhibit DNA damage.

Cyclohexane Monoterpenes↗
PubMed2003

Activity and mechanisms of action of selected biocidal agents on Gram-positive and -negative bacteria.

AIMS: This study investigates the antimicrobial activity and mode of action of two natural products, eugenol and thymol, a commonly utilized biostatic agent, triclocarban (TCC), and two surfactants, didecyldimethylammonium chloride (DDDMAC) and C10-C16 alkyldimethyl amine N-oxides (ADMAO). METHODS AND RESULTS: Methods used included: determination of minimum inhibitory concentrations (MICs), lethal effect studies with suspension tests and the investigation of sub-MIC concentrations on growth of E. coli, Staph. aureus and Ps. aeruginosa using a Bioscreen microbiological analyser. Leakage of intracellular constituents and the effects of potentiating agents were also investigated. Only DDDMAC was bactericidal against all of the organisms tested. Eugenol, thymol and ADMAO showed bacteriostatic and bactericidal activity, but not against Ps. aeruginosa. TCC was only bacteristatic against Staph. aureus, but like the other agents, it did affect the growth of the other organisms in the Bioscreen experiments. All of the antimicrobial agents tested were potentiated by the permeabilizers to some extent and leakage of potassium was seen with all of the agents except TCC. CONCLUSIONS: DDDMAC was bactericidal against all organisms tested and all compounds had some bacteriostatic action. Low level static effects on bacterial growth were seen with sub-MIC concentrations. Membrane damage may account for at least part of the mode of action of thymol, eugenol, DDDMAC and ADMAO. SIGNIFICANCE AND IMPACT OF THE STUDY: The ingredients evaluated demonstrated a range of bactericidal and bacteriostatic properties against the Gram-negative and -positive organisms evaluated and the membrane (leakage of intracellular components) was implicated in the mode of action for most (except TCC). Sub-MIC levels of all ingredients did induce subtle effects on the organisms which impacted bacterial growth, even for those which had no true inhibitory effects.

Anti-Bacterial Agents↗
PubMed2001

Local anaesthetic activity of (+)- and (-)-menthol.

In this work we studied the local anaesthetic activity of (+)- and (-)-menthol, a substance used after topical application to induce a feeling of coolness. We compared its activity to two chemically related compounds thymol and (-)-menthone. Anaesthetic activity was evaluated in vivo in the rabbit conjunctival reflex test and in vitro in a rat phrenic nerve hemidiaphragm preparation. Both enatiomers of menthol (10(-4)-1 micrograms/ml), but not thymol and (-)-menthone, were able to drastically reduce, in a dose-dependent manner, the electrically evoked contractions of rat phrenic hemidiaphragm. In the rabbit conjunctival reflex test, treatment with a solution of (+)- and (-)-menthol (30-100 micrograms/ml) allowed a dose-dependent increase in the number of stimuli necessary to provoke the reflex, thus confirming in vivo the local anaesthetic activity observed in vitro. Similar to the in vitro results, thymol and (-)-menthone were ineffective also in the in vivo test. In conclusion, these data evidence the local anaesthetic activity of menthol, which appears to be strictly dependent on its chemical structure.

Anesthetics, Local↗
PubMed1980

A spin-label study of the effects of drugs on calcium release from isolated sarcoplasmic reticulum vesicles.

The effects of caffeine, thymol, and procaine on calcium release from fragmented sarcoplasmic reticulum (FSR) from rabbit skeletal white muscle were investigated by the spin label method at the organellar level. Two thiol-directed spin labels, 4-maleimide-2,2,6,6-tetramethylpiperidinooxyl and 4-(2-iodoacetamide)-2,2,6,6-tetramethylpiperidinooxyl, were used for the labeling of SR proteins. The ratio (W/S) of the weakly (W) and strongly (S) immobilized ESR signals was measured for the maleimide and iodoacetamide labeled FSR. The two labels gave different W/S values, which means that the two labels report conformational changes at different loci of SR proteins. The dependences of the W/S ratios on the concentration of the drugs showed that conformational changes of SR proteins induced by these drugs are not the same. From measurements of the distribution of 5-doxyldecanoic acid methylester between the lipid and water phases, it was found that the conformational changes of the SR proteins caused by thymol or procaine induced a disorder in local regions of the phospholipid bilayers of FSR, while such disordering was not induced by caffeine. On the other hand, caffeine and thymol showed definite effects on calcium release from FSR, while procaine did not. These results indicate that the effects of the drugs on the protein conformations can be well characterized at the organellar level by means of the spin label technique and that some specific changes in the conformations of SR proteins are necessary for calcium release from FSR.

Animals↗