Thymol-loaded PLGA nanoparticles: an efficient approach for acne treatment.

BACKGROUND: Acne is a common skin disorder that involves an infection inside the hair follicle, which is usually treated with antibiotics, resulting in unbalanced skin microbiota and microbial resistance. For this reason, we developed polymeric nanoparticles encapsulating thymol, a natural active compound with antimicrobial and antioxidant properties. In this work, optimization physicochemical characterization, biopharmaceutical behavior and therapeutic efficacy of this novel nanostructured system were assessed. RESULTS: Thymol NPs (TH-NP) resulted on suitable average particle size below 200 nm with a surface charge around - 28 mV and high encapsulation efficiency (80%). TH-NP released TH in a sustained manner and provide a slow-rate penetration into the hair follicle, being highly retained inside the skin. TH-NP possess a potent antimicrobial activity against Cutibacterium acnes and minor effect towards Staphylococcus epidermis, the major resident of the healthy skin microbiota. Additionally, the stability and sterility of developed NPs were maintained along storage. CONCLUSION: TH-NP showed a promising and efficient alternative for the treatment of skin acne infection, avoiding antibiotic administration, reducing side effects, and preventing microbial drug resistance, without altering the healthy skin microbiota. Additionally, TH-NP enhanced TH antioxidant activity, constituting a natural, preservative-free, approach for acne treatment.

Nanocomplexation between thymol and soy protein isolate and its improvements on stability and antibacterial properties of thymol.

The complexation of thymol with soy protein isolate (SPI) at various mixing mass ratios, as well as some physicochemical characteristics, stability and antibacterial properties of the resultant complexes, was evaluated. The loading capacity of thymol in complexes formed at a mixing mass ratio of 2.5:12 was 10.36%, and the particles were spherical with a z-average diameter less than 110 nm. Fluorescence spectroscopy results indicated the SPI-thymol nanocomplexes were formed mainly through hydrophobic interactions. Upon nanocomplexation, the solubility, sustained release, thermal stability and antibacterial activity of thymol were greatly improved. Moreover, the encapsulation efficiency and solubility of thymol in complexes were improved with the increasing mixing mass ratio, while the stability and antibacterial activity of thymol were not significantly different among all the complexes. These findings suggest that SPI could be used as a nanocarrier for improving solubility and stability of thymol.

Electrospun thymol-loaded porous cellulose acetate fibers with potential biomedical applications.

Drug toxicity induced by burst release has become a great challenge in clinical therapeutics. In most studies of drug delivery, great attention has been given to achieving sustained drug release by enhancing the surface hydrophobicity of drug carriers. However, many of them improved surface hydrophobicity through chemical methods, which could be toxic and time-consuming. This paper aims at providing a facile way to improve surface hydrophobicity of drug carriers. Here, a kind of porous cellulose acetate (CA) fibrous membranes containing different amount of thymol (THY) for sustained drug release were prepared, by co-electrospinning technique. The ellipse-shaped nanopores were generated on the surfaces of electrospun fibers in situ, which trapped a part of air at the interface and thus enhanced the hydrophobicity of fibrous membranes. The in vitro drug release results showed that the porous THY-loaded fibrous membranes had slower initial drug release and extended drug release time, compared with nonporous THY-loaded fibrous membranes. In addition, the higher specific surface area of porous THY-loaded CA fibrous membranes contributed to a higher drug utilization ratio. Antibacterial results demonstrated that porous THY-loaded CA fibrous membranes possessed more effective inhibition against S. aureus and E. coli, with only 0.07% and 0.09% of bacterial survival rate, respectively. Furthermore, the combination of porous surface structure with a controllable drug release improved the proliferation of L929 cells, indicating a better cytocompatibility. Taken together, the porous THY-loaded CA fibrous membrane offer significant promise as novel wound healing materials.

Molecular Docking and Dynamics Simulation Analysis of Thymoquinone and Thymol Compounds from Nigella sativa L. that Inhibits P38 Protein: Probable Remedies for Hepatocellular Carcinoma.

BACKGROUND: Currently, a novel antagonist against p38 is being designed and applied to inhibit hepatocellular carcinoma. Protein-ligand interaction plays a major role in the identification of the possible mechanism for the pharmacological action. The involvement of p38 remains an important target for anticancer drug development as its activation induces apoptosis in hepatoma cells. OBJECTIVE: The aim is to identify the best candidate from the plants of N. sativa which binds with the hepatocellular carcinoma (HCC) targets by computational approach. MATERIALS AND METHODS: The reported phytoconstituents such as thymoquinone and thymol present in the plant, N. sativa were docked with the HCC target such as p38. Structures of phytoconstituents were prepared using ChemDraw Ultra 10 software and converted into its 3D PDB structure and minimized using Discovery Studio client 2.5. The target protein, p38 was retrieved from RCSB PDB. Lipinski's rule and ADMET toxicity profiling were carried out on the phytoconstituents of the N. sativa, and the compounds were further promoted for molecular docking and MD simulation analysis. RESULTS: The docking results revealed promising inhibitory potential of thymoquinone against p38 with binding energy of -7.67 kcal/mole as compared to its known standard doxorubicin having binding energy of -6.68 kcal/mol respectively. Further, molecular dynamic (MD) simulations for 5ns were conducted for optimization, flexibility prediction, and determination of folded p38 stability. The p38-thymoquinone complex was found to be quite stable with RMSD value of 0.2 nm. CONCLUSION: Obtained results propose thymoquinone binding energy on the selected targets. Hence, this compound bears outstanding potential against hepatocellular carcinoma and has to be taken up for experimental work against hepatocellular carcinoma.

Extraction, formulation and characterization of an in vitro and ex-vivo evaluation of Thymus serpyllum L. (Thymus oil) from topical preparations using dialysis cellulose membrane and natural rabbit skin.

Herbal remedies like the Thymus serpyllum L. is useful in traditional medicine for the treatment of many diseases especially congestion, and bronchitis. The purpose of this study was to formulate a micro-emulsion, a gel and an ointment containing the plant hydro distilled thymus oil extracted from Thymus serpyllum L. collected from Ziarat, Balochistan. The prepared formulations were subjected to in-vitro and ex vivo study release, High performance Liquid Chromatography (HPLC), Thin Layer Chromatography (TLC), to justify their suitability for topical use. The in-vitro and ex-Vivo release was studied using Franz Cells and using two different kinds of membrane synthetic dialysis cellulose membrane and natural rabbit skin and the amount of drug released was determined by HPLC at λ 274nm. The three formulations result obtained through dialysis cellulose membrane showed the faster release than the natural rabbit skin. However, the micro-emulsion, gel formulation showed the same release except ointment. The release from the above mentioned formulation can be arranged in the following descending order. micro-emulsion > Gel > Ointment. The best fit of release kinetics was achieved by Krosmeyer- Peppas, the TLC and HPLC identifies the Thymol, isolation and quantification of the marker. This study demonstrates that it is necessary to assess the impact of release and permeability pattern of different formulations. In vitro and ex-vivo diffusion cell experiments can be utilized to develop formulations of traditional medicines identifies.

Pharmacokinetic study of thymol after intravenous injection and high-dose inhalation in mouse model.

Thymol is generally recognized as a safe substance by the FDA and has been widely used in the pharmaceutical, food, and cosmetic industries. Pharmacokinetic (PK) studies of thymol have been previously conducted for oral administration, but there has been no PK study for inhalation administration or intravenous (IV) injection. This study aims at exploring and comparing the inhalation and IV PK profile of thymol in a mouse model. The inhalation PK for mouse model was corrected with fur/skin absorption. Thirty-two male CD-1 mice were randomized into two study arms, Arm-A for intravenous (n = 16) and Arm-B for inhalation (n = 16). The amount of thymol in the mouse serum was measured for Arm-A and for Arm-B at the highest dose. Furthermore, 48 mice were utilized for fur/skin absorption of thymol. In total, 320 mouse serum samples for thymol were analyzed by LC/MS method. After inhalation, the peak concentration of thymol in mouse serum was 42.3 ng/mL (Cmax ) and occurred at 2 minutes (tmax ). The AUC of the inhaled thymol at 0-60 minutes (AUC0-60) was 464 ng/mL/min. From 10-60 minutes post-dose, the PK inhalation curve appeared to be higher than that for the IV injection. This is likely attributed to the effect of absorption of thymol through the fur/skin of mice. After an adjustment by fur/skin absorption, the PK profile for net inhalation closely matched the two-compartment model. In fact, the bioavailability for the net inhalation of thymol was 74% and 77% relative to that for IV injection per AUC0-60min and AUC0-infinite, respectively.

Lipid nanoparticles as carriers of cyclodextrin inclusion complexes: A promising approach for cutaneous delivery of a volatile essential oil.

Solid inclusion complexes with cyclodextrins (CD) may be used to overcome volatility and solubility problems of essential oils of pharmacological interest. However, they lack the many dermatological advantages of lipid nanoparticles. This study intends to evaluate the ability of nanostructured lipid carriers (NLC) to encapsulate hydroxypropyl-ß-cyclodextrin inclusion complexes of Lippia origanoides essential oil (EO) and to maintain the desirable aspects of lipid colloids interaction with the skin, specifically follicular accumulation and controlled delivery. CD and NLC were also evaluated separately. Thymol (TML) was used as the essential oil marker and to produce control formulations. As expected, CD alone, though effective in overcoming volatility and low aqueous solubility of TML, were ineffective in controlling marker release (˜50% of EO released after 3 h, Hixson-Crowell kinetics). Even though NLC controlled drug release (˜20% EO released after 12 h, zero-order kinetics) enabling TML penetration into the skin (> 40 µg/cm2after 12 h), NLC alone were not efficient in preventing TML volatility, especially at higher temperatures (calculated shelf-life of 2 days at 35 °C). The combined approach resulted in a synergistic effect (˜20% EO released after 12 h; shelf life of 6 days). The lack of statistical difference of TML skin penetration from NLC and NLC-CD suggests the developed system maintained all skin interaction aspects of lipid colloids, including follicular accumulation forming a depot for controlled delivery. In conclusion, lipid nanoparticles demonstrated to be promising carriers for inclusion complexes of this particular volatile essential oil.

Tissue oxidative damage mediates impairment on phosphotransfer network during thymol intake: Effects on hepatic and renal bioenergetics.

Recent evidences demonstrated that ingestion of several monoterpenes cause hepatic and renal damage due to impairment on mitochondrial energy production, eliciting a collapse on adenosine triphosphate (ATP) synthesis and consequently impairment on bioenergetic homeostasis. Thus, the aim of this study was to evaluate whether phosphotransfer network, catalyzed by creatine kinase (CK), adenylate kinase (AK), and pyruvate kinase (PK), can be a pathway to explain hepatic and renal bioenergetics homeostasis impairment due to thymol ingestion. Daily intake of thymol (40 mg/kg) significantly cause a decreased kidney weight and relative kidney weight compared to control group. The same dose of thymol inhibited renal cytosolic and mitochondrial CK activity as well as renal PK activity compared to control group. Finally, thymol (40 mg/kg) elicited a significant increase on renal reactive oxygen species and lipid damage levels, as well as an inhibition on antioxidant capacity against peroxyl radicals and non-protein thiol levels, which did not occur liver. Doses of 10 and 20 mg/kg of thymol administered orally for 30 consecutive days non-changed these variables. Based on these evidence, the data supported that intake of a high dose of thymol severely inhibits cytosolic and mitochondrial CK activity, a crucial enzyme to maintain cellular energy homeostasis. Moreover, high dietary thymol intake impaired communication between CK isoenzymes, which inhibits the attempts to regenerate ATP or to facilitate the CK/PCr shuttle to improve the intracellular ATP utilization and consumption. Moreover, the inhibition of renal CK and PK activities appears to be mediated by the renal oxidation of lipids and thiol groups, as well as by the reduction of the renal antioxidant capacity.

Blood-brain barrier breakdown, memory impairment and neurotoxicity caused in mice submitted to orally treatment with thymol.

Several evidences have related the biochemical and pharmacological properties of thymol, but the possible neurotoxic effects of this compound remain unknown and not evaluated. Thus, the purpose of this study was to evaluate whether intake of thymol in different doses (10, 20 and 40 mg/kg) induce neurotoxicity and behavioral alterations using mice as experimental model, as well as the involvement of blood-brain barrier (BBB) and brain neurotransmitters in these alterations. Thymol (20 and 40 mg/kg) significantly decrease latency time to inhibitory avoidance task when compared to control group, indicating a memory loss after 30 days of oral treatment. Also, thymol (20 and 40 mg/kg) induced a significant increase on BBB permeability to Evan's blue dye when compared to control group, which is an indicative of BBB breakdown. Moreover, a significant increase of brain acetylcholinesterase (AChE) was observed in mice treated with 40 mg/kg of thymol, while the activity of sodium-potassium pump (Na+, K+-ATPase) was inhibited in mice treated with 20 and 40 mg/kg thymol when compared to control group. Finally, mice that received 20 and 40 mg/kg thymol showed a significant increase on cerebral reactive oxygen species (ROS) levels and cerebral xanthine oxidase (XO) activity compared to control group. Based on these evidences, the rupture of BBB can be considered an important pathway linked in thymol-induced memory loss. Also, the augmentation of brain ROS levels elicited by increase on XO activity may be a via involved in the damage to BBB, and an oxidative pathway that impairs the activity of brain neurotransmitters, as AChE and Na+, K+-ATPase. In summary, the dose of 10 mg/kg thymol can be safe and without neurotoxic effects in a period of 30 days of intake.

Pharmacokinetic analysis of thymol, carvacrol and diallyl disulfide after intramammary and topical applications in healthy organic dairy cattle.

Mastitis is among the most costly concerns for dairy producers whether cattle are managed conventionally or organically. Unfortunately, there are no USFDA-approved mastitis treatments that allow dairy cows in the United States to maintain organic dairy status. We investigated the plasma pharmacokinetics of three organic mastitis products currently used by organic producers and organic dairy veterinarians. Those products include intramammary, topical and intravaginal preparations, each dosed at two levels. Additionally, tissue data were collected for kidney, liver and fat in order to estimate a withholding time for each of the products. The lower limit of quantification (LOQ) and lower limit of detection (LOD) were 0.001 and 0.0005 µg ml-1, respectively, in plasma and all tissues except fat for both thymol and carvacrol. Fat had an LOQ of 0.01 µg ml-1 and an LOD of 0.005 µg ml-1 for thymol and carvacrol. Diallyl disulfide had an LOQ of 0.005 µg ml-1 and LOD of 0.001 µg ml-1 in all tissues. For diallyl disulfide (garlic), no levels above 0.001 µg ml-1 were measurable in plasma or tissues. For topical and intramammary products, levels were measurable in the plasma, liver, kidney and fat up to 72 h after the last dose. The plasma half-lives were short for thymol (approximately 1.6 h) and carvacrol (approximately 1.5 h), whereas the estimated half-lives for these substances in tissues ranged from 13.9 to 31.5 h for thymol and from 16.9 to 25 h for carvacrol. The predicted amount of time that the molecules would be found in the body based on the slowest depletion time of liver tissue was 13 days for thymol and 10 days for carvacrol. The apparent half-life of topically applied carvacrol was approximately 4.5 h in plasma, with an estimated withhold time of 10 days. These times were calculated using the USFDA's tolerance limit method for meat withdrawal times.

Identification and quantification of thymol metabolites in plasma, liver and duodenal wall of broiler chickens using UHPLC-ESI-QTOF-MS.

In the present study, we aimed to develop a method for thymol sulfate and thymol glucuronide determination in plasma, liver and duodenal wall of broiler chickens after feeding with a Thymus vulgaris essential oil at the different concentrations (0.01, 0.05 and 0.1% w/w). UHPLC coupled with accurate-mass QTOF-MS was used for identification and quantification of thymol metabolites. Novel Waters Oasis Prime HLB solid-phase extraction cartridges were applied to sample clean-up with extraction recoveries ranged from 85 to 92%. The presence of thymol glucuronide was confirmed by MS software according to molecular formula, score, mass error and double bond equivalent. In terms of validation, calibration curves of thymol sulfate were constructed in matrix samples with linearity from 3.91 to 250.0 ng/mL and correlation coefficients were within the range of 0.9979-0.9995. Limits of detection were 0.97, 0.29 and 0.63 ng/mL and limits of quantification were 3.23, 0.97 and 2.09 ng/mL for plasma, liver and duodenal wall, respectively. Intra-day and inter-day precision expressed as relative standard deviation were <4.35%. To highlight, thymol metabolites were directly detected for the first time in liver and duodenal wall and this method was shown to be successfully applicable for investigation of thymol metabolism in chickens after thyme essential oil ingestion.

Effect of Thyme Essential Oil Supplementation on Thymol Content in Blood Plasma, Liver, Kidney and Muscle in Broiler Chickens.

The absorption and metabolism of phytogenic feed additives in poultry is studied related to the metabolism and deposition of their main compounds in tissues intended for food production. Fifty-six non-sexed Ross 308 broilers were allocated to seven dietary treatments and fed a diet containing graded levels of thyme (Thymus vulgaris L.) essential oil (EO) (0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.1%, w/w). Thymol concentration was measured in plasma, liver, kidney and breast muscle tissue using solid phase micro-extraction followed by gas chromatography/mass spectrometry. We found the highest concentrations of thymol in kidney and plasma, and the lowest in breast muscle and liver. Thymol content in plasma and kidney significantly increased when 0.05 and 0.1%, w/w, EO and in liver and breast muscle only when 0.1%, w/w, EO was added to the diet (p<0.05). Our results indicate intensive metabolism of thymol in liver and its accumulation in kidney tissue. We confirm low deposition of thymol in the muscle tissue. It is necessary to.-keep in mind the selection of a sufficient concentration of EO in the feed additive for animals without the risk of thymol residues in edible tissues.

Encapsulation and modified-release of thymol from oral microparticles as adjuvant or substitute to current medications.

The aim of this study was to encapsulate, thymol, in natural polymers in order to obtain (i) taste masking effect and, then, enhancing its palatability and (ii) two formulations for systemic and local delivery of herbal drug as adjuvants or substitutes to current medications to prevent and treat several human and animal diseases. Microspheres based on methylcellulose or hydroxypropyl methylcellulose phthalate (HPMCP) were prepared by spray drying technique. Microparticles were in vitro characterized in terms of yield of production, drug content and encapsulation efficiency, particle size, morphology and drug release. Both formulations were in vivo orally administered and pharmacokinetic analysis was carried out. The polymers used affect the release and, then, the pharmacokinetic profile of thymol. Encapsulation into methylcellulose microspheres leads to short half/life but bioavailability remarkably increases compared to the free thymol. In contrast, enteric formulation based on HPMCP shows very limited systemic absorption. These formulations could be proposed as alternative or adjuvants for controlling pathogen infections in human or animal. In particular, methylcellulose microspheres can be used for thymol systemic administration at low doses and HPMCP particles for local treatment of intestinal infections.

Improvement of thymol properties by complexation with cyclodextrins: in vitro and in vivo studies.

Thymol, an effective agent for microbial diseases, has a low aqueous solubility and a strong bitter/irritating taste. These physicochemical characteristics need to be improved to develop pharmaceutical preparations. This study evaluates whether ß-cyclodextrin and a copolymer based on dimethylaminoethyl methacrylate (DMAEMA) interact with thymol in order to control powderization, solubilization, and taste-masking properties. The thymol-ß-cyclodextrin complex was prepared by co-precipitation and sealed-heating methods. The DMAEMA copolymer was mixed with the complex using a new approach, instead of spray coating, to decrease thymol volatility. In vivo studies were performed. Sealed-heating is a suitable method for including thymol in ß-cyclodextrin with a good loading efficiency; thymol volatility control is achieved by mixing the complex with the DMAEMA copolymer. ß-Cyclodextrin accelerates the in vivo thymol absorption rate compared with the free drug; the thymol half-life is still long. Therefore, a low number of administrations per day are required. Although bioavailability is unchanged with respect to free thymol, high doses could be administered of a selected formulation without compromising the compliance. Furthermore, thymol that is not absorbed is held along the intestine, where it can useful in the treatment and/or prevention of intestinal bacterial diseases.

Nanocapsular dispersion of thymol for enhanced dispersibility and increased antimicrobial effectiveness against Escherichia coli O157:H7 and Listeria monocytogenes in model food systems.

Essential oils are marginally soluble in water, making it challenging to evenly disperse them in foods and resulting in an increased tendency to bind with food lipids and proteins, resulting in lowered antimicrobial efficacy. In the current study, free and nano-dispersed (ND) thymol were compared in terms of their antimicrobial efficacies against Escherichia coli O157:H7 ATCC 43889 and 43894 and Listeria monocytogenes strains Scott A and 101 in apple cider and 2% reduced-fat milk. Apple cider was adjusted to pHs 5.5 and 3.5, and antimicrobial tests were performed at 0.3-, 0.5-, 0.75-, and 1.0-g/liter thymol concentrations at 35, 32, 25, and 4°C. Overall, 0.5 and 1.0 g/liter thymol in nano-dispersion and along with free thymol were inhibitory and bactericidal, respectively, against bacterial strains under all treatment conditions. At pH 5.5, 0.5 g/liter ND thymol was bacteriostatic against L. monocytogenes and E. coli for up to 48 h. At pH 3.5, L. monocytogenes controls did not survive beyond 12 h but E. coli survived and was inhibited by 0.5 g/liter ND thymol after 12 and 48 h in apple cider. E. coli strains were significantly sensitive to 4°C and pH 3.5 (P < 0.05). When bacteria were tested in 2% reduced-fat milk at 35 or 32°C, ND and free thymol demonstrated inhibition at 4.5 g/liter. Thus, the current technology seems to be promising and novel, enabling thymol-containing nano-dispersions that are not only transparent but also effective against pathogens in food applications, especially in clear beverages.

Visual analysis of vaginal cell binding and retention of a gynecological douche.

AIM: Gynecological douches may contain various molecules that need to cover and be retained by cutaneous and mucosal cells if they are to act efficaciously in treating local conditions. The aim of this study was to investigate the possibility of directly visualising the ability of a commercial medical gynecological douche to bind to, and be retained by human vaginal cells. METHODS: The commercial gynecological douche under study was "Saugella Attiva douche", bought at local chemist. The vaginal epithelial cells were obtained from healthy, non-pregnant, regularly menstruating women aged 24-52 years. The cells were obtained from the mucosal surface of the mid-vaginal wall by means of gentle scraping with a sterile spatula. Ferric oxide particles and Escherichia coli were used as inorganic and organic markers in order to visualize the adherence of the transparent thin film of a gynecological douche to human vaginal cells by means of Nomarski interference contrast microscopy and scanning electron microscopy. RESULTS: Both markers made it possible to clearly visualize the binding and retention of the transparent thin layer of the douche also at the dilution 1:2 and 1:4. CONCLUSIONS: The fact that the douche can be locally retained is useful because its formulation contains thymol and eugenol, which are known to have antibacterial, antifungal and antioxidant effects but need a period of contact before they act fully.

[Oxytocin and syndrome of inappropriate secretion of antidiuretic neonatal hormone. Case report of early severe hyponatremia and literature review]. / Oxitocina y sindrome de secreción inapropiada de hormona antidiurética neonatal. Reporte de un caso de hiponatremia severa temprana y revisión de la bibliografia.

This is a clinical case presentation of a full term newborn infant who suffered severe hyponatremia and early seizures, associated with maternal fluid overload with electrolyte free solutions and high doses of oxytocin for labor augmentation. Although this condition has been recognized since the 1960's with isolated reports, this particular case has features that needs further investigation, not only for the unsually severe hyponatremia, but most importantly we think, for the prominent signs of fluid retention, the infant had, that suggest excessive antidiuretic activity probably due to oxytocin. These findings are consistent with syndrome of inappropriate secretion of antidiuretic hormone. Although until now there is no proof that oxytocin by itself produces this syndrome. We think the association is possible in certain clinical circumstances, such as those found in this case. We also, briefly discussed the pathophysiology of perinatal hyponatremia, the neonatal treatment of this condition and the current guidelines for the women in labor. Hyponatremia should not be considered a benign condition, since in the neonate, it may affect brain function.

Increase in activity of essential oil components carvacrol and thymol against Escherichia coli O157:H7 by addition of food stabilizers.

The major components of oregano and thyme essential oils that had previously been shown to inhibit Escherichia coli O157:H7 were determined by high-performance liquid chromatography with UV detection and liquid chromatographic tandem mass spectrometry. The MICs and MBCs of carvacrol, thymol, p-cymene, and gamma-terpinene against a strain of E. coli O157: H7 phage type 34 isolated from bovine feces were determined by microdilution assay. The constituents were then tested in checkerboard assays to detect possible interactions. Carvacrol and thymol displayed bacteriostatic and bactericidal properties with MICs of 1.2 mmol/liter and were additive in combination. p-Cymene and gamma-terpinene displayed no measurable antibacterial activity up to 50 mmol/liter, and neither influenced the activity of carvacrol or thymol. Growth curves in the presence of nonlethal concentrations of carvacrol with the addition of agar (0.05%, wt/vol) or carrageenan (0.125%, wt/vol) as stabilizer were produced by optical density measurement. The stabilizers agar and carrageenan both significantly improved the effectiveness of carvacrol in broth, possibly because of a delay in the separation of the hydrophobic substrate from the aqueous phase of the medium. When carvacrol was dissolved in ethanol before addition to broth, stabilizers were not needed. Carvacrol and thymol, particularly when used in combination with a stabilizer or in an ethanol solution, may be effective in reducing the number or preventing growth of E. coli O157:H7 in liquid foods.

Comparison between two thymol formulations in the control of Varroa destructor: effectiveness, persistence, and residues.

An apiary trial on the use of two acaricide formulations (gel-Apiguard and vermiculite and Api Life VAR) in the control of Varroa destructor (Anderson & Trueman) was conducted in summer 2001 in Sardinia (Italy). The main goals were 1) to determine their effectiveness against V. destructor, taking into account natural mite mortality in control hives; and simultaneously 2) to determine the persistence of both formulations and residues in honey and wax, by using a new extraction method. Both thymol formulations, after the treatments, reduced significantly the levels of mite infestations of adult bees and sealed brood, but their efficacy, expressed as percentage of mortality, was lower for both products (Api Life VAR 74.8 +/- 13.1 and 81.3 +/- 15.5, Apiguard 90.4 +/- 8.3 and 95.5 +/- 8.7 for sealed brood and adult bees, respectively) than the efficacy previously obtained with the same products in other experimental conditions. Moreover, a considerable colony-to-colony variability was recorded, and a significant negative effect of the thymol treatments on colony development was observed. During 2 wk of treatment, the bees removed nearly 95% of all the applied product (gel or vermiculite). Residues found in honey collected from the nest varied from 0.12 to 4.03 mg/kg for Api Life VAR and from 0.40 to 8.80 mg/kg for Apiguard. The residues were relatively higher in wax (Api Life VAR = 21.6 +/- 13.0; Apiguard = 147.7 +/- 188.9) than in honey, because thymol is a fat-soluble ingredient.

Systemic availability and pharmacokinetics of thymol in humans.

Essential oil compounds such as found in thyme extract are established for the therapy of chronic and acute bronchitis. Various pharmacodynamic activities for thyme extract and the essential thyme oil, respectively, have been demonstrated in vitro, but availability of these compounds in the respective target organs has not been proven. Thus, investigation of absorption, distribution, metabolism, and excretion are necessary to provide the link between in vitro effects and in vivo studies. To determine the systemic availability and the pharmacokinetics of thymol after oral application to humans, a clinical trial was carried out in 12 healthy volunteers. Each subject received a single dose of a Bronchipret TP tablet, which is equivalent to 1.08 mg thymol. No thymol could be detected in plasma or urine. However, the metabolites thymol sulfate and thymol glucuronide were found in urine and identified by LC-MS/MS. Plasma and urine samples were analyzed after enzymatic hydrolysis of the metabolites by headspace solid-phase microextraction prior to GC analysis and flame ionization detection. Thymol sulfate, but not thymol glucuronide, was detectable in plasma. Peak plasma concentrations were 93.1+/-24.5 ng ml(-1) and were reached after 2.0+/-0.8 hours. The mean terminal elimination half-life was 10.2 hours. Thymol sulfate was detectable up to 41 hours after administration. Urinary excretion could be followed over 24 hours. The amount of both thymol sulfate and glucuronide excreted in 24-hour urine was 16.2%+/-4.5% of the dose.