Determination of octanol-water partition coefficient for terpenoids using reversed-phase high-performance liquid chromatography

Antioxidant, Antibacterial, and Cytotoxic Activities of the Ethanolic Origanum vulgare Extract and Its Major Constituents

Oregano is a perennial shrub that grows in the mountains of the Mediterranean and Euro/Irano-Siberian regions. This study was conducted to identify the major constituents of the ethanolic Origanum vulgare extract and examine the cytotoxic, antioxidant, and antibacterial properties of the extract but more importantly the contribution of its specific major constituent(s) or their combination to the overall extract biological activity. Gas chromatography/mass spectroscopy analysis showed that the extract contained monoterpene hydrocarbons and phenolic compounds, the major ones being carvacrol and thymol and to a lesser extent p-cymene, 1-octacosanol, creosol, and phytol. A549 epithelial cells challenged with the extract showed a concentration-dependent increase in cytotoxicity. A combination of thymol and carvacrol at equimolar concentrations to those present in the extract was less cytotoxic. The A549 cells pretreated with nonlethal extract concentrations protected against hydrogen-peroxide-induced cytotoxicity, an antioxidant effect more effective than the combination of equimolar concentrations of thymol/carvacrol. Inclusion of p-cymene and/or 1-octacosanol did not alter the synergistic antioxidant effects of the carvacrol/thymol mixture. The extract also exhibited antimicrobial properties against Gram-positive and Gram-negative bacterial strains including clinical isolates. In conclusion, the oregano extract has cytotoxic, antioxidant, and antibacterial activities mostly attributed to carvacrol and thymol.

Biotechnological production of limonene in microorganisms

This mini review describes novel, biotechnology-based, ways of producing the monoterpene limonene. Limonene is applied in relatively highly priced products, such as fragrances, and also has applications with lower value but large production volume, such as biomaterials. Limonene is currently produced as a side product from the citrus juice industry, but the availability and quality are fluctuating and may be insufficient for novel bulk applications. Therefore, complementary microbial production of limonene would be interesting. Since limonene can be derivatized to high-value compounds, microbial platforms also have a great potential beyond just producing limonene. In this review, we discuss the ins and outs of microbial limonene production in comparison with plant-based and chemical production. Achievements and specific challenges for microbial production of limonene are discussed, especially in the light of bulk applications such as biomaterials.

Novel oxazine and oxazone dyes: aggregation behavior and physicochemical properties

Novel compounds exhibited good properties in comparison with the corresponding starting reagent and satisfy the conditions of a potential drug.

Volatile Biomarkers in Breath Associated With Liver Cirrhosis - Comparisons of Pre- and Post-liver Transplant Breath Samples

Background

The burden of liver disease in the UK has risen dramatically and there is a need for improved diagnostics.

Aims

To determine which breath volatiles are associated with the cirrhotic liver and hence diagnostically useful.

Methods

A two-stage biomarker discovery procedure was used. Alveolar breath samples of 31 patients with cirrhosis and 30 healthy controls were mass spectrometrically analysed and compared (stage 1). 12 of these patients had their breath analysed after liver transplant (stage 2). Five patients were followed longitudinally as in-patients in the post-transplant period.

Results

Seven volatiles were elevated in the breath of patients versus controls. Of these, five showed statistically significant decrease post-transplant: limonene, methanol, 2-pentanone, 2-butanone and carbon disulfide. On an individual basis limonene has the best diagnostic capability (the area under a receiver operating characteristic curve (AUROC) is 0.91), but this is improved by combining methanol, 2-pentanone and limonene (AUROC curve 0.95). Following transplant, limonene shows wash-out characteristics.

Conclusions

Limonene, methanol and 2-pentanone are breath markers for a cirrhotic liver. This study raises the potential to investigate these volatiles as markers for early-stage liver disease. By monitoring the wash-out of limonene following transplant, graft liver function can be non-invasively assessed.

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Breath volatiles were compared for cirrhotic patients and controls and pre- and post-liver transplant.

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Three volatiles (limonene, methanol, 2-pentanone) have been found to have excellent diagnostic capabilities.

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Limonene shows washout characteristics following transplant supporting a hypothesis that it accumulates in fat.

There are numerous previous studies investigating breath volatiles in patients with liver disease but with conflicting results. It is impossible to tell which volatiles from previous studies may be false discoveries, and which are actually associated with the disease. We measured breath samples in patients and controls and in patients after transplant. Methanol, 2-pentanone and limonene show differences not only between patients and controls but also in cases pre- and post-transplant and have excellent diagnostic capabilities. We show evidence that limonene accumulates in the body, probably because the cirrhotic liver fails to metabolise dietary limonene.

Large-scale preparation of clove essential oil and eugenol-loaded liposomes using a membrane contactor and a pilot plant

Based on our previous study where optimal conditions were defined to encapsulate clove essential oil (CEO) into liposomes at laboratory scale, we scaled-up the preparation of CEO and eugenol (Eug)-loaded liposomes using a membrane contactor (600 mL) and a pilot plant (3 L) based on the principle of ethanol injection method, both equipped with a Shirasu Porous Glass membrane for injection of the organic phase into the aqueous phase. Homogenous, stable, nanometric-sized and multilamellar liposomes with high phospholipid, Eug loading rates and encapsulation efficiency of CEO components were obtained. Saturation of phospholipids and drug concentration in the organic phase may control the liposome stability. Liposomes loaded with other hydrophobic volatile compounds could be prepared at large scale using the ethanol injection method and a membrane for injection.

Structural and biophysical characterization of human cytochromes P450 2B6 and 2A6 bound to volatile hydrocarbons: analysis and comparison

X-ray crystal structures of complexes of cytochromes CYP2B6 and CYP2A6 with the monoterpene sabinene revealed two distinct binding modes in the active sites. In CYP2B6, sabinene positioned itself with the putative oxidation site located closer to the heme iron. In contrast, sabinene was found in an alternate conformation in the more compact CYP2A6, where the larger hydrophobic side chains resulted in a significantly reduced active-site cavity. Furthermore, results from isothermal titration calorimetry indicated a much more substantial contribution of favorable enthalpy to sabinene binding to CYP2B6 as opposed to CYP2A6, consistent with the previous observations with (+)-α-pinene. Structural analysis of CYP2B6 complexes with sabinene and the structurally similar (3)-carene and comparison with previously solved structures revealed how the movement of the F206 side chain influences the volume of the binding pocket. In addition, retrospective analysis of prior structures revealed that ligands containing -Cl and -NH functional groups adopted a distinct orientation in the CYP2B active site compared with other ligands. This binding mode may reflect the formation of Cl-π or NH-π bonds with aromatic rings in the active site, which serve as important contributors to protein-ligand binding affinity and specificity. Overall, the findings from multiple techniques illustrate how drugs metabolizing CYP2B6 and CYP2A6 handle a common hydrocarbon found in the environment. The study also provides insight into the role of specific functional groups of the ligand that may influence the binding to CYP2B6.

High-Throughput Determination of Octanol-Water Partition Coefficients by Ultrasound-Assisted Liquid-Phase Microextraction

A method of high-throughput determination, which is based on ultrasound-assisted liquid-phase microextraction, was developed to measure directly the partition coefficients of n-octanol-water. In ultrasound-assisted liquid-phase microextraction, ultrasonic energy can facilitate the mass transfer process of six or more microextractors simultaneously. Therefore, high-throughput determination of n-octanol-water partition coefficients can be performed favorably, and the equilibrium time of each microextractor can be decreased effectively. Several experimental parameters including ultrasonic power and frequency, centrifugation conditions, extractant volume and sample concentration were analyzed and optimized at 25°C. Under the optimum conditions, it only takes 2 min to reach extraction equilibrium, and the solutions of sample can be separated by centrifugation in 4 min. After centrifugation, the concentrations in n-octanol phases are analyzed with gas chromatography. The method was further evaluated with eight reference compounds and the findings demonstrated that this method is suitable to determine the partition coefficients of organic compounds accurately and quickly. Next, the method was exploited to measure the partition coefficients of n-octanol-water containing 20 organic compounds, which cover the [Formula: see text] values from 0.05 to 4.36, with comparatively low relative standard deviation (RSD) directly. The results of this study illustrated that the RSD (n = 6) was under 3%.

Optimisation of rosemary oil encapsulation in polycaprolactone and scale-up of the process

Rosemary essential oil (REO) has many biological activities, such as antioxidant, anticarcinogenic, cognition-enhancing, analgesic and antimicrobial activities. The aim of this study was to prepare, at laboratory scale and larger scale, nanoencapsulating REO in order to reduce its volatilisation, light sensitivity and to enhance its water solubility. The nanoprecipitation method was applied to prepare polycaprolactone (PCL)-based nanocapsules loaded with REO at laboratory scale and then the optimal formulation obtained was scaled-up (×6) using the membrane contactor technique. The effect of several parameters, such as the evaporation method, the type of emulsifiers and the amount of the formulation products (PCL, REO, emulsifiers, etc.) on the REO-loaded nanocapsules properties (mean size, polydispersity index (PdI), zeta potential and REO loss) was evaluated at laboratory scale in order to obtain the optimal formulation. REO-loaded nanocapsules obtained from nanoprecipitation presented a nanometric mean size (220 ± 10 nm) with a PdI below 0.25, indicating an adequate homogeneity of the system, a negative zeta potential (-19.9 ± 4.6 mV) and a high encapsulation efficiency (∼99% for the major components). In addition, the membrane contactor technique gave similar results using an adequate pressure of the organic phase (0.8-1.2 bar). It is then suggested that the nanoprecipitation method can be suitable for the preparation of essential oil-loaded nanocapsules.

Study of lipophilicity of alpha-asarone derivatives and their deterrent activity against the Colorado potato beetle

Five positional isomers and thirty derivatives of alpha-asarone wereobtained as a bioactive set of substances, and their deterrent activity against the Colorado potato beetle was studied. The lipophilicity values of thirty-six compounds were determined by using experimental, chromatographic and theoretical methods. The logk w values for all compounds were determined by reversed-phase high-performance liquid chromatography using five different columns. The octan-1-ol/water partition coefficients values were determined experimentally as a measure of lipophilicity. For the purpose of comparison, theoretical lipophilic parameters for all compounds were calculated with the use of chemical programs. The experimental, chromatographic and calculated values were compared using linear regression analysis. The most significant correlations were found between the chromatographic lipophilicities using methanol/water for all tested columns and calculated values. It has been found that 13 compounds have the lowest lipophilicities, which correspond to deterrent activity. The presented results show that the computational method is useful for determining the lipophilicity of a series of homologues, but not for positional isomers. In addition, this study shows that determination of lipophilicity using HPLC with various stationary phases is practical and reasonable for all alpha-asarone derivatives.

Improving permeability and oral absorption of mangiferin by phospholipid complexation

Mangiferin is an active ingredient of medicinal plant with poor hydrophilicity and lipophilicity. Many reports focused on improving aqueous solubility, but oral bioavailability of mangiferin was still limited. In this study, we intended to increase not only solubility, but also membrane permeability of mangiferin by a phospholipid complexation technique. The new complex's physicochemical properties were characterized in terms of scanning electron microscopy (SEM), differential scanning calorimetry (DSC), infrared absorption spectroscopy (IR), aqueous solubility, oil-water partition coefficient and in vitro dissolution. The intestinal absorption of the complex was studied by the rat in situ intestinal perfusion model. After oral administration of mangiferin-phospholipid complex and crude mangiferin in rats, the concentrations of mangiferin were determined by a validated RP-HPLC method. Results showed that the solubility of the complex in water and in n-octanol was enhanced and the oil-water partition coefficient was improved by 6.2 times and the intestinal permeability in rats was enhanced significantly. Peak plasma concentration and AUC of mangiferin from the complex (Cmax: 377.66 μg/L, AUC: 1039.94 μg/L*h) were higher than crude mangiferin (Cmax: 180 μg/L, AUC: 2355.63 μg/L*h). In view of improved solubility and enhanced permeability, phospholipid complexation technique can increase bioavailability of mangiferin by 2.3 times in comparison to the crude mangiferin.

Structural and thermodynamic basis of (+)-α-pinene binding to human cytochrome P450 2B6

Despite recent advances in atomic-level understanding of drug and inhibitor interactions with human cytochromes P450, the decades-old questions of chemical and structural determinants of hydrocarbon binding are still unanswered. (+)-α-Pinene is a monoterpene hydrocarbon that is widely distributed in the environment and a potent P450 2B inhibitor. Therefore, a combined biophysical and structural analysis of human P450 2B6 interactions with (+)-α-pinene was undertaken to elucidate the basis of the very high affinity binding. Binding of (+)-α-pinene to the P450 active site was demonstrated by a Type I spectral shift. Thermodynamics of ligand binding were explored using isothermal titration calorimetry and compared to those of P450 2A6, which is much less flexible than 2B6 based on comparison of multiple X-ray crystal structures. Consistent with expectation, entropy is the major driving force for hydrocarbon binding to P450 2A6, as evidenced by the calorimetric results. However, formation of the 2B6-(+)-α-pinene complex has a significant enthalpic component. A 2.0 Å resolution crystal structure of this enzyme-ligand complex reveals that the highly plastic 2B6 utilizes previously unrecognized rearrangements of protein motifs. The results indicate that the specific components of enthalpic contribution to ligand binding are closely tied to the degree of enzyme flexibility.

Physicochemical properties and photodynamic activity of novel derivatives of triarylmethane and thiazine

Triarylmethane and thiazine dyes have attracted attention as anticancer and antimicrobial agents, due to their structural features and selective localizations. Although these dyes have been initially explored in the context of photodynamic therapy, some of these such as New Fuchsin and Azure B have still not been extensively investigated. For this reason, we evaluated the chemical stability, aggregation effect, and lipophilicity, as well as the photodynamic activity against LM-2 murine mammary carcinoma cells of five new brominated dyes of triarylmethane and thiazine. These cationic compounds were obtained at high purities and unequivocally characterized by conventional techniques. The introduction of bromine atoms into the chromophoric system of New Fuchsin and Azure B dyes gave rise to a moderate bathochromic shift and increased the lipophilicity, thereby improving their photophysical and photochemical properties for biomedical applications. Moreover, the in vitro photodynamic activity demonstrated that, as the degree of bromination increased, the phototoxicity remained unchanged or decreased. The lower efficiency to inactivate cultured tumor cells may be attributed to the formation of the colorless carbinol pseudobase and aggregation effects for triarylmethane and thiazine dyes, respectively. A promising strategy to reverse the biological activity decrease observed might be the design of third-generation photosensitizers.

Memantine-sulfur containing antioxidant conjugates as potential prodrugs to improve the treatment of Alzheimer's disease

The approved treatments for Alzheimer's disease (AD) exploit mainly a symptomatic approach based on the use of cholinesterase inhibitors or N-methyl-D-aspartate (NMDA) receptor antagonists. Natural antioxidant compounds, able to pass through the blood-brain barrier (BBB), have been extensively studied as useful neuroprotective agents. A novel approach towards excitotoxicity protection and oxidative stress associated with excess β amyloid (Aβ) preservation in AD is represented by selective glutamatergic antagonists that possess as well antioxidant capabilities. In the present work, GSH (1) or (R)-α-lipoic acid (LA) (2) have been covalently linked with the NMDA receptor antagonists memantine (MEM). The new conjugates, proposed as potential antialzheimer drugs, should act both as glutamate receptor antagonists and radical scavenging agents. The physico-chemical properties and "in vitro" membrane permeability, the enzymatic and chemical stability, the demonstrated "in vitro" antioxidant activity associated to the capacity to inhibit Aβ(1-42) aggregation makes at least compound 2 a promising candidate for treatment of AD patients.

Glycosylation facilitates transdermal transport of macromolecules

Stratum corneum, the outermost layer of skin, allows transport of only low-molecular weight (<500) lipophilic solutes. Here, we report a surprising finding that avicins (Avs), a family of naturally occurring glycosylated triterpenes with a molecular weight > 2,000, exhibit skin permeabilities comparable to those of small hydrophobic molecules, such as estradiol. Systematic fragmentation of the Av molecule shows that deletion of the outer monoterpene results in a 62% reduction in permeability, suggesting an important role for this motif in skin permeation. Further removal of the tetrasaccharide residue results in a further reduction of permeability by 79%. These results, taken in sum, imply that synergistic effects involving both hydrophobic and hydrophilic residues may hold the key in facilitating translocation of Avs across skin lipids. In addition to exhibiting high permeability, Avs provided moderate enhancements of skin permeability of estradiol and polysaccharides, including dextran and inulin but not polyethylene glycol.

Integrated bioprocess for the stereospecific production of linalool oxides from linalool with Corynespora cassiicola DSM 62475

Linalool oxides are of interest to the flavour industry because of their lavender notes. Corynespora cassiicola DSM 62475 has been identified recently as a production organism because of high stereoselectivity and promising productivities [Mirata et al. (2008) J Agric Food Chem 56(9):3287-3296]. In this work, the stereochemistry of this biotransformation was further investigated. Predominantly (2R)-configured linalool oxide enantiomers were produced from (R)-(-)-linalool. Comparative investigations with racemic linalool suggest that predominantly (2S)-configured derivatives can be expected by using (S)-(+)-configured substrate. Substrate and product inhibited growth even at low concentrations (200 mg l⁻¹). To avoid toxic effects and supply sufficient substrates, a substrate feeding product removal (SFPR) system based on hydrophobic adsorbers was established. Applying SFPR, productivity on the shake flask scale was increased from 80 to 490 mg l⁻¹ day⁻¹. Process optimisation increased productivity to 920 mg l⁻¹ day⁻¹ in a bioreactor with an overall product concentration of 4.600 mg l⁻¹ linalool oxides.

Yeast cells as microcapsules. Analytical tools and process variables in the encapsulation of hydrophobes in S. cerevisiae

Yeast cells can be used as biocompatible and biodegradable containers for the microencapsulation of a variety of actives. Despite the wide application of this process, e.g. in the food industry, mechanism and controlling factors are yet poorly known. In this study we have studied kinetics and mechanistic aspects of the spontaneous internalization of terpenes (as model hydrophobic compounds) in Saccharomyces cerevisiae, quantifying their encapsulation through HPLC analysis and fluorescent staining of lipidic bodies with Nile Red, while in parallel monitoring cell viability. Our results showed that this encapsulation process is essentially a phenomenon of passive diffusion with negligible relevance of active transport. Further, our evidence shows that the major determinant of the encapsulation kinetics is the solubility of the hydrophobe in the cell wall, which is inversely related to partition coefficient (log P).

Persistency assessment and aerobic biodegradation of selected cyclic sesquiterpenes present in essential oils

Sesquiterpenes are ubiquitous in essential oils but an assessment of their environmental behavior is still required for their use as components of natural fragrance ingredients and oral care flavors. Persistency plays a key role in hazard and risk assessment, but the current knowledge on the biodegradation of sesquiterpenes in the aquatic environment is limited. This could have important consequences for the persistent, bioaccumulative and toxic (PBT) assessment of essential oils because most of the sesquiterpene components have a log K(OW) of >4.5 and are identified as potentially bioaccumulating according to REACH screening criteria. In the present study, a persistency screening assessment was conducted on 11 cyclic sesquiterpenes selected from 10 different families of sesquiterpenes characterized by their carbon skeleton. Current biodegradation prediction models (BioWin™, BioHCwin, and Catalogic) were found to be of limited use because most of the sesquiterpenes studied were outside the structural domain of the models. Aerobic biodegradation was measured in a standard or prolonged Organisation for Economic Co-operation and Development (OECD) 301F Manometric Respirometry test for ready biodegradability. α-Bisabolol, α-humulene, β-caryophyllene, α-cedrene, cedrol, longifolene, and δ-cadinene exceeded the pass level of 60% degradation and can be regarded as not persistent. Alpha-gurjunene, himachalenes (α, β, γ), and (-)-thujopsene almost achieved the pass level reaching between 51% and 56% ultimate biodegradation. Although germacrene D only achieved 24% ultimate biodegradation, specific analysis at the end of the test did indicate complete primary degradation. Given that the shape of the biodegradation curves indicates poor bioavailability and ready biodegradability tests are very stringent, it is expected that all the sesquiterpenes tested in the present study would be degraded under environmental conditions.

Physicochemical characterization of NPC 1161C, a novel antimalarial 8-aminoquinoline, in solution and solid state

NPC 1161C is a novel antimalarial drug of interest because of its superior curative and prophylactic activity, and favorable toxicity profile against in vivo and in vitro models of malaria, pneumocystis carinii pneumonia, and leishmaniasis. The preformulation studies performed included determination of pK(a)s, aqueous and pH solubility, cosolvent solubility, log P, pH stability, thermal analysis, and preliminary hygroscopicity studies. The mean pK(a1), pK(a2), and pK(a3) were determined to be 10.12, 4.07, and 1.88, respectively. The aqueous solubility was found to be 2.4×10(-4) M having a saturated solution pH of 4.3-5.0 and a low intrinsic solubility of 1.6×10(-6) M. A mathematical model of the pH-solubility profile was derived from pH 2.2 to 8.0. An exponential decrease in solubility was observed with increasing pH. The excess solid phase in equilibrium with the solution in aqueous buffers was determined to be the free-base form of the drug. A significant increase in solubility was observed with all the cosolvents studied, in both unbuffered and buffered systems. Mean log P of the salt and the free base were estimated to be 2.18 and 3.70, respectively. The compound had poor stability at pH 7.0 at 37 °C, with a t (90) of 3.58 days. Thermal analysis of the drug using DSC and TGA revealed that the drug is present as a semi-crystalline powder, which transformed into the amorphous state after melting. The drug was also found to sublime at higher temperatures. Determination of physicochemical properties of NPC 1161C provided useful information for the development of a dosage form and preclinical evaluation.

Levels of mint and wintergreen flavorants: smokeless tobacco products vs. confectionery products

Nicotine and flavorant compound levels were measured in 10 "mint"-related sub-brands and 8 "wintergreen" sub-brands of smokeless tobacco (SLT). Also analyzed were "mint"-related and "wintergreen" confectionery products. Of the "mint" SLT, "Timberwolf Packs Mint Pouches" contained the highest menthol level (5.3 mg/g); the average for the five most-highly mentholated SLT products was 4.3 mg/g. The average for the most five most-highly mentholated confectionery products was 3.5 mg/g. For hard candy, a reported average of maximum use levels is 2.1 mg/g (Burdock, 2009). Of the "wintergreen" SLT, "Hawken Wintergreen" was found to contain the highest methyl salicylate (MS) level (29.7 mg/g). The average of the five highest SLT MS levels was 23.8 mg/g, i.e., 5x higher than the level found in the confectionery product with the highest MS level (LifeSavers Wint O Green Sugar Free, 4.6 mg/g). For hard candy, a reported average of maximum use levels is 2.0 mg/g (Burdock, 2009). Assuming 23.8 mg/g MS in SLT, SLT use at 15 g/day, 100% bodily absorption of the MS, and 60 kg body weight, the average daily intake would be 6.0 mg/kg-day, i.e., 12x the acceptable daily intake (ADI) of 0.5 mg/kg-day established for this compound by a joint FAO/WHO committee.

Development of a new genotyping assay for detection of the BDNF Val66Met polymorphism using melting-curve analysis

Brain-derived neurotrophic factor (BDNF) plays a critical role in the growth, differentiation and survival of neurons in the CNS. Recent research has suggested that BDNF may be implicated in the etiology of mood disorders and schizophrenia, as well as in the therapeutic action of some drugs, such as antidepressants and antipsychotics. This study aimed to develop a simple, fast and accurate new method for detecting the Val66Met polymorphism of the BDNF gene in schizophrenia patients using melting-curve analysis and a DNA-specific dye, SYBR Green I. A group of 30 schizophrenia patients were analyzed to detect the BDNF Val66Met polymorphism (rs6265) using the new genotyping method based on the analysis of fluorescence melting curves of PCR products that were labeled with SYBR Green I. The genotype results were confirmed for all 30 samples using the specific BDNF TaqMan allele discrimination assay. This new method allows the analysis of both alleles in the same reaction tube using SYBR Green I, with no need for additional steps. The addition of a GC clamp makes this method universally applicable, since the melting temperature of one allele can be adjusted as necessary to give the distinctive separation of melting curves. Therefore, this new method is simple, fast and accurate for determining the presence of the BDNF Val66Met polymorphism. It may also be useful for the analysis of other SNPs in pharmacogenetic studies.

Pharmacokinetics of 1,8-cineole, a dietary toxin, in the brushtail possum (Trichosurus vulpecula): Significance for feeding

1,8-Cineole (cineole) is a Eucalyptus leaf toxin that defends against predation by herbivores such as the brushtail possum (Trichosurus vulpecula). The aim of the current study was to characterize the pharmacokinetics of cineole in the possum to improve understanding about how possums can avoid cineole toxicity when eating a Eucalyptus diet. Nine male possums were trapped in the wild and acclimated to captivity; a subcutaneous port was then implanted for venous blood sampling. Cineole was administered intravenously (10 and 15 mg kg(-1)) via a lateral tail vein and orally (30, 100 and 300 mg kg(-1)) by gavage, and blood concentrations of cineole and its metabolites were determined by gas chromatography. Cineole had a large terminal volume of distribution (V(z) = 27 l kg(-1)) and a high clearance (43 ml min(-1) kg(-1)), equal to hepatic blood flow. The terminal half-life was approximately 7 h. Oral bioavailability was low (F = 0.05) after low doses, but increased tenfold with dose, probably due to saturable first-pass metabolism. These findings indicate that when possums feed on a cineole diet, they eat until the cineole consumed is sufficient to saturate pre-systemic metabolism, leading to a rapid rise in bioavailability and cineole blood levels, and a cessation of the feeding bout. This is the first report on the pharmacokinetics of a dietary toxin in a wild herbivore, and provides insights into the interactions between the blood concentration of a plant secondary metabolite and the browsing behaviour of a herbivore.

LogD: lipophilicity for ionisable compounds

The octanol/water partition coefficient (Kow) for organic compounds is widely used in predictive environmental studies. A significant proportion of contaminants of surface and ground water are ionisable (e.g. many pesticides, pharmaceuticals, metabolites). Such compounds may be partially ionised dependent on the pH. Since the neutral and ionic species exhibit different polarities, the Kow value of ionisable pesticides is pH dependent. It is therefore essential to determine Kow values over the full range of pH that occurs in the environment in order to get appropriate predictors. Numerous methods are available to measure lipophilicity but only a few are appropriate for ionisable pesticides (e.g. pH metric and filter probe methods). Parameters such as pH and ionic strength need to be carefully controlled when working with ionisable compounds. Variation of these factors probably explains why literature can yield Kow values that differ by more than one order of magnitude for some compounds. In this article, Kow values obtained for six acidic pesticides with three different methods are compared as well (data from the literature, measured by pH metric method and calculated with five computer programs). The values used in predictive regression equations needs to be either measured with a suitable method or selected from the literature with great care.

A new hazard index of complex mixtures integrates bioconcentration and toxicity to refine the environmental risk assessment of effluents

A new methodology to evaluate the overall environmental hazard of unknown mixtures, based on bioconcentration potential and toxicity, was developed using a combination of two methodologies: 1) the estimation of the octanol-water partition coefficient (K(ow)) using reverse-phase high performance liquid chromatography (RP-HPLC) and 2) the toxicity identification evaluation (TIE). Forty seven compounds with known K(ow) and different molecular structures where used for the calibration of the log K(ow) in relation to the retention time in reverse-phase high performance liquid chromatography (RP-HPLC). A linear regression with an R(2)=0.81 and an sd=0.69 was established between log K(ow) and RP-HPLC retention time. This K(ow) estimation method was furthermore validated using seven additional compounds, showing acceptable estimations of the log K(ow) of unknown substances. Two different mixtures were tested, one containing 3,4 Dichloroaniline, Diazinon and 4-Nonylphenol and another one containing a mixture of 16 pesticides. Both mixtures were first tested as a whole effluent and then fractionated and tested, using a miniaturized Daphnia magna test. An equation is presented, that combines both methodologies and establishes a relative hazard index RHI, ranging from 1 to 10 for any particular mixture of chemicals. The results show how the method presented can refine the security factors that could be included in the environmental risk assessment of effluents in the future.

Mechanisms of flavor release in chewing gum: cinnamaldehyde

Recently we reported that the release profile of cinnamaldehyde from a sugar-free chewing gum was correlated to the release of the sugar alcohol phase or was not in agreement with the log P model. The objective of this study was therefore to investigate mechanisms of cinnamaldehyde release from a sugar-free chewing gum; p-cresol (similar log P value) was also analyzed for comparison. Breath analysis of the chewing gum samples over an 8 min consumption period reported that the maximum concentration of cinnamaldehyde was 2- to 3-fold higher during the initial phase of mastication in comparison to the later phase, whereas the concentration of p-cresol was relatively constant over these two time periods. By contrast the release profile of cinnamaldehyde from a flavored gum base (no sugar alcohol phase) was constant over the 8 min consumption period and similar to the release of cresol from the flavored gum base. On the basis of tandem mass spectrometry, cinnamaldehyde was reported to react with sorbitol and generate hemiacetal reaction products that were not stable under slight alkaline conditions; it was suggested to revert back to free cinnamaldehyde and sugar alcohol in the oral cavity. The increased polarity of these transient cinnamaldehyde-sorbitol hemiacetal reaction products would result in a more rapid release rate of cinnamaldehyde than would be typically predicted based on the affinity of cinnamaldehyde for the gum base.