Temperature as a variable in liquid chromatography: development and application of a model for the separation of model drugs using water as the eluent

The use of high temperatures in liquid chromatography allows for the use of a purely aqueous mobile phase. At elevated temperatures water possesses many of the characteristics of organic solvents in terms of eluotropic strength, as well as having a lower viscosity. A model is developed, based on data obtained using a range of model drugs, which demonstrates the relationship between temperature, flow and pressure. Experimental data from different column types, at temperatures from 40 degrees C to 180 degrees C, is presented which matches well with the predicted data from the model.     

镜像配基筛选:克服“酶屏障”的多肽、寡核苷酸药物研发技术

生物体内存在的酶屏障是功能性多肽和寡核苷酸成药的重要瓶颈.以镜像噬菌体展示技术(mirror-image phage display)和镜像适配体筛选技术(Spiegelmer technology)为代表的镜像配基筛选技术能有效地克服这一屏障,获得对靶点具有特异识别能力且在生理条件下高度稳定的D型多肽和L型寡核苷酸配基,有望成为多肽或寡核苷酸类特异性药物研发的有利工具.本文主要综述镜像配基筛选技术的原理及其在药学领域的研究进展.     

Capillary electrophoretic methods in the development of metal-based therapeutics and diagnostics: new methodology and applications

In recent years, capillary electrophoresis (CE) has matured to a standard method in medicinal inorganic chemistry. More and more steps of the drug discovery process are followed by CE. However, not only the number of applications has steadily increased but also the variety of used methodology has significantly broadened and, as compared to a few years ago, a wider scope of separation modes and hyphenated systems has been used. Herein, a summary of the newly utilized CE methods and their applications in metallodrug research in the timeframe 2006-2011 is presented, following related reviews from 2003 and 2007 (Electrophoresis, 2003, 24, 2023-2037; Electrophoresis 2007, 28, 3436-3446). Areas covered include impurity profiling, quality control of pharmaceutical formulations, lipophilicity estimation, interactions between metallodrugs and proteins or nucleotides, and characterization and also quantification of metabolites in biological matrices and real-world samples.     

Topical application of 5-aminolevulinic acid and its methylester,hexylester and octylester derivatives: considerations for dosimetry in mouse skin model

Ester derivatives of 5-aminolevulinic acid (ALA-esters) have been proposed as alternative drugs for ALA in photodynamic therapy. After topical application of creams containing ALA, ALA methylester (ALA-Me), ALA hexylester (ALA-Hex) and ALA octylester (ALA-Oct) on mouse skin, typical fluorescence excitation and emission spectra of protoporphyrin IX (PpIX) were recorded, exhibiting a similar spectral shape for all the drugs in the range of concentrations (0.5-20%) studied. The accumulation kinetics of PpIX followed nearly a similar profile for all the drug formulations. The fluorescence of PpIX peaked at around 6-12 h of continuous cream application. Nevertheless, some differences in pharmacokinetics were noticed. For ALA cream, the highest PpIX fluorescence was achieved using 20% of ALA in an ointment. Conversely, 10% of ALA-Me and ALA-Hex, but not of ALA-Oct, in the cream was more efficient (P < 0.05) than was 20%. The cream becomes rather fluid when 20% of any of these ALA-esters is used in ointment, whereas 10% and lower concentrations of ALA-esters do not significantly increase fluidity of the cream. The dependence of PpIX accumulation on the concentration of ALA and ALA-ester in the applied cream followed (P < 0.002) kinetics as described by a mathematical model based on the Michaelis-Menten equation for enzymatic processes. Under the present conditions, the PpIX amount in the skin increased by around 50% by the application of ALA-Me, ALA-Hex or ALA-Oct for 4-12 h as compared with ALA for the same period. Observations of the mice under exposure to blue light showed that after 8-24 h of continuous application of ALA, the whole mouse was fluorescent, whereas in the case of ALA-Me, ALA-Hex and ALA-Oct the fluorescence of PpIX was located only at the area of initial cream application. The amount of the active compound in the applied cream necessary to induce 90% of the maximal amount of PpIX was determined for normal mouse skin. Optimal PpIX fluorescence can be attained using around 5% ALA, 10% ALA-Me and 5% ALA-Hex creams during short application times (2-4 h). Topical application of ALA-Oct may not gain optimal PpIX accumulation for short applications (<5 h). For long application times (8-12 h), it seems that around 1% ALA, 4% ALA-Me, 6% ALA-Hex and 16% ALA-Oct can give optimal PpIX fluorescence. But for long application times and high concentrations, systemic effect of ALA applied topically on relatively large areas should be considered.     

Sensitive method for the determination of rocilinostat in small volume mouse plasma by LC‐MS/MS and its application to a pharmacokinetic study in mice

A highly sensitive, specific and rapid LC‐ESI‐MS/MS method has been developed and validated for the quantification of rocilinostat in small volume mouse plasma (20 μL) using vorinostat as an internal standard (IS) as per regulatory guidelines. Sample preparation was accomplished through a protein precipitation procedure with acetonitrile. Chromatography was achieved on Prodigy ODS‐2 column using a binary gradient using mobile phase A (0.2% formic acid in water) and B (acetonitrile) at a flow rate of 0.38 mL/min. The total chromatographic run time was 4.1 min and the elution of rocilinostat and IS occurred at ~3.2 and 2.9 min, respectively. A linear response function was established in the concentration range of 0.28–1193 ng/mL in mouse plasma. The intra‐ and inter‐day accuracy and precisions were in the ranges of 3.12–8.93 and 6.41–11.6%, respectively. This novel method has been applied to a pharmacokinetic study in mice. Copyright © 2016 John Wiley & Sons, Ltd.     

Furan precursors in food: a model study and development of a simple headspace method for determination of furan

Furan was previously detected in foods that had undergone thermal treatment. Because furan is now classified as a possible human carcinogen, a model system was developed to investigate the origins of furan. Also, a simple, rapid isotope dilution (d4-furan) headspace method was developed to measure furan. Two pathways of furan formation have been identified in the model systems tested so far. The first is the oxidation of polyunsaturated fatty acids at elevated temperatures, and the second is linked to the decomposition of ascorbic acid derivatives. The analytical procedure, based on the use of a 50 microL injection (from the headspace of a 1.5 mL vial containing 0.5 mL water) into the split/splitless injection port of a gas chromatograph/mass spectrometer (electron ionization, selected-ion monitoring), showed linearity in the 10-1000 ng/g range with a limit of detection of 1 ng/g.     

Intramolecularly sensitized precipitons: a model system for application to metal sequestration

We have investigated light-triggered or catalytically activated precipitation agents and have proposed the name "precipiton" for such molecules or molecular fragments. A phase separation is induced when the precipiton isomerizes to a low-solubility form. In this paper we describe the first intramolecularly activated precipitons. The isomerization process is induced by intramolecular triplet energy transfer from a covalently attached metal complex. As expected, intramolecular sensitization leads to a more rapid isomerization than can be achieved by intermolecular sensitization at accessible concentrations. Two isomeric bichromophoric precipiton species, each containing [Ru(bpy)(3)](2+) and 1,2-bis(biphenyl)ethene units covalently linked together by an ether tether, have been synthesized and characterized, and their photochemical properties have been investigated. The rates of photoisomerization of these complexes, [((Z)-1,2-bis(biphenyl)ethene-bpy)Ru(bpy)(2)](PF(6))(2) (2Z) and [((E)-1,2-bis(biphenyl)ethene-bpy)Ru(bpy)(2)](PF(6))(2) (2E), were compared to those of their untethered analogues, (Z)-1,2-bis(biphenyl)ethene-OTBS (1Z) and (E)-1,2-bis(biphenyl)ethene-OTBS (1E), where ruthenium sensitization occurred through an intermolecular pathway. Upon irradiation with visible light (lambda > or = 400 nm) in degassed solution, 2Z/E and 1Z/E obeyed reversible first-order rate kinetics. The intramolecularly sensitized precipiton 2Z isomerized 250 times faster (k(2Z-->2E) = 1.0 x 10(-3) s(-1) with a 51% neutral density filter) than the intermolecular case 1Z (k(1Z-->1E) = 0.80 x 10(-5) s(-1)). For 1E and 2E, the isomerization rates were k(1E-->1Z) = 11.0 x 10(-5) s(-1) and k(2E-->2Z) = 1.6 x 10(-3) s(-1), respectively. The average Z/E mole ratio at the photostationary state was 62/38 for 2Z/E and 93/7 for 1Z/E. The impetus for this study was our desire to evaluate the possibility of using metal-binding precipitons that would precipitate only upon metal-to-precipiton binding and would be inert to visible light in the absence of metals.     

Historical Review. Of garlic,mice and Gmelin: the odor of trimethylarsine

In the 19th century, rooms were frequently decorated with wallpaper containing arsenical pigments; illness and fatalities often resulted. In 1839, Leopold Gmelin described a mouse‐like odor under those conditions. Much later, it was recognized that the problem was the formation of toxic and volatile trimethylarsine by fungal action. Gmelin's observation was misreported as a garlic‐like odor that is characteristic of trimethylarsine. Gmelin's original article in German and an English translation are included, and possible explanations for the incorrect reporting and for the original observation are described. Copyright © 2002 John Wiley & Sons, Ltd.     

Recombinant adeno-associated virus mediated gene transfer in a mouse model for homocystinuria

Homocystinuria is a metabolic disorder caused by a deficiency of cystathionine beta-synthase (CBS). The major clinical symptoms of this disease are mental retardation, lens dislocation, vascular disease with life-threatening thromboembolisms, and skeletal deformities. The major treatments for CBS deficiency include pharmacologic doses of pyridoxine or dietary restriction of methionine. There is currently no effective long-term treatment to lower the elevated plasma levels of homocysteine. However, gene therapy could be an effective novel approach for the treatment of homocystinuria. A recombinant adeno- associated virus vector carrying human CBS cDNA (rAAV-hCBS) was constructed and administered to CBS-/- mice by intramuscular (IM) and intraperitoneal (IP) injections. Serum homocysteine concentrations significantly decreased in treated mice compared with age-matched controls two weeks after treatment. The treated CBS-/- mice had life spans 3-7 days longer compared with untreated CBS-/- mice. In CBS-/- mice treated with rAAV-hCBS via IP injection, the vector was detected in all organs examined including liver, spleen, and kidney, and CBS gene expression was observed by immunohistochemical staining in the liver. These results indicate the efficacy of gene delivery and demonstrate the possibility of gene therapy mediated by AAV gene transfer in this mouse model of homocystinuria.     

Topical application of temoporfin-loaded invasomes for photodynamic therapy of subcutaneously implanted tumours in mice: a pilot study

Temoporfin (mTHPC) represents a very potent second-generation synthetic photosensitizer. It has shown to be effective in the photodynamic therapy of early or recurrent oral carcinomas, in the palliative treatment of refractory oral carcinomas and in the treatment of primary non-melanomatous tumours of the skin of the head and neck. Until now for all positive findings an intravenous application of the photosensitizer was mandatory. In the case of cutaneous malignant or non-malignant diseases a topical application of the drug onto the site of the disease followed by illumination, would be advantageous. Unfortunately, mTHPC is a highly hydrophobic drug with a low percutaneous absorption. The purpose of this experiment was to investigate the photodynamic efficacy of novel mTHPC-loaded invasomes after their topical application onto the skin of mice bearing the subcutaneously implanted human colorectal tumour HT29 followed by photoirradiation. Invasomes are vesicles containing in addition to phospholipids a mixture of terpenes (cineole, citral and d-limonene) or only one terpene (citral) and ethanol, as penetration enhancers. This was a pilot study since until now no data are available about the efficacy of mTHPC in the photodynamic therapy of HT29 tumours after its topical application. The aim of this experiment was to investigate whether a mTHPC-loaded invasome formulation can reduce tumour size by photodynamic therapy or at least to find a formulation slowing down tumour growth compared to the control group (mice without any treatment). The groups of mice treated with mTHPC–invasomes containing 1% of the terpene mixture prior to photoirradiation showed a significantly smaller (p < 0.05) tumour increase compared to control groups (mice without any treatment and mice only photoirradiated).     

Approximate rate constants for nonideal diffusion and their application in a stochastic model

Rate constants are presented for diffusion in dilute nonideal solutions with or without the presence of a spatially varying potential field. Expressions for the rate constants have been derived by earlier workers, and essentially the same derivation is reviewed and expanded in this paper to justify the expressions used for the rate constants. The diffusion rate constants are used in a random walker model to demonstrate how solution nonidealities can be captured accurately using this approach. Examples are presented of ideal solute diffusion as well as nonideal diffusion of nonelectrolytes and simple electrolytes in water. The use of the approach to simulate advection is described, and a possible strategy for extending the approach to more concentrated solutions is briefly discussed.     

Validation of a chiral LC‐MS/MS‐ESI method for the simultaneous quantification of darolutamide diastereomers in mouse plasma and its application to a stereoselective pharmacokinetic study in mice

A simple, selective and reliable LC‐MS/MS method was validated for simultaneous quantitation of darolutamide diastereomers in 50 μL mouse plasma using warfarin as an internal standard (IS) as per regulatory guidelines. Plasma samples were extracted by liquid–liquid extraction and the chromatographic separation was achieved on a Chiralpak IA column with an isocratic mobile phase 5 mm ammonium acetate–absolute alcohol (20:80, v/v) at a flow rate of 1.0 mL/min. Detection and quantitation was done in multiple reaction monitoring mode following the transitions m/z 397 → 202 and 307 → 250 for darolutamide diastereomers and the IS, respectively, in the negative ionization mode. The linearity range was 100–2400 ng/mL for each diastereomer. The intra‐ and inter‐day precisions were in the ranges of 1.78–4.20 and 4.34–14.6, and 3.63–4.74 and 4.78–5.15 for diastereomer‐1 and diastereomer‐2, respectively. Both diastereomers were found to be stable under different stability conditions. The validated method was applied to a pharmacokinetic study in mice. Following oral administration of darolutamide at 10 mg/kg, maximum concentration in plasma was 4189 and 726 ng/mL for diastereomer‐1 and diastereomer‐2, respectively. The terminal half‐life was found to be ~0.50 h for both the diastereomers. The AUC_(0–t) was found to be 18,961 ng*h/mL for diastereomer‐1 and 1340 ng*h/mL diastereomer‐2.     

Activity of a cationic carotenoid derivative in a mouse model of protoporphyria

Prior work using cell culture has shown that certain synthetic carotenoid derivatives are more effective than natural carotenoids in preventing photosensitized cell killing. These carotenoid derivatives are either cationic or are weak bases. We have now found that of one of these derivatives, the Girard's reagent T derivative of beta-apo-8'-carotenal (GRT-carotenal) decreases acute photosensitivity in a mouse model of protoporphyria. When GRT-carotenal was added to the diet of SKH1 mice, both GRT-carotenal and its metabolites accumulated in the skin of the mice. Protoporphyria was induced in SKH1 mice by adding collidine to their diet. When the porphyric mice were exposed to 400 nm light (2.6+/-0.1 mW cm(-2)) for a period of 2h, the skin on the backs of these animals increased in thickness. Increased vascularity also developed in the skin of the mouse ears. Animals, that were fed a diet containing both collidine and GRT-carotenal and then exposed to light, had significantly smaller increases in skin thickness and less prominent increases in the vascular pattern on their ears.     

Restatement and a new method of application of the Avrami model

Restatement of the Avrami equation in its nonlinear form, presentation of a convenient method of applying it, and application of the analysis to experimental results are presented. The physical meaning of the model parameters and advantages of applying the nonlinear equation are discussed.

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Zusammenfassung Es werden die nichtlineare Form der Avrami-Gleichung und anhand eines experimentellen Beispiels ein neues geeignetes Anwendungsverfahren beschrieben. Die physikalische Bedeutung der Modellparameter und die Vorteile der Anwendung dieser nichtlinearen Gleichung werden diskutiert.

     

Slimy partners: the mucus barrier and gut microbiome in ulcerative colitis

Ulcerative colitis (UC) is a chronic recurrent intestinal inflammatory disease characterized by high incidence and young onset age. Recently, there have been some interesting findings in the pathogenesis of UC. The mucus barrier, which is composed of a mucin complex rich in O-glycosylation, not only provides nutrients and habitat for intestinal microbes but also orchestrates the taming of germs. In turn, the gut microbiota modulates the production and secretion of mucins and stratification of the mucus layers. Active bidirectional communication between the microbiota and its ‘slimy’ partner, the mucus barrier, seems to be a continually performed concerto, maintaining homeostasis of the gut ecological microenvironment. Any abnormalities may induce a disorder in the gut community, thereby causing inflammatory damage. Our review mainly focuses on the complicated communication between the mucus barrier and gut microbiome to explore a promising new avenue for UC therapy.Subject terms: Glycobiology, Ulcerative colitis     

Multivariate calibration on NIR data: development of a model for the rapid evaluation of ethanol content in bakery products

A new NIR method based on multivariate calibration for determination of ethanol in industrially packed wholemeal bread was developed and validated. GC-FID was used as reference method for the determination of actual ethanol concentration of different samples of wholemeal bread with proper content of added ethanol, ranging from 0 to 3.5% (w/w). Stepwise discriminant analysis was carried out on the NIR dataset, in order to reduce the number of original variables by selecting those that were able to discriminate between the samples of different ethanol concentrations. With the so selected variables a multivariate calibration model was then obtained by multiple linear regression. The prediction power of the linear model was optimized by a new “leave one out” method, so that the number of original variables resulted further reduced.     

Determination of epacadostat,a novel IDO1 inhibitor in mouse plasma by LC–MS/MS and its application to a pharmacokinetic study in mice

A sensitive, specific and rapid LC‐ESI‐MS/MS method has been developed and validated for the quantification of epacadostat in mouse plasma using tolbutamide as an internal standard (IS) as per regulatory guidelines. Sample preparation was accomplished through a protein precipitation. Chromatographic separation was performed on an Atlantis dC₁₈ column using a binary gradient using mobile phase A (acetonitrile) and B (0.2% formic acid in water) at a flow rate of 0.90 mL/min. Elution of epacadostat and IS occurred at ~2.41 and 2.51 min, respectively. The total chromatographic run time was 3.2 min. A linear response function was established in the concentration range of 1.07–533 ng/mL. The intra‐ and inter‐day accuracy and precision were in the ranges of 1.81–12.9 and 3.80–11.1%, respectively. This novel method has been applied to a pharmacokinetic study in mice.     

Kinetic justification of the solubility product: application of a general kinetic dissolution model

Using a simple, feldspar-like model and the crystal-based reaction mechanism for water-rock kinetics being developed before, we show directly how the dissolution of euhedral faces of crystals are governed by the nonlinear quantity represented by the solubility product. The kinetic approach requires recognition of the essential role played by the correlation of the dynamics of neighboring sites in a crystal, the statistical dynamics of steps, the coupling of the various kink sites on the surface by the crystal structure, and the inclusion of bond formation as well as bond rupture into the kinetic reaction mechanism. The same kinetic approach, which accounts for the role of the solubility product (or DeltaG) in the overall rate, is then shown also to explain the observed inhibition behavior in feldspars as well as the often-written phenomenological rate law, involving a product of a pH term, an activation energy term, and a DeltaG term.