Identification of metabolites in WZS‐miniature pig urine after oral administration of Danshen decoction by HPLC coupled with diode array detection with electrospray ionization tandem ion trap and time‐of‐flight mass spectrometry

Danshen (DS) is a widely used traditional Chinese medicine for treating cardiovascular and cerebrovascular diseases. A simple, rapid and sensitive method was developed for identification of the in vivo metabolites in urine of WZS‐miniature pigs after oral administration of DS decoction by HPLC coupled with diode array detection with electrospray ionization tandem ion trap and time‐of‐flight mass spectrometry. This method has been successfully applied to simultaneous identification of 50 compounds (including 11 new ones) in pig urine. In addition, one new compound, (3‐hydroxyphenyl) crylic acid glycine methyl ester (C1), along with eight known ones were first isolated by column chromatography and identified by spectroscopic means, including 1D/2DNMR and mass spectrometry, as reference substances. Ten phenolic compounds (protocatechuic aldehyde, protocatechuic acid, caffeic acid, danshensu, ferulic acid, isoferulic acid, rosmarinic acid and salvianolic acid A/B/D) were found to be the main absorbed original constituents of DS decoction, which underwent the metabolic reactions of glucuronidation, sulfation, methylation, hydrogenation and glycine conjugation in vivo. In conclusion, the developed method is applicable to the analysis and identification of constituents in biological matrices after administration of DS decoction. Copyright © 2012 John Wiley & Sons, Ltd.     

Stabilization of zeylenone in rat plasma by the presence of esterase inhibitors and its LC‐MS/MS assay for pharmacokinetic study

Six esterase inhibitors, namely EDTA·2Na⁺, NaF, phenylmethanesulfonyl fluoride, dichlorvos, bis‐nitrophenyl phosphate (BNPP) and thenoyltrifluoroacetone, and the mixture of NaF and BNPP, were evaluated for the stabilization of labile benzoate containing zeylenone in rat plasma. The mixture appeared to exhibit the most effectively stabilizing effect with the degraded content of zeylenone decreasing from >60% (in the absence of inhibitors) to <6%. Following the stabilization by the addition of NaF (5 mm ) and BNPP (5 mm ), the analytes in rat plasma were acidified by formic acid and extracted into ethyl acetate at 0°C. After chromatographic separation, the detection of zeylenone was performed on a 3200 Q‐Trap with positive ion electrospray mode, monitoring the ion transition m/z 383.2 → 105.0. The method was validated over the range from 2.68 to 1340 ng/mL with inter‐ and intra‐run precision for the quality control samples being less than 6.8%. The assay accuracy was within 100 ± 7.0%. The validated method was successfully applied to a pharmacokinetic study in rats after the intratracheal administration of zeylenone in free drug or polymeric micellar solutions. The results showed that the pulmonary absorption of zeylenone loaded in micelles was significantly retarded compared with that of free drug solutions. Copyright © 2012 John Wiley & Sons, Ltd.     

In vitro metabolism study of Strychnos alkaloids using high‐performance liquid chromatography combined with hybrid ion trap/time‐of‐flight mass spectrometry

In this report, the in vitro metabolism of Strychnos alkaloids was investigated using liquid chromatography/high‐resolution mass spectrometry for the first time. Strychnine and brucine were selected as model compounds to determine the universal biotransformations of the Strychnos alkaloids in rat liver microsomes. The incubation mixtures were separated by a bidentate‐C₁₈ column, and then analyzed by on‐line ion trap/time‐of‐flight mass spectrometry. With the assistance of mass defect filtering technique, full‐scan accurate mass datasets were processed for the discovery of the related metabolites. The structural elucidations of these metabolites were achieved by comparing the changes in accurate molecular masses, calculating chemical component using Formula Predictor software and defining sites of biotransformation based upon accurate MSⁿ spectral information. As a result, 31 metabolites were identified, of which 26 metabolites were reported for the first time. These biotransformations included hydroxylation, N‐oxidation, epoxidation, methylation, dehydrogenation, de‐methoxylation, O‐demethylation, as well as hydrolysis reactions. Copyright © 2013 John Wiley & Sons, Ltd.     

Ultra‐high pressure LC for astaxanthin determination in shrimp by‐products and active food packaging

Nowadays, there is increasing interest in natural antioxidants from food by‐products. Astaxanthin is a potent antioxidant and one of the major carotenoids in crustaceans and salmonids. An ultra‐high pressure liquid chromatographic method was developed and validated for the determination of astaxanthin in shrimp by‐products, and its migration from new packaging materials to food simulants was also studied. The method uses an UPLC® BEH guard‐column (2.1 × 5 mm, 1.7 µm particle size) and an UPLC® BEH analytical column (2.1 × 50 mm, 1.7 µm particle size). Chromatographic separation was achieved using a programmed gradient mobile phase consisting of (A) acetonitrile–methanol (containing 0.05 m ammonium acetate)–dichloromethane (75:20:5, v/v/v) and (B) ultrapure water. This method was evaluated with respect to validation parameters such as linearity, precision, limit of detection, limit of quantification and recovery. Low‐density polyethylene films were prepared with different amounts of the lipid fraction of fermented shrimp waste by extrusion, and migration was evaluated into food simulants (isooctane and ethanol 95%, v/v). Migration was not detected under the tested conditions. Copyright © 2012 John Wiley & Sons, Ltd.     

Significant change in water contact angle of electrospray‐synthesized SiO2 films depending on their surface morphology

Amorphous SiO₂ films were deposited by means of an electrospray technique. The relation between the water contact angle (WCA) of the deposited SiO₂ films and the surface morphology is investigated. The feeding rate of the electrospray process greatly affects the morphology of the synthesized SiO₂ films. There is also a significant change in the WCA on the surface of the films: the rougher the surface, the greater the WCA. A model based on the Cassie–Baxter formulation is used to explain the change observed in the WCA on the SiO₂ films. Copyright © 2012 John Wiley & Sons, Ltd.     

Characterization of internal structure of hydrated agar and gelatin matrices by cryo‐SEM

There has been a considerable interest in recent years in developing polymer gel matrices for many important applications such as 2DE for quantization and separation of a variety of proteins and drug delivery system to control the release of active agents. However, a well‐defined knowledge of the ultrastructures of the gels has been elusive. In this study, we report the characterization of two different polymers used in 2DE: Gelatin, a naturally occurring polymer derived from collagen (protein) and agar, a polymer of polysaccharide (sugar) origin. Low‐temperature SEM is used to examine the internal structure of these gels in their frozen natural hydrated states. Results of this study show that both polymers have an array of hollow cells that resembles honeycomb structures. While agar pores are almost circular, the corresponding Gaussian curve is very broad exhibiting a range of radii from nearly 370 to 700 nm. Gelatin pores are smaller and more homogeneous reflecting a narrower distribution from nearly 320 to 650 nm. Overall, these ultrastructural findings could be used to correlate with functions of the polymers.     

Dielectrophoresis with 3D microelectrodes fabricated by surface tension assisted lithography

This paper demonstrates the utilization of 3D semispherical shaped microelectrodes for dielectrophoretic manipulation of yeast cells. The semispherical microelectrodes are capable of producing strong electric field gradients, and in turn dielectrophoretic forces across a large area of channel cross‐section. The semispherical shape of microelectrodes avoids the formation of undesired sharp electric fields along the structure and also minimizes the disturbance of the streamlines of nearby passing fluid. The advantage of semispherical microelectrodes over the planar microelectrodes is demonstrated in a series of numerical simulations and proof‐of‐concept experiments aimed toward immobilization of viable yeast cells.     

Effect of Alcohols on the CMC and Thermodynamic Functions of Anionic Surfactants in DMF/Long‐Chain Alcohol Using Microcalorimetric Method

The critical micelle concentration (CMC) of two kinds of anionic surfactant (including sodium laurate (SLA) and sodium dodecyl sulfate (SDS)) in mixed alcohol and N, N‐dimethyl formamide solvent (DMF) were investigated through measuring power‐time curves by titration microcalorimetry. From data of the lowest point and the area of the power‐time curves, their CMC and ΔH _m ⁰ can be obtained. According to standard thermodynamic equations, ΔG _m ⁰ and ΔS _m ⁰ also can be calculated. For different surfactant, the influences of the carbon number and the concentration of alcohol on the CMC and standard thermodynamic functions are different in DMF polar medium. These thermodynamic functions for micelle formation can be further interpreted.