Quantification of oxyresveratrol analog trans-2,4,3',5'-tetramethoxystilbene in rat plasma by a rapid HPLC method: application in a pre-clinical pharmacokinetic study

A rapid HPLC method was developed and validated for the quantification of oxyresveratrol analog trans‐2,4,3′,5′‐tetramethoxystilbene (oxyresveratrol tetramethyl ether, OTE) in rat plasma. Chromatographic separation was achieved on an RP‐HPLC column, which was protected by a guard column through a 12 min gradient delivery of a mixture of acetonitrile–water at 50°C. The UV absorbance at 325 nm was recorded. The retention time of OTE and trans‐stilbene (internal standard) was about 7.7 and 8.4 min, respectively. The calibration curves were linear (R² ≥ 0.9986) with a lower limit of quantification of 15 ng/mL. The intra‐ and inter‐day variations, in terms of RSD, were all lower than 9.8% while the intra‐day and inter‐day bias ranged from ?8.3 to +9.2%. The pharmacokinetics of OTE was assessed in rats using 2‐hydroxypropyl‐β‐cyclodextrin as a dosing vehicle. After intravenous administration, OTE possessed a long terminal elimination half‐life (t_{1/2 λz} = 481 ± 137 min) and slow clearance (Cl = 29.1 ± 3.7 mL/min/kg). Upon oral administration, OTE was rapidly absorbed. However, it only displayed minimal plasma exposure and its absolute oral bioavailability (F) was as low as 4.5 ± 3.2%. Fortunately, the levels of OTE after single oral administration were sufficient to inhibit human cytochrome P450 1B1. Copyright © 2010 John Wiley & Sons, Ltd.     

Development of Batch and Continuous Processes on Biodiesel Production in a Packed-Bed Reactor by a Mixture of Immobilized Candida rugosa and Rhizopus oryzae Lipases

In this study, transesterification and esterification were investigated in batch and continuous process using immobilized Candida rugosa and Rhizopus oryzae lipases. In the case of batch process, stepwise reaction method was investigated to prevent the lipase deactivation. Reaction conditions were as follows: temperature, 45 °C; agitation speed, 250 rpm; enzyme concentration, 20%; and water contents 10%. And then, conversion yield was 98.33% at 4 h. In the case of continuous process, circulation and long-term continuous system were investigated for development of efficient mass transfer system. Optimal reaction conditions were as follows: temperature, 45 °C; flow rate, 0.8 mL/min; and water contents, 10%. And then, conversion yield of biodiesel was 97.98% at 3 h. Especially, the maximum conversion yield using a mixture of immobilized lipases exceeded over 90% for 108 h in long-term continuous system under optimal reaction conditions (45 °C; flow rate, 0.8 mL/min; and water contents, 10%). These results should help in determining the best method for the biodiesel production and improving the design and operation of large scale by enzymatic systems.     

Electrospinning fabrication and characterization of poly(vinyl alcohol)/montmorillonite/silver hybrid nanofibers for antibacterial applications

Poly(vinyl alcohol) (PVA)/montmorillonite clay (MMT)/silver (Ag) nanoparticles have been electrospun for fabricating PVA/MMT/Ag nanofiber in aqueous solutions. Since PVA is a water-soluble and biocompatible polymer, it is one of the best materials for preparation of antibacterial nanofiber. MMT has been used as an inorganic filler to enhance properties of homopolymeric nanofiber. The PVA/MMT/Ag nanofiber diameter increases with increasing contents of MMT clay and Ag nanoparticles. In preservation test, the PVA/MMT/Ag nanofiber confirms an excellent antibacterial performance, elucidating for practical uses as a new preservative. Moreover, the PVA/MMT/Ag nanofiber shows improved thermal properties.     

A universal approach for continuum solvent pK a calculations: are we there yet?

This paper reviews several pK _a calculation strategies that are commonly used in aqueous acidity predictions. Among those investigated were the direct or absolute method, the proton exchange scheme, and the hybrid cluster–continuum (Pliego and Riveros) and implicit–explicit (Kelly, Cramer and Truhlar) models. Additionally, these protocols are applied in the pK _a calculation of 55 neutral organic and inorganic acids in conjunction with various solvent models, including the CPCM-UAKS/UAHF, IPCM, SM6 and COSMO-RS, with a view to identifying a universal approach for accurate pK _a predictions. The results indicate that the direct method is unsuitable for general pK _a calculations, although moderately accurate results (MAD <3 units) are possible for certain classes of acids, depending on the choice of solvent model. The proton exchange scheme generally delivers good results (MAD <2 units), with CPCM-UAKS giving the best performance. Furthermore, the sensitivity of this approach to the choice of reference acid can be substantially lessened if the solvation energies for ionic species are calculated via the IPCM cluster–continuum approach. Reference-independent hybrid approaches that include explicit water molecules can potentially give reasonably accurate values (MAD generally ~2 units) depending on the solvent model and the number of explicit water molecules added.     

Ultrasound‐assisted dispersive liquid–liquid microextraction coupled with capillary gas chromatography for simultaneous analysis of nine pyrethroids in domestic wastewaters

A simple and rapid ultrasound‐assisted dispersive liquid–liquid microextraction method coupled with GC‐flame ionization detection was developed for simultaneous determination of nine pyrethroids in domestic wastewater samples. An ultrasound‐assisted process was applied to accelerate the formation of the fine cloudy solution using small volume of disperser solvent, which markedly increased the extraction efficiency and reduced the equilibrium time. Various parameters affecting the extraction efficiency were investigated, including the type and volume of extraction solvent and disperser solvent, extraction and ultrasonic time. Good linearity was obtained for all analytes in the range of 0.8–100 μg/L with the correlation coefficient (r²)≥0.998. The recoveries at three spiking levels ranged from 75.3 to 101.2% with the RSD less than 8.7% (n=5). Under the optimum condition, the enrichment factors for the nine pyrethroids ranged from 728‐ to 1725‐fold. This method offered a good alternative for routine analysis due to its simplicity and reliability.     

Microchip electrophoretic separation for the fast diagnosis of Anaplasma phagocytophilum infection in cattle

We report a diagnostic method for Anaplasma phagocytophilum (A. phagocytophilum) infection in cattle using a nested PCR and microchip electrophoresis (ME). A. phagocytophilum causes human granulocytic anaplasmosis and granulocytic ehrlichiosis, which are emerging tick‐borne zoonotic diseases. Nested PCR was used to amplify genomic DNA samples extracted from cattle blood. The amplified PCR products were analyzed under a sieving gel matrix of 0.7% poly(ethyleneoxide) (M_r=8 000 000) in a conventional glass microchip. In the ME assay, A. phagocytophilum was analyzed within 35 s with a relative standard deviation of 1.30% (n=5) using a programmed field strength gradient (PFSG) as follows: 615.3 V/cm for 0–24 s, 66.7 V/cm for 24–34 s, 615.3 V/cm for 34–100 s. The ME‐PFSG assay was clinically validated by comparing the 16S rRNA gene levels obtained by this method with those measured using conventional slab gel electrophoresis performed with ten cattle blood samples suspected of A. phagocytophilum infection. In contrast to slab gel electrophoresis, the proposed ME‐PFSG methodology had increased sensitivity (200–450 pg/μL), a faster analysis time (<35 s), and required a smaller sample volume (～162 fL).     

Computational design of a self-assembling β-peptide oligomer

The first computationally designed self-assembling oligomer consisting of exclusively β-amino acids (βAAs) is presented. The packing of a β-3(14) helix into coiled-coils of varying stoichiometries as a function of amino acid sequence is examined. β-Peptides with hVal repeating every third residue in the sequence appeared to have a strong propensity to pack into hexameric bundles. The designed sequence was synthesized and characterized with CD spectroscopy, NMR, and analytical ultracentrifugation, suggesting that the peptide adopts a well-folded hexameric structure.     

The Design of Polymer‐based Nanocarriers for Effective Transdermal Delivery

This study reports a facile and practical means to non‐invasively deliver biologically active ingredients through the skin using polymer‐based nanocarriers. For this, polymer nanocapsules were fabricated with different surface charges as well as glass transition temperatures and we observed their ability to deliver the encapsulated active ingredient, coenzyme Q10, through the skin layer. Direct imaging of a probe molecule, Nile Red, and a matrix polymer labeled with fluorescence moiety, Lucifer Yellow, allowed us to demonstrate that the probe molecule readily permeates into the deep skin, while the matrix polymer stays in the stratum corneum layer due to electrostatic interactions. Quantitative characterization of the penetrating amount of coenzyme Q10 using the Frantz cell method proved that, to achieve improved delivery efficiency, the nanocapsule should have a low glass transition temperature as well as positive surface charges.