Glass capillary column chromatography of mixed derivatives of primary prostaglandins, 6-keto prostaglandin F1α and thromboxane B2

This work describes the use of glass capillary columns (GCC) in the rapid concurrent analysis of primary prostaglandins (PGs) (e. g. PGE₂, PGE₂, PGF_2α) and other functionally significant metabolites of arachidonic acid (AA) such as TXB₂ and 6-keto PGF_1α. The use of a new multistep mixed derivatization approach that generates the methyl esters of n-butylboronate, pentafluorobenzyloxime, trimethylsilyl ether derivatives of these compounds remarkably simplifies the GC profiling of the three main pathways of AA metabolism (PGs, thromboxane, and prostacyclin). Furthermore, isomeric species giving very similar or identical mass spectral patterns can be easily identified by their relative retention times on high efficiency capillary columns.     

Nano-LC-MS/MS for the quantitation of prostanoids in immune cells

Prostanoids, derivatives of arachidonic acid, are involved in inflammation and immune reactions. To understand the role of prostanoids produced by diverse immune cells, a highly sensitive quantitation method for prostaglandin E₂ (PGE₂), prostaglandin D₂ (PGD₂), 6-keto prostaglandin F_1α (6-keto PGF_1α), prostaglandin F_2α (PGF_2α), and thromboxane B₂ (TXB₂) by means of nano-liquid chromatography-tandem mass spectrometry has been developed. It was validated according to the guidelines of the Food and Drug Administration (FDA) in terms of linearity, precision, accuracy, recovery, stability, and lower limit of quantitation (LLOQ). The LLOQ were 25 pg/mL in the injected solution (75 fg on column (o.c.)) for PGE₂ and PGD₂ and 37.5 pg/mL (112.5 fg on column) for 6-keto PGF_1α, PGF_2α, and TXB₂, respectively. It was successfully applied to murine mast cells isolated from paws after zymosan injection and to CD4⁺ and CD8⁺ T lymphocytes from blood of sensitized versus non-sensitized mice in context of a delayed type hypersensitivity model. About 5,000 (T cells) to 40,000 (mast cells) cells were sufficient for quantitation. In the mast cells, the production of PGE₂ increased at a significantly higher extent than the synthesis of the other prostanoids. The T lymphocytes did not show any difference in prostanoid production, no matter whether they were obtained from sensitized mice or non-sensitized mice.     

Automated preparative HPLC of prostanoids

Summary The separation of prostaglandins (PG) PGE₁, PGE₂, PGF_1α , PGF_2α and PGF_2β on Silasorb 600 columns with a water-containing mobile phases is described. A flexible, automated, preparative liquid-chromatographic (PLC) system has been used involving column switching, column temperature control, solvent selection and automated fraction collection.     

The occurrence of prostaglandins PGE2 and PGF2α in a plant - the red alga Gracilaria Lichenoides.

Prostaglandins PGE₂ and PGF_2α were isolated from the aqueous extract of the red alga $\text{Gracilaria lichenoides}$, after an investigation of the extract's anti-hypertensive properties.     

Differences in the low-energy collision-activated dissociation of carboxylate anions from structurally similar prostaglandins: E2, F2α, D2, and DHKF2α

Some intriguing discoveries were made concerning the collision-activated dissociation behavior of the derivatized carboxylate anions of PGE₂ and PGF_2α. The carboxylate anion [MPFB]^? formed from electron-capture negative chemical ionization of the pentafluorobenzyl ester-trimethylsilyl derivative of PGF_2α showed little fragmentation under typical collision gas pressures and energies (<2.0 mtorr N₂ and <20 eV). In contrast, the daughter spectra of the carboxylate anion of the methoxime-pentafluorobenzyl ester-trimethylsilyl derivative of PGE₂ produced many intense fragments under the same conditions.     

Development of an extraction method for the determination of prostaglandins in biological tissue samples using liquid chromatography–tandem mass spectrometry: Application to gonads of Atlantic cod (Gadus morhua)

A simple extraction method for the analysis of PGE₂ and PGF_2α in gonad samples from Atlantic cod and further quantification by using liquid chromatography–tandem mass spectrometry is proposed. The evaluation of the best solvent extraction conditions and the analytical performance parameters are reported. The method was highly selective for both prostaglandins and the calibration curves, based on the internal standard method, were linear between 5 and 1000 ng mL⁻¹ for PGE₂ and PGF_2α, with limits of detection of 1 ng mL⁻¹ and 1.5 ng mL⁻¹ and recovery values of 99.999 ± 0.002 and 99.967 ± 0.023 respectively. The homogenization of samples using liquid nitrogen combined with the developed extraction protocol can be implemented in different types of biological tissues.     

Role of CA2+ ion in the abortifacient action of prostaglandins. II. Molecular orbital and conformation energy calculations of PGA1

This paper reports some theoretical studies of PGA₁ using conformational and molecular orbital techniques. The conformation energy (CE ) calculations, using empirical potential-energy functions, for intrinsic torsional rotations around C₁₂? C₁₃ (θ), C₇? C₈ (Ψ), and C₁₄? C₁₅ (?) show a number of energy minima. The relative value of the CE for these minima ranges from 4.09 to 8.01 kcal/mol. An additional rotation around C₄? C₅ (χ) giving “twist” to the carboxyl chains lowers the CE value by 2–3 kcal/mol and a conformation with CE value 2.39 kcal/mol less than crystallographic one is obtained. The interchain interaction energy showed changes with conformations. No significant change in the interchain interaction energy was observed due to “twist” in the carboxyl chain. The isopotential mapping study demonstrated the probable ionic binding site near the carboxyl and the ring (O₉) oxygens. Conformational and molecular orbital results are discussed in the light of the reduced abortifacient potency of PGA₁ with respect to PGF_2α and the possible role of Ca²⁺ ions in this action.     

Determination of prostaglandin profiles in lipopolysaccharide‐challenged guinea pig spleen

We previously reported that splenic extract from lipopolysaccharide (LPS)‐challenged guinea pigs inhibits the exaggerated febrile response of splenectomized guinea pigs, suggesting that the spleen generates an inhibitory factor. Earlier results indicate that the factor is a lipid. In an effort to identify this factor, lipid fractions, isolated from splenic extracts of control and LPS‐challenged guinea pigs, were analyzed with emphasis on identifying and quantifying prostanoids, which according to current knowledge are the likely bioactive factors. Prostaglandins have been extensively implicated in central and peripheral thermoregulation, and thus these lipids were targeted for characterization in the spleen. Analysis was done on the splenic extracts using solid‐phase extraction, analytical and preparative thin‐layer chromatography (TLC) and high‐performance liquid chromatography–mass spectrometry (HPLC‐MS/MS). Four prostaglandins (PGs, 6‐keto‐PGF_1α, PGF_2α, PGE₂ and PGD₂) were identified and quantified. Our data shows that these PG levels are doubled in LPS‐treated guinea pig spleen compared with the control group. The methods used in this investigation to characterize PG in the spleen offer significant advantages over immunoassays previously used to identify and quantify PG in the spleen and other biological tissues. These methods will be utilized in further research needed to definitively characterize the role of splenic‐derived PG in modulation of the febrile response induced by LPS. Copyright © 2012 John Wiley & Sons, Ltd.     

Total synthesis of PGF2α and 6,15-diketo-PGF1α and formal synthesis of 6-keto-PGF1α via three-component coupling

The asymmetric total synthesis of PGF_2α and 6,15-diketo-PGF_1α and formal synthesis of 6-keto-PGF_1α from a common key intermediate are described. The key intermediate, which has a chiral cyclopentane backbone possessing suitable functional groups with required stereochemistry for both side chains, was prepared from (R)-4-silyloxy-2-cyclopentenone through a three-component coupling reaction. The Wittig reaction, Nozaki-Hiyama-Kishi (NHK) coupling and cross metathesis completed the synthesis of PGF_2α, 6,15-diketo-PGF_1α and 6-keto-PGF_1α.     

Determination of urinary prostanoids by capillary gas chromatography/high-resolution mass spectrometry

A stable isotope-dilution gas-chromatography/high-resolution mass spectrometry method for the determination of prostaglandin E₂ (PGE₂) and 6-keto-prostaglandin F_1α (6-keto-PGF_1α) in urine as their methoxime/t-butyldimethylsilyl ether/t-butyl-dimethylsilyl ester derivatives is described. The derivatives are prepared by a novel derivatization scheme in which the pentafluorobenzyl esters are formed prior to the silylation step in which the t-butyldimethylsilyl esters are formed in an apparent exchange reaction. Recoveries through the entire extraction and derivatization procedure are 70.6% for PGE₂ and 64.4% for 6-keto-PGF_1α. Quantitation at mass resolutions approaching 10 000 eliminated all interferences in the PGE₂ chromatograms while lower resolutions were sufficient for 6-keto-PGF_1α. Limits of detection of 50 pg ml^?1 for each prostanoid were obtained. For PGE₂, a lower limit of detection was obtained at a mass resolution of 10 000 (50 pg ml^?1) than was obtained at a mass resolution of 1000 (80 pg ml^?1), illustrating the selectivity of detection.     

Determination of 8‐epi PGF2α concentrations as a biomarker of oxidative stress using triple‐stage liquid chromatography/tandem mass spectrometry

F2‐isoprostanes are a family of prostaglandin F2‐like compounds that are formed by free‐radical‐catalyzed peroxidation of arachidonic acid. Several F2‐isoprostanes, but in particular 8‐epi PGF_2α, are widely used as oxidative stress biomarkers. An analytical method based on liquid chromatography with negative electrospray ionization (ESI) coupled to tandem mass spectrometric detection (LC/MS/MS) was developed for the determination of 8‐epi PGF_2α concentrations in human plasma, whole blood, erythrocytes and urine. 8‐epi PGF_2α‐d4, a stable isotope derivative of 8‐epi PGF_2α, was used as an internal standard (IS). A 50 µL sample was focused on‐column and separated on two 3 µm particle size SUPELCOSIL? ABZ+Plus HPLC columns (15 cm × 4.6 mm and 7.5 cm × 4.6 mm) connected in series. An Applied Biosystems 4000 Q TRAP LC/MS/MS system with ESI was operated in multiple reaction monitoring (MRM) mode with the precursor‐to‐product ion transitions m/z 353.4 → 193.1 (8‐epi PGF_2α), 357.4 → 197.1 (8‐epi PGF_2α‐d4), used for quantification. The assay was fully validated and found to have adequate accuracy, precision, linearity, sensitivity and selectivity. The mass limit of detection (mLOD) was 1 pg of analyte eluting from the column. The assay has been successfully applied to the analysis of human plasma, whole blood, erythrocytes and urine samples. Copyright © 2009 John Wiley & Sons, Ltd.     

The conversion of asperuloside to an optically active prostaglandin intermediate

Synthesis of optically active intermediate $\text{1a}$ for PGF_2α or (+)-11-deoxy-11α-hydroxymethyl PGF_2α from asperuloside is described.     

Differences in the Low-Energy Collision-Activated Dissociation of Car☐ylate Anions from Structurally Similar Prostaglandins: E2, F2α, D2 and DHKF2α

Some intriguing discoveries were made concerning the collision-activated dissociation behavior of the derivatized car☐ylate anions of PGE₂ and PGF_2α. The car☐ylate anion [M-PFB]⁻ formed from electron-capture negative chemical ionization of the pentafluorobenzyl ester-trimethylsilyl derivative of PGF_2α showed little fragmentation under typical collision gas pressures and energies (<2.0 mtorr N₂ and <20 eV). In contrast, the daughter spectra of the car☐ylate anion of the methoxime-pentafluorobenzyl ester-trimethylsilyl derivative of PGE₂ produced many intense fragments under the same conditions.     

Stereoselective synthesis of novel N-(α-l-arabinofuranos-1-yl)-l-amino acids

In lead detoxification, the α-anomer of N-glycocyl-l-amino acid is more potent than its β-anomer. Here a six-step-reaction route for stereoselectively preparing N-(α-l-arabinose-1-yl)-l-amino acids is reported. Treating l-arabinose with acetic anhydride and sodium acetate provided 1,2,3,5-tetra-O-acetyl-l-arabinofuranose in 90% yield. After removing the 1-acetyl group, the thus formed 2,3,5-tri-O-acetyl-l-arabinofuranose and N-(2-nitrophenylsulfonyl)-l-amino acid t-butylesters were treated with triphenylphosphine to perform Mitsunobu dehydration and form 2,3,5-tri-O-acetyl-l-arabinofuranosyl-l-[N-(2-nitrophenylsulfonyl)]amino acid t-butylesters 2a–f, and the ratios of their α- to β-anomer ranged from 8/1 to 9/1. Chromatographic separation provided epimerically pure 2a–f-α and 2a–f-β. In the presence of CF₃CO₂H, 2a–f-α and 2a–f-β were converted to α- and β-anomers of N-(2,3,5-tri-O-acetyl-l-arabinofuranosyl)-N-(2-nitrobenzenesulfonyl)-l-amino acids, 3a–f-α and 3a–f-β, in 87–92% yields. While in the presence of NaOCH₃, 3a–f-α and 3a–f-β were converted to α- and β-anomers of N-(l-arabinofuranosyl)-N-(2-nitrobenzenesulfonyl)-l-amino acids, 4a–f-α and 4a–f-β, in 90–96% yields. Treating 4a–f-α and 4a–f-β with N-ethyldiisopropylamine (DIPEA) and thiophenol, their 2-nitrophenylsulfonyl groups were removed, and the α- and β-anomers of N-(l-arabinose-1-yl)-l-amino acids were formed in 70–79% yields. The bioassay confirmed that the lead detoxification activity of the α-anomer was significantly higher than that of the β-anomer.     

Compatibility effects of herb pair Phellodendri chinensis cortex and Anemarrhenae rhizoma on benign prostatic hyperplasia using targeted metabolomics

Phellodendri chinensis cortex (P. C. cortex) and Anemarrhenae rhizoma (A. rhizoma) herb pair is a core component of traditional Chinese medicines used to treat inflammation and benign prostatic hyperplasia (BPH). The present study was designed to profile the arachidonic acid (AA) metabolomic characteristics in rat plasma and prostate after being treated with P. C. cortex and A. rhizoma as well as their combination. Plasma and prostate samples from sham group, BPH model group, herb pair group and two single herb groups were collected on days 7, 14, 21 and 28. Then, a systemic metabolomic analysis based on UFLC‐MS/MS was employed to quantify AA and its cyclooxygenase and lipoxygenase pathway metabolites (15‐HETE, 12‐HETE, 5‐HETE, AA, PGI₂, PGF_2α, 8‐HETE, PGD₂, PGE₂ and LTB₄). The results demonstrated that BPH led a significant increase of 10 biomarkers in plasma and tissue (p < 0.05). The clusters of herb pair group and single herb groups showed a tendency to return to the initial space, and the AA and its metabolites from those groups were differently downregulated to a healthier level, with the combination of single herbs most obvious. The present study demonstrated that P. C. cortex–A. rhizoma herb pair might produce synergistic or complementary compatibility effects on suppressing inflammatory processes occurring in BPH.     

Manganese,Iron, Cobalt,and Nickel Oxo‐, Peroxo‐, and Superoxoclusters: A Density Functional Theory Study

The 3d‐transition‐metal dioxo‐, peroxo‐, and superoxoclusters with the general composition MO₂, M(O₂), and MOO (M=Mn, Fe, Co, and Ni) were studied by DFT by the B1LYP functional. The dioxides in their ground states represent the global minima for the M+O₂ system. Both ground‐state dioxides and the lowest‐energy peroxides are in their (d‐only) highest spin states. The ⁶A₁ state of Co(O₂) exceeds the d‐only spin‐multiplicity value (quartet), being nearly isoenergetic with the ⁴A₁ state of Co(O₂). The energy gain on transforming the peroxides to the corresponding dioxides decreases in the order Mn(O₂)>Fe(O₂)>Co(O₂)>Ni(O₂) and varies in the range 0.27–1.8 eV. The dissociation energy to M+O₂ for all studied peroxides is less than 1 eV being the lowest (0.47 eV) for Mn(O₂). The Mn and Fe peroxides need less than 0.3 eV to rupture one of the MO bonds to form the corresponding superoxide. Mn and Fe superoxides are less stable than the corresponding peroxides; the superoxide of Co is more stable than its peroxide, while Ni superoxide is unstable—its energy is above the limit of dissociation to Ni+O₂. According to the electrostatic potential maps, the oxygen atoms in the peroxides are more nucleophilic than those in the dioxides and superoxides, in which the terminal oxygen atom is more nucleophilic than the M‐bonded oxygen atom. This result differs from the expectations based on charge‐distribution analysis.     

Activities and their relation to cation distribution in NiAl2O4MgAl2O4 spinel solid solutions

The activity of NiAl₂O₄ in NiAl₂O₄MgAl₂O₄ solid solutions has been measured by using a solid oxide galvanic cell of the type, Pt, Ni + NiAl₂O₄ + Al₂O₃(α)/CaOZrO₂/Ni + Ni_xMg_1?xAl₂O₄ + Al₂O₃(α). Pt, in the temperature range 750–1150°C. The activities in the spinel solid solutions show negative deviations from Raoult's law. The cation distribution in the solid solutions has been calculated using site preference energies independent of composition for Ni²⁺, Mg²⁺, and Al³⁺ ions obtained from crystal field theory and measured cation disorder in pure NiAl₂O₄ and MgAl₂O₄, and assumi g ideal mixing of cations on the tetrahedral and octahedral positions. The calculated values correctly predict the decrease in the fraction, α, of Ni²⁺ ions on tetrahedral sites for 1>x>0.25, observed by Porta et al. [J. Solid State Chem.11, 135 (1974)] but do not support their tentative evidence for an increase in α for x < 0.25. The measured excess free energy of mixing can be completely accounted for by using either the calculated or the measured cation distributions. This suggests that the Madelung energy is approximately a linear function of composition in the solid solutions. The composition of NiOMgO solid solutions in equilibrium with NiAl₂O₄MgAl₂O₄ solid solutions has been calculated from the results and information available in literature.     

Synthesis,crystal structure and properties of a neodymium(III) coordination polymer of 1D chain structure based on typical plenary Keggin cluster

A 1D zigzag chain compound, [{Nd(NMP)₆}(PMo₁₂O₄₀)] _n , has been synthesized by reaction of α-H₃PMo₁₂O₄₀?·?nH₂O, Nd₂O₃ and NMP (NMP?=?N-methyl-2-pyrrolidone) in acetonitrile–water mixture, and characterized by elemental analysis, IR and UV spectra, and X-ray single crystal structural analysis. The crystal structure indicates that the title compound forms a one-dimensional zigzag chain built from alternating polyanions and cationic units through Mo–O_t–Nd–O_t–Mo links. In the compound, Nd³⁺ are eight-coordinate with a bicapped trigonal prism geometry of oxygen atoms, from six NMP molecules and two adjacent polyanions, and two terminal oxygen atoms of the polyanions occupying the caps. The powder ESR spectrum at 110?K of the title compound after being exposed to sunshine shows the signal of Mo⁵⁺, g?=?1.96. The CV shows that the title compound undergoes five two-electron reversible reductions and that [PMo₁₂O₄₀]^3? are active centers for electrochemical redox in solutions; cations have a small effect on electrochemical redox.     

The Binary System Tetradecanedioic Acid–Hexadecanedioic Acid: Polymorphism of the Components and Experimental Phase Diagram

Complementary techniques had to be applied to investigate the binary system tetradecanedioic acid (C₁₄H₂₆O₄)–hexadecanedioic acid (C₁₆H₃₀O₄), because all the forms observed have the same space group (P2₁/c; Z = 2). We studied the polymorphism of the two single compounds and of their mixtures by X‐ray powder diffraction, differential‐scanning calorimetry (DSC), infrared spectroscopy (IR), scanning electron microscopy (SEM), and thermo‐optical microscopy (TOM). The two diacids were found to be isopolymorphic. At low temperature, they crystallize in the same ordered C‐form, and, on heating, adopt the ordered C_h‐form, 1° below their melting point. In contrast to similar compounds (unbranched alkanes, alkanols, and fatty acids), the solid–solid and solid–liquid phase‐transition temperatures decrease with increasing chain length. At low temperature, a new monoclinic form, C_i, appears as a result of the disorder of composition in the mixed samples. There are two [C + C_i]‐type solid–solid domains. On heating, the solid domains are related to solid–liquid domains by a peritectic invariant for compositions rich in C₁₄H₂₆O₄, and by a eutectic invariant for compositions rich in C₁₆H₃₀O₄. At higher temperature, there appears a second peritectic invariant for compositions rich in C₁₄H₂₆O₄, together with a metatectic invariant for compositions rich in C₁₆H₃₀O₄. All the solid forms observed in this binary system are isostructural. Nevertheless, the equilibrium between them is complex near the melting point, and their miscibility in the solid state is reduced.     

Chemical constituents from Gueldenstaedtia verna and their anti-inflammatory activity

A new triterpenoid glycoside (1) and 15 known compounds (2–16) were isolated from the whole plants of Gueldenstaedtia verna. The new compound (1) was identified as complogenin 22-O-β-d-glucopyranoside by extensive spectroscopic techniques including 1D (¹H and ¹³C) and 2D NMR experiments (HSQC, HMBC and NOESY), HR-DART-MS and chemical methods. Most of the isolates were evaluated for their inhibitory activities on LPS-induced NO production in RAW 264.7 cells. The inhibitory effects of the active compounds, sulphuretin (8) and (22E,24S)-5α,8α-epidioxy-24-methyl-cholesta-6,9(11),22-trien-3β-ol (13), on the production of pro-inflammatory mediators (including IL-6, IL1β and PGE₂) were further estimated in vitro by ELISA in RAW 264.7 macrophages.