Light-Controlled Destruction and Assembly: Switching between Two Differently Composed Cage-Type Complexes

We report on two regioisomeric, diazocine ligands 1 and 2 that can both be photoswitched between the E- and Z-configurations with violet and green light. The self-assembly of the four species (1-Z, 1-E, 2-Z, 2-E) with Co^II ions was investigated upon changing the coordination vectors as a function of the ligand configuration (E vs Z) and regioisomer (1 vs 2). With 1-Z, Co₂ (1-Z)₃ was self-assembled, while a mixture of ill-defined species (oligomers) was observed with 2-Z. Upon photoswitching with 385 nm to the E configurations, the opposite was observed with 1-E forming oligomers and 2-E forming Co₂ (2-E)₃ . Light-controlled dis/assembly was demonstrated in a ligand competition experiment with sub-stoichiometric amounts of Co^II ions; alternating irradiation with violet and green light resulted in the reversible transformation between Co₂ (1-Z)₃ and Co₂ (2-E)₃ over multiple cycles without significant fatigue by photoswitching.

M-CPOnes: transition metal complexes with cyclopropenone-based ligands for light-triggered carbon monoxide release

A new class of CO-releasing molecules, M-CPOnes, was prepared combining cyclopropenone-based ligands for CO release with the modular scaffold of transition metal complexes. In proof-of-concept studies, M-CPOnes based on Zn^II, Fe^II and Co^II are stable in the dark but undergo light-triggered CO release with the cyclopropenone substituents and metal ions enabling tuning of the photophysical properties. Furthermore, the choice of metal allows the use of different spectroscopic methods to monitor photodecarbonylation from fluorescence spectroscopy to UV/vis spectroscopy and paramagnetic NMR spectroscopy. The modularity of M-CPOnes from the metal ion to the cyclopropenone substitution and potential for further functionalisation of the ligand make M-CPOnes appealing for tailored functionality in applications.

A Paramagnetic NMR Spectroscopy Toolbox for the Characterisation of Paramagnetic/Spin-Crossover Coordination Complexes and Metal-Organic Cages

The large paramagnetic shifts and short relaxation times resulting from the presence of a paramagnetic centre complicate NMR data acquisition and interpretation in solution. As a result, NMR analysis of paramagnetic complexes is limited in comparison to diamagnetic compounds and often relies on theoretical models. We report a toolbox of 1D (1H, proton-coupled 13C, selective 1H-decoupling 13C, steady-state NOE) and 2D (COSY, NOESY, HMQC) paramagnetic NMR methods that enables unprecedented structural characterisation and in some cases, provides more structural information than would be observable for a diamagnetic analogue. We demonstrate the toolbox's broad versatility for fields from coordination chemistry and spin-crossover complexes to supramolecular chemistry through the characterisation of CoII and high-spin FeII mononuclear complexes as well as a Co4L6 cage.

2-Azo-, 2-diazocine-thiazols and 2-azo-imidazoles as photoswitchable kinase inhibitors: limitations and pitfalls of the photoswitchable inhibitor approach

In photopharmacology, photoswitchable compounds including azobenzene or other diarylazo moieties exhibit bioactivity against a target protein typically in the slender E-configuration, whereas the rather bulky Z-configuration usually is pharmacologically less potent. Herein we report the design, synthesis and photochemical/inhibitory characterization of new photoswitchable kinase inhibitors targeting p38α MAPK and CK1δ. A well characterized inhibitor scaffold was used to attach arylazo- and diazocine moieties. When the isolated isomers, or the photostationary state (PSS) of isomers, were tested in commonly used in vitro kinase assays, however, only small differences in activity were observed. X-ray analyses of ligand-bound p38α MAPK and CK1δ complexes revealed dynamic conformational adaptations of the protein with respect to both isomers. More importantly, irreversible reduction of the azo group to the corresponding hydrazine was observed. Independent experiments revealed that reducing agents such as DTT (dithiothreitol) and GSH (glutathione) that are typically used for protein stabilization in biological assays were responsible. Two further sources of error are the concentration dependence of the E-Z-switching efficiency and artefacts due to incomplete exclusion of light during testing. Our findings may also apply to a number of previously investigated azobenzene-based photoswitchable inhibitors.

The supportive effect of supplementation with α-keto acids on physical training in type 2 diabetes mellitus

The supplementation with α-keto acids provides supportive effects in type 2 diabetes patients undergoing physical training by improving training effects and prolonging benefit in glucose control.

LC-MS assay for quantitative determination of cardio glycoside in human blood samples

A method is described for liquid chromatography-mass spectrometry analysis of the cardio glycosides digoxin and digitoxin in biological samples. The method was optimized for use in the forensic field and, therefore, comprises the determination from whole blood and tissue samples. Sample cleanup by solid phase extraction (SPE) on a functionalized polymeric phase was sufficient to limit matrix suppression to <10% for all analytes. Chromatographic separation was achieved using an RP-8 column. Detection of the cardio glycosides was performed with electrospray ionization in the positive mode. The system was run in single ion monitoring mode, measuring the sodium adducts (M + Na)+ of the analyte and of the internal standard, respectively. The method was fully validated for the analysis of blood samples and was also successfully applied in forensic cases. The method was accurate and precise over a linear concentration range up to 50 ng/g blood. Lower limit of quantitation was 0.2 ng/g for digoxin and 2 ng/g for digitoxin, respectively. As deuterated analyte was used as internal standard, we also present a new microwave-enhanced method for the fast preparation of the labelled analyte within 20 min.

Quantitative determination of taxine B in body fluids by LC–MS–MS

A new specific and sensitive LC-MS-MS method for the detection of taxine B and isotaxine B, the main toxic pseudo-alkaloids from yew (Taxus sp.), in biological samples (blood, urine, gastric content) was developed. Biological samples were prepared for LC-MS-MS by means of solid-phase extraction (SPE) procedure and yielded a recovery of 86%. Chromatographic separation was achieved using an RP(18) column. Detection of taxine B and isotaxine B was performed using multiple reaction monitoring with m/z 584.2 as precursor ion, i.e. [M+H](+), of both isomers and m/z 194.3 and m/z 107.1 as product ions after collision-induced dissociation. Docetaxel was applied as internal standard. The method was fully validated for the analysis of blood samples. Linearity was proven in the range from 0.1-500 ng/g. The limit of detection and the limit of quantitation are 0.4 and 2 ng/g, respectively. The method was applied to the determination of taxine B and isotaxine B in four fatal cases (two humans, two horses) with suspected yew intoxication. Blood levels were 105, 168, 174 and 212 ng/g.

Development of a psilocin immunoassay for serum and blood samples

After the immunisation of rabbits with a psilocin-specific immunogen, polyclonal antisera were obtained. With these antisera a competitive, heterogeneous radioimmunoassay for the detection of psilocin was developed. As tracer a derivative of psilocin was synthesised, which contained a tritiated CH(3) group. The antisera showed a specific reaction with psilocin. The cross-reactivity of structurally related endogenous substances like serotonin, tryptophan and tyrosine was below 0.01%. Also common drugs of abuse (Delta(9)-tetrahydrocannabinol, cocaine, morphine, amphetamine) showed negligible cross-reactivity (0.01-2%). Only tricyclic neuroleptics with a (dimethylamino)ethyl side-chain showed some cross-reactivity (20%). Spiked serum and blood samples were analysed with this new immunoassay and the results obtained were compared with the values measured with a validated GC-MS method.

Novel 3-dodecanoylindole-2-carboxylic acid inhibitors of cytosolic phospholipase A(2)

Derivatives of 1-[2-(4-carboxyphenoxy)ethyl]-3-dodecanoylindole-2-carboxylic acid (4) with modified substituents at the indole-1-position were synthesized and evaluated for their ability to inhibit the arachidonic acid release in human platelets mediated by the cytosolic phospholipase A(2). One of the most active compounds obtained was 26 with an IC(50) of 0.44 microM.

Comparison of the inhibition of the cytosolic phospholipase A2-mediated arachidonic acid release by several indole-2-carboxylic acids and 3-(pyrrol-2-yl)propionic acids in bovine and in human platelets

The inhibition of the cytosolic phospholipase A2 (cPLA2)-mediated arachidonic acid release by several indole-2-carboxylic acids and 3-(pyrrol-2-yl)propionic acids was measured in intact human platelets using calcium ionophore A23187 as stimulant. The comparison of the obtained data with the inhibition data evaluated with bovine platelets showed that analogous results were obtained with both cell types.

Involvement of different protein kinases and phospholipases A2 in phorbol ester (TPA)-induced arachidonic acid liberation in bovine platelets

The effect of various phospholipase A2 and protein kinase inhibitors on the arachidonic acid liberation in bovine platelets induced by the protein kinase activator 12-O-tetradecanoylphorbol-13-acetate (TPA) was studied. TPA stimulates arachidonic acid release mainly by activating group IV cytosolic PLA2 (cPLA2), since inhibitors of this enzyme markedly inhibited arachidonic acid formation. However, group VI Ca2+-independent PLA2 (iPLA2) seems to contribute to the arachidonic acid liberation too, since the relatively specific iPLA2 inhibitor bromoenol lactone (BEL) decreased arachidonic acid generation in part. The pronounced inhibition of the TPA-induced arachidonic acid release by the protein kinase C (PKC) inhibitors GF 109203X and Ro 31-82220, respectively, and by the p38 MAP kinase inhibitor SB 202190 suggests that the activation of the PLA2s by TPA is mediated via PKC and p38 MAP kinase.

Bilobalide, a constituent of Ginkgo biloba, inhibits NMDA-induced phospholipase A2 activation and phospholipid breakdown in rat hippocampus

In rat hippocampal slices superfused with magnesium-free buffer, glutamate (1 mM) caused the release of large amounts of choline due to phospholipid breakdown. This phenomenon was mimicked by N-methyl-D-aspartate (NMDA) in a calcium-sensitive manner and was blocked by NMDA receptor antagonists such as MK-801 and 7-chlorokynurenate. The NMDA-induced release of choline was not caused by activation of phospholipase D but was mediated by phospholipase A2 (PLA2) activation as the release of choline was accompanied by the formation of lyso-phosphatidylcholine (lyso-PC) and glycerophospho-choline (GPCh) and was blocked by 5-[2-(2-carboxyethyl)-4-dodecanoyl-3,5-dimethylpyrrol-1-yl]pentano ic acid, a PLA2 inhibitor. Bilobalide, a constituent of Ginkgo biloba, inhibited the NMDA-induced efflux of choline with an IC50 value of 2.3 microM and also prevented the formation of lyso-PC and GPCh. NMDA also caused a release of choline in vivo when infused into the hippocampus of freely moving rats by retrograde dialysis. Again, the effect was completely inhibited by bilobalide which was administered systemically (20 mg/kg i.p.). Interestingly, convulsions which were observed in the NMDA-treated rats were almost totally suppressed by bilobalide. We conclude that release of choline is a sensitive marker for NMDA-induced phospholipase A2 activation and phospholipid breakdown. Bilobalide inhibited the glutamatergic excitotoxic membrane breakdown both in vitro and in vivo, an effect which may be beneficial in the treatment of brain hypoxia and/or neuronal hyperactivity.

Structure-activity relationships of (4-acylpyrrol-2-yl)alkanoic acids as inhibitors of the cytosolic phospholipase A2: variation of the substituents in positions 1, 3, and 5

Derivatives of 3-(1,3,5-trimethyl-4-octadecanoylpyrrol-2-yl)propionic acid (1) and (1,3,5-trimethyl-4-octadecanoylpyrrol-2-yl)acetic acid (4) were prepared and evaluated for their ability to inhibit the cytosolic phospholipase A2 of intact bovine platelets. While replacement of one of the methyl groups in position 1, 3, or 5 of the acetic acid 4 by a benzyl residue did not influence the inhibitory potency significantly, the introduction of a dodecyl chain led to compounds which even enhanced the enzymatic activity. Stepwise elongation of the alkyl substituent in position 1 showed that the ability to inhibit the enzyme was lost when the alkyl chain exceeded a length of five carbons in case of compound 1 or six carbons in case of compound 4. Introduction of a polar functional group at the end of the 1-alkyl chain of these inactive pyrroles, however, restored or even elevated inhibitory potency. The most preferable of the polar terminal functions investigated was the carboxylic acid moiety. 6-[2-(2-Carboxyethyl)-4-dodecanoyl-3,5-dimethylpyrrol-1-yl]hexanoi c acid (65c) and 6-[2-(carboxymethyl)-4-dodecanoyl-3,5-dimethylpyrrol-1-yl]nonanoic acid (66f) were the synthesized inhibitors with the greatest potency. With IC50 values of 3.4 and 3.3 microM, respectively, they were about 3-fold more active than the standard cPLA2 inhibitor arachidonyl trifluoromethyl ketone (IC50: 11 microM).

Synthesis, biological evaluation, and structure-activity relationships of 3-acylindole-2-carboxylic acids as inhibitors of the cytosolic phospholipase A2

3-Acylindole-2-carboxylic acid derivatives were prepared and evaluated for their ability to inhibit the cytosolic phospholipase A2 of intact bovine platelets. To define the structural requirements for enzyme inhibition, the carboxylic acid group, the acyl residue, and the moiety in position 1 were systematically modified. Furthermore, different substituents were introduced into the phenyl part of the indole. Replacement of the carboxylic acid group in position 2 of the indole with an acetic or propionic acid substituent led to a decrease of inhibitory potency. Enzyme inhibition was optimal when the acyl residue in position 3 had a length of 12 or more carbons. Conformational restriction of the acyl residue did not influence activity. Introduction of alkyl chains at position 1 of the indole with 8 or more carbons resulted in a loss of activity. However, replacing the omega-methyl group of such compounds with a carboxylic acid moiety was found to increase inhibitory potency significantly. Among the tested indole derivatives, 1-[2-(4-carboxyphenoxy)ethyl]-3-dodecanoylindole-2-carboxyli c acid (29b) had the highest potency. With an IC50 of 0.5 microM it was about 20-fold more active than the standard cPLA2 inhibitor arachidonyl trifluoromethyl ketone (IC50: 11 microM).

3-(3,5-Dimethyl-4-octadecanoylpyrrol-2-yl)propionic acids as inhibitors of 85 kDa cytosolic phospholipase A2

3-(1,4-Diacylpyrrol-2-yl)propionic acids were designed as inhibitors of cytosolic phospholipase A2. Enzyme inhibition was assayed by evaluation of calcium ionophore A23187-induced arachidonic acid release from bovine platelets. While the synthesized bisacyl compound 3-[3,5-dimethyl-4-octadecanoyl-1-(3-phenylpropionyl)pyrrol-2-yl] propionic acid was inactive at 33 microM, the related monoacylated 3-(3,5-dimethyl-4-octadecanoylpyrrol-2-yl)-propionic acid and 3-(1,3,5-trimethyl-4-octadecanoylpyrrol-2-yl)-propionic acid proved to be inhibitors of cytosolic phospholipase A2(IC50: 24 microM and 13 microM, respectively).

3-(Octadecanoylaminomethyl)indole-2-carboxylic acid derivatives and 1-methyl-3-octadecanoylindole-2-carboxylic acid as inhibitors of cytosolic phospholipase A2

3-(1-Acylaminooctadecyl)indole-2-carboxylic acids and 3-(1-acylaminooctadecyl)-1-methylindole-2-carboxylic acids were designed and synthesized as inhibitors of cytosolic phospholipase A2. Enzyme inhibition was assayed by evaluation of calcium ionophore A23187-induced arachidonic acid release from bovine platelets. While compounds with 1-octadecanoylaminooctadecyl groups in position 3 of the indole were inactive inhibition data for 3-[1-(3-phenylpropionylamino)octadecyl]indole-2-carboxylic acids could not be evaluated because of lysis of the platelets. However 3-(octadecanoylaminomethyl)indole-2-carboxylic acid derivatives and 1-methyl-3-octadecanoylindole-2-carboxylic acid proved to be inhibitors of cytosolic phospholipase A2. The most active inhibitor was the latter compound with an IC50 of 8 microM.

Nonsteroidal antiinflammatory agents, XVII: Inhibition of bovine cyclooxygenase and 5-lipoxygenase by N-alkyldiphenyl-pyrrolyl acetic and propionic acid derivatives

A series of 19 N-alkyl-diarylpyrrolyl-acetic and-propionic acid derivatives was synthesized and tested. Using bovine blood as enzyme source the inhibition of cyclooxygenase and 5-lipoxygenase, respectively, was applied to determine the antiinflammatory activity. In general all compounds tested inhibit 5-lipoxygenase more effectively than cyclooxygenase. A structure-activity relationship is discussed.

In-vitro evaluation of 5-lipoxygenase and cyclo-oxygenase inhibitors using bovine neutrophils and platelets and HPLC

Inhibition of 5-lipoxygenase has been determined by monitoring the formation of leukotriene B4 and 5-hydroxyeicosatetraenoic acid in bovine polymorphonuclear leucocytes. For evaluating the inhibition of cyclo-oxygenase two different test systems are presented: the first uses 12-hydroxyheptadecatrienoic acid produced by bovine platelets as an indicator of the cyclo-oxygenase activity; the second test system monitors the prostaglandin E2 formation by bovine platelets. All arachidonic acid metabolites are quantified by reverse-phase HPLC with UV-detection.

[Aroma of the papaya fruit (Carica papaya, L.): indication of volatile precursors of terpene compounds]

In fruit pulp of papaya (Carica papaya, L.) the enzymes were inhibited by Hg2+. These sample were compared with others, in which the enzymes had not been inhibited. After separation and prefractionation of volatiles by means of high vacuum distillation/solvent extraction and subsequent adsorption chromatography on silicagel, capillary gas chromatography-mass spectrometry showed that in the experiment with Hg2+ the formation of terpene alcohols and hydrocarbons as well as benzylisothiocyanate was totally inhibited. The formation of linalooloxides and related compounds was inhibited to about 60%. From these results the occurrence of bound terpene precursors in papaya fruit may be postulated, from which the free volatile terpenes are enzymatically liberated after decompartmentalization of tissue during fruit pulp preparation.

Monitor of chemotherapy in gestational trophoblastic neoplasm by radioimmunoassay of the beta-subunit of human chorionic gonadotropin

Radioimmunoassays and bioassays based on the reactions of the native molecule of human chorionic gonadotropin (HCG) fail to differentiate HCG from pituitary luteinizing hormone (LH). An assay based on the beta-subunit of HCG which detects HCG exclusively has been used in our laboratory to monitor patients undergoing chemotherapy for gestational trophoblastic disease (GTD). We have been able to differentiate minimal, persisting tumor activity from normal levels of pituitary gonadotropins and have based therapy on these findings. Alternatively, treatment has been terminated when HCG is no longer detectable in the serum. Tumor activity has been detected in the beta-subunit assay at a time when biologic activity in the urine indicated remission.