Jochen Lehmann

Tacrine–Ferulic Acid–Nitric Oxide (NO) Donor Trihybrids as Potent, Multifunctional Acetyl- and Butyrylcholinesterase Inhibitors

In search of multifunctional cholinesterase inhibitors as potential anti-Alzheimer drug candidates, tacrine-ferulic acid-NO donor trihybrids were synthesized and tested for their cholinesterase inhibitory activities, release of nitric oxide, vasodilator properties, cognition improving potency, and hepatotoxicity. All of the novel target compounds show higher in vitro cholinesterase inhibitory activity than tacrine. Three selected compounds (3a, 3f, and 3k) produce moderate vasorelaxation in vitro, which correlates with the release of nitric oxide. Compared to its non-nitrate dihybrid analogue (3u), the trihybrid 3f exhibits better performance in improving the scopolamine-induced cognition impairment (mice) and, furthermore, less hepatotoxicity than tacrine.

Functional Screening of G Protein—Coupled Receptors by Measuring Intracellular Calcium with a Fluorescence Microplate Reader

Ligand binding studies reveal information about affinity to G protein—coupled receptors (GPCRs) rather than functional properties. Increase in intracellular Ca2+ appears to represent a universal second messenger signal for a majority of recombinant GPCRs. Here, we exploit Ca2+ signaling as a fast and sensitive functional screening method for a number of GPCRs coupled to different G proteins. Ca2+ fluorescence measurements are performed using Oregon Green 488 BAPTA-1/AM and a microplate reader equipped with an injector. Buffer alone or test compounds dissolved in buffer are injected into a cell suspension, and fluorescence intensity is recorded for 30 s. Each of the GPCRs tested—Gq-coupled P2Y2, Gs-coupled dopamine D1 and D5, Gi-coupled dopamine D2L, and Gq/11-coupled muscarinic acetylcholine M1—yielded a significant rise in intracellular free [Ca2+] on agonist stimulation. Agonist stimulation was dose dependent, as shown for ATP or UTP stimulation of P2Y2 receptors (EC50 = 1 μM), SKF38393 stimulation of hD1 and hD5 (EC50 = 18.1 nM and 2.7 nM), and quinpirole at hD2L (EC50 = 6.5 nM). SCH23390 (at hD1 and hD5) and spiperone, haloperidol, and clozapine (at hD2L) competitively antagonized the Ca2+ response. Furthermore, the Ca2+ assay served to screen suramin analogs for antagonistic activity at P2Y2 receptors. Screening at dopamine receptors revealed LE300, a new lead for a dopamine receptor antagonist. Advantages of the assay include fast and simple 96- or 384-well plate format (high-throughput screening), use of a visible light-excitable fluorescent dye, applicability to a majority of GPCRs, and simultaneous analysis of distinct Ca2+ fluxes.

The conversion of 2,6-anhydro-1-deoxy-d-galacto-hept-1-enitol into 1-deoxy-d-galacto-heptulose by β-d-galactosidase

Abstract 2,6-Anhydro-1-deoxy- d - galacto -hept-1-enitol ( 22 ) was prepared by a multistep synthesis from 2,6-anhydro- d - glycero - l - manno -heptonic acid methyl ester ( 9 ). β- d -Galactosidase catalysed the conversion of 22 into 1-deoxy- d - galacto -heptulose ( 24 ), and in the presence of glycerol, glyceryl 2,6-anhydro-1-deoxy-β- d - galacto -heptuloside ( 25 ) was also formed; 25 was a substrate for β- d -galactosidase. The facile, enzyme-catalysed addition of water or glycerol to the double bond of 22 is compared with the normal β- d -galactoside cleavage in terms of a common triggering process. The enzyme-catalysed hydrolysis of 25 is the first example of a ketoside being cleaved by an aldosidase.

Effects of ginger constituents on the gastrointestinal tract: role of cholinergic M3 and serotonergic 5-HT3 and 5-HT4 receptors.

The herbal drug ginger (Zingiber officinale Roscoe) may be effective for treating nausea, vomiting, and gastric hypomotility. In these conditions, cholinergic M (3) receptors and serotonergic 5-HT (3) and 5-HT (4) receptors are involved. The major chemical constituents of ginger are [6]-gingerol, [8]-gingerol, [10]-gingerol, and [6]-shogaol. We studied the interaction of [6]-gingerol, [8]-gingerol, [10]-gingerol (racemates), and [6]-shogaol with guinea pig M (3) receptors, guinea pig 5-HT (3) receptors, and rat 5-HT (4) receptors. In whole segments of guinea pig ileum (bioassay for contractile M (3) receptors), [6]-gingerol, [8]-gingerol, [10]-gingerol, and [6]-shogaol slightly but significantly depressed the maximal carbachol response at an antagonist concentration of 10 µM. In the guinea pig myenteric plexus preparation (bioassay for contractile 5-HT (3) receptors), 5-HT maximal responses were depressed by [10]-gingerol from 93 ± 3 % to 65 ± 6 % at an antagonist concentration of 3 µM and to 48 ± 3 % at an antagonist concentration of 5 µM following desensitization of 5-HT (4) receptors and blockade of 5-HT (1) and 5-HT (2) receptors. [6]-Shogaol (3 µM) induced depression to 61 ± 3 %. In rat esophageal tunica muscularis mucosae (bioassay for relaxant 5-HT (4) receptors), [6]-gingerol, [8]-gingerol, [10]-gingerol, and [6]-shogaol (2-6.3 µM) showed no agonist effects. The maximal 5-HT response remained unaffected in the presence of the compounds. It is concluded that the efficiency of ginger in reducing nausea and vomiting may be based on a weak inhibitory effect of gingerols and shogaols at M (3) and 5-HT (3) receptors. 5-HT (4) receptors, which play a role in gastroduodenal motility, appear not to be involved in the action of these compounds.

Synthesis and Antitumor Activity of Ethyl 2-Substituted-aminothiazole-4-carboxylate Analogs

The synthesis of several new ethyl 2‐substituted‐aminothiazole‐4‐ carboxylate analogs is described. The prepared compounds were tested for their in vitro antitumor activity against 60 human tumor cell lines by the National Cancer Institute (NCI) and showed potential anticancer activity. Ethyl 2‐[3‐(diethylamino)‐propanamido]‐thiazole‐4‐carboxylate (14) exhibited remarkable activity against RPMI‐8226 leukemia cell line with GI50 value of 0.08 μM, and a broad spectrum activity against all the tumor cell lines used with GI50 (MG‐MID) value of 38.3 μM. The detailed synthesis and antitumor screening data are reported.

Resolution of newly synthesized racemic dihydropyridines with different chiral selectors by means of capillary electrophoresis.

The racemates of newly synthesized 4-aryl-1,4-dihydropyridine derivatives attracting interest in the treatment of coronary insufficience were resolved via the formation of diastereomeric salts. In order to check the quality of the preparative resolution, capillary electrophoresis using neutral cyclodextrins (CDs) was developed. In particular, the alpha-CD was found to be a powerful discriminator of the enantiomers. Additionally, taking amlodipine and nicardipine into consideration, a mechanism of the chiral recognition with alpha-CD could be proposed.

Interaction of ionic liquids ions with natural cyclodextrins.

The interaction of natural α-, β-, and γ-cyclodextrins (CDs) with 14 hydrophobic ionic moieties of ionic liquids (ILs) was systematically examined in dilute aqueous solutions using isothermal titration microcalorimetry (ITC) and NMR spectroscopy. The studied cationic and anionic moieties involved some recently developed heavily fluorinated structures, as well as some others of common use. To isolate the effect of a given ion, the measurements were performed on salts containing the hydrophobic IL ion in question and a complexation-inactive counterion. Additional ITC experiments on ILs whose both cation and anion can interact appreciably with the CD cavity demonstrated that to resolve the effect of individual ions from such data is generally a tricky task and confirmed the superiority of the isolation strategy adopted for the purpose throughout this work. The binding constant, enthalpy and entropy determined at 298.15 K for the 1:1 (ion:CD) inclusion complex formation range in broad limits, being 0 < K < 2 × 10(5), 0 < -Δ(r)H°/(kJ·mol(-1)) < 44, and -28 < TΔ(r)S°/(kJ·mol(-1)) < 14, respectively. The stabilities of complexes of perfluorohexyl bearing ions with β-CD belong to the highest ever observed with natural CDs in water. The established binding affinity scales were discussed in both thermodynamic and molecular terms. The concepts of hydrophobic interaction and guest-host size matching supported by simple molecular modeling proved useful to rationalize the observed widely different binding affinities and suggest possible binding modes. Enthalpy and entropy contributions to the stability of the ion-CD complexes were found to compensate each other considerably obeying more or less the linear compensation relationship marked by existing literature data on binding other guests to natural CDs. As outliers to this pattern, the most stable complexes of -C(6)F(13) bearing ions with β-CD were found to receive an enhanced inherent entropy stabilization due to extraordinarily high extent of desolvation occurring in the course of binding.

The stereochemistry of the addition of glycerol to D-galactal, catalyzed by β-D-galactosidase☆

On incubation with beta-D-galactosidase, D-galactal-2-d (1) plus glycerol yielded 1-deoxyglycerol-1-yl 2-deoxy-beta-D-lyxo-hexopyranoside-2(S)-d. By 1H-n.m.r. analysis, it was shown that the hydrogen atom introduced on C-2 is trans-related to the aglycon moiety. In contrast to this stereospecific, enzyme-catalyzed addition, the reaction of phenol with peracetylated 1, catalyzed by p-toluenesulfonic acid, which yields phenyl 3,4,6-tri-O-acetyl-2-deoxy-alpha-D-lyxo-hexopyranoside-2-d, was shown to entail both a trans and a cis addition.

Nitric oxide donors - current trends in therapeutic applications

The nitric oxide (NO) radical, endogenously produced from L-arginine, is a natural vasodilator also involved in many other physiological and pathological processes. The increasing knowledge of the multiple roles of NO keeps extending its range of potential therapeutic applications. However, these many applications require individually designed exogenous molecular sources of NO. To date, NO donors such as diazeniumdiolates, S-nitrosothiols, sydnonimines, nitroso complexes, organic nitrates and nitrites are claimed to be useful for the treatment of cardiovascular, renal, respiratory, gastrointestinal, neurodegenerative, inflammatory and infectious diseases. Development of new NO donors differs from common drug development because the active drug (NO) has already been determined, therefore research involves the development of devices to deliver NO. An alternative strategy is to link an NO releasing moiety to other well-established bioactive molecules creating NO donor hybrids. Different hybrid compounds can offer various drug actions with synergistic effects, reduced toxicity and no detrimental side effects. Among others, Hou, Janczuk and Wang [1], and a few years previously Stamler and Feelisch [2], have issued systematic and comprehensive reviews on NO donors. In view of the huge number of publications on this topic, this article will restrictively focus on NO donors and pathological situations and diseases which are claimed in the important therapeutic patents issued between 1997 and 2000. Table 1 gives the relevant diseases and classes of NO donors, gathered from these patents.

Potency and in vitro tolerance of organic nitrates : Partially denitrated metabolites contribute to the tolerance-devoid activity of pentaerythrityl tetranitrate

Neither therapeutic dosage of nitrovasodilators nor the development of tolerance correlates with nitrate groups in these molecules. Clinically, low dosages of glyceryl trinitrate (GTN) develop tolerance, but 100-fold higher dosages of pentaerythrityl tetranitrate (PETN) do not. Vasorelaxation was studied on prostaglandian F2α (PGF2α)-precontracted porcine pulmonary arteries in organ bath procedure. In vitro tolerance was induced by incubating the arteries with different nitrate concentrations and thereafter concentration-response curves were repeated. Furthermore, 14 mg/kg PETN were daily administered to rats by gavage; PETN and metabolites were measured in feces and blood. In vitro, the vasodilator potencies increased from mononitrates to tetranitrates (pD2: 4.14 to 8.18); PETN was the most potent vasodilator. In vitro tolerance was found with PETN and trinitrates but not with dinitrates and mononitrates. Thus, in vitro tolerance correlated with the in vitro potency of nitrates but not with the vasodilator potency of NO donors in general, because S-nitroso-N-aectyl-D-penicillamine and N-phenylpiperazin-NONOate were more potent than GTN but did not induce tolerance. After feeding of rats with PETN, pentaerythrityl dinitrate (PEdiN) and mononitrate (PEmonoN) but neither PETN nor PEtriN (both detected in feces) were found in the blood. The missing systemic bioavailability of PETN and PEtriN may explain the discrepancy between in vitro and in vivo findings. We conclude that the partially denitrated metabolites PEdiN and PEmonoN contribute to the moderate and tolerance-devoid clinical activity of PETN.