Antioxidant activity of melatonin and a pinoline derivative on linoleate model system.

This study aimed at investigating the in vitro protective effects of GWC22, a novel pinoline derivative [6-ethyl-1-(3-methoxyphenyl)-2-propyl-1,2,3,4-tetrahydro-beta-carboline] chlorhydrate, against radiation-induced oxidation of linoleate initiated by hydroxyl radicals ((*)OH). Using linoleate micelles (10(-2) m) as lipid model, two indexes of peroxidation have been measured, i.e. conjugated dienes and hydroperoxides. Similar determinations were performed with melatonin in order to compare the protective effects of the two compounds. It was observed that, the higher the concentration of GWC22 (or melatonin) (3 x 10(-5) to 10(-4) m), the stronger the antioxidant ability. In these in vitro assays, GWC22 showed a better antioxidant effect than melatonin for a given antioxidant concentration. A reaction scheme has been proposed to explain the inhibitory effect of an antioxidant via the propagating steps of the lipid peroxidation. Indeed, we have suggested that melatonin and GWC22 may compete with the fatty acid to scavenge lipid peroxyl radicals (LOO(*)). We have estimated a lower limit for the LOO(*) rate constant for GWC22 (>/=1.4 x 10(5)/m/s) and for melatonin (>/=2.8 x 10(4)/m/s) assuming that the k-value of the propagating step in linoleate (LOO(*) + linoleate) was 1.4 x 10(3)/m/s. The difference of reactivity between melatonin and GWC22 in this model system is assumed to be related to their relative lipophilicity.

Determination of ionization constants of N-imidazole derivatives, aromatase inhibitors, using capillary electrophoresis and influence of substituents on pKa shifts.

Capillary electrophoresis (CE) was used as a method to determine the acidity constants of eight aromatase inhibitors. This method was validated by comparison of results obtained with a traditional method, UV spectroscopy, and additionally with computational calculations. We confirmed here, with our series of compounds, that capillary electrophoresis is an attractive method for pKa measurements which is based on migration time or mobilities of the ionic species over a range of pH values. The precision of pKa measurements of N-imidazole derivatives is useful to observe pKa shifts induced by chemical modifications introduced on adjacent aromatic rings such as heterocycle (benzoxa- or benzothiazolinone) or substituted benzyle. The knowledge of these pKa values is a great interest to predict migration of solutes and qualitative interactions with ionized cyclodextrines as chiral selectors in further enantioseparative CE studies.

Exposure to glycol ethers in a population of French men evaluated by measurement of urinary alkoxycarboxylic acids.

OBJECTIVES: Glycol ethers are solvents that are present in a large number of products used commercially and domestically. During recent years, ethylene glycol ether derivatives, in particular ethylene glycol methyl ether and ethylene glycol ethyl ether, have been progressively replaced by propylene glycol ether derivatives, which are less toxic. The aim of this study was to estimate the level of exposure to glycol ethers in a sample population of French men employed by the Paris Municipality by measuring the amount of alkoxycarboxylic acid metabolites in their urine. METHODS: Urine samples were collected at the end of two different working weeks from 109 men, 54 of whom were judged to be occupationally exposed to glycol ether-containing products. Five alkoxyacetic acids (methoxyacetic, ethoxyacetic, n-propoxyacetic, phenoxyacetic, butoxyacetic acids) from ethylene glycol derivatives, and one alkoxypropionic acid (2-methoxypropionic) from a propylene glycol derivative, were simultaneously analysed by gas chromatography coupled to electron-capture detection. RESULTS: 2-Methoxypropionic was the most frequently found alkoxycarboxylic acid. The concentration of this metabolite reached 5.6 mmol/mol creatinine. The second most common alkoxycarboxylic acid was phenoxyacetic (up to 2.3 mmol/mol creatinine). The concentrations of the other alkoxycarboxylic acids were less than 1 mmol/mol creatinine. Although the concentration of alkoxycarboxylic acids was higher among men occupationally exposed to glycol ether-containing products than among unexposed men, the difference was significant only for butoxyacetic acid. CONCLUSIONS: Our data suggest that the use and exposure levels of glycol ethers have qualitatively and quantitatively changed dramatically over recent years. Particular attention should be paid in the future to alkoxypropionic acids derived from minor isomers of propylene glycol ether derivatives.

Design, synthesis and in vitro evaluation of novel benzo[b]thiophene derivatives as serotonin N-acetyltransferase (AANAT) inhibitors.

Serotonin N-acetyltransferase (arylalkylamine N-acetyltransferase, AANAT) is the penultimate enzyme in melatonin (5-methoxy-N-acetyltryptamine) biosynthesis. It is the key-enzyme responsible of the nocturnal rhythm of melatonin production in the pineal gland. Specific AANAT inhibitors could be useful for treatment of different physiopathological disorders encountered in diseases such as seasonal affective disorders or obesity. On the basis of previous works and 3D-QSAR studies carried out in our laboratory, we have synthesized and evaluated four novel benzo[b]thiophene derivatives designed as AANAT inhibitors. Compound 13 exhibited high inhibitory activity (IC50 = 1.4 microM) and low affinities for both MT, (1100 nM) and MT2 (1400 nM) receptors.

Design, synthesis and in vitro evaluation of novel derivatives as serotonin N-acetyltransferase inhibitors.

Serotonin N-acetyltransferase (arylalkylamine N-acetyl-transferase, AANAT) is an enzyme that catalyses the first rate limiting step in the biosynthesis of melatonin (5-methoxy-N-acetyltryptamine). Different physiopathological disorders in human may be due to abnormal secretion of melatonin leading to an inappropriate exposure of melatonin receptors to melatonin. For that reason, we have designed, synthesized and evaluated as inhibitors of human serotonin N-acetyltransferase, a series of compounds that were able to react with coenzyme A to give a bisubstrate analog inhibitor. Compound 12d was found to be a potent AANAT inhibitor (IC50 = 0.18 microM).

Three-dimensional quantitative structure-activity relationships of cyclo-oxygenase-2 (COX-2) inhibitors: a comparative molecular field analysis.

The three-dimensional quantitative structure-activity relationship (3D-QSAR) approach using comparative molecular field analysis (CoMFA) was applied to an extensive series of 305 varied diarylheterocyclic derivatives known as COX-2 selective inhibitors. X-ray crystal structure of COX-2 bound with SC-558, a selective COX-2 inhibitor, was used to derive the putative bioactive conformation of these inhibitors. Five statistically significant models were obtained from the randomly constituted training sets (229 compounds) and subsequently validated with the corresponding test sets (76 compounds). The best predictive model (n = 229, q(2) = 0.714, N = 8, r(2) = 0.905, s = 0.291, F = 261.545) was selected for further comparison of the CoMFA contour maps obtained for steric, electrostatic, and lipophilic fields with the enzyme structure. The high level of compatibility with the COX-2 enzyme topology shows the great accuracy of this model that can predict inhibitory activities for a wide range of compounds and offers important structural insight into designing novel antiinflammatory drugs prior to their synthesis.

Conformational analysis of tripeptide Ac-Lys-Pro-Val-NH2, COOH-terminal sequence of alpha-MSH.

Alpha-melanocyte stimulating hormone (alpha-MSH) is an endogenous linear tridecapeptide which interacts with the melanocortin receptors (MC1-R to MC5-R) to mediate its biological effects. Antipyretic and anti-inflammatory activities of alpha-MSH are due to the COOH-terminal peptide sequence, Lys-Pro-Val (alpha-MSH[11-13]). This tripeptide might be useful as a therapeutic agent in the control of fever and inflammatory reactions. With this aim, a theoretical conformational study of the tripeptide has been carried out using molecular dynamics. The obtained conformational space has been classified into families according to the letter-code convention to partition the phi-psi map. The lowest energy conformations of each family were used as templates to design six models of conformationally constrained nonpeptide analogues.

Melatonin receptor agents: synthesis, resolution by HPLC on polysaccharides chiral stationary phases, absolute configuration, and pharmacology of the enantiomers of (+/-)-N-[[2[(7-fluoro-1,2,3,4-tetrahydronaphthalen-1-yl)ethyl]acetamide.

In order to obtain milligram amounts of the enantiomers of tetrahydronaphthalenic derivative 5 to be tested for binding to the melatonin sites, preparative HPLC employed a mobile phase consisting of n-hexane-alcohol and a silica-based cellulose tris-methylbenzoate (Chiralcel OJ) using isocratic conditions and multiple repetitive injections. The preparative separation was optimized by adjusting the sample size from a scale-up of the analytical method. The enantiomeric elution order was reversed by the change from the carbamate type phase (Chiralcel OD-H) to the benzoate type phase (Chiralcel OJ) in analytical mode. The optical rotation and the circular dichroism spectra of the single enantiomers were determined after separation. The absolute stereochemistry of the two enantiomers of (+/-)-N-[2-(7-fluoro-1,2,3,4-tetrahydronaphthalen-1-yl)ethyl]acetamide 5 was established by X-ray crystallographic analysis. The purity obtained was sufficient for a first screen of their biochemical properties: the (-)-(S) enantiomer shows more affinity for melatonin receptors MT1, MT2 and is responsible of the selectivity towards MT2.

Direct separation of the stereoisomers of methoxytetrahydronaphthalene derivatives, new agonist and antagonist ligands for melatonin receptors, by liquid chromatography on cellulose chiral stationary phases.

Analytical HPLC methods using derivatized cellulose chiral stationary phases were developed for the direct separation of the stereoisomers of disubstituted tetralin derivatives with two chiral centers, new agonist and antagonist ligands for melatonin receptors. The separations were made using normal-phase methodology with a mobile phase consisting of n-hexane-alcohol (methanol, ethanol, 1-propanol or 2-propanol) in various proportions, and a silica-based cellulose tris-3,5-dimethylphenylcarbamate (Chiralcel OD-H), or tris-methylbenzoate (Chiralcel OJ). The effects of concentration of various aliphatic alcohols in the mobile phase were studied. A better separation was achieved on cellulose carbamate phase compared with the cellulose ester phase. The effects of structural features of the solutes on the discrimination between the stereoisomers were examined. Baseline separation (Rs>1.5) was easily obtained in many cases.

Synthesis and pharmacological evaluation of analgesic 6-substituted 2(3H)-benzothiazolones.

A series of novel 6-substituted-2(3H)-benzothiazolones were synthesized and studied as analgesic agents. Among these compounds, two of them were found to exhibit potent analgesic activity in several in vivo tests (acetic acid writhing, Koster, carrageenan and PGE2 hyperalgesia). In these tests the most active compound of this series, i.e. 6-benzoyl-2(3H)-benzothiazolone (4a) was found to be superior to acetylsalicylic acid and equivalent to glafenine. The present study allows to conclude that 4a represents a new type of antinociceptive agent acting in periphery by inhibiting the cyclo-oxygenase pathway and promoting the release of an opioid peptide.

Synthesis and pharmacological evaluation of new pyrazolidine-3, 5-diones as AT(1) angiotensin II receptor antagonists.

On the basis of the structure of the non-peptide receptor antagonist irbesartan, a new series of AT(1) ligands was designed. In these compounds the central imidazolone nucleus of irbesartan was replaced by a pyrazolidine-3,5-dione structure. The key intermediate N-alkylpyrazolidine-3,5-diones were synthesized according to a new and general method. The most active compounds possess a spirocyclopentane ring at position 4, a linear butyl chain at position 1, and the [2'-(5-tetrazolyl)biphenyl-4-yl]methyl or [2'-(benzoylaminosulfonyl)biphenyl-4-yl]methyl group at position 2. Affinity toward the AT(1) and AT(2) receptors was assessed by the ability of the compounds to competitively displace [(3)H]AII from its specific binding sites. The most active compounds, 28 and 48, displayed high affinity for the AT(1) receptor, good selectivity AT(1) versus AT(2), and potent in vitro antagonist activity.

[New naphthalenic ligands of melatoninergic receptors]. / Nouveaux ligands naphtaléniques des récepteurs mélatoninergiques.

Twenty three naphthalenic bio-isosteres of melatonin have been synthesized. The main structural variations concerned the acylamino substituents of the side chain and the alkoxy group on the 7-position of the naphthalene. Some of these compounds show greater affinity than melatonin itself for the melatonin receptor. The results of this study provide new informations on the structure affinity relationships and on the mode of interaction at the melatonin binding site.