Novel ebselen-porphyrin conjugates: synthesis and nucleic acid interaction study

Novel porphyrins bearing ebselen (2-phenyl-1,2-benzisoselenazol-3[2H]-one) moiety were synthesized and characterized. Their interactions with herring sperm DNA were studied by means of UV-visible, fluorescence, circular dichroism spectroscopy, and gel electrophoresis.     

The ligand-to-metal charge transfer excited state of [Re(dmpe)3]2+

Photosynthesis Research - The ligand-to-metal charge transfer (LMCT) transitions of [Re(dmpe)3]2+ (dmpe?=?bis-1,2-(dimethylphosphino)ethane) were interrogated using UV/Vis absorbance...     

Ebselen has dehydroascorbate reductase and thioltransferase-like activities

Ebselen (2-phenyl-1,2-benzisoselenazol-3(2H)-one), a seleno-organic compound, has been reported to mimic glutathione peroxidase (GPX). Since bovine erythrocyte GPX showed dehydroascorbic acid (DHA) reductase and thioltransferase (TTase) activities, ebselen was also examined for DHA reductase and TTase-like activities. Evidence is reported that, in the presence of GSH, ebselen catalyzed the in vitro reduction of DHA to L-ascorbic acid in a dose-dependent manner. Using S-sulfocysteine and GSH as co-substrates, ebselen catalyzed the in vitro formation of glutathione disulfide in a dose-dependent manner, thereby acting as a TTase mimic. 1-Chloro-2,4-dinitrobezene (CDNB), a co-substrate with GSH for glutathione S-transferase, was used to measure rates of adduct formation with ebselen pretreated with GSH and compared with GSH alone. The reaction rate was proportional to ebselen, and ebselen was about 250 times more reactive than GSH on an equimolar basis. The DHA reductase and TTase-like activities, in addition to the powerful nucleophilic reactivity of ebselen selenol, may contribute to ebselen's significant anti-inflammatory and anti-oxidative properties in vivo.     

Essential role for mitochondrial thioredoxin reductase in hematopoiesis, heart development, and heart function

Oxygen radicals regulate many physiological processes, such as signaling, proliferation, and apoptosis, and thus play a pivotal role in pathophysiology and disease development. There are at least two thioredoxin reductase/thioredoxin/peroxiredoxin systems participating in the cellular defense against oxygen radicals. At present, relatively little is known about the contribution of individual enzymes to the redox metabolism in different cell types. To begin to address this question, we generated and characterized mice lacking functional mitochondrial thioredoxin reductase (TrxR2). Ubiquitous Cre-mediated inactivation of TrxR2 is associated with embryonic death at embryonic day 13. TrxR2(TrxR2(-/-)minus;/TrxR2(-/-)minus;) embryos are smaller and severely anemic and show increased apoptosis in the liver. The size of hematopoietic colonies cultured ex vivo is dramatically reduced. TrxR2-deficient embryonic fibroblasts are highly sensitive to endogenous oxygen radicals when glutathione synthesis is inhibited. Besides the defect in hematopoiesis, the ventricular heart wall of TrxR2(TrxR2(-/-)minus;/TrxR2(-/-)minus;) embryos is thinned and proliferation of cardiomyocytes is decreased. Cardiac tissue-restricted ablation of TrxR2 results in fatal dilated cardiomyopathy, a condition reminiscent of that in Keshan disease and Friedreich's ataxia. We conclude that TrxR2 plays a pivotal role in both hematopoiesis and heart function.     

Free radical scavengers can modulate the DNA-damaging action of alloxan

Alloxan can generate diabetes in experimental animals and its action can be associated with the production of free radicals. It is therefore important to check how different substances often referred to as free radical scavengers may interact with alloxan, especially that some of these substance may show both pro- and antioxidant activities. Using the alkaline comet assay we showed that alloxan at concentrations 0.01-50 microM induced DNA damage in normal human lymphocytes in a dose-dependent manner. Treated cells were able to recover within a 120-min incubation. Vitamins C and E at 10 and 50 microM diminished the extent of DNA damage induced by 50 microM alloxan. Pre-treatment of the lymphocytes with a nitrone spin trap, alpha-(4-pyridil-1-oxide)- N-t-butylnitrone (POBN) or ebselen (2-phenyl-1,2-benzisoselenazol-3(2H)-one), which mimics glutathione peroxides, reduced the alloxan-evoked DNA damage. The cells exposed to alloxan and treated with formamidopyrimidine-DNA glycosylase (Fpg) and 3-methyladenine-DNA glycosylase II (AlkA), enzymes recognizing oxidized and alkylated bases, respectively, displayed greater extent of DNA damage than those not treated with these enzymes. The results confirmed that free radicals are involved in the formation of DNA lesions induced by alloxan. The results also suggest that alloxan can generate oxidized DNA bases with a preference for purines and contribute to their alkylation.     

Limbetazulone: a new 'decahydro-8-oxanaphtho[2,1-f]azulen-7-one' diterpenoid from Ballota limbeta, and occurrence of two conformational isomers in the crystal

A new diterpenoid, limbetazulone (= (3S,4S,4aR,12bS)-1,2,3,4,4a,5,6,11,12,12b-decahydro-3-hydroxy-4-(hydroxymethyl)naphtho[1',2': 5,6]cyclohepta[1,2-b]furan-7(7H)-one; 1), with the very rare 'naphtho[2,1-f]azulene-7-one' skeleton, was isolated from the aerial parts of the Asian medicinal plant Ballota limbeta. Its structure was established by extensive spectroscopic investigations, especially 1D and 2D NMR. X-Ray diffraction studies showed the presence of two conformational isomers (1a and 1b) in the crystal.     

Fc epsilon RI signaling of mast cells activates intracellular production of hydrogen peroxide: role in the regulation of calcium signals

Earlier studies, including our own, revealed that activation of mast cells is accompanied by production of reactive oxygen species (ROS) that help to mediate the release of the inflammatory mediators, including histamine and eicosanoids. However, little is known about the mechanisms of ROS production, including the species of oxidants produced. In this study we show that in both the RBL-2H3 mast cell line and bone marrow-derived mast cells, FcepsilonRI cross-linking stimulates intracellular oxidative burst, including hydrogen peroxide (H(2)O(2)) production, as defined with the oxidant-sensitive dyes dichlorofluorescein and scopoletin and the selective scavenger ebselen (2-phenyl-1,2-benzisoselenazol-3(2H)-one). The oxidative burst was observed immediately after stimulation and was most likely due to an NAD(P)H oxidase. Experiments using selective pharmacological inhibitors demonstrated that activation of tyrosine kinases and phosphatidylinositol-3-kinase is required for induction of the oxidative burst. Blockade of the oxidative burst by diphenyleneiodonium impaired the release of preformed granular mediators, such as histamine and beta-hexosaminidase, and the secretion of newly synthesized leukotriene C(4), whereas selective scavenging H(2)O(2) by ebselen impaired leukotriene C(4) secretion, but not degranulation. Sustained elevation of cytosolic calcium through store-operated calcium entry was totally abolished when ROS production was blocked. In contrast, selective depletion of H(2)O(2) caused a considerable decrease and delay of the calcium response. Finally, tyrosine phosphorylation of phospholipase Cgamma and the linker for activation of T cells, an event required for calcium influx, was suppressed by diphenyleneiodonium and ebselen. These studies demonstrate that activation of the intracellular oxidative burst is an important regulatory mechanism of mast cell responses.     

Synthesis, antioxidant and toxicological study of novel pyrimido quinoline derivatives from 4-hydroxy-3-acyl quinolin-2-one

A series of novel pyrimido and other fused quinoline derivatives like 4-methyl pyrimido [5,4-c]quinoline-2,5(1H,6H)-dione (4a), 4-methyl-2-thioxo-1,2-dihydropyrimido [5,4-c]quinoline-5(6H)-one (4b), 2-amino-4-methyl-1,2-dihydropyrimido [5,4-c]quinolin-5(6H)-one (4c), 3-methylisoxazolo [4,5-c]quinolin-4(5H)-one (4d), 3-methyl-1H-pyrazolo [4,3-c]quinoline-4(5H)-one (5e), 5-methyl-1H-[1,2,4] triazepino [6,5-c]quinoline-2,6(3H,7H)-dione (5f), 5-methyl-2-thioxo-2,3-dihydro-1H-[1,2,4]triazepino [6,5-c]quinolin-6(7H)-one (5 g) were synthesized regioselectively from 4-hydroxy-3-acyl quinolin-2-one 3. They were screened for their in vitro antioxidant activities against radical scavenging capacity using DPPH(), Trolox equivalent antioxidant capacity (TEAC), total antioxidant activity by FRAP, superoxide radical (O(2)(°-)) scavenging activity, metal chelating activity and nitric oxide scavenging activity. Among the compounds screened, 4c and 5 g exhibited significant antioxidant activities.     

Discovery of novel antitubercular 1,5-dimethyl-2-phenyl-4-([5-(arylamino)-1,3,4-oxadiazol-2-yl]methylamino)-1,2-dihydro-3H-pyrazol-3-one analogues

In search of potential therapeutics for tuberculosis, we describe herewith the synthesis, characterization and antimycobacterial activity of 1,5-dimethyl-2-phenyl-4-([5-(arylamino)-1,3,4-oxadiazol-2-yl]methylamino)-1,2-dihydro-3H-pyrazol-3-one analogues. Among the synthesized compounds, 4-[(5-[(4-fluorophenylamino]-1,3,4-oxadiazol-2-yl)methylamino]-1,2-dihydro-1,5-dimethyl-2-phenylpyrazol-3-one (4a) was found to be the most promising compound active against Mycobacterium tuberculosis H(37)Rv and isoniazid resistant M. tuberculosis with minimum inhibitory concentrations, 0.78 and 3.12μg/mL, respectively, free from any cytotoxicity (>62.5μg/mL).     

Determination of the relative contributions of the diselenide and selenol forms of ebselen in the mechanism of its glutathione peroxidase-like activity.

The molecular basis of the glutathione peroxidase activity of ebselen (2-phenyl-1,2-benzisoselenazol-3(2H)-one) was investigated by the use of synthesised, authentic intermediates identical to those formed by the reaction of ebselen with glutathione. The second order rate constants for the reaction of ebselen (0.29 mM-1 min-1), ebselen-glutathione selenosulfide (less than or equal to 0.01 mM-1 min-1), ebselen selenol (2.8 mM-1 min-1) and ebselen diselenide (0.32 mM-1 min-1) with hydrogen peroxide reveal that the selenol is particularly active in this respect. The determination of the relative amounts of ebselen selenol and diselenide under typical peroxidase assay conditions implies that the selenol is the predominant molecular species responsible for the glutathione--(70%)--and dithiothreitol--(96%)--dependent peroxidase activity of ebselen.     

Synthesis, spectroscopy (IR, multinuclear NMR, ESI-MS), diffraction, density functional study and in vitro antiproliferative activity of pyrazole-beta-diketone dihalotin(IV) compounds on 5 melanoma cell lines

Novel 4-acylpyrazolon-5-ato-dihalotin(IV) complexes, [Q2SnX2], (X = F, Cl, Br or I); HQ = HQ(CHPh2) (1,2-dihydro-3-methyl-1-phenyl-4-(2,2-diphenylacetyl)pyrazol-5-one), HQ(Bn) (1,2-dihydro-3-methyl-1-phenyl-4-(2-phenylacetyl)pyrazol-5-one) or HQ(CF3,py) (4-(2,2,2-trifluoroacetyl)-1,2-dihydro-3-methyl-1-(pyridin-2-yl)pyrazol-5-one) have been synthesized and characterized by spectroscopic (IR, 1H, 13C, 19F and 119Sn NMR, electrospray ionisation mass spectrometry (ESI-MS)), analytical and structural methods (X-ray and density functional theory). 119Sn chemical shifts depend on the nature of the halides bonded to tin. Isomer conversion, detected in solution by NMR spectroscopy, is related to the acyl moiety bulkiness while the cis(Cl)-cis(acyl)-trans(pyrazolonato) scheme is found in the solid state. The in vitro antiproliferative tests of three derivatives on three human melanoma cell lines (JR8, SK-MEL-5, MEL501) and two melanoma cell clones (2/21 and 2/60) show dose-dependent decrease of cell proliferation in all cell lines. The activity correlates with the nature of the substituent on position 1 of pyrazole, decreasing in the order pyridyl>Ph>methyl. The activity for (Q(CF3,py))2SnCl2 on the SK-MEL-5 cell line is IC50 = 50 microM.     

Development of imidazopyrazinone red-chemiluminescent probes for detecting superoxide anions via a chemiluminescence resonance energy transfer method.

During the development of useful probes for detecting superoxide anions via chemiluminescence with longer wavelengths than that of green, chemiluminescent probes that emit red light (lambda(max) 610 nm) when induced by superoxide anions were synthesized and characterized. These red-chemiluminescent probes consist of a 6-(4-methoxyphenyl)imidazo[1,2-a] pyrazin-3(7H)-one moiety, which reacts with superoxide anions to generate energy, and a sulphorhodamine 101 moiety, which accepts the energy and emits red light. Using a hypoxanthine-xanthine oxidase system for the generation of superoxide anions, it was shown that the superoxide anion-induced chemiluminescences of red-chemiluminescent probes (3 and 4) were more intense than those of the blue- and green-chemiluminescent probes 2-methyl-6-(4-methoxyphenyl)imidazo[1,2-a] pyrazin-3(7H)-one (MCLA) and 6-[4-[2-[N'-(5-fluoresceinyl)thioureido]-ethoxy]phenyl]-2-methylimidazo[1,2-a]pyrazin-3(7H)-one (FCLA), respectively, which are generally considered to be the most sensitive chemiluminescent probes. The ratio between the superoxide-dependent and background chemiluminescence intensities for 3 was comparable to those of MCLA and FCLA, but higher than that of 4. Due to its highly intense superoxide anion-induced chemiluminescence at low probe concentrations, red-chemiluminescent probe 3 is superior to MCLA and FCLA for measurement of superoxide anions.     

Cyclodextrin-bound 6-(4-methoxyphenyl)imidazo[1,2-alpha+/-]pyrazin-3(7H)-ones with fluorescein as green chemiluminescent probes for superoxide anions

In providing chemiluminescent probes that have high chemiluminescence intensity and high specificity to superoxide anions, novel chemiluminescent probes involving cyclodextrins covalently bound to 6-(4-methoxyphenyl)imidazo[1,2-alpha]pyrazin-3(7H)-one with fluorescein were synthesized and characterized. Using the hypoxanthine-xanthine oxidase system for the generation of the superoxide anions, these novel chemiluminescent probes showed higher superoxide-induced chemiluminescence intensity than that of 6-[4-[2-[N(')-(5-fluoresceinyl)thioureido]-ethoxy]phenyl]-2-methylimidazo[1,2-alpha]pyrazin-3(7H)-one (FCLA). When tested at a probe concentration of 1.0 microM, compound 6, in which 6-(4-methoxyphenyl)imidazo[1,2-alpha]pyrazin-3(7H)-one and fluorescein are covalently attached on the secondary and primary hydroxyl faces of gamma-cyclodextrin, respectively, showed green luminescence intensity that was 26 times that of FCLA, which was also the highest luminescence intensity in this present study. At probe concentrations of less than 1.0 microM, the ratio of the superoxide-dependent chemiluminescence intensity to the background chemiluminescence intensity for compound 6 was higher than that of FCLA. This high superoxide-induced chemiluminescence intensity and superoxide specificity in low probe concentrations indicates that 6 can be more effective than FCLA toward the measurement of superoxide anions.     

Estrogenic and anti-estrogenic compounds from the Thai medicinal plant, Smilax corbularia (Smilacaceae)

From the rhizomes of Smilax corbularia Kunth. (Smilacaceae), 11 compounds, (2R,3R)-2″-acetyl astilbin, (2R,3R)-3″-acetyl astilbin, (2R,3R)-4″-acetyl astilbin, (2R,3R)-3″-acetyl engeletin, (2R,3S)-4″-acetyl isoastilbin, 2-(4-hydroxyphenyl)-3,4,9,10-tetrahydro-3,5-dihydroxy-10-(3,4-dihydroxyphenyl)-(2R,3R,10R)-2H,8H-benzo [1,2-b:3,4-b′] dipyran-8-one, 2-(4-hydroxyphenyl)-3,4,9,10-tetrahydro-3,5-dihydroxy-10-(3,4-dihydroxyphenyl)-(2R,3R,10S)-2H, 8H-benzo [1,2-b:3,4-b′] dipyran-8-one, 3,4-dihydro-7-hydroxy-4-(3,4-dihydroxyphenyl)-5-[(1E)-2-(4-hydroxyphenyl) ethenyl]-2H-1-benzopyran-2-one, 3,4-dihydro-7-hydroxy-4-(3,4-dihydroxy-phenyl)-5-[(1E)-2-(3,4-dihydroxyphenyl) ethenyl]-2H-1-benzopyran-2-one, 3,4-dihydro-7-hydroxy-4-(4-hydroxy-3-methoxyphenyl)-5-[(1E)-2-(4-hydroxyphenyl) ethenyl]-2H-1-benzopyran-2-one, and 5,7,3′,4′-tetrahydroxy-3-phenylcoumarin along with 34 known compounds were isolated and characterized as 19 flavonoids, 14 catechin derivatives, 6 stilbene derivatives, and 6 miscellaneous substances. All isolates had their estrogenic and anti-estrogenic activities determined using the estrogen-responsive human breast cancer cell lines MCF-7 and T47D. The major constituents were recognized as flavanonol rhamnosides by the suppressive effect on estradiol induced cell proliferation at a concentration of 1 μM. Meanwhile, flavanonol rhamnoside acetates demonstrated estrogenic activity in both MCF-7 and T47D cells at a concentration of 100 μM, and they enhanced the effects of co-treated E2 on T47D cell proliferation at concentrations of more than 0.1 μM.     

Evaluation of the antimicrobial activity of ebselen: role of the yeast plasma membrane H+-ATPase

Ebselen (2-phenyl-1,2-benzisoselenazol-3(2H)-one) is a selenium-containing antioxidant demonstrating anti-inflammatory and cytoprotective properties in mammalian cells and cytotoxicity in lower organisms. The mechanism underlying the antimicrobial activity of ebselen remains unclear. It has recently been proposed that, in lower organisms like yeast, the plasma membrane H+-ATPase (Pma1p) could serve as a potential target for this synthetic organoselenium compound. Using yeast and bacteria, the present study found ebselen to inhibit microbial growth in a concentration- and time-dependent manner, and yeast and Gram-positive bacteria to be more sensitive to this action (IC50 approximately 2-5 microM) than Gram-negative bacteria (IC50 < 80 microM). Washout experiments and scanning electron microscopic analysis revealed ebselen to possess fungicidal activity. In addition, ebselen was found to inhibit medium acidification by PMA1-proficient haploid yeast in a concentration-dependent manner. Additional studies comparing PMA1 (+/-) and PMA1 (+/+) diploid yeast cells revealed the mutant to be more sensitive to treatment with ebselen than the wild type. Ebselen also inhibited the ATPase activity of Pma1p from S. cerevisiae in a concentration-dependent manner. The interaction of ebselen with the sulfhydryl-containing compounds L-cysteine and reduced glutathione resulted in the complete and partial prevention, respectively, of the inhibition of Pma1p ATPase activity by ebselen. Taken together, these results suggest that the fungicidal action of ebselen is due, at least in part, to interference with both the proton-translocating function and the ATPase activity of the plasma membrane H+-ATPase.     

Natural bromophenols from the marine red alga Polysiphonia urceolata (Rhodomelaceae): structural elucidation and DPPH radical-scavenging activity

Three new natural occurring bromophenols, 3-(3-bromo-4,5-dihydroxyphenyl)-2-(3,5-dibromo-4-hydroxyphenyl)propionic acid (1), (E)-4-(3-bromo-4,5-dihydroxyphenyl)-but-3-en-2-one (2), and (3,5-dibromo-4-hydroxyphenyl) acetic acid butyl ester (3), together with one known bromophenol, 1,2-bis(3-bromo-4,5-dihydroxyphenyl)ethane (4), were isolated and identified from the marine red alga Polysiphonia urceolata. The structures of these compounds were elucidated by extensive analysis of 1D and 2D NMR and IR spectra and MS data. Each of the isolated compounds was evaluated for scavenging alpha, alpha-diphenyl-beta-picrylhydrazyl (DPPH) radical activity and all of them exhibited significant activity with IC(50) values ranging from 9.67 to 21.90 microM, compared to the positive control, a well-known antioxidant butylated hydroxytoluene (BHT), with IC(50) 83.84 microM.     

The chemical constituents of the fungus Stereum sp

Four new compounds, including a sesquiterpene and three aromatic compounds, and a known compound were isolated from a culture broth of the fungus Stereum sp. The novel sesquiterpene was determined to be stereumone A ((+)-2,3,4a,5,6,7,8a,9-octahydro-5-hydroxy-6,6,9-trimethyl-4,8a-epoxynaphtho[2,3-b]furan-8(8H)-one; 1), and the three new aromatic compounds were elucidated as 3,5-dihydroxy-4-(3-methylbut-2-enyl)benzene-1,2-dicarbaldehyde (2), 5,7-dihydroxy-6-(3-methylbut-2-enyl)isobenzofuran-1(3H)-one (3), butyl 2,4-dihydroxy-6-methylbenzoate (4), together with the known compound methyl 2,4-dihydroxy-6-methylbenzoate (5). The structures were established by spectroscopic methods including 2D-NMR techniques. Compounds 2 and 4 showed evident nematicidal activity against nematode Panagrellus redivivus.     

4,5-dihydropyridazin-3-one derivatives as histamine H₃ receptor inverse agonists

H(3)R structure-activity relationships for a new class of 4,5-dihydropyridazin-3-one H(3)R antagonists/inverse agonists are disclosed. Modification of the 4,5-dihydropyridazinone moiety to block in vivo metabolism identified 4,4-dimethyl-6-{4-[3-((R)-2-methyl-pyrrolidin-1-yl)-propoxy]-phenyl}-4,5-dihydro-2H-pyridazin-3-one 22 as a lead candidate demonstrating potent in vivo functional H(3)R antagonism in the rat dipsogenia model and robust wake promoting activity in the rat EEG/EMG model.     

Spiro-imidazo[1,2-a]indeno[1,2-e]pyrazine-4-one derivatives are mixed AMPA and NMDA glycine-site antagonists active in vivo

Original spiro-imidazo[1,2-a]indeno[1,2-e]pyrazine-4-one derivatives were synthesised and led to the identification of 3e which showed good affinities for both the AMPA and the NMDA glycine-site receptors, and displayed good anticonvulsant effects after i.p. and i.v. administrations in the electroshock-induced convulsion assay in mice. The corresponding dextrorotatory isomer (+)-3e was notably more potent than the levorotatory isomer (-)-3e in in vitro and in vivo assays.