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At least 397 records · Page 22Linked to original sources
PubMed2003

Detection of five new hydroxyl analogues of azaspiracids in shellfish using multiple tandem mass spectrometry.

The polyether dinoflagellate toxins, azaspiracids, are responsible for azaspiracid poisoning (AZP), a new human toxic syndrome arising from the consumption of shellfish. To date, five azaspiracids have been isolated and fully structurally elucidated, including, AZA1, its 8-methyl and 22-demethyl analogues, AZA2 and AZA3, respectively, and two hydroxyl derivatives of AZA3, named AZA4 and AZA5. Using a recently developed method involving liquid chromatography with multiple tandem mass spectrometry (LC-MS(n)), five new azaspiracids, AZA7-AZA11, have been found in mussels (Mytilus edulis). AZA6 is a positional isomer of AZA1 and four of the new compounds are isomers with a mass of 857.5 amu. AZA7 and AZA8 are hydroxyl analogues of AZA1 while AZA9 and AZA10 are hydroxyl analogues of AZA6. AZA11 is a hydroxyl analogue of AZA2. The separation of all 11 azaspiracids was achieved using isocratic reversed phase liquid chromatography using a combination of eluent additives, trifluoroacetic acid and ammonium acetate. The ion-trap MS experiments, with electrospray ionisation, involved the fragmentation of the protonated molecule [M+H](+), trapping and fragmenting the product ions due to the loss of a water molecule [M+H-H(2)O](+), together with mass spectral data analysis that included the characteristic A-ring fragmentation for each compound.

Animals↗
PubMed2005

Multicomponent synthesis of spiroisoxazolines.

A three-component one-pot procedure (3-MCR) was developed to assemble the spiroisoxazoline nucleus from commercially available materials. This new methodology affords the title compounds in high yields and without the use of chromatography.

Isoxazoles↗
PubMed2004

Activity of alpha7-selective agonists at nicotinic and serotonin 5HT3 receptors expressed in Xenopus oocytes.

Nicotinic receptors containing alpha7 subunits are widely distributed in the central nervous system and are thought to be involved in a number of functions. However, it has been difficult to study alpha7-containing receptors in vivo because of a paucity of selective agonists. A new spirooxazolidinone compound, AR-R17779, was recently described as potent agonist at alpha7 receptors, but electrophysiological studies at other types of nicotinic receptors have not been carried out. We characterized the activity of AR-R17779 at alpha7, alpha4beta2, alpha3beta4, alpha3beta2, alpha3beta2alpha5 receptors expressed in Xenopus oocytes. In addition, since there is significant homology between nicotinic alpha7 and serotonin 5HT(3) receptors, the activity of AR-R17779 at expressed 5HT(3a) receptors was also examined. Finally, actions of tropisetron and ondansetron, two 5HT(3) antagonists, were explored. AR-R17779 was found to activate alpha7 receptors, but had no activity at other types of nicotinic receptors, and also had no activity at 5HT(3a) receptors. Tropisetron activated, while ondansetron acted as an antagonist, at alpha7 nicotinic receptors. The two 5HT(3) antagonists also acted as antagonists at alpha4beta2 and alpha3beta4 nicotinic receptors. Thus, AR-R17779 was confirmed to be a selective nicotinic alpha7 receptor agonist and to be without activity at 5HT(3) receptors. In contrast, the actions of tropisetron and ondansetron on nicotinic receptors were complex.

Animals↗
PubMed2005

Recognition of the oxidized lesions spiroiminodihydantoin and guanidinohydantoin in DNA by the mammalian base excision repair glycosylases NEIL1 and NEIL2.

8-Oxoguanine (8-oxoG) is an unstable mutagenic DNA lesion that is prone to further oxidation. High valent metals such as Cr(V) and Ir(IV) readily oxidize 8-oxoG to form guanidinohydantoin (Gh), its isomer iminoallantoin (Ia), and spiroiminodihydantoin (Sp). When present in DNA, these lesions show enhanced base misincorporation over the parent 8-oxoG lesion leading to G --> T and G --> C transversion mutations and polymerase arrest. These findings suggested that further oxidized lesions of 8-oxoG are more mutagenic and toxic than 8-oxoG itself. Repair of oxidatively damaged bases, including Sp and Gh/Ia, are initiated by the base excision repair (BER) system that involves the DNA glycosylases Fpg, Nei, and Nth in E. coli. Mammalian homologs of two of these BER enzymes, OGG1 and NTH1, have little or no affinity for Gh/Ia and Sp. Herein we report that two recently identified mammalian glycosylases, NEIL1 and NEIL2, showed a high affinity for recognition and cleavage of DNA containing Gh/Ia and Sp lesions. NEIL1 and NEIL2 recognized both of these lesions in single-stranded DNA and catalyzed the removal of the lesions through a beta- and delta-elimination mechanism. NEIL1 and NEIL2 also recognized and excised the Gh/Ia lesion opposite all four natural bases in double-stranded DNA. NEIL1 was able to excise the Sp lesion opposite the four natural bases in double-stranded DNA, however, NEIL2 showed little cleavage activity against the Sp lesion in duplex DNA although DNA trapping studies show recognition and binding of NEIL2 to this lesion. This work suggests that NEIL1 and NEIL2 are essential in the recognition of further oxidized lesions arising from 8-oxoG and implies that these BER glycosylases may play an important role in the repair of DNA damage induced by carcinogenic metals.

Animals↗
PubMed2004

Determination of the enantiomeric purity of the phytoalexins spirobrassinins by 1H NMR using chiral solvation.

A simple and inexpensive method for enantiomeric discrimination of the phytoalexins spirobrassinin (1), 1-methoxyspirobrassinin (2) and synthetic analog 1-methylspirobrassinin (6) using the chiral solvating agent 2,2,2-trifluoro-1-(9-anthryl)ethanol in C(6)D(6) is described. Using this method the enantiomeric composition of each sample can be determined accurately by (1)H NMR and the compounds can be recovered readily by chromatography.

Magnetic Resonance Spectroscopy↗
PubMed2001

[Chemical constituents from the leaves of crataegus pinnatifida Bge. var. major N.E.Br].

AIM: To study the chemical constituents in the leaves of Crataegus pinnatifida Bge. var. major N.E.Br.. METHODS: Compounds were isolated by using porous resin, silica gel, polyamide chromatographic techniques etc. Their structures were elucidated by chemical and spectroscopic methods. RESULTS: Eight compounds were identified as pinnatifin I (1), quercetin (2), 3-O-beta-D-glucopyranosyl quercetin (3), 3-O-beta-D-galacopyranosyl quercetin (4), 3-O-beta-D-glucopyranosyl (6-->1)-alpha-L-rhamnosyl quercetin (5), 3-O-beta-D-galacopyranosyl (6-->1)-alpha-L-rhamnosyl quercetin (6), kaempferol (7), 7-O-alpha-L-rhamnosyl-3-O-beta-D- glucopyranosyl kaempferol (8). CONCLUSION: Compound 1 is a new compound. Compound 8 was isolated from this plant for the first time.

Crataegus↗
PubMedDate not supplied

Anticonvulsant properties of N-(4-methylpiperazin-1-yl)- and N-[3-(4-methyl-piperazin-1-yl)propyl] derivatives of 3-aryl- and 3-spirocycloalkyl-pyrrolidine-2,5-dione.

Two series of N-(4-methylpiperazin-1-yl)- and N-[3-(4-methylpiperazin-1-yl)-propyl]-3-aryl- and 3-spirocycloalkyl-pyrrolidine-2,5-dione derivatives were synthesized and tested for anticonvulsant activity in the maximum electroshock (MES) seizure and pentetrazole (sc PTZ) seizure threshold tests. Compounds with an aromatic ring at position-3 of pyrrolidine-2,5-dione exhibited anticonvulsant activity in the MES test. For that series of compounds, ED50 values were determined. The most potent in the series were derivatives and with a chlorine atom at position-3 or 4 of the aromatic ring. Those compounds exhibited strong anticonvulsant activity, and their ED50 values ranged from 29 to 48 mg/kg. Introduction of the spirocycloalkyl ring into the position-3 of pyrrolidine-2,5-dione made those compounds inactive.

Animals↗
PubMed2004

Liquid chromatography/tandem mass spectrometry of unusual phenols from Yucca schidigera bark: comparison with other analytical techniques.

Qualitative and quantitative analyses of phenolic compounds are of interest for both medicinal and food plants. In the present work, the phenolic fraction from Yucca schidigera, a plant bearing the GRAS (Generally Recognized as Safe) label approved by the US Food and Drug Administration, was studied. Crude extracts of Y. schidigera bark were investigated by liquid chromatography/UV spectrophotometry with diode-array detection, liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS) and liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS), in order to develop and optimize simple and rapid techniques to determine both stilbenes and yuccaols for the purposes of quality control of collected material. With optimal LC and MS conditions, stilbenes and yuccaols were quantified with all the proposed methods and the results were compared. Sensitivity was evaluated and the results indicated that MS/MS detection in the multiple reaction monitoring mode is easily applicable to this plant and allows the rapid and direct identification and quantification of these peculiar compounds in crude plant extracts.

Chromatography, Liquid↗
PubMed2003

Potent antibacterial activity of halogenated metabolites from Malaysian red algae, Laurencia majuscula (Rhodomelaceae, Ceramiales).

Red algae genus Laurencia (Rhodomelaceae, Ceramiales) are known to produce a wide range of chemically interesting secondary halogenated metabolites. This investigation delves upon extraction, isolation, structural elucidation and antibacterial activity of inherently available secondary metabolites of Laurencia majuscula Harvey collected from two locations in waters of Sabah, Malaysia. Two major halogenated compounds, identified as elatol (1) and iso-obtusol (2) were isolated. Structures of these compounds were determined from their spectroscopic data such as IR, 1H-NMR, 13C-NMR and optical rotation. Antibacterial bioassay against human pathogenic bacteria was conducted using disc diffusion (Kirby-Bauer) method. Elatol (1) inhibited six species of bacteria, with significant antibacterial activities against Staphylococcus epidermis, Klebsiella pneumonia and Salmonella sp. while iso-obtusol (2) exhibited antibacterial activity against four bacterial species with significant activity against K. pneumonia and Salmonella sp. Elatol (1) showed equal and better antibacterial activity compared with tested commercial antibiotics while iso-obtusol (2) only equaled the potency of commercial antibiotics against K. pneumonia and Salmonella sp. Further tests conducted using dilution method showed both compounds as having bacteriostatic mode of action against the tested bacteria.

Anti-Bacterial Agents↗