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Biomedical subjects

A Linden

Publications and source records attributed to A Linden.

At least 37 records · Page 2Linked to original sources
PubMed2001

Dispiro[fluorene-9,5'-[1,2,3,4]tetrathiane-6',9"-fluorene.

The tetrathiane ring of the title compound, C26H16S4, has a chair conformation and the molecule has approximate C2 symmetry. Each of the two fluorene ring systems is virtually planar, with the ring planes intersecting at an angle of 67.58 (5) degrees. This novel compound has been formed as a side product from the treatment of 9H-fluorene-9-thione with methyl N-[(benzylidene)phenyl]glycinate in the presence of LiBr and 1,6-diazabicyclo[5.4.0]undecane.

Journal Article↗
PubMed2001

(+/-)-6-Benzyl-3,3-dimethylmorpholine-2,5-dione and its 5-monothio and 2,5-dithio derivatives.

The morpholine ring of the title dione, C(13)H(15)NO(3), shows a boat conformation that is distorted towards a twist-boat, with the boat ends being the two Csp(3) atoms of the ring. The benzyl substituent is in the favoured 'exo' position. In the monothione derivative, (+/-)-6-benzyl-3,3-dimethyl-5-thioxomorpholin-2-one, C(13)H(15)NO(2)S, this ring has a much flatter conformation that is midway between a boat and an envelope, with the dimethyl end being almost planar. The orientation of the benzyl group is 'endo'. The dithione derivative, (+/-)-6-benzyl-3,3-dimethylmorpholine-2,5-dithione, C(13)H(15)NOS(2), has two symmetry-independent molecules, which show different puckering of the morpholine ring. One molecule has a flattened envelope conformation distorted towards a screw-boat, while the conformation in the other molecule is similar to that in the monothione derivative. Intermolecular hydrogen bonds link the molecules in the three compounds, respectively, into centrosymmetric dimers, infinite chains, and dimers made up of one of each of the symmetry-independent molecules.

Journal Article↗
PubMed2001

Flavonoid, iridoid, and lignan glycosides from Putoria calabrica.

From the aerial parts of Putoria calabrica, two new flavonol triglycosides were isolated and their structures were elucidated as quercetin-3-O-[alpha-L-rhamnopyranosyl-(1-->2)-alpha-L-arabinopyranoside]-7-O-beta-D-glucopyranoside (1, calabricoside A) and quercetin-3-O-[4' "-O-caffeoyl-alpha-L-rhamnopyranosyl-(1-->2)-alpha-L-arabinopyranoside]-7-O-beta-D-glucopyranoside (2, calabricoside B). Additionally, seven iridoid and three lignan glycosides were isolated and characterized. Radical scavenging activities of all compounds were determined by quantifying their effects on luminol-enhanced chemiluminescence in formyl-methionyl-leucyl-phenylalanine (FMLP) stimulated human polymorphonuclear neutrophils (PMNs). Calabricoside A and B showed strong radical scavenging activity with IC(50) values of 0.25 and 0.3 microM, respectively.

Chromatography↗
PubMed2000

Camphor-based alpha-bromo ketones for the asymmetric darzens reaction

(1R)-2-endo-Bromoacetyl-1,7,7-trimethylbicyclo[2.2.1]heptan-2-ol (endo-2-bromoacetylisoborneol) 4 and its trimethylsilyl ether 3 are presented as efficient reagents for the asymmetric Darzens reaction. From the alpha,beta-epoxy ketone adducts the chiral inductor camphor is removed, by treatment with ceric(IV) ammonium nitrate, to yield the corresponding epoxy acids which are isolated as their dicyclohexylammonium salts.

Journal Article↗
PubMed2000

Single-step purification of a recombinant thermostable alpha-amylase after solubilization of the enzyme from insoluble aggregates.

The expression of the gene encoding a thermostable alpha-amylase (EC 3.2.1.1) (optimal activity at 100 degrees C) from the hyperthermophilic archaeon Pyrococcus woesei in the mesophilic hosts Escherichia coli and Halomonas elongata resulted in the formation of insoluble aggregates. More than 85% of the recombinant enzyme was present within the cells as insoluble but catalytically active aggregates. The recombinant alpha-amylase was purified to homogeneity in a single step by hydrophobic interaction chromatography on a phenyl superose column after solubilization of the enzyme under nondenaturing conditions. The enzyme was purified 258-fold with a final yield of 54%.

Chromatography, Liquid↗
PubMed2000

alpha-Oxymethyl Ketone Enolates for the Asymmetric Mannich Reaction. From Acetylene and N-Alkoxycarbonylimines to beta-Amino Acids This work was supported by the University of the Basque Country, the Basque Government (Projects UPV 170.215-G47/98, EX-1998-124) and in part by M. E. C. (Project PB 98-0549). Grants to A.S. and M.C.G. from the Basque Government, and to C.L. from the Government of Navarra and M.E.C. are acknowledged.

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Journal Article↗
PubMed2000

Increased elastase and myeloperoxidase activity associated with neutrophil recruitment by IL-17 in airways in vivo.

BACKGROUND: A recent study demonstrated that intratracheal administration of the T-lymphocyte cytokine IL-17 recruits neutrophils into airways in vivo by C-X-C chemokine release. It is not known whether IL-17 may also activate airway neutrophils. OBJECTIVE: Our purpose was to evaluate whether IL-17 activates neutrophils in airways in vivo and, if so, whether the proinflammatory cytokine IL-1beta modulates this action of IL-17. METHODS: Intratracheal administration of human (h) IL-17 or rat (r) IL-1beta or hIL-17 plus rIL-1beta in anesthetized, spontaneously breathing rats was followed by bronchoalveolar lavage (BAL) 6 hours later. The BAL fluid was characterized in terms of neutrophil count, of the activity for myeloperoxidase (MPO), and in some cases of the activity for elastase (ELA). Isolated rat neutrophils were stimulated with hIL-17 in vitro, followed by characterization of MPO activity in the cell medium. RESULTS: hIL-17 (1 microg) increased the ELA and the MPO activity, as well as the neutrophil count in BAL fluid, whereas the proinflammatory cytokine rIL-1beta (2.5 ng) did not. Pretreatment with rIL-1beta enhanced IL-17induced ELA and MPO activity, without increasing the neutrophil count. The BAL ELA activity was inhibited by a specific inhibitor of neutrophil serine proteases. Stimulation with hIL-17 in vitro did not increase MPO activity in isolated neutrophils. CONCLUSION: IL-17 can activate neutrophils in association with their recruitment into the airways in vivo and this effect is probably achieved through induced release of mediators from other airway cells.

Animals↗
PubMed2000

Novel extracellular diterpenoids with biological activity from the cyanobacterium Nostoc commune.

Five novel extracellular metabolites with an unprecedented diterpenoid skeleton, 5-[(5-carboxy-2-hydroxy)benzyl]-11-hydroxymethyl-2,5,6,8a, 11-pentamethyldodecahydrocyclopenta naphthalene (1), 5-[(5-carboxy-2-hydroxy)benzyl]-11-formyl-2,5,6,8a, 11-pentamethyl-dodecahydrocyclopenta naphthalene (2), 5-[(5-carboxy-2-hydroxy)benzyl]-11-carboxy-2,5,6,8a, 11-pentamethyl-dodecahydrocyclopenta naphthalene (3), 5-[(5-carboxy-2-hydroxy)benzyl]-11-dihydroxymethyl-2,5,6,8a, 11-pentamethyldodecahydrocyclopenta naphthalene (4), and 5-[(5-carboxy-2-hydroxy)benzyl]-11-acetyl-2,5,6, 8a-tetramethyldodecahydrocyclopenta naphthalene (5), have been isolated from the culture medium of the terrestrial cyanobacterium Nostoc commune by means of bioguided isolation. The molecules were designated as comnostins A-E. The structures were determined by spectroscopic methods, mainly NMR and mass spectrometry. The relative stereochemistry of comnostin A was confirmed by single-crystal X-ray structure analysis. All comnostins showed antibacterial activities. Additionally, cytotoxic and molluscicidal activities were found for comnostin B.

Cyanobacteria↗
PubMed2000

Cloning and expression of alpha-amylase from the hyperthermophilic archaeon Pyrococcus woesei in the moderately halophilic bacterium Halomonas elongata.

An extracellular alpha-amylase gene from the hyperthermophilic archaeon Pyrococcus woesei has been cloned and sequenced. The 1.4-kb protein-coding sequence is identical to that of the corresponding alpha-amylase gene of the closely related species P. furiosus. By using a shuttle cloning vector for halophilic bacteria, the P. woesei alpha-amylase was expressed in the moderate halophile Halomonas elongata, under the control of a native H. elongata promoter. The hyperthermophilic amylase activity expressed in the halophilic host was recovered completely in the crude membrane fraction of cell homogenates, suggesting the formation of inclusion bodies or that the secretion machinery of H. elongata may fail to recognize and release the pyrococcal alpha-amylase to the extracellular medium. However, thermal stability, metal ion interactions, optimal temperature and pH values for the crude and purified recombinant alpha-amylase were comparable with those of the native pyrococcal enzyme. The P. woesei amylase activity expressed in H. elongata was consistently detected in the cells upon growth on a wide range of NaCl concentrations (0.7-2.5 mol l-1). To our knowledge, this is the first report on the expression of an archaeal gene (P. woesei alpha-amylase) in a moderate halophilic host which serves as a cell factory able to grow under extreme salt conditions and with very simple nutritional requirements.

Base Sequence↗
PubMed2000

(M)- and (P)-8-[(1S,2R)-2-hydroxy-1-methyl-2-phenylethyl]-8-methyl-8, 9-dihydro-7H-dinaphth[2,1-c:1',2'-e]azepinium bromide solvates.

The title compounds are diastereoisomers with antipodean axial chirality. The M isomer crystallizes as a (1/3) acetone solvate, C(32)H(30)NO(+).Br(-).3C(3)H(6)O, while the P isomer crystallizes as a (1/1) dichloromethane solvate, C(32)H(30)NO(+).Br(-).CH(2)Cl(2). In each structure, O-H.Br hydrogen bonds link the cations and anions to give ion pairs. The seven-membered azepinium ring adopts the usual twisted-boat conformation and its ring strain causes a slight curvature of the plane of each naphthyl ring.

Azepines↗
PubMed1999

Polynuclear chloromercurate(II) systems in their chloropyridinium salts.

The chloromercurate(II) salts of 2-, 3- and 4-chloropyridine display a variety of anion stoichiometries and structures, including the rare [Hg(3)Cl(10)](4-) stoichiometry. 2-Chloropyridinium trichloromercurate(II), (I), (C(5)H(5)ClN)[HgCl(3)], monoclinic, P2(1)/n, a = 9.094 (8), b = 18.143 (4), c = 12.902 (3) Å, beta = 106.13 (4) degrees with Z = 8, has the [HgCl(3)](-) stoichiometry, but the anions are infinite chains composed of [HgCl(3)](-), HgCl(2) and Cl(-) moieties linked by longer Hg.Cl contacts. Hydrogen bonds link the cations to the formal Cl(-) ions. Tetrakis(3-chloropyridinium) decachlorotrimercurate(II), (II), (C(5)H(5)ClN)(4)[Hg(3)Cl(10)], monoclinic, P2(1)/n, a = 7.522 (2), b = 28.046 (3), c = 9.165 (2) Å, beta = 105.78 (2) degrees with Z = 2, has the rare [Hg(3)Cl(10)](4-) stoichiometry and contains infinite one-dimensional double-stranded {([HgCl(4)](2-))(2) [HgCl(2)]}(n) anionic chains made up of linear HgCl(2) and distorted [HgCl(4)](2-) entities linked together by longer Hg.Cl contacts. The HgCl(2) moieties are joined by double [HgCl(4)](2-) bridges. Hydrogen bonds link the cations to the sides of the anionic columns. Tetrakis(4-chloropyridinium) decachlorotrimercurate(II), (III), (C(5)H(5)ClN)(4)[Hg(3)Cl(10)], triclinic, P1;, a = 9.907 (3), b = 13.226 (2), c = 7.282 (2) Å, alpha = 84.41 (2), beta = 74.81 (2), gamma = 87.34 (2) degrees with Z = 1, also has the [Hg(3)Cl(10)](4-) stoichiometry and the same type of {([HgCl(4)](2-))(2)[HgCl(2)]}(n) anionic chains that were found in compound (II), but the formal HgCl(2) and [HgCl(4)](2-) moieties are more discrete with much weaker contacts linking the individual units. Bifurcated hydrogen bonds with the cations cross-link the anionic chains to form an infinite two-dimensional network. Second forms of the 3- and 4-chloropyridinium salts were also obtained. 3-Chloropyridinium trichloromercurate(II), (IV), (C(5)H(5)ClN)[HgCl(3)], monoclinic, P2(1)/c, a = 7.243 (5), b = 22.145 (8), c = 12.320 (3) Å, beta = 99.52 (3) degrees with Z = 8, has the [HgCl(3)](-) stoichiometry, but the anions are infinite chains composed of distorted [Hg(2)Cl(6)](2-) moieties. Bifurcated hydrogen bonds from the cations cross-link the anionic chains to form infinite two-dimensional layers. Bis(4-chloropyridinium) hexachlorodimercurate(II), (V), (C(5)H(5)ClN)(2)[Hg(2)Cl(6)], monoclinic, C2/m, a = 13.447 (3), b = 7.534 (2), c = 9.939 (2) Å, beta = 97.48 (2) degrees with Z = 2, contains highly symmetrical discrete [Hg(2)Cl(6)](2-)anions. Bifurcated hydrogen bonds from the cations interconnect the anions to form infinite one-dimensional chains.

Journal Article↗
PubMed1999

Plocamium hamatum and its monoterpenes: chemical and biological investigations of the tropical marine red alga.

The polyhalogenated monoterpene content of six samples of the tropical marine red alga Plocamium hamatum, collected from the southern, central and northern regions of The Great Barrier Reef, Australia, was assessed. In all but two of the samples, the polyhalogenated monoterpene content was shown to differ markedly. In total, eleven previously reported compounds were isolated and characterised (1-11). Compound 2 was obtained for the first time as a pure natural product. For compound 4 a single crystal X-ray crystallographic analysis was undertaken which established its absolute configuration as (1S,2S,4R,5R,1'E)-2-bromo-1- bromomethyl-1,4-dichloro-5-(2'-chloroethenyl)-5-methylcyclohexa ne. Complete and unambiguous 1H and 13C NMR data are reported for 2 and 4. For 6-8, some prior 13C NMR assignments are revised. The biological activities of compounds 2-8 and 11 were assessed and indicated 4 to have potent antialgal activity towards Chlorella fusca in an agar diffusion bioassay, as well as being moderately antitubercular and cytotoxic. Compound 6 demonstrated moderate cytotoxicity.

Anti-Infective Agents↗
PubMed1999

Iridoid glycosides of Leonurus persicus.

Two new iridoid glucosides, 6-O-acetylajugol (1) and 7, 8-epoxy-8-epi-loganic acid (2), together with five known iridoid glucosides, galiridoside (3), ajugoside (4), 10-deoxygeniposidic acid (5), 7-deoxy-8-epi-loganic acid (6), and 8-O-acetylharpagide (7), have been isolated from the aerial parts of Leonurus persicus. Leucosceptoside A (8), eugenyl beta-rutinoside (9), and kaempferol 3-O-glucoside (10) were also isolated. The structures of 1 and 2 were elucidated by extensive 1D- and 2D-NMR spectroscopy and molecular modeling. The structure of 3 was confirmed by single-crystal X-ray diffraction. Antimicrobial activity of compounds (1-10) was also evaluated against a panel of gram-positive and gram-negative bacteria and two strains of fungi.

Anti-Bacterial Agents↗