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  • 1
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    Asperentin B, a New Inhibitor of the Protein Tyrosine Phosphatase 1B (2017)
    MDPI
    In:  Marine Drugs, 15 (6). p. 191.
    Details
    Publication Date: 2020-02-06
    Description: In the frame of studies on secondary metabolites produced by fungi from deep-sea environments we have investigated inhibitors of enzymes playing key roles in signaling cascades of biochemical pathways relevant for the treatment of diseases. Here we report on a new inhibitor of the human protein tyrosine phosphatase 1B (PTP1B), a target in the signaling pathway of insulin. A new asperentin analog is produced by an Aspergillus sydowii strain isolated from the sediment of the deep Mediterranean Sea. Asperentin B (1) contains an additional phenolic hydroxy function at C-6 and exhibits an IC50 value against PTP1B of 2 μM in vitro, which is six times stronger than the positive control, suramin. Interestingly, asperentin (2) did not show any inhibition of this enzymatic activity. Asperentin B (1) is discussed as possible therapeutic agents for type 2 diabetes and sleeping sickness.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.3390/md15060191
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  • 2
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    Lysoquinone-TH1, a New Polyphenolic Tridecaketide Produced by Expressing the Lysolipin Minimal PKS II in Streptomyces albus (2018)
    MDPI
    In:  Antibiotics, 7 (3). Art.Nr. 53.
    Details
    Publication Date: 2021-02-08
    Description: The structural repertoire of bioactive naphthacene quinones is expanded by engineering Streptomyces albus to express the lysolipin minimal polyketide synthase II (PKS II) genes from Streptomyces tendae Tü 4042 (llpD-F) with the corresponding cyclase genes llpCI-CIII. Fermentation of the recombinant strain revealed the two new polyaromatic tridecaketides lysoquinone-TH1 (7, identified) and TH2 (8, postulated structure) as engineered congeners of the dodecaketide lysolipin (1). The chemical structure of 7, a benzo[a]naphthacene-8,13-dione, was elucidated by NMR and HR-MS and confirmed by feeding experiments with [1,2-13C2]-labeled acetate. Lysoquinone-TH1 (7) is a pentangular polyphenol and one example of such rare extended polyaromatic systems of the benz[a]napthacene quinone type produced by the expression of a minimal PKS II in combination with cyclases in an artificial system. While the natural product lysolipin (1) has antimicrobial activity in nM-range, lysoquinone-TH1 (7) showed only minor potency as inhibitor of Gram-positive microorganisms. The bioactivity profiling of lysoquinone-TH1 (7) revealed inhibitory activity towards phosphodiesterase 4 (PDE4), an important target for the treatment in human health like asthma or chronic obstructive pulmonary disease (COPD). These results underline the availability of pentangular polyphenolic structural skeletons from biosynthetic engineering in the search of new chemical entities in drug discovery
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.3390/antibiotics7030053
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  • 3
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    First Evidence of Dehydroabietic Acid Production by a Marine Phototrophic Gammaproteobacterium, the Purple Sulfur Bacterium Allochromatium vinosum MT86 (2018)
    MDPI
    In:  Marine Drugs, 16 (8). Art.Nr. 270.
    Details
    Publication Date: 2021-03-19
    Description: The production of secondary metabolites by a new isolate of the purple sulfur bacterium Allochromatium vinosum, which had shown antibiotic activities during a preliminary study, revealed the production of several metabolites. Growth conditions suitable for the production of one of the compounds shown in the metabolite profile were established and compound 1 was purified. The molecular formula of compound 1 (C20H28O2) was determined by high resolution mass spectra, and its chemical structure by means of spectroscopic methods. The evaluation of these data revealed that the structure of the compound was identical to dehydroabietic acid, a compound known to be characteristically produced by conifer trees, but so far not known from bacteria, except cyanobacteria. The purified substance showed weak antibiotic activities against Bacillus subtilis and Staphylococcus lentus with IC50 values of 70.5 µM (±2.9) and 57.0 µM (±3.3), respectively.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.3390/md16080270
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  • 4
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    Streptocollin, a Type IV Lanthipeptide Produced by Streptomyces collinus Tü 365 (2015)
    Wiley
    In:  ChemBioChem, 16 (18). pp. 2615-2623.
    Details
    Publication Date: 2018-06-20
    Description: Lanthipeptides are ribosomally synthesized and post-translationally modified microbial secondary metabolites. Here, we report the identification and isolation of streptocollin from Streptomyces collinus Tü 365, a new member of class IV lanthipeptides. Insertion of the constitutive ermE* promoter upstream of the lanthipeptide synthetase gene stcL resulted in peptide production. The streptocollin gene cluster was heterologously expressed in S. coelicolor M1146 and M1152 with 3.5- and 5.5-fold increased yields, respectively. The structure and ring topology of streptocollin were determined by high resolution MS/MS analysis. Streptocollin contains four macrocyclic rings, with one lanthionine and three methyllanthionine residues. To the best of our knowledge, this is the first report on the isolation of a class IV lanthipeptide in preparative amounts, and on the successful heterologous expression of a class IV lanthipeptide gene cluster.
    Type: Article , PeerReviewed
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    DOI: 10.1002/cbic.201500377
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  • 5
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    Calcarides A–E, Antibacterial Macrocyclic and Linear Polyesters from a Calcarisporium Strain (2013)
    MDPI
    In:  Marine Drugs, 11 (9). pp. 3309-3323.
    Details
    Publication Date: 2018-03-02
    Description: Bioactive compounds were detected in crude extracts of the fungus, Calcarisporium sp. KF525, which was isolated from German Wadden Sea water samples. Purification of the metabolites from the extracts yielded the five known polyesters, 15G256α, α-2, β, β-2 and π (1–5), and five new derivatives thereof, named calcarides A–E (6–10). The chemical structures of the isolated compounds were elucidated on the basis of one- and two-dimensional NMR spectroscopy supported by UV and HRESIMS data. The compounds exhibited inhibitory activities against Staphylococcus epidermidis, Xanthomonas campestris and Propionibacterium acnes. As the antibacterial activities were highly specific with regard to compound and test strain, a tight structure-activity relationship is assumed.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
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    DOI: 10.3390/md11093309
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  • 6
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    Spirocyclic Drimanes from the Marine Fungus Stachybotrys sp. Strain MF347 (2014)
    MDPI
    In:  Marine Drugs, 12 (4). pp. 1924-1938.
    Details
    Publication Date: 2018-03-02
    Description: A novel spirocyclic drimane coupled by two drimane fragment building blocks 2 and a new drimane 1 were identified in mycelia and culture broth of Stachybotrys sp. MF347. Their structures were established by spectroscopic means. This is the first example of spirocyclic drimane coupled by a spirodihydrobenzofuranlactam unit and a spirodihydroisobenzofuran unit; and the connecting position being N-C instead of an N and N connecting unit. Strain MF347 produced also the known spirocyclic drimanes stachybocin A (12) and stachybocin B (11) featured by two sesquiterpene-spirobenzofuran structural units connected by a lysine residue; the known spirocyclic drimanes chartarlactam O (5); chartarlactam K (6); F1839A (7); stachybotrylactam (8); stachybotramide (9); and 2α-acetoxystachybotrylactam acetate (10); as well as ilicicolin B (13), a known sesquiterpene. The relative configuration of two known spirobenzofuranlactams (3 and 4) was determined. All compounds were subjected to biological activity tests. The spirocyclic drimane 2, 11, and 12, as well as the sesquiterpene 13, exhibited antibacterial activity against the clinically relevant methicillin-resistant Staphylococcus aureus (MRSA).
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.3390/md12041924
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  • 7
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    Synthesis and Cytotoxic Activity of a Small Naphthoquinone Library: First Synthesis of Juglonbutin (2014)
    Wiley
    In:  European Journal of Organic Chemistry, 2014 (24). pp. 5318-5330.
    Details
    Publication Date: 2018-06-20
    Description: A synthetic protocol has been designed to synthesize grecoketidone (2k), 5-hydroxylapachol (2g), and the recently discovered natural products juglonbutin (2o) and its derivatives, leading to a small library of different 1,4-naphthoquinones with the intention of finding new active compounds. Within our collection, 2-O-alkylated naphthoquinones with an ester functionality in the side-chain and a free OH group at C-5 showed the best activities. Compounds 2f, 2m, and 2n showed GI50 values against 12 tumor cell lines in the lower micromolar range and juglonbutin (2o) showed remarkably efficient inhibition of the glycogen synthase kinase 3β with an IC50 value of 2.03 μM. Furthermore, studies on the mode of action of the most active cytotoxic compounds have been carried out. To the best of our knowledge, this is the first report on the synthesis of juglonbutin (2o) and its biological activity.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1002/ejoc.201402272
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  • 8
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    Champacyclin, a New Cyclic Octapeptide from Streptomyces Strain C42 Isolated from the Baltic Sea (2013)
    MDPI
    In:  Marine Drugs, 11 (12). pp. 4834-4857.
    Details
    Publication Date: 2018-03-02
    Description: New isolates of Streptomyces champavatii were isolated from marine sediments of the Gotland Deep (Baltic Sea), from the Urania Basin (Eastern Mediterranean), and from the Kiel Bight (Baltic Sea). The isolates produced several oligopeptidic secondary metabolites, including the new octapeptide champacyclin (1a) present in all three strains. Herein, we report on the isolation, structure elucidation and determination of the absolute stereochemistry of this isoleucine/leucine (Ile/Leu = Xle) rich cyclic octapeptide champacyclin (1a). As 2D nuclear magnetic resonance (NMR) spectroscopy could not fully resolve the structure of (1a), additional information on sequence and configuration of stereocenters were obtained by a combination of multi stage mass spectrometry (MSn) studies, amino acid analysis, partial hydrolysis and subsequent enantiomer analytics with gas chromatography positive chmical ionization/electron impact mass spectrometry (GC-PCI/EI-MS) supported by comparison to reference dipeptides. Proof of the head-to-tail cyclization of (1a) was accomplished by solid phase peptide synthesis (SPPS) compared to an alternatively side chain cyclized derivative (2). Champacyclin (1a) is likely synthesized by a non-ribosomal peptide synthetase (NRPS), because of its high content of (d)-amino acids. The compound (1a) showed antimicrobial activity against the phytopathogen Erwinia amylovora causing the fire blight disease of certain plants.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.3390/md11124834
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  • 9
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    Two New Antibiotic Pyridones Produced by a Marine Fungus, Trichoderma sp. Strain MF106 (2014)
    MDPI
    In:  Marine Drugs, 12 (3). pp. 1208-1219.
    Details
    Publication Date: 2018-03-02
    Description: Two unusual pyridones, trichodin A (1) and trichodin B (2), together with the known compound, pyridoxatin (3), were extracted from mycelia and culture broth of the marine fungus, Trichoderma sp. strain MF106 isolated from the Greenland Seas. The structures of the new compounds were characterized as an intramolecular cyclization of a pyridine basic backbone with a phenyl group. The structure and relative configuration of the new compounds were established by spectroscopic means. The new compound 1 and the known compound 3 showed antibiotic activities against the clinically relevant microorganism, Staphylococcus epidermidis, with IC50 values of 24 μM and 4 μM, respectively.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.3390/md12031208
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  • 10
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    Spatial distribution of sponge-associated bacteria in the Mediterranean sponge Tethya aurantium (2007)
    Wiley
    In:  FEMS Microbiology Ecology, 59 (1). pp. 47-63.
    Details
    Publication Date: 2019-09-23
    Description: The local distribution of the bacterial community associated with the marine sponge Tethya aurantium Pallas 1766 was studied. Distinct bacterial communities were found to inhabit the endosome and cortex. Clear differences in the associated bacterial populations were demonstrated by denaturing gradient gel electrophoresis (DGGE) and analysis of 16S rRNA gene clone libraries. Specifically associated phylotypes were identified for both regions: a new phylotype of Flexibacteria was recovered only from the sponge cortex, while Synechococcus species were present mainly in the sponge endosome. Light conduction via radiate spicule bundles conceivably facilitates the unusual association of Cyanobacteria with the sponge endosome. Furthermore, a new monophyletic cluster of sponge-derived 16S rRNA gene sequences related to the Betaproteobacteria was identified using analysis of 16S rRNA gene clone libraries. Members of this cluster were specifically associated with both cortex and endosome of T. aurantium.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1111/j.1574-6941.2006.00217.x
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