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  • 1
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    PANGAEA
    In:  Supplement to: Ramesh, Kirti; Melzner, Frank; Griffith, Andrew W; Gobler, Christopher J; Rouger, Caroline; Tasdemir, Deniz; Nehrke, Gernot (2018): In vivo characterization of bivalve larval shells: a confocal Raman microscopy study. Journal of The Royal Society Interface, 15(141), 20170723, https://doi.org/10.1098/rsif.2017.0723
    Publication Date: 2019-04-30
    Description: In vivo confocal Raman microscopy (CRM), polarized light microscopy and Fourier transform infrared spectroscopy (FTIR) were used to determine if a significant amount of amorphous calcium carbonate (ACC) exists within larval shells of Baltic mytilid mussels (Mytilus edulis-like) and whether the amount of ACC varies during larval development. No evidence for ACC was found from the onset of shell deposition at 21 h post-fertilization (hpf) until 48 hpf. Larval Mytilus shells were crystalline from 21 hpf onwards and exhibited CRM and FTIR peaks characteristic of aragonite. Prior to shell deposition at 21 hpf, no evidence for carbonates was observed through in vivo CRM. We further analysed the composition of larval shells in three other bivalve species, Mercenaria mercenaria, Crassostrea gigas and Crassostrea virginica and observed no evidence for ACC, which is in contrast to previous work on the same species. Our findings indicate that larval bivalve shells are composed of crystalline aragonite and we demonstrate that conflicting results are related to sub-optimal measurements and misinterpretation of CRM spectra. Our results demonstrate that the common perception that ACC generally occurs as a stable and abundant precursor during larval bivalve calcification needs to be critically reviewed.
    Type: Dataset
    Format: text/tab-separated-values, 143020 data points
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  • 2
    Publication Date: 2019-02-11
    Description: Oceans cover 〉70% of the earth and encompass variable habitats concerning salinity, temperature, pressure, light availability. The deep sea (〉1000 m water depth) constitutes more than 60% of the ocean´s biosphere and harbors an unparalleled biodiversity. It constitutes an extreme habitat due to high pressure, darkness and often low nutrient and oxygen concentrations. In order to ensure their survival, microorganisms thriving in such environments have to develop unique metabolic adaptations, thus represent an interesting resource for the discovery of new molecules. However, due to access difficulties to deep-sea habitats and the lack of suitable and affordable sampling techniques, deep-sea microorganisms have remained untapped for their potential in marine biodiscovery. In this study, we obtained deep-sea sediment samples from Arctic Ocean (-2432 m), sampled by an ROV during RV Polarstern expedition 108. Isolation of microorganisms has been performed using two specific media for bacteria and fungi, respectively. Isolates were identified by amplification of the 16S rRNA gene (bacteria) and ITS1-2 region (fungi) followed by Sanger sequencing. In total, 70 bacterial isolates were identified covering four phyla (52 Firmicutes, 1 Actinobacteria, 11 Proteobacteria and 6 Bacteroidetes) and seven fungal strains from two different phyla (6 Ascomycota and 1 Basidiomycota). Selected isolates were cultivated in two different media, followed by solvent (EtOAc) extraction and bioactivity screenings against a panel of clinically relevant microbial pathogens and six cancer cell lines. At 100 µg/mL concentration, three bacterial extracts showed antitumor activity (〉70%), whereas 17 exhibited activity (〉65%) against methicillin-resistant Staphylococcus aureus (MRSA). Notably, only one fungus showed a cultivation medium dependent-high antifungal activity (〉90%), highlighting the impact of culture media on the production of bioactive secondary metabolites.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , NonPeerReviewed
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  • 3
    Publication Date: 2014-08-27
    Description: Chemical analysis of the Indonesian sponge Plakortis cfr. lita afforded two new analogues of the potent trypanocidal agent manadoperoxide B (1), namely 12-isomanadoperoxide B (2) and manadoperoxidic acid B (3). These compounds were isolated along with a new short chain dicarboxylate monoester (4), bearing some interesting relationships with the polyketide endoperoxides found in this sponge. Some semi-synthetic analogues of manadoperoxide B (6-8) were prepared and evaluated for antitrypanosomal activity and cytotoxicity. These studies revealed crucial structure-activity relationships that should be taken into account in the design of optimized and simplified endoperoxyketal trypanocidal agents.
    Type: Article , PeerReviewed
    Format: text
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  • 4
    Publication Date: 2015-01-06
    Type: Article , PeerReviewed
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  • 5
    Publication Date: 2014-08-27
    Description: Recent studies have revealed that plasmodial enoyl-ACP reductase (pfENR, FabI), one of the crucial enzymes in the plasmodial type II fatty acid synthesis II (FAS II) pathway, is a promising target for liver stage malaria infections. Hence, pfENR inhibitors have the potential to be used as causal malarial prophylactic agents. In this study, we report the design, synthesis, structural characterization and evaluation of a new class of pfENR inhibitors. The search for inhibitors began with a virtual screen of the iResearch database by molecular docking. Hits obtained from the virtual screen were ranked according to their Glide score. One hit was selected as a lead and modified to improve its binding to pfENR; from this, a series of phenylamino acetic acid benzylidene hydrazides were designed and synthesized. These molecules were thoroughly characterized by IR, (1) H, (13) C, (15) N, 2D-NMR (COSY, NOESY, (1) H-(13) C, (1) H-(15) N HSQC and HMBC), and X-ray diffraction. NMR studies revealed the existence of conformational/configurational isomers around the amide and imine functionalities. The major species in DMSO solution is the E, E form, which is in dynamic equilibrium with the Z, E isomer. In the solid state, the molecule has a completely extended conformation and forms helical structures that are stabilized by strong hydrogen bond interactions, forming a helical structure stabilized by N-H…O interactions, a feature unique to this class of compounds. Furthermore, detailed investigation of the NMR spectra indicated the presence of a minor impurity in most compounds. The structure of this impurity was deduced as an imidazoline-4-one derivative based on (1) H-(13) C and (1) H-(15) H HMBC spectra and was confirmed from the NOESY spectra. The molecules were screened for in vitro activity against recombinant pfENR enzyme by a spectrophotometric assay. Four molecules, viz. 17, 7, 10, and 12 were found to be active at 7, 8, 10, and 12 μm concentration, respectively, showing promising pfENR inhibitory potential. A classification model was derived based on a binary QSAR approach termed recursive partitioning (RP) to highlight structural characteristics that could be tuned to improve activity.
    Type: Article , PeerReviewed
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  • 6
    Publication Date: 2014-08-27
    Description: Twenty-one samples of traditionally-prepared (home-made) and ready-made (commercial) St. John’s Wort olive oil macerates were profiled for their in vitro antimicrobial and antiprotozoal activity. Their cytotoxic potential was evaluated on MRC-5 fibroblasts. In the antiprotozoal assays, ten of the oils inhibited Trypanosoma brucei rhodesiense (IC50 15.9–64.5 μg/mL), while only one oil exerted antimicrobial activity towards Staphylococcus aureus (IC50 = 88.7 μg/mL). LC–DAD–MS data revealed the presence of pseudohypericin (0.135–3.280 μg/g) and hypericin (0.277–6.634 μg/g) in all the oils, whereas chlorogenic acid (1.063 μg/g) was detected only in one oil sample. Hyperforin was detected in four (0.977–2.399 μg/g) and adhyperforin in six samples (0.005–3.165 μg/g). Hypericin and pseudohypericin were common in the active oils, whereas hyperforin, adhyperforin, and chlorogenic acid were absent in these samples. Our results indicated that if the correct plant material is used, the infused oils from Hypericum perforatum may contain active components.
    Type: Article , PeerReviewed
    Format: text
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  • 7
    Publication Date: 2014-10-02
    Description: Resin glycosides are secondary metabolites exclusive to the convolvulaceous plants. In this study, crypthophilic acids A–C (1–3), the first resin glycosides occurring in another family (Scrophulariaceae), and the other constituents of Scrophularia cryptophila were examined for in vitro antiprotozoal and antimycobacterial potentials. Except for crypthophilic acid B (2), all tested compounds exhibited growth-inhibitory effect against Trypanosoma brucei rhodesiense, with l-tryptophan (6) and buddlejasaponin III (7) being the most potent ones (IC50's 4.1 and 9.7 μg/ml). In contrast, the activity towards Trypanosoma cruzi was poor, and only crypthophilic acid C (3), 6 and 7 were trypanocidal at concentrations above 40 μg/ml. With the exception of 2 and 6, all compounds were active against Leishmania donovani. Harpagide (4) and 3 emerged as the best leishmanicidal agents (IC50's 2.0 and 5.8 μg/ml). Only compounds 3, 6 and 7 showed antimalarial activity against Plasmodium falciparum with IC50 values of 4.2, 16.6 and 22.4 μg/ml. Overall the best and broadest spectrum activity was presented by compounds 3 and 7, as they inhibited all four parasitic protozoa. None of the isolates had significant activity against Mycobacterium tuberculosis (MICs 〉100 μg/ml) or were toxic towards mammalian (L6) cells. This is the first report of antiprotozoal activity for natural resin glycosides, as well as for harpagide (4), acetylharpagide (5), tryptophan (6) and buddlejasaponin III (7).
    Type: Article , PeerReviewed
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  • 8
    Publication Date: 2014-08-20
    Description: The ethanolic root extract of Scrophularia lepidota, an endemic plant of the Turkish flora, has been investigated for its anti-protozoal and inhibitory effect towards plasmodial enoyl-ACP reductase (FabI), a key enzyme of fatty acid biosynthesis in Plasmodium falciparum. Chromatographic separation of the extract yielded 10 iridoids (1–10), two of which are new, and a known phenylethanoid glycoside (11). The structures of the new compounds were determined as 3,4-dihydro-methylcatalpol (8) and 6-O-[4″-O-trans-(3,4-dimethoxycinnamoyl)-α-l-rhamnopyranosyl]aucubin (scrolepidoside, 9) by spectroscopic means. The remaining metabolites were characterized as catalpol (1), 6-O-methylcatalpol (2), aucubin (3), 6-O-α-l-rhamnopyranosyl-aucubin (sinuatol, 4), 6-O-β-d-xylopyranosylaucubin (5), ajugol (6), ajugoside (7), an iridoid-related aglycone (10) and angoroside C (11). Nine isolates were active against Leishmania donovani, with the new compound 9 being most potent (IC50 6.1 μg/ml). Except for 4, all pure compounds revealed some trypanocidal potential against Trypanosoma brucei rhodesiense (IC50 values 29.3–73.0 μg/ml). Only compound 10 showed moderate anti-plasmodial (IC50 40.6 μg/ml) and FabI enzyme inhibitory activity (IC50 100 μg/ml). 10 is the second natural product inhibiting the fatty acid biosynthesis of Plasmodium falciparum.
    Type: Article , PeerReviewed
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  • 9
    Publication Date: 2014-08-19
    Description: Microcionamides A (1) and B (2) have been isolated from the Philippine marine sponge Clathria (Thalysias) abietina. These new linear peptides are cyclized via a cystine moiety and have their C-terminus blocked by a 2-phenylethylenamine group. Their total structures, including absolute stereochemistry, were determined by a combination of spectral and chemical methods. Compound 1 was shown to slowly isomerize about the C-36/C-37 double bond when stored in DMSO. Microcionamides A (1) and B (2) exhibited significant cytotoxicity against the human breast tumor cells lines MCF-7 and SKBR-3 and displayed inhibitory activity against Mycobacterium tuberculosis H37Ra.
    Type: Article , PeerReviewed
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  • 10
    Publication Date: 2014-08-12
    Description: Topoisomerase IIalpha (top2) is a target of some of the most useful anticancer drugs. All clinically approved top2 drugs act to stabilize a drug-enzyme-DNA cleavable complex. Here we report the novel top2 activity of neoamphimedine, an isomer of the marine pyridoacridine amphimedine. Neoamphimedine was cytotoxic in yeast and mammalian cell lines. Neoamphimedine exhibited enhanced toxicity in top2 over-expressing yeast cells and was toxic in every mammalian cell line tested. However, neoamphimedine did not possess enhanced toxicity in a mammalian cell line sensitive to stabilized cleavable complexes. Therefore, we hypothesized that neoamphimedine is a top2-dependent drug, whose primary mechanism of action is not the stabilization of cleavable complexes. Top2-directed activity was determined in purified enzyme systems. Neoamphimedine-induced catenation of plasmid DNA only in the presence of active top2. This catenation correlated with the ability of neoamphimedine to aggregate DNA. Catenation was also observed using a filter-binding assay and transmission electron microscopy. Catenation was confirmed when only restriction enzyme digestion could resolve the catenated plasmid complex to monomer length plasmid DNA. Neoamphimedine also showed potent anti-neoplastic activity in human xenograft tumors in athymic mice. Neoamphimedine was as effective as etoposide in mice bearing KB tumors and as effective as 9-aminocamptothecin in mice bearing HCT-116 tumors. Amphimedine did not induce DNA aggregation or catenation in vitro, nor did it display any significant anti-neoplastic activity. These results suggest that neoamphimedine has a novel top2-mediated mechanism of cytotoxicity and anticancer potential.
    Type: Article , PeerReviewed
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