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The Lacinutrix genus was discovered in 2005 and includes 12 Gram-negative bacterial species. To the best of our knowledge, the secondary metabolite production potential of this genus has not been explored before, and examination of Lacinutrix species may reveal novel chemistry. As part of a screening project of Arctic marine bacteria, the Lacinutrix sp. strain M09B143 was cultivated, extracted, fractionated and tested for antibacterial and cytotoxic activities. One fraction had antibacterial activity and was subjected to mass spectrometry analysis, which revealed two compounds with elemental composition that did not match any known compounds in databases. This resulted in the identification and isolation of two novel isobranched lyso-ornithine lipids, whose structures were elucidated by mass spectrometry and NMR spectroscopy. Lyso-ornithine lipids consist of a 3-hydroxy fatty acid linked to the alpha amino group of an ornithine amino acid through an amide bond. The fatty acid chains were determined to be iso-C15:0 (1) and iso-C16:0 (2). Compound 1 was active against the Gram-positive S. agalactiae, while 2 showed cytotoxic activity against A2058 human melanoma cells.

A series of novel quinoline-based tetracyclic ring-systems were synthesized and evaluated in vitro for their antiplasmodial, antiproliferative and antimicrobial activities. The novel hydroiodide salts 10 and 21 showed the most promising antiplasmodial inhibition, with compound 10 displaying higher selectivity than the employed standards. The antiproliferative assay revealed novel pyridophenanthridine 4b to be significantly more active against human prostate cancer (IC50 = 24 nM) than Puromycin (IC50 = 270 nM) and Doxorubicin (IC50 = 830 nM), which are used for clinical treatment. Pyridocarbazoles 9 was also moderately effective against all the employed cancer cell lines and moreover showed excellent biofilm inhibition (9a: MBIC = 100 µM, 9b: MBIC = 100 µM).

Streptomyces remains one of the prolific sources of structural diversity, and a reservoir to mine for novel natural products. Continued screening for new Streptomyces strains in our laboratory led to the isolation of Streptomyces sp. RK44 from the underexplored areas of Kintampo waterfalls, Ghana, Africa. Preliminary screening of the metabolites from this strain resulted in the characterization of a new 2-alkyl-4-hydroxymethylfuran carboxamide (AHFA) 1 together with five known compounds, cyclo-(L-Pro-Gly) 2, cyclo-(L-Pro-L-Phe) 3, cyclo-(L-Pro-L-Val) 4, cyclo-(L-Leu-Hyp) 5, and deferoxamine E 6. AHFA 1, a methylenomycin (MMF) homolog, exhibited anti-proliferative activity (EC50 = 89.6 &micro, M) against melanoma A2058 cell lines. This activity, albeit weak is the first report amongst MMFs. Furthermore, the putative biosynthetic gene cluster (ahfa) was identified for the biosynthesis of AHFA 1. DFO-E 6 displayed potent anti-plasmodial activity (IC50 = 1.08&micro, M) against P. falciparum 3D7. High-resolution electrospray ionization mass spectrometry (HR ESIMS) and molecular network assisted the targeted-isolation process, and tentatively identified six AHFA analogues, 7&ndash, 12 and six siderophores 13&ndash, 18.

A new strategy for the identification of known compounds in Streptomyces extracts that can be applied in the discovery of natural products is presented. The strategy incorporates screening a database of 5555 natural products including 5098 structures from Streptomyces sp., using a high-throughput LCMS data processing algorithm that utilizes HRMS data and predicted LC retention times (tR) as filters for rapid identification of known compounds in the natural product extract. The database, named StrepDB, contains for each compound the structure, molecular formula, molecular mass, and predicted LC retention time. All identified compounds are annotated and color coded for easier visualization. It is an indirect approach to quickly assess masses (which are not annotated) that may potentially lead to the discovery of new or novel structures. In addition, a spectral database named MbcDB was generated using the ACD/Spectrus DB Platform. MbcDB contains 665 natural products, each with structure, experimental HRESIMS, MS/MS, UV, and NMR spectra. StrepDB was used to screen a mutant Streptomyces albus extract, which led to the identification and isolation of two new compounds, legonmaleimides A and B, the structures of which were elucidated with the aid of MbcDB and spectroscopic techniques. The structures were confirmed by computer-assisted structure elucidation (CASE) methods using ACD/Structure Elucidator Suite. The developed methodology suggests a pipeline approach to the dereplication of extracts and discovery of novel natural products.

A library of 28 small cationic 1,4-substituted 1,2,3-triazoles was prepared for studies of antimicrobial activity. The structures addressed the pharmacophore model of small antimicrobial peptides and an amphipathic motif found in marine antimicrobials. Eight compounds showed promising antimicrobial activity, of which the most potent compound 10b displayed minimum inhibitory concentrations of 4-8μg/mL against Streptococcus agalacticae, Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Enterococcus faecalis. The simple syntheses and low degree of functionalization make these 1,4-substituted 1,2,3-triazoles interesting for further optimizations.

This is an Accepted Manuscript of an article published by Taylor & Francis in Natural Product Research on 20 February 2019, available online: https://www.tandfonline.com/doi/full/10.1080/14786419.2019.1574788. The new guanidine alkaloid Dendrobeaniamine A (1) was isolated from the organic extract of the Arctic marine bryozoan Dendrobeania murrayana. The chemical structure of 1 was elucidated by spectroscopic experiments, including 1D and 2D NMR and HRESIMS analysis. Compound 1 is a lipoamino acid, consisting of a C12 fatty acid anchored to the amino acid arginine. The bioactivity of 1 was evaluated using cellular and biochemical assays, but the compound did not show cytotoxic, antimicrobial, anti-inflammatory or antioxidant activities

Source at https://doi.org/10.1016/j.ejmech.2019.111671. The rapid emergence and spread of multi-resistant bacteria have created an urgent need for new antimicrobial agents. We report here a series of amphipathic α,α-disubstituted β-amino amide derivatives with activity against 30 multi-resistant clinical isolates of Gram-positive and Gram-negative bacteria, including isolates with extended spectrum β-lactamase – carbapenemase (ESBL-CARBA) production. A variety of halogenated aromatic side-chains were investigated to improve antimicrobial potency and minimize formation of Phase I metabolites. Net positive charge and cationic character of the derivatives had an important effect on toxicity against human cell lines. The most potent and selective derivative was the diguanidine derivative 4e with 3,5-di-brominated benzylic side-chains. Derivative 4e displayed minimum inhibitory concentrations (MIC) of 0.25–8 μg/mL against Gram-positive and Gram-negative reference strains, and 2–32 μg/mL against multi-resistant clinical isolates. Derivative 4e showed also low toxicity against human red blood cells (EC50 > 200 μg/mL), human hepatocyte carcinoma cells (HepG2: EC50 > 64 μg/mL), and human lung fibroblast cells (MRC-5: EC50 > 64 μg/mL). The broad-spectrum antimicrobial activity and low toxicity of diguanylated derivatives such as 4e make them attractive as lead compounds for development of novel antimicrobial drugs.

Accepted manuscript version. Published version available at https://doi.org/10.1016/j.bioorg.2018.11.024. Licensed CC BY-NC-ND 4.0. The marine environment remains a rich source for the discovery and development of novel bioactive compounds. The present paper describes the design, synthesis and biological evaluation of a library of small molecule heterocyclic mimetics of the marine 2,5-diketopiperazine barettin which is a powerful natural antioxidant. By mainly focusing on the influence from the brominated indole and heterocyclic core of barettin, a library of 19 compounds was prepared. The compounds comprised a heterocyclic core, either a 2,5 diketopiperazine, an imidazolidinedione or a thioxothiazolidinone, which were mainly monosubstituted with ranging bulky substituents. The prepared compounds were screened for activity in a cellular lipid peroxidation assay using HepG2 cells. Several of the synthetic compounds showed antioxidant properties superior to the positive control barettin. Two of the prepared compounds displayed inhibitory activity similar to commercial antioxidants with significant inhibition at low µg/mL concentrations. The toxicity of the compounds was also investigated against MRC-5 lung fibroblasts and none of the included compounds displayed any toxicity at 50 µg/mL.

Barettin, 8,9-dihydrobarettin, bromoconicamin and a novel brominated marine indole were isolated from the boreal sponge Geodia barretti collected off the Norwegian coast. The compounds were evaluated as inhibitors of electric eel acetylcholinesterase. Barettin and 8,9-dihydrobarettin displayed significant inhibition of the enzyme, with inhibition constants (Ki) of 29 and 19 μM respectively towards acetylcholinesterase via a reversible noncompetitive mechanism. These activities are comparable to those of several other natural acetylcholinesterase inhibitors of marine origin. Bromoconicamin was less potent against acetylcholinesterase, and the novel compound was inactive. Based on the inhibitory activity, a library of 22 simplified synthetic analogs was designed and prepared to probe the role of the brominated indole, common to all the isolated compounds. From the structure-activity investigation it was shown that the brominated indole motif is not sufficient to generate a high acetylcholinesterase inhibitory activity, even when combined with natural cationic ligands for the acetylcholinesterase active site. The four natural compounds were also analysed for their butyrylcholinesterase inhibitory activity in addition and shown to display comparable activities. The study illustrates how both barettin and 8,9-dihydrobarettin display additional bioactivities which may help to explain their biological role in the producing organism. The findings also provide new insights into the structure-activity relationship of both natural and synthetic acetylcholinesterase inhibitors.

The marine secondary metabolite stryphnusin (1) was isolated from the boreal sponge Stryphnus fortis, collected off the Norwegian coast. Given its resemblance to other natural acetylcholinesterase antagonists, it was evaluated against electric eel acetylcholinesterase and displayed inhibitory activity. A library of twelve synthetic phenethylamine analogs, 2a–7a and 2b–7b, containing tertiary and quaternary amines respectively were synthesized to investigate the individual structural contributions to the activity. Compound 7b was the strongest competitive inhibitor of both acetylcholinesterase and butyrylcholinesterase with IC50 values of 57 and 20 μM, respectively. This inhibitory activity is one order of magnitude higher than the positive control physostigmine, and is comparable with several other marine acetylcholinesterase inhibitors. The physiological effect of compound 7b on muscle function and neuromuscular transmission was studied and revealed a selective mode of action at the investigated concentration. This data is of importance as the interference of therapeutic acetylcholinesterase inhibitors with neuromuscular transmission can be problematic and lead to unwanted side effects. The current findings also provide additional insights into the structure–activity relationship of both natural and synthetic acetylcholinesterase inhibitors.

A new ecdysteroid, ponasterone F (1) and the previously reported compound ponasterone A (2) were isolated from specimens of the Arctic marine bryozoan Alcyonidium gelatinosum collected at Hopenbanken, off the coast of Edge&oslash, ya, Svalbard. The structure of 1 was elucidated, and the structure of 2 confirmed by spectroscopic methods including 1D and 2D NMR and analysis of HR-MS data. The compounds were evaluated for their ability to affect bacterial survival and cell viability, as well as their agonistic activities towards the estrogen receptors &alpha, and &beta, The compounds were not active in these assays. Compound 2 is an arthropod hormone controlling molting and are known to act as an allelochemical when produced by plants. Even though its structure has been previously reported, this is the first time a ponasterone has been isolated from a bryozoan. A. gelatinosum produced 1 and 2 in concentrations surpassing those expected of hormonal molecules, indicating their function as defence molecules against molting predators. This work adds to the chemical diversity reported from marine bryozoans and expanded our knowledge of the chemical modifications of the ponasterones.

A new siderophore containing a 4,5-dihydroimidazole moiety was isolated from Pseudoalteromonas piscicida S2040 together with myxochelins A and B, alteramide A and its cycloaddition product, and bromo- and dibromoalterochromides. The structure of pseudochelin A was established by spectroscopic techniques including 2D NMR and MS/MS fragmentation data. In bioassays selected fractions of the crude extract of S2040 inhibited the opportunistic pathogen Pseudomonas aeruginosa. Pseudochelin A displayed siderophore activity in the chrome azurol S assay at concentrations higher than 50 mu M, and showed weak activity against the fungus Aspergillus fumigatus, but did not display antibacterial, anti-inflammatory or anticonvulsant activity. (C) 2017 Elsevier Ltd. All rights reserved.

A library of 29 small 1,4-substituted 1,2,3-triazoles was prepared for studies of antimicrobial activity. The pharmacophore model investigated with these substrates was based on small peptidomimetics of antimicrobial peptides and antimicrobials isolated from marine organisms from sub-arctic regions. Using methyl 1,2,3-triazole-carboxylates and 1,2,3-triazole methyl ketones prepared through “click” chemistry we were able to synthesize the different cationic amphiphiles through three steps or less. Several structural modifications to the lipopohilic side and hydrophilic sides of the amphiphiles were investigated and compared with regards to antimicrobial activity and cytotoxicity in particular. The most promising amphiphile 10f displayed minimum inhibitory concentrations (MICs) between 4 - 16 µg/mL against Gram-positive Enterococcus faecalis, Staphylococcus aureus, Streptococcus agalacticae, and Gram-negative Escherichia coli and Pseudomonas aeruginosa. The decent level of antimicrobial activity and biofilm inhibition, short synthesis, and accessible reagents, makes this type of amphiphilic mimics interesting leads for further development. © 2017 Elsevier Ltd. All rights reserved. This is the authors' accepted and refereed manuscript to the article. Locked until 29 July 2019 due to copyright restrictions

This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of natural products, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/np401002s. Pulmonarins A and B are two new dibrominated marine acetylcholinesterase inhibitors that were isolated and characterized from the sub-Arctic ascidian Synoicum pulmonaria collected off the Norwegian coast. The structures of natural pulmonarins A and B were tentatively elucidated by spectroscopic methods and later verified by comparison with synthetically prepared material. Both pulmonarins A and B displayed reversible, noncompetitive acetylcholinesterase inhibition comparable to several known natural acetylcholinesterase inhibitiors. Pulmonarin B was the strongest inhibitor, with an inhibition constant (Ki) of 20 μM. In addition to reversible, noncompetitive acetylcholinesterase inhibition, the compounds displayed weak antibacterial activity but no cytotoxicity or other investigated bioactivities.

Drug discovery strategies include from broad random screening to focussed target-based approaches. Structure and substrate information greatly enables target-based design, but this is limited to relatively few targets; cell-based screening can identify new targets but often suffers from low hit rates and difficult hit optimization. Thus, newer approaches are needed that can improve the efficiency of screening and hit optimization. Here, we describe an efficient approach for hit generation, which may be called “biofocussed chemoprospecting.” With bio-likeness and ease of synthesis as priority criteria, libraries may be constructed with good optimization potential, physicochemical diversity, drug likeness and low cost. Following this approach, two libraries based on linear and cyclic dipeptide scaffolds were designed, first as virtual libraries comprising of more than 30000 compounds, and after subsequent filtering, as a small library of a total of 51 compounds. These provided good diversity at low cost, and were tested for bioactivities. The discovery of six active compounds demonstrates a hit rate greater than 10%. This is comparable to target-based approaches, but the “chemoprospecting” method described here has the additional potential to identify new targets and mechanisms.

A metabolomic approach was used to identify known and new natural products from the marine sponges Geodia baretti and G. macandrewii. G. baretti is known to produce bioactive natural products such as barettin (1), 8,9-dihydrobarettin (2), and bromobenzisoxazolone barettin (3), while secondary metabolites from G. macandrewii are not reported in the literature. Specimens of the two sponges were collected from different sites along the coast of Norway, and their extracts were analyzed using UHPLC-HR-MS. Metabolomic analyses revealed that extracts from both species contained barettin (1) and 8,9-dihydrobarettin (2), and all samples of G. baretti contained higher amounts of both compounds compared to G. macandrewii. The analysis of the MS data also revealed that samples of G. macandrewii contained a compound that was not present in any of the G. baretti samples. This new compound was isolated and identified as the N-acyl-taurine geodiataurine (4), and it was tested for antioxidant, anticancer, and antibacterial properties.

Source at http://dx.doi.org/10.3390/molecules22071236 A novel brominated alkaloid, Securidine A, was isolated from the cold water marine bryozoan Securiflustra securifrons. Securidine A was isolated using semi-preparative HPLC, and the structure was elucidated by spectroscopic methods. The isolated Securidine A was tested for cytotoxic, antibacterial, and anti-diabetic activities as well as for its potential for inhibition of biofilm formation. No significant biological activity was observed in the applied bioassays, thus expanded bioactivity profiling is required, in order to reveal any potential applications for Securidine A

Synoxazolidinone C is a new member of the synoxazolidinone family of compounds which are dibrominated guanidinium 4-oxazolidinones isolated from the sub-Arctic ascidian Synoicum pulmonaria. The compound was isolated along with synoxazolidinones A and B from the same ascidian extract. Spectroscopic methods revealed that the synoxazolidinone C differed from the other synoxazolidinones by an unprecedented bicyclic partial structure, containing an additional pyrrolidine ring. Synoxazolidinone C exhibited both antibacterial and anticancer activities.

The marine polyunsaturated lipid-derived natural product all-(Z)-5,7-dihydroxy-2-(4Z,7Z,10Z,13Z,16Z-nonadecapentaenyl) (1) and four analogs 5-8 have been synthesized and evaluated as antioxidants in two cell-based assays. The natural product 1 and the analog 5 exhibited interesting antioxidant effects with IC50-values of 14±9 and 29±3μM, respectively, in a cellular lipid peroxidation antioxidant activity assay using HepG2 cells. Moreover, in the HepG2 cellular antioxidant activity assay, the natural product 1 exhibited strong protective effects against reactive oxygen species with an IC50=160±25μM.

Bioassay-guided fractionation of the sub-Arctic ascidian Synoicum pulmonaria collected off the Norwegian coast led to the isolation of a novel family of brominated guanidinium oxazolidinones named synoxazolidinones A and B (1 and 2). The backbone of the compounds contains a 4-oxazolidinone ring rarely seen in natural products. The structure of the compounds was determined by spectroscopic methods. The synoxazolidinones exhibited antibacterial and antifungal activities.

Two bacterial isolates from the Barents Sea, both belonging to the genus Algibacter, were found to yield extracts with anti-bacterial bioactivity. Mass spectrometry guided dereplication and purification of the active extracts lead to the isolation of the same active principle in both extracts. The structure of the bioactive compound was identified via mass spectrometry and nuclear resonance spectroscopy and it turned out to be the known lipopeptide Lipid 430. We discovered and determined its previously unknown anti-bacterial activity against Streptococcus agalactiae and revealed a cytotoxic effect against the A2058 human melanoma cell line at significantly lower concentrations compared to its anti-bacterial concentration. Flow cytometry and microscopy investigations of the cytotoxicity against the melanoma cell line indicated that Lipid 430 did not cause immediate cell lysis. The experiments with melanoma cells suggest that the compound functions trough more complex pathways than acting as a simple detergent.