Anti-Biofilm Extracts and Molecules from the Marine Environment.

Pathogenic bacteria and their biofilms are involved in many diseases and represent a major public health problem, including the development of antibiotic resistance. These biofilms are known to cause chronic infections for which conventional antibiotic treatments are often ineffective. The search for new molecules and innovative solutions to combat these pathogens and their biofilms has therefore become an urgent need. The use of molecules with anti-biofilm activity would be a potential solution to these problems. The marine world is rich in micro- and macro-organisms capable of producing secondary metabolites with original skeletons. An interest in the chemical strategies used by some of these organisms to regulate and/or protect themselves against pathogenic bacteria and their biofilms could lead to the development of bioinspired, eco-responsible solutions. Through this original review, we listed and sorted the various molecules and extracts from marine organisms that have been described in the literature as having strictly anti-biofilm activity, without bactericidal activity.

Chemical Investigation of the Calcareous Marine Sponge Pericharax heteroraphis, Clathridine-A Related Derivatives Isolation, Synthesis and Osteogenic Activity.

As a result of screening a panel of marine organisms to identify lead molecules for the stimulation of endochondral bone formation, the calcareous sponge Pericharax heteroraphis was identified to exhibit significant activity during endochondral differentiation. On further molecular networking analysis, dereplication and chemical fractionation yielded the known clathridine A-related metabolites 3-6 and the homodimeric complex (clathridine A)2 Zn2+ (9), together with the new unstable heterodimeric complex (clathridine A-clathridimine)Zn2+ (10). With the presence of the zinc complexes annotated through the LC-MS analysis of the crude extract changing due to the instability of some metabolites and complexes constituting the mixture, we combined the isolation of the predicted molecules with their synthesis in order to confirm their structure and to understand their reactivity. Interestingly, we also found a large quantity of the contaminant benzotriazoles BTZ (7) and its semi-dimer (BTZ)2CH2 (8), which are known to form complexes with transition metals and are used for preventing corrosion in water. All isolated 2-aminoimidazole derivatives and complexes were synthesized not only for structural confirmation and chemical understanding but to further study their bioactivity during endochondral differentiation, particularly the positively screened imidazolone derivatives. Compounds leucettamine B, clathridine A and clathridimine were found to increase type X collagen transcription and stimulate endochondral ossification in the ATDC5 micromass model.

Cultivable epiphytic bacteria of the Chlorophyta Ulva sp.: diversity, antibacterial, and biofilm-modulating activities.

AIMS: Macroalgae harbor a rich epiphytic microbiota that plays a crucial role in algal morphogenesis and defense mechanisms. This study aims to isolate epiphytic cultivable microbiota from Ulva sp. surfaces. Various culture media were employed to evaluate a wide range of cultivable microbiota. Our objective was to assess the antibacterial and biofilm-modulating activities of supernatants from isolated bacteria. METHODS AND RESULTS: Sixty-nine bacterial isolates from Ulva sp. were identified based on 16S rRNA gene sequencing. Their antibacterial activity and biofilm modulation potential were screened against three target marine bacteria: 45%, mostly affiliated with Gammaproteobacteria and mainly grown on diluted R2A medium (R2Ad), showed strong antibacterial activity, while 18% had a significant impact on biofilm modulation. Molecular network analysis was carried out on four bioactive bacterial supernatants, revealing new molecules potentially responsible for their activities. CONCLUSION: R2Ad offered the greatest diversity and proportion of active isolates. The molecular network approach holds promise for both identifying bacterial isolates based on their molecular production and characterizing antibacterial and biofilm-modulating activities.

The amnesic shellfish poisoning toxin, domoic acid: The tattoo of the king scallop Pecten maximus.

Domoic acid (DA) is a potent neurotoxin produced by diatoms of the genus Pseudo-nitzschia and is responsible for Amnesic Shellfish Poisoning (ASP) in humans. Some fishery resources of high commercial value, such as the king scallop Pecten maximus, are frequently exposed to toxic Pseudo-nitzschia blooms and are capable of accumulating high amounts of DA, retaining it for months or even a few years. This poses a serious threat to public health and a continuous economical risk due to fishing closures of this resource in the affected areas. Recently, it was hypothesized that trapping of DA within autophagosomic-vesicles could be one reason explaining the long retention of the remaining toxin in P. maximus digestive gland. To test this idea, we follow the kinetics of the subcellular localization of DA in the digestive glands of P. maximus during (a) the contamination process - with sequential samplings of scallops reared in the field during 234 days and naturally exposed to blooms of DA-producing Pseudo-nitzschia australis, and (b) the decontamination process - where highly contaminated scallops were collected after a natural bloom of toxic P. australis and subjected to DA-depuration in the laboratory for 60 days. In the digestive gland, DA-depuration rate (0.001 day-1) was much slower than contamination kinetics. The subcellular analyses revealed a direct implication of early autophagy in DA sequestration throughout contamination (r = 0.8, P < 0.05), while the presence of DA-labeled residual bodies (late autophagy) appeared to be strongly and significantly related to slow DA-depuration (r = -0.5) resembling an analogous DA-tattooing in the digestive glands of P. maximus. This work provides new evidence about the potential physiological mechanisms involved in the long retention of DA in P. maximus and represents the baseline to explore procedures to accelerate decontamination in this species.

An Eco-Friendly Extraction and Purification Approach for Obtaining Active Ingredients for Cosmetics from Two Marine Brown Seaweeds.

Brown seaweeds are attracting attention due to their richness in bioactive compounds, in particular, their phlorotannins. We present here a case study of two Fucales, Ascophyllum nodosum and Halidrys siliquosa, sustainably collected, to produce active polyphenols for the cosmetics sector. Phenolic contents of crude extracts, obtained by Accelerated Solvent Extraction (ASE), were more elevated in H. siliquosa at 100.05 mg/g dry weight (DW) than in A. nodosum (29.51 mg/g DW), considering 3 cycles with cell inversion. The temperature of extraction for a high phenolic content and high associated antioxidant activities close to positive controls was 150 °C for both algae and the use of only one cycle was enough. A semi-purification process using Solid-phase Extraction (SPE) was carried out on both ASE crude extracts (one per species). The majority of phlorotannins were found in the ethanolic SPE fraction for A. nodosum and the hydroethanolic one for H. siliquosa. The SPE process allowed us to obtain more concentrated fractions of active phenolic compounds (×1.8 and 2 in A. nodosum and H. siliquosa, respectively). Results are discussed in regard to the exploitation of seaweeds in Brittany and to the research of sustainable processes to produce active natural ingredients for cosmetics.

Extracts from Wallis Sponges Inhibit Vibrio harveyi Biofilm Formation.

Pathogenic bacteria and their biofilms are involved in many human and animal diseases and are a major public health problem with, among other things, the development of antibiotic resistance. These biofilms are known to induce chronic infections for which classical treatments using antibiotic therapy are often ineffective. Sponges are sessile filter-feeding marine organisms known for their dynamic symbiotic partnerships with diverse microorganisms and their production of numerous metabolites of interest. In this study, we investigated the antibiofilm efficacy of different extracts from sponges, isolated in Wallis, without biocidal activity. Out of the 47 tested extracts, from 28 different genera, 11 showed a strong activity against Vibrio harveyi biofilm formation. Moreover, one of these extracts also inhibited two quorum-sensing pathways of V. harveyi.

Revision of the genus Fascaplysinopsis, the type species Fascaplysinopsis reticulata (Hentschel, 1912) (Porifera, Dictyoceratida, Thorectidae) and descriptions of two new genera and seven new species.

The present study examines the taxonomy of sponge specimens with unique chemistry collectively known as Fascaplysinopsis reticulata (Hentschel, 1912). Examination of Hentschels original species upon which the genus Fascaplysinopsis Bergquist, 1980 was based in conjunction with a comparison with recent Indo-west Pacific collections, using morphological and molecular analyses (ITS and 28S rDNA), revealed extensive variation. Fascaplysinopsis reticulata was found to be a species complex comprising the genus Fascaplysinopsis, as well as two new genera: Skolosachlys gen. nov. and Rubrafasciculus gen. nov. The new species of Fascaplysinopsis described are F. palauensis sp. nov., F. klobos sp. nov. and F. ronquinni sp. nov. The new species of Skolosachlys gen. nov. described herein are: S. enlutea sp. nov. and S. nidus sp. nov. The new species described of Rubrafasciculus gen. nov. includes: R. cerasus sp. nov. and R. fijiensis sp. nov..

Isolation, Synthesis and Absolute Configuration of the Pericharaxins A and B, Epimeric Hydroxy-Polyene Glycerol Ethers from the Calcarean Sponge Pericharax heteroraphis.

Naturally occurring epimeric hydroxy-polyene glycerol ether pericharaxins A (1a) and B (1b) were isolated from the calcarean sponge Pericharax heteroraphis. The structural and stereochemical characterization of both diastereoisomers were established on the basis of spectroscopic data analysis and total synthesis in seven steps. The mixture of pericharaxins A (1a) and B (1b) was proven to be epimeric by chiral-phase HPLC analysis of both synthetic and natural samples. Further separation of the epimers and application of Mosher's method to the synthetic compounds allowed unequivocal absolute configuration assignment. While natural products and the synthetic intermediates were shown to be non-cytotoxic on the HCT116 cell line, the endochondral differentiation activity using human type X collagen transcription activity in ATDC5 cells is interesting.

Bioactive Bromotyrosine Derivatives from the Pacific Marine Sponge Suberea clavata (Pulitzer-Finali, 1982).

Chemical investigation of the South-Pacific marine sponge Suberea clavata led to the isolation of eight new bromotyrosine metabolites named subereins 1-8 (2-9) along with twelve known co-isolated congeners. The detailed configuration determination of the first representative major compound of this family 11-epi-fistularin-3 (11R,17S) (1) is described. Their chemical characterization was achieved by HRMS and integrated 1D and 2D NMR (nuclear magnetic resonance) spectroscopic studies and extensive comparison with literature data. For the first time, a complete assignment of the absolute configurations for stereogenic centers C-11/17 of the known members (11R,17S) 11-epi-fistularin-3 (1) and 17-deoxyfistularin-3 (10) was determined by a combination of chemical modifications, Mosher's technology, and ECD spectroscopy. Consequently, the absolute configurations of all our new isolated compounds 2-9 were determined by the combination of NMR, Mosher's method, ECD comparison, and chemical modifications. Interestingly, compounds 2-7 were obtained by chemical transformation of the major compound 11-epi-fistularin-3 (1). Evaluation for acetylcholinesterase inhibition (AChE), DNA methyltransferase 1 (DNMT1) modulating activity and antifouling activities using marine bacterial strains are also presented.

Quorum Sensing Inhibitory and Antifouling Activities of New Bromotyrosine Metabolites from the Polynesian Sponge Pseudoceratina n. sp.

Four new brominated tyrosine metabolites, aplyzanzines C-F (1-4), were isolated from the French Polynesian sponge Pseudoceratina n. sp., along with the two known 2-aminoimidazolic derivatives, purealidin A (5) and 6, previously isolated, respectively, from the sponges Psammaplysilla purpurea and Verongula sp. Their structures were assigned based on the interpretation of their NMR and HRMS data. The compounds exhibited quorum sensing inhibition (QSi) and antifouling activities against several strains of bacteria and microalgae. To our knowledge, the QSi activity of this type of bromotyrosine metabolite is described here for the first time.

Bioactive Bromotyrosine-Derived Alkaloids from the Polynesian Sponge Suberea ianthelliformis.

Herein, we describe the isolation and spectroscopic identification of eight new tetrabrominated tyrosine alkaloids 2⁻9 from the Polynesian sponge Suberea ianthelliformis, along with known major compound psammaplysene D (1), N,N-dimethyldibromotyramine, 5-hydroxy xanthenuric acid, and xanthenuric acid. Cytotoxicity and acetylcholinesterase inhibition activities were evaluated for some of the isolated metabolites. They exhibited moderate antiproliferative activity against KB cancer cell lines, but psammaplysene D (1) displayed substantial cytotoxicity as well as acetylcholinesterase inhibition with IC50 values of 0.7 μM and 1.3 μM, respectively.

Unguiculins A-C: cytotoxic bis-guanidine alkaloids from the French Polynesian sponge, Monanchora n. sp.

Two new acyclic bis-guanidine alkaloids, unguiculins B-C (2-3), were isolated from a French Polynesian sponge Monanchora n. sp. together with the known compound unguiculin A (1). Their structures were established by spectroscopic data interpretation and comparison with the literature. Unguiculins A-C displayed antiproliferative and cytotoxic efficacy against several human cancer cells with IC50 values in the micromolar range.

An Unprecedented Blue Chromophore Found in Nature using a "Chemistry First" and Molecular Networking Approach: Discovery of Dactylocyanines A-H.

Guided by a "chemistry first" approach using molecular networking, eight new bright-blue colored natural compounds, namely dactylocyanines A-H (3-10), were isolated from the Polynesian marine sponge Dactylospongia metachromia. Starting from ilimaquinone (1), an hemisynthetic phishing probe (2) was prepared for annotating and matching structurally related natural substances in D. metachromia crude extract network. This strategy allowed characterizing for the first time in Nature the blue zwitterionic quinonoid chromophore. The solvatochromic properties of the latter are reported.

Cytotoxic Guanidine Alkaloids from a French Polynesian Monanchora n. sp. Sponge.

Four bicyclic and three pentacyclic guanidine alkaloids (1-7) were isolated from a French Polynesian Monanchora n. sp. sponge, along with the known alkaloids monalidine A (8), enantiomers 9-11 of known natural product crambescins, and the known crambescidins 12-15. Structures were assigned by spectroscopic data interpretation. The relative and absolute configurations of the alkaloids were established by analysis of (1)H NMR and NOESY spectra and by circular dichroism analysis. The new norcrambescidic acid (7) corresponds to interesting biosynthetic variation within the pentacyclic core. All compounds exhibited antiproliferative and cytotoxic efficacy against KB, HCT116, HL60, MRC5, and B16F10 cancer cells, with IC50 values ranging from 4 nM to 10 µM.

Plakilactones from the marine sponge Plakinastrella mamillaris. Discovery of a new class of marine ligands of peroxisome proliferator-activated receptor γ.

In this paper we report the isolation and the molecular characterization of a new class of PPARγ ligands from the marine environment. Biochemical characterization of a library of 13 oxygenated polyketides isolated from the marine sponge Plakinastrella mamillaris allowed the discovery of gracilioether B and plakilactone C as selective PPARγ ligands in transactivation assays. Both agents covalently bind to the PPARγ ligand binding domain through a Michael addition reaction involving a protein cysteine residue and the α,ß-unsaturated ketone in their side chains. Additionally, gracilioether C is a noncovalent agonist for PPARγ, and methyl esters 1 and 2 are noncovalent antagonists. Structural requirements for the interaction of these agents within the PPARγ ligand binding domain were obtained by docking analysis. Gracilioether B and plakilactone C regulate the expression of PPARγ-dependent genes in the liver and inhibit the generation of inflammatory mediators by macrophages.

Pipestelides A-C: cyclodepsipeptides from the Pacific marine sponge Pipestela candelabra.

Pipestelides A-C (2-4) are three new NRPS-PKS hybrid macrolides containing uncommon moieties, isolated from the Pacific marine sponge Pipestela candelabra. Their structures were elucidated on the basis of spectroscopic data. These cyclodepsipeptides appear to be biosynthetically related to jaspamide (aka jasplakinolide) (1) by chemical modification of the building blocks of the polyketide or peptide chains. Pipestelides A-C (2-4) contain a bromotyrosine [3-amino-3-(bromo-4-hydroxyphenyl)propanoic acid] unit, a polypropionate with a Z double bond, and a 2-hydroxyquinolinone, respectively. Revised chemical shift assignments are provided for the co-isolated known jasplakinolide C(a) (5). In addition, compounds 2 and 3 exhibited cytotoxic activities in the micromolar range.

4-Methylenesterols from Theonella swinhoei sponge are natural pregnane-X-receptor agonists and farnesoid-X-receptor antagonists that modulate innate immunity.

We report the isolation and the structural elucidation of a family of polyhydroxylated steroids from the marine sponge Theonella swinhoei. Decodification of interactions of these family with nuclear receptors shows that these steroids are potent agonists of human pregnane-X-receptor (PXR) and antagonists of human farnesoid-X-receptor (FXR) with the putative binding mode to nuclear receptors (NRs) obtained through docking experiments. By using monocytes isolated from transgenic mice harboring hPXR, we demonstrated that swinhosterol B counter-regulates induction of pro-inflammatory cytokines in a PXR-dependent manner. Exposure of CD4(+) T cells to swinhosterol B upregulates the expression of IL-10 causing a shift toward a T cells regulatory phenotype in a PXR dependent manner. These results pave the way to development of a dual PXR agonist/FXR antagonist with a robust immunomodulatory activity and endowed with the ability to modulate the expression of bile acid-regulated genes in the liver.

Bioactive indole derivatives from the South Pacific marine sponges Rhopaloeides odorabile and Hyrtios sp.

Indole derivatives including bromoindoles have been isolated from the South Pacific marine sponges Rhopaloeides odorabile and Hyrtios sp. Their structures were established through analysis of mass spectra and 1D and 2D NMR spectroscopic data. Their potential inhibitory phospholipase A2 (PLA2), antioxidant and cytotoxic activities were evaluated. The new derivative 5,6-dibromo-L-hypaphorine (9) isolated from Hyrtios sp. revealed a weak bee venom PLA2 inhibition (IC50 0.2 mM) and a significant antioxidant activity with an Oxygen Radical Absorbance Capacity (ORAC) value of 0.22. The sesquiterpene aureol (4), also isolated from Hyrtios sp., showed the most potent antioxidant activity with an ORAC value of 0.29.

Towards new ligands of nuclear receptors. Discovery of malaitasterol A, an unique bis-secosterol from marine sponge Theonella swinhoei.

Malaitasterol A, an unprecedented bis-secosterol, was isolated from a Solomon collection of Theonella swinhoei. The structure was elucidated on the basis of a combination of comprehensive 1D and 2D NMR analysis, high-resolution mass spectrometry and DFT (13)C chemical shift calculations. The biological characterization of malaitasterol A provided evidence that this compound is a potent agonist of pregnane-X-receptor and its putative binding mode to PXR has been obtained through docking calculations.

Solomonsterols A and B from Theonella swinhoei. The first example of C-24 and C-23 sulfated sterols from a marine source endowed with a PXR agonistic activity.

The finding of new PXR modulators as potential leads for treatment of human disorders characterized by dysregulation of innate immunity and with inflammation is of wide interest. In this paper, we report the identification of the first example of natural marine PXR agonists, solomonsterols A and B, from a Theonella swinhoei sponge. The structures were determined by interpretation of NMR and ESIMS data, and the putative binding mode to PXR has been obtained through docking calculations.