Carmabins A and B, new lipopeptides from the Caribbean cyanobacterium Lyngbya majuscula

Structure and Biosynthesis of Hectoramide B, a Linear Depsipeptide from Marine Cyanobacterium Moorena producens JHB Discovered via Coculture with Candida albicans

The tropical marine cyanobacterium Moorena producens JHB is a prolific source of secondary metabolites with potential biomedical utility. Previous studies on this strain led to the discovery of several novel compounds such as hectochlorins and jamaicamides. However, bioinformatic analyses of its genome indicate the presence of numerous cryptic biosynthetic gene clusters that have yet to be characterized. To potentially stimulate the production of novel compounds from this strain, it was cocultured with Candida albicans. From this experiment, we observed the increased production of a new compound that we characterize here as hectoramide B. Bioinformatic analysis of the M. producens JHB genome enabled the identification of a putative biosynthetic gene cluster responsible for hectoramide B biosynthesis. This work demonstrates that coculture competition experiments can be a valuable method to facilitate the discovery of novel natural products from cyanobacteria.

Enzymatic Halogenation of Terminal Alkynes

The biosynthetic installation of halogen atoms is largely performed by oxidative halogenases that target a wide array of electron-rich substrates, including aromatic compounds and conjugated systems. Halogenated alkyne-containing molecules are known to occur in Nature; however, halogen atom installation on the terminus of an alkyne has not been demonstrated in enzyme catalysis. Herein, we report the discovery and characterization of an alkynyl halogenase in natural product biosynthesis. We show that the flavin-dependent halogenase from the jamaicamide biosynthetic pathway, JamD, is not only capable of terminal alkyne halogenation on a late-stage intermediate en route to the final natural product but also has broad substrate tolerance for simple to complex alkynes. Furthermore, JamD is specific for terminal alkynes over other electron-rich aromatic substrates and belongs to a newly identified family of halogenases from marine cyanobacteria, indicating its potential as a chemoselective biocatalyst for the formation of haloalkynes.

Structure and Biosynthesis of Hectoramide B, a Linear Depsipeptide from the Marine Cyanobacterium Moorena producens JHB Discovered via Co-culture with Candida albicans

The tropical marine cyanobacterium Moorena producens JHB is a prolific source of secondary metabolites with potential biomedical utility. Previous studies of this strain led to the discovery of several novel compounds such as the hectochlorins and jamaicamides; however, bioinformatic analyses of its genome suggested that there were many more cryptic biosynthetic gene clusters yet to be characterized. To potentially stimulate the production of novel compounds from this strain, it was co-cultured with Candida albicans. From this experiment, we observed the increased production of a new compound that we characterize here as hectoramide B. Bioinformatic analysis of the M. producens JHB genome enabled the identification of a putative biosynthetic gene cluster responsible for hectoramide B biosynthesis. This work demonstrates that co-culture competition experiments can be a valuable method to facilitate the discovery of novel natural products from cyanobacteria.

The toxic cosmopolitan cyanobacteria Moorena producens: insights into distribution, ecophysiology and toxicity

Moorena producens is a benthic filamentous cyanobacteria that has been widely documented for its toxicity. This cyanobacterium colonizes both temperate (37%) and tropical (63%) regions, making it a cosmopolitan cyanobacterium with a global distribution. M. producens grows across coral reefs in multiple locations but recurringly blooms in Queensland, Australia. Today, nuisance blooms of M. producens have resulted in major disruptions to recreational activities along coastal areas and are known to cause adverse effects on organism and human health upon contact or ingestion. Specifically, marine organisms such as the green turtle Chelonia mydas and hawksbill turtle Eretmochelys imbricata were fatally poisoned by M. producens after consumption of this cyanobacterium. Reports record a range of effects on human health, from pain and blistering or even death upon ingestion of contaminated seafood. Blooms of M. producens are triggered by influxes of nitrogen, phosphate and iron, from surrounding coastal runoffs or sewage effluents. Additions of these nutrients can result in an increase in growth rate by 4-16 times. Iron bioavailability also plays a crucial role in bloom formation. A total of 231 natural products from 66 groups were identified from M. producens, with the three dominant groups: malyngamides, microcolins and dolastatins. These bioactive secondary metabolites have displayed toxicities against a range of carcinoma cell lines and organisms such as brine shrimp Artemia salina and goldfish Carassius auratus. This review provides a thorough insight to the distribution, ecophysiology and toxicity of M. producens, with reports on bloom events and implications on organism and human health.

Cryptic halogenation reactions in natural product biosynthesis

Covering: Up to December 2020Enzymatic halogenation reactions are essential for the production of thousands of halogenated natural products. However, in recent years, scientists discovered several halogenases that transiently incorporate halogen atoms in intermediate biosynthetic molecules to activate them for further chemical reactions such as cyclopropanation, terminal alkyne formation, C-/O-alkylation, biaryl coupling, and C-C rearrangements. In each case, the halogen atom is lost in the course of biosynthesis to the final product and is hence termed "cryptic". In this review, we provide an overview of our current knowledge of cryptic halogenation reactions in natural product biosynthesis.

A look around the West Indies: The spices of life are secondary metabolites

Natural products possess a wide range of bioactivities with potential for therapeutic usage. While the distribution of these molecules can vary greatly there is some correlation that exists between the biodiversity of an environment and the uniqueness and concentration of natural products found in that region or area. The Caribbean and pan-Caribbean area is home to thousands of species of endemic fauna and flora providing huge potential for natural product discovery and by way, potential leads for drug development. This can especially be said for marine natural products as many of are rapidly diluted through diffusion once released and therefore are highly potent to achieve long reaching effects. This review seeks to highlight a small selection of marine natural products from the Caribbean region which possess antiproliferative, anti-inflammatory and antipathogenic properties while highlighting any synthetic efforts towards bioactive analogs.

Current Status and Future Strategies to Increase Secondary Metabolite Production from Cyanobacteria

Cyanobacteria, given their ability to produce various secondary metabolites utilizing solar energy and carbon dioxide, are a potential platform for sustainable production of biochemicals. Until now, conventional metabolic engineering approaches have been applied to various cyanobacterial species for enhanced production of industrially valued compounds, including secondary metabolites and non-natural biochemicals. However, the shortage of understanding of cyanobacterial metabolic and regulatory networks for atmospheric carbon fixation to biochemical production and the lack of available engineering tools limit the potential of cyanobacteria for industrial applications. Recently, to overcome the limitations, synthetic biology tools and systems biology approaches such as genome-scale modeling based on diverse omics data have been applied to cyanobacteria. This review covers the synthetic and systems biology approaches for advanced metabolic engineering of cyanobacteria.

Applying a Chemogeographic Strategy for Natural Product Discovery from the Marine Cyanobacterium Moorena bouillonii

The tropical marine cyanobacterium Moorena bouillonii occupies a large geographic range across the Indian and Western Tropical Pacific Oceans and is a prolific producer of structurally unique and biologically active natural products. An ensemble of computational approaches, including the creation of the ORCA (Objective Relational Comparative Analysis) pipeline for flexible MS¹ feature detection and multivariate analyses, were used to analyze various M. bouillonii samples. The observed chemogeographic patterns suggested the production of regionally specific natural products by M. bouillonii. Analyzing the drivers of these chemogeographic patterns allowed for the identification, targeted isolation, and structure elucidation of a regionally specific natural product, doscadenamide A (1). Analyses of MS² fragmentation patterns further revealed this natural product to be part of an extensive family of herein annotated, proposed natural structural analogs (doscadenamides B–J, 2–10); the ensemble of structures reflect a combinatorial biosynthesis using nonribosomal peptide synthetase (NRPS) and polyketide synthase (PKS) components. Compound 1 displayed synergistic in vitro cancer cell cytotoxicity when administered with lipopolysaccharide (LPS). These discoveries illustrate the utility in leveraging chemogeographic patterns for prioritizing natural product discovery efforts.

Unique Polyhalogenated Peptides from the Marine Sponge Ircinia sp

Two new bromopyrrole peptides, haloirciniamide A (1) and seribunamide A (2), have been isolated from an Indonesian marine sponge of the genus Ircinia collected in the Thousand Islands (Indonesia). The planar structure of both compounds was assigned on the basis of extensive 1D and 2D NMR spectroscopy and mass spectrometry. The absolute configuration of the amino acid residues in 1 and 2 was determined by the application of Marfey’s method. Compound 1 is the first dibromopyrrole cyclopeptide having a chlorohistidine ring, while compound 2 is a rare peptide possessing a tribromopyrrole ring. Both compounds failed to show significant cytotoxicity against four human tumor cell lines, and neither compound was able to inhibit the enzyme topoisomerase I or impair the interaction between programmed cell death protein PD1 and its ligand, PDL1.

Design, Synthesis and Biological Evaluation of Jahanyne Analogs as Cell Cycle Arrest Inducers

Jahanyne, a lipopeptide with a unique terminal alkynyl and OEP (2-(1-oxo-ethyl)-pyrrolidine) moiety, exhibits anticancer activity. We synthesized jahanyne and analogs modified at the OEP moiety, employing an α-fluoromethyl ketone (FMK) strategy. Preliminary bioassays indicated that compound 1b (FMK-jahanyne) exhibited decreased activities to varying degrees against most of the cancer cells tested, whereas the introduction of a fluorine atom to the α-position of a hydroxyl group (2b) enhanced activities against all lung cancer cells. Moreover, jahanyne and 2b could induce G0/G1 cell cycle arrest in a concentration-dependent manner.

Cyanobacterial bioactive metabolites-A review of their chemistry and biology

Cyanobacterial blooms occur when algal densities exceed baseline population concentrations. Cyanobacteria can produce a large number of secondary metabolites. Odorous metabolites affect the smell and flavor of aquatic animals, whereas bioactive metabolites cause a range of lethal and sub-lethal effects in plants, invertebrates, and vertebrates, including humans. Herein, the bioactivity, chemistry, origin, and biosynthesis of these cyanobacterial secondary metabolites were reviewed. With recent revision of cyanobacterial taxonomy by Anagnostidis and Komárek as part of the Süβwasserflora von Mitteleuropa volumes 19(1-3), names of many cyanobacteria that produce bioactive compounds have changed, thereby confusing readers. The original and new nomenclature are included in this review to clarify the origins of cyanobacterial bioactive compounds. Due to structural similarity, the 157 known bioactive classes produced by cyanobacteria have been condensed to 55 classes. This review will provide a basis for more formal procedures to adopt a logical naming system. This review is needed for efficient management of water resources to understand, identify, and manage cyanobacterial harmful algal bloom impacts.

Nature's Combinatorial Biosynthesis Produces Vatiamides A-F

Hybrid type I PKS/NRPS biosynthetic pathways typically proceed in a collinear manner wherein one molecular building block is enzymatically incorporated in a sequence that corresponds to gene arrangement. In this work, genome mining combined with the use of a fluorogenic azide-based click probe led to the discovery and characterization of vatiamides A-F, three structurally diverse alkynylated lipopeptides, and their brominated analogues, from the cyanobacterium Moorea producens ASI16Jul14-2. These derive from a unique combinatorial non-collinear PKS/NRPS system encoded by a 90 kb gene cluster in which an upstream PKS cassette interacts with three separate cognate NRPS partners. This is facilitated by a series of promiscuous intermodule PKS-NRPS docking motifs possessing identical amino acid sequences. This interaction confers a new type of combinatorial capacity for creating molecular diversity in microbial systems.

Acetylenic Aquatic Anticancer Agents and Related Compounds

Although acetylenes are common as components of terrestrial plants, it is only within the last 30 years that biologically active polyacetylenes having unusual structural features have been reported from aquatic organisms: cyanobacteria, algae, fungi, invertebrates, and other sources. Naturally occurring aquatic acetylenes are of particular interest since many of them display important biological activities and possess antitumor, antibacterial, antimicrobial, antifouling, antifungal, pesticidal, phototoxic, HIV inhibitory, and immuno-suppressive properties. There is no doubt that they are of great interest, especially for the medicinal and/or pharmaceutical industries. This review presents structures and describes cytotoxic and anticancer activities of more than 230 acetylenic metabolites isolated from aquatic organisms. With the computer program PASS some additional biological activities are also predicted, which point toward possible new applications of these compounds. This review emphasizes the role of aquatic acetylenic compounds as an important source of leads for drug discovery.

Cyanobacterial bioactive metabolites-A review of their chemistry and biology

Cyanobacterial blooms occur when algal densities exceed baseline population concentrations. Cyanobacteria can produce a large number of secondary metabolites. Odorous metabolites affect the smell and flavor of aquatic animals, whereas bioactive metabolites cause a range of lethal and sub-lethal effects in plants, invertebrates, and vertebrates, including humans. Herein, the bioactivity, chemistry, origin, and biosynthesis of these cyanobacterial secondary metabolites were reviewed. With recent revision of cyanobacterial taxonomy by Anagnostidis and Komárek as part of the Süβwasserflora von Mitteleuropa volumes 19(1-3), names of many cyanobacteria that produce bioactive compounds have changed, thereby confusing readers. The original and new nomenclature are included in this review to clarify the origins of cyanobacterial bioactive compounds. Due to structural similarity, the 157 known bioactive classes produced by cyanobacteria have been condensed to 55 classes. This review will provide a basis for more formal procedures to adopt a logical naming system. This review is needed for efficient management of water resources to understand, identify, and manage cyanobacterial harmful algal bloom impacts.

Isolation and Characterization of Anaephenes A-C, Alkylphenols from a Filamentous Cyanobacterium ( Hormoscilla sp., Oscillatoriales)

Three related new alkylphenols, termed anaephenes A-C (1-3), containing different side chains, were isolated from an undescribed filamentous cyanobacterium (VPG 16-59) collected in Guam. Our 16S rDNA sequencing efforts indicated that VPG 16-59 is a member of the marine genus Hormoscilla (Oscillatoriales). The structures of anaephenes A-C (1-3) were elucidated by spectroscopic methods, and compounds assayed for growth inhibitory activity against prokaryotic and eukaryotic cell lines. Anaephene B (2), possessing a terminal alkyne, displayed moderate activity against Bacillus cereus and Staphylococcus aureus with MIC values of 6.1 μg/mL. While 1 and 3 showed no pronounced activity in these assays, their structural features highlight the unusual biosynthetic capacity of this cyanobacterium and warrant further study.

Trichophycins B-F, Chlorovinylidene-Containing Polyketides Isolated from a Cyanobacterial Bloom

NMR-guided isolation (based on 1D ¹H and ¹³C NMR resonances consistent with a chlorovinylidene moiety) resulted in the characterization of five new highly functionalized polyketides, trichophycins B-F (1-5), and one nonchlorinated metabolite tricholactone (6) from a collection of Trichodesmium bloom material from the Gulf of Mexico. The planar structures of 1-6 were determined using 1D and 2D NMR spectroscopy, mass spectrometry, and complementary spectroscopic procedures. Absolute configuration analysis of 1 and 2 were carried out by ¹H NMR analysis of diastereomeric Mosher esters in addition to ECD spectroscopy, J-based configuration analysis, and DFT calculations. The absolute configurations of 3-6 were proposed on the basis of comparative analysis of ¹³C NMR chemical shifts, relative configurations, and optical rotation values to compounds 1 and 2. Compounds 1-5 represent new additions to the trichophycin family and are hallmarked by a chlorovinylidene moiety. These new trichophycins and tricholactone (1-6) feature intriguing variations with respect to putative biosynthetic starting units, halogenation, and terminations, and trichophycin E (4) features a rare alkynyl bromide functionality. The phenyl-containing trichophycins showed low cytotoxicity to neuro-2A cells, while the alkyne-containing trichophycins showed no toxicity.

Total Synthesis of the Highly N-Methylated Peptides Carmabin A and Dragomabin

The first total synthesis of carmabin A and dragomabin was achieved at 52.3 mg and 43.8 mg scale, respectively. The synthesis led to determination of the configuration of carmabin A and reassignment of the configuration of dragomabin at the stereogenic centre on the alkyne-bearing fragment.

Cyanobacteria-derived peptide antibiotics discovered since 2000

Members of cyanobacteria, including Moorea spp., Okeania spp., Lyngbya spp., Schizothrix spp., Leptolyngbya spp., Microcystis spp., Symploca spp., Hassallia sp., Anabaena spp., Planktothrix sp., Tychonema spp., Oscillatoria spp., Tolypothrix sp., Nostoc sp., and Hapalosiphon sp. produce an enormously diverse range of peptide antibiotics with huge potential as pharmaceutical drugs and biocontrol agents following screening of structural analogues and analysis of structure-activity relationships (SAR). The need for novel antibiotic lead compounds is urgent, and this review summarizes 78 cyanobacteria-derived compounds reported since 2000, including 32 depsipeptides, 18 cyclic lipopeptides, 13 linear lipopeptides, 14 cyclamides, and one typical cyclic peptide. The current and potential therapeutic applications of these peptides are discussed, including for SAR, antituberculotic, antifungal, antibacterial, antiviral, and antiparasitic (anti-plasmodial, antitrypanosomal and antileishmanial) activities.

Total Synthesis of Desmethyl Jahanyne and Its Lipo-Tetrapeptide Conjugates Derived from Parent Skeleton as BCL-2-Mediated Apoptosis-Inducing Agents

The total synthesis of highly potent and scarcely available marine natural product (-)-jahanyne was attempted resulting in a solution-phase synthesis of pruned versions with comparable activity. A simple and facile synthetic route was employed for the preparation of pruned congeners and would be scalable. The lipophilic tail of the natural product was synthesized from R-(+)-citronellol, utilizing easily available chemicals. All the synthesized compounds were screened for apoptotic activity against a panel of cell lines. These compounds depicted marked binding to B cell lymphoma 2 till 50 °C in cellular thermal shift analysis.

Total Synthesis of the Highly N-Methylated Acetylene-Containing Anticancer Peptide Jahanyne

The first total synthesis of the highly N-methylated acetylene-containing lipopeptide jahanyne, an apoptosis-inducing natural product from marine cyanobacteria, is reported. A late-stage solution-phase coupling enabled introduction of the C-terminal ketone pyrrolidine moiety. A modified Fmoc solid-phase synthesis strategy was adopted to effectively couple multiple sterically hindered N-methylated amino acids while suppressing epimerization. The total synthesis has enabled confirmation of the proposed absolute configuration of natural jahanyne.

Marine natural product peptides with therapeutic potential: Chemistry, biosynthesis, and pharmacology

The oceans are a uniquely rich source of bioactive metabolites, of which sponges have been shown to be among the most prolific producers of diverse bioactive secondary metabolites with valuable therapeutic potential. Much attention has been focused on marine bioactive peptides due to their novel chemistry and diverse biological properties. As summarized in this review, marine peptides are known to exhibit various biological activities such as antiviral, anti-proliferative, antioxidant, anti-coagulant, anti-hypertensive, anti-cancer, antidiabetic, antiobesity, and calcium-binding activities. This review focuses on the chemistry and biology of peptides isolated from sponges, bacteria, cyanobacteria, fungi, ascidians, and other marine sources. The role of marine invertebrate microbiomes in natural products biosynthesis is discussed in this review along with the biosynthesis of modified peptides from different marine sources. The status of peptides in various phases of clinical trials is presented, as well as the development of modified peptides including optimization of PK and bioavailability.

Antibiotics from Gram-negative bacteria: a comprehensive overview and selected biosynthetic highlights

Covering: up to 2017The overwhelming majority of antibiotics in clinical use originate from Gram-positive Actinobacteria. In recent years, however, Gram-negative bacteria have become increasingly recognised as a rich yet underexplored source of novel antimicrobials, with the potential to combat the looming health threat posed by antibiotic resistance. In this article, we have compiled a comprehensive list of natural products with antimicrobial activity from Gram-negative bacteria, including information on their biosynthetic origin(s) and molecular target(s), where known. We also provide a detailed discussion of several unusual pathways for antibiotic biosynthesis in Gram-negative bacteria, serving to highlight the exceptional biocatalytic repertoire of this group of microorganisms.

Alkynyl-Containing Peptides of Marine Origin: A Review

Since the 1990s, a number of terminal alkynyl residue-containing cyclic/acyclic peptides have been identified from marine organisms, especially cyanobacteria and marine mollusks. This review has presented 66 peptides, which covers over 90% marine peptides with terminal alkynyl fatty acyl units. In fact, more than 90% of these peptides described in the literature are of cyanobacterial origin. Interestingly, all the linear peptides featured with terminal alkyne were solely discovered from marine cyanobacteria. The objective of this article is to provide an overview on the types, structural characterization of these unusual terminal alkynyl fatty acyl units, as well as the sources and biological functions of their composed peptides. Many of these peptides have a variety of biological activities, including antitumor, antibacterial, antimalarial, etc. Further, we have also discussed the evident biosynthetic origin responsible for formation of terminal alkynes of natural PKS (polyketide synthase)/NRPS (nonribosome peptide synthetase) hybrids.

Unique marine derived cyanobacterial biosynthetic genes for chemical diversity

Cyanobacteria are a prolific source of structurally unique and biologically active natural products that derive from intriguing biochemical pathways. Advancements in genome sequencing have accelerated the identification of unique modular biosynthetic gene clusters in cyanobacteria and reveal a wealth of unusual enzymatic reactions involved in their construction. This article examines several interesting mechanistic transformations involved in cyanobacterial secondary metabolite biosynthesis with a particular focus on marine derived modular polyketide synthases (PKS), nonribosomal peptide synthetases (NRPS) and combinations thereof to form hybrid natural products. Further, we focus on the cyanobacterial genus Moorea and the co-evolution of its enzyme cassettes that create metabolic diversity. Progress in the development of heterologous expression systems for cyanobacterial gene clusters along with chemoenzymatic synthesis makes it possible to create new analogs. Additionally, phylum-wide genome sequencing projects have enhanced the discovery rate of new natural products and their distinctive enzymatic reactions. Summarizing, cyanobacterial biosynthetic gene clusters encode for a large toolbox of novel enzymes that catalyze unique chemical reactions, some of which may be useful in synthetic biology.

Integrating mass spectrometry and genomics for cyanobacterial metabolite discovery

Filamentous marine cyanobacteria produce bioactive natural products with both potential therapeutic value and capacity to be harmful to human health. Genome sequencing has revealed that cyanobacteria have the capacity to produce many more secondary metabolites than have been characterized. The biosynthetic pathways that encode cyanobacterial natural products are mostly uncharacterized, and lack of cyanobacterial genetic tools has largely prevented their heterologous expression. Hence, a combination of cutting edge and traditional techniques has been required to elucidate their secondary metabolite biosynthetic pathways. Here, we review the discovery and refined biochemical understanding of the olefin synthase and fatty acid ACP reductase/aldehyde deformylating oxygenase pathways to hydrocarbons, and the curacin A, jamaicamide A, lyngbyabellin, columbamide, and a trans-acyltransferase macrolactone pathway encoding phormidolide. We integrate into this discussion the use of genomics, mass spectrometric networking, biochemical characterization, and isolation and structure elucidation techniques.

Almiramide D, cytotoxic peptide from the marine cyanobacterium Oscillatoria nigroviridis

Marine benthic cyanobacteria are widely known as a source of toxic and potentially useful compounds.These microorganisms have been studied from many Caribbean locations, which recently include locations in the Colombian Caribbean Sea. In the present study, six lipopeptides named almiramides D to H, together with the known almiramide B are identified from a mat characterized as Oscillatoria nigroviridis collected at the Island of Providence (Colombia, S.W. Caribbean Sea). The most abundant compounds, almiramides B and D were characterized by NMR and HRESIMS, while the structures of the minor compounds almiramides E to H were proposed by the analysis of their HRESIMS and MS2 spectra. Almiramides B and D were tested against six human cell lines including a gingival fibroblast cell line and five human tumor cell lines (A549, MDA-MB231, MCF-7, HeLa and PC3) showing a strong but not selective toxicity.

Combining Mass Spectrometric Metabolic Profiling with Genomic Analysis: A Powerful Approach for Discovering Natural Products from Cyanobacteria

An innovative approach was developed for the discovery of new natural products by combining mass spectrometric metabolic profiling with genomic analysis and resulted in the discovery of the columbamides, a new class of di- and trichlorinated acyl amides with cannabinomimetic activity. Three species of cultured marine cyanobacteria, Moorea producens 3L, Moorea producens JHB, and Moorea bouillonii PNG, were subjected to genome sequencing and analysis for their recognizable biosynthetic pathways, and this information was then compared with their respective metabolomes as detected by MS profiling. By genome analysis, a presumed regulatory domain was identified upstream of several previously described biosynthetic gene clusters in two of these cyanobacteria, M. producens 3L and M. producens JHB. A similar regulatory domain was identified in the M. bouillonii PNG genome, and a corresponding downstream biosynthetic gene cluster was located and carefully analyzed. Subsequently, MS-based molecular networking identified a series of candidate products, and these were isolated and their structures rigorously established. On the basis of their distinctive acyl amide structure, the most prevalent metabolite was evaluated for cannabinomimetic properties and found to be moderate affinity ligands for CB1.

Jahanyne, an apoptosis-inducing lipopeptide from the marine cyanobacterium Lyngbya sp

An acetylene-containing lipopeptide, jahanyne, was isolated from the marine cyanobacterium Lyngbya sp. Its gross structure was established by spectroscopic analyses, and the absolute configuration was clarified based on a combination of chiral HPLC analyses, spectroscopic analyses, and derivatization reactions. Jahanyne significantly inhibited the growth of human cancer cells and induced apoptosis in HeLa cells.

Lipopeptides from the tropical marine cyanobacterium Symploca sp

A collection of the tropical marine cyanobacterium Symploca sp., collected near Kimbe Bay, Papua New Guinea, previously yielded several new metabolites including kimbeamides A-C, kimbelactone A, and tasihalide C. Investigations into a more polar cytotoxic fraction yielded three new lipopeptides, tasiamides C-E (1-3). The planar structures were deduced by 2D NMR spectroscopy and tandem mass spectrometry, and their absolute configurations were determined by a combination of Marfey's and chiral-phase GC-MS analysis. These new metabolites are similar to several previously isolated compounds, including tasiamide (4), grassystatins (5, 6), and symplocin A, all of which were isolated from similar filamentous marine cyanobacteria.

Molecular networking as a dereplication strategy

A major goal in natural product discovery programs is to rapidly dereplicate known entities from complex biological extracts. We demonstrate here that molecular networking, an approach that organizes MS/MS data based on chemical similarity, is a powerful complement to traditional dereplication strategies. Successful dereplication with molecular networks requires MS/MS spectra of the natural product mixture along with MS/MS spectra of known standards, synthetic compounds, or well-characterized organisms, preferably organized into robust databases. This approach can accommodate different ionization platforms, enabling cross correlations of MS/MS data from ambient ionization, direct infusion, and LC-based methods. Molecular networking not only dereplicates known molecules from complex mixtures, it also captures related analogues, a challenge for many other dereplication strategies. To illustrate its utility as a dereplication tool, we apply mass spectrometry-based molecular networking to a diverse array of marine and terrestrial microbial samples, illustrating the dereplication of 58 molecules including analogues.

The chemical ecology of cyanobacteria

This review covers the literature on the chemically mediated ecology of cyanobacteria, including ultraviolet radiation protection, feeding-deterrence, allelopathy, resource competition, and signalling. To highlight the chemical and biological diversity of this group of organisms, evolutionary and chemotaxonomical studies are presented. Several technologically relevant aspects of cyanobacterial chemical ecology are also discussed.

Cytotoxic veraguamides, alkynyl bromide-containing cyclic depsipeptides from the marine cyanobacterium cf. Oscillatoria margaritifera

A family of cancer cell cytotoxic cyclodepsipeptides, veraguamides A-C (1-3) and H-L (4-8), were isolated from a collection of cf. Oscillatoria margaritifera obtained from the Coiba National Park, Panama, as part of the Panama International Cooperative Biodiversity Group program. The planar structure of veraguamide A (1) was deduced by 2D NMR spectroscopy and mass spectrometry, whereas the structures of 2-8 were mainly determined by a combination of 1H NMR and MS2/MS3 techniques. These new compounds are analogous to the mollusk-derived kulomo'opunalide natural products, with two of the veraguamides (C and H) containing the same terminal alkyne moiety. However, four veraguamides, A, B, K, and L, also feature an alkynyl bromide, a functionality that has been previously observed in only one other marine natural product, jamaicamide A. Veraguamide A showed potent cytotoxicity to the H-460 human lung cancer cell line (LD50=141 nM).

Genomic insights into the physiology and ecology of the marine filamentous cyanobacterium Lyngbya majuscula

Filamentous cyanobacteria of the genus Lyngbya are important contributors to coral reef ecosystems, occasionally forming dominant cover and impacting the health of many other co-occurring organisms. Moreover, they are extraordinarily rich sources of bioactive secondary metabolites, with 35% of all reported cyanobacterial natural products deriving from this single pantropical genus. However, the true natural product potential and life strategies of Lyngbya strains are poorly understood because of phylogenetic ambiguity, lack of genomic information, and their close associations with heterotrophic bacteria and other cyanobacteria. To gauge the natural product potential of Lyngbya and gain insights into potential microbial interactions, we sequenced the genome of Lyngbya majuscula 3L, a Caribbean strain that produces the tubulin polymerization inhibitor curacin A and the molluscicide barbamide, using a combination of Sanger and 454 sequencing approaches. Whereas ∼ 293,000 nucleotides of the draft genome are putatively dedicated to secondary metabolism, this is far too few to encode a large suite of Lyngbya metabolites, suggesting Lyngbya metabolites are strain specific and may be useful in species delineation. Our analysis revealed a complex gene regulatory network, including a large number of sigma factors and other regulatory proteins, indicating an enhanced ability for environmental adaptation or microbial associations. Although Lyngbya species are reported to fix nitrogen, nitrogenase genes were not found in the genome or by PCR of genomic DNA. Subsequent growth experiments confirmed that L. majuscula 3L is unable to fix atmospheric nitrogen. These unanticipated life history characteristics challenge current views of the genus Lyngbya.

The unique mechanistic transformations involved in the biosynthesis of modular natural products from marine cyanobacteria

Cyanobacteria are abundant producers of natural products well recognized for their bioactivity and utility in drug discovery and biotechnology applications. In the last decade, characterization of several modular gene clusters that code for the biosynthesis of these compounds has revealed a number of unusual enzymatic reactions. In this article, we review several mechanistic transformations identified in marine cyanobacterial biosynthetic pathways, with an emphasis on modular polyketide synthase(PKS)/non-ribosomal peptide synthetase (NRPS) gene clusters. In selected instances, we also make comparisons between cyanobacterial gene clusters derived from marine and freshwater strains. We then provide an overview of recent developments in cyanobacterial natural products biosynthesis made available through genome sequencing and new advances in bioinformatics and genetics.

Dragonamide E, a modified linear lipopeptide from Lyngbya majuscula with antileishmanial activity

Tropical parasitic and infectious diseases, such as leishmaniasis, pose enormous global health threats, but are largely neglected in commercial drug discovery programs. However, the Panama International Cooperative Biodiversity Group (ICBG) has been working to identify novel treatments for malaria, Chagas' disease, and leishmaniasis through an investigation of plants and microorganisms from Panama. We have pursued activity-guided isolation from an extract of Lyngbya majuscula that was found to be active against leishmaniasis. A new modified linear peptide from the dragonamide series was isolated, dragonamide E (1), along with two known modified linear peptides, dragonamide A (2) and herbamide B (3). Dragonamides A and E and herbamide B exhibited antileishmanial activity with IC50 values of 6.5, 5.1, and 5.9 microM, respectively. Spectroscopic and stereochemical data for dragonamide E (1) and herbamide B (3; the spectroscopic and stereochemical data for this substance is incomplete in the literature) are presented as well as comparisons of biological activity within the dragonamide compound family. Biosynthetic differences among marine compounds with a terminal free amide are also discussed.

Marine natural products

This review covers the literature published in 2007 for marine natural products, with 948 citations(627 for the period January to December 2007) referring to compounds isolated from marine microorganisms and phytoplankton, green algae, brown algae, red algae, sponges, cnidarians,bryozoans, molluscs, tunicates, echinoderms and true mangrove plants. The emphasis is on new compounds (961 for 2007), together with the relevant biological activities, source organisms and country of origin. Biosynthetic studies, first syntheses, and syntheses that lead to the revision of structures or stereochemistries, have been included.1 Introduction, 2 Reviews, 3 Marine microorganisms and phytoplankton, 4 Green algae, 5 Brown algae, 6 Red algae, 7 Sponges, 8 Cnidarians, 9 Bryozoans, 10 Molluscs, 11 Tunicates (ascidians),12 Echinoderms, 13 Miscellaneous, 14 Conclusion, 15 References.

Viridamides A and B, lipodepsipeptides with antiprotozoal activity from the marine cyanobacterium Oscillatoria nigro-viridis

Parallel chemical and phylogenetic investigation of a marine cyanobacterium from Panama led to the isolation of two new PKS-NRPS-derived compounds, viridamides A and B. Their structures were determined by NMR and mass spectroscopic methods, and the absolute configurations assigned by Marfey's method and chiral HPLC analysis. In addition to six standard, N-methylated amino and hydroxy acids, these metabolites contained the structurally novel 5-methoxydec-9-ynoic acid moiety and an unusual proline methyl ester terminus. Morphologically, this cyanobacterium was identified as Oscillatoria nigro-viridis, and its 16S rDNA sequence is reported here for the first time. Phylogenetic analysis of these sequence data has identified O. nigro-viridis strain OSC3L to be closely related to two other marine cyanobacterial genera, Trichodesmium and Blennothrix. Viridamide A showed antitrypanosomal activity with an IC50 of 1.1 microM and antileishmanial activity with an IC50 of 1.5 microM.

Biosynthesis and function of polyacetylenes and allied natural products

Polyacetylenic natural products are a substantial class of often unstable compounds containing a unique carbon-carbon triple bond functionality, that are intriguing for their wide variety of biochemical and ecological functions, economic potential, and surprising mode of biosynthesis. Isotopic tracer experiments between 1960 and 1990 demonstrated that the majority of these compounds are derived from fatty acid and polyketide precursors. During the past decade, research into the metabolism of polyacetylenes has swiftly advanced, driven by the cloning of the first genes responsible for polyacetylene biosynthesis in plants, moss, fungi, and actinomycetes and the initial characterization of the gene products. The current state of knowledge of the biochemistry and molecular genetics of polyacetylenic secondary metabolic pathways will be presented together with an up-to-date survey of new terrestrial and marine natural products, their known biological activities, and a discussion of their likely metabolic origins.

Antimalarial linear lipopeptides from a Panamanian strain of the marine cyanobacterium Lyngbya majuscula

As part of the Panama International Cooperative Biodiversity Groups (ICBG) project, two new (2, 4) and two known (1, 3) linear alkynoic lipopeptides have been isolated from a Panamanian strain of the marine cyanobacterium Lyngbya majuscula. Carmabin A (1), dragomabin (2), and dragonamide A (3) showed good antimalarial activity (IC50 4.3, 6.0, and 7.7 microM, respectively), whereas the nonaromatic analogue, dragonamide B (4), was inactive. The planar structures of all four compounds were determined by NMR spectroscopy in combination with mass spectrometry, and their stereoconfigurations were established by chiral HPLC and by comparison of their optical rotations and NMR data with literature values.

Anticancer activity of natural and synthetic acetylenic lipids

This review is a comprehensive survey of acetylenic lipids and their derivatives, obtained from living organisms, that have anticancer activity. Acetylenic metabolites belong to a class of molecules containing triple bond(s). They are found in plants, fungi, microorganisms, and marine invertebrates. Although acetylenes are common as components of terrestrial plants, fungi, and bacteria, it is only within the last 30 years that biologically active polyacetylenes having unusual structural features have been reported from plants, cyanobacteria, algae, invertebrates, and other sources. Naturally occurring aquatic acetylenes are of particular interest since many of them display important biological activities and possess antitumor, antibacterial, antimicrobial, antifouling, antifungal, pesticidal, phototoxic, HIV-inhibitory, and immunosuppressive properties. There is no doubt that they are of great interest, especially for the medicinal and/or pharmaceutical industries. This review presents structures and describes cytotoxic and anticancer activities only for more than 300 acetylenic lipids and their derivatives isolated from living organisms.

Trungapeptins A-C, cyclodepsipeptides from the marine cyanobacterium Lyngbya majuscula

Trungapeptins A-C (1-3) were isolated from the marine cyanobacterium Lyngbya majuscula collected from Trung Province, Thailand. Their gross structures were elucidated by interpretation of spectroscopic data. The absolute configurations of the amino acids and phenyllactic acid were determined by Marfey's and chiral HPLC analyses, respectively. The relative stereochemistry of 3-hydroxy-2-methyl-7-octynoic acid (Hmoya) of trungapeptin A was elucidated by application of the J-based configuration analysis, and its absolute stereochemistry was established to be 2S, 3R by Mosher's method. The structures of compounds 1-3 are closely related to the antanapeptins, a series of depsipeptides isolated from a Madagascan collection of L. majuscula.

Cyanobacterial peptides — Nature's own combinatorial biosynthesis

Cyanobacterial secondary metabolites have attracted increasing scientific interest due to bioactivity of many compounds in various test systems. Among the known structures, oligopeptides are often found with many congeners sharing conserved substructures, while being highly variable in others. A major part of known oligopeptides are of non-ribosomal origin and can be grouped into classes with conserved structural properties. Thus, the overall structural diversity of cyanobacterial oligopeptides only seemingly suggests an equally high diversity of biosynthetic pathways and respective genes. For each class of peptides, some of which have been found in all major branches of the cyanobacterial evolutionary tree, homologous synthetases and genes can be inferred. This implies that non-ribosomal peptide synthetase genes are a very ancient part of the cyanobacterial genome and presumably have evolved by recombination and duplication events to reach the present structural diversity of cyanobacterial oligopeptides. In addition, peptide synthetases would appear to be an essential part of the cyanobacterial evolution and physiology. The present review presents an overview of the biosynthesis of cyanobacterial peptides and corresponding gene clusters, the structural diversity of structural types and structural variations within peptide classes, and implications for the evolution and plasticity of biosynthetic genes and the potential function of cyanobacterial peptides.

Characterization of the initial enzymatic steps of barbamide biosynthesis

Barbamide is a mixed polypeptide-polyketide natural product that contains an unusual trichloromethyl group. The origin of the trichloromethyl group was previously shown to be through chlorination of the pro-R methyl group of L-leucine. Trichloroleucine is subsequently decarboxylated and oxidized to trichloroisovaleric acid and then extended with an acetate unit to form the initial seven carbons of barbamide. In this study we used a combination of biosynthetic feeding experiments and enzymatic analysis to characterize the initial steps required for formation of trichloroleucine and its chain-shortened product, trichloroisovaleric acid. Results from isotope-labeled feeding experiments showed that both dichloroleucine and trichloroleucine are readily incorporated into barbamide; however, monochloroleucine is not. This suggests that halogenation of the pro-R methyl group of leucine occurs as two discrete reactions, with the first involving incorporation of at least two halogen atoms and the second converting dichloroleucine to trichloroleucine. Additionally, the initial tandem dichlorination must occur before substrate can be further processed by the remainingbar pathway enzymes. In vitro analysis of the first five open reading frames (ORFs; barA, barB1, barB2, bar C, barD) of the barbamide gene cluster has yielded new insights into the processing of leucine to form the trichloroisovaleryl-derived unit in the final product.

Utilizing the Power of Microbial Genetics to Bridge the Gap Between the Promise and the Application of Marine Natural Products

Marine organisms are a rich source of secondary metabolites. They have yielded thousands of compounds with a broad range of biomedical applications. Thus far, samples required for preclinical and clinical studies have been obtained by collection from the wild, by mariculture, and by total chemical synthesis. However, for a number of complex marine metabolites, none of these options is feasible for either economic or environmental reasons. In order to proceed with the development of many of these promising therapeutic compounds, a reliable and renewable source must be found. Over the last twenty years, the study of microbial secondary metabolites has greatly advanced our understanding of how nature utilizes simple starting materials to yield complex small molecules. Much of this work has focused on polyketides and nonribosomal peptides, two classes of molecules that are prevalent in marine micro- and macroorganisms. The lessons learned from the study of terrestrial metabolite biosynthesis are now being applied to the marine world. As techniques for cloning and heterologous expression of biosynthetic pathways continue to improve, they may provide our greatest hope for bridging the gap between the promise and application of many marine natural products.

Biosynthetic pathway and gene cluster analysis of curacin A, an antitubulin natural product from the tropical marine cyanobacterium Lyngbya majuscula

Curacin A (1) is a potent cancer cell toxin obtained from strains of the tropical marine cyanobacterium Lyngbya majuscula found in Curaçao. Its structure is unique in that it contains the sequential positioning of a thiazoline and cyclopropyl ring, and it exerts its potent cell toxicity through interaction with the colchicine drug binding site on microtubules. A series of stable isotope-labeled precursors were fed to cultures of curacin A-producing strains and, following NMR analysis, allowed determination of the metabolic origin of all atoms in the natural product (one cysteine, 10 acetate units, two S-adenosyl methionine-derived methyl groups) as well as several unique mechanistic insights. Moreover, these incorporation experiments facilitated an effective gene cloning strategy that allowed identification and sequencing of the approximately 64 kb putative curacin A gene cluster. The metabolic system is comprised of a nonribosomal peptide synthetase (NRPS) and multiple polyketide synthases (PKSs) and shows a very high level of collinearity between genes in the cluster and the predicted biochemical steps required for curacin biosynthesis. Unique features of the cluster include (1) all but one of the PKSs are monomodular multifunctional proteins, (2) a unique gene cassette that contains an HMG-CoA synthase likely responsible for formation of the cyclopropyl ring, and (3) a terminating motif that is predicted to function in both product release and terminal dehydrative decarboxylation.

Structure and Biosynthesis of the Jamaicamides, New Mixed Polyketide-Peptide Neurotoxins from the Marine Cyanobacterium Lyngbya majuscula

A screening program for bioactive compounds from marine cyanobacteria led to the isolation of jamaicamides A-C. Jamaicamide A is a novel and highly functionalized lipopeptide containing an alkynyl bromide, vinyl chloride, beta-methoxy eneone system, and pyrrolinone ring. The jamaicamides show sodium channelblocking activity and fish toxicity. Precursor feeding to jamaicamide-producing cultures mapped out the series of acetate and amino acid residues and helped develop an effective cloning strategy for the biosynthetic gene cluster. The 58 kbp gene cluster is composed of 17 open reading frames that show an exact colinearity with their expected utilization. A novel cassette of genes appears to form a pendent carbon atom possessing the vinyl chloride functionality; at its core this contains an HMG-CoA synthase-like motif, giving insight into the mechanism by which this functional group is created.

Structure and absolute stereochemistry of hectochlorin, a potent stimulator of actin assembly

Hectochlorin (1) was isolated from marine isolates of Lyngbya majuscula collected from Hector Bay, Jamaica, and Boca del Drago Beach, Bocas del Toro, Panama. The planar structure was deduced by one- and two-dimensional NMR spectroscopy. X-ray crystallography was used to determine the absolute stereochemistry of hectochlorin as 2S,3S,14S,22S. Hectochlorin is equipotent to jasplakinolide (5) in its ability to promote actin polymerization, but unlike jasplakinolide, is unable to displace a fluorescent phalloidin analogue from polymerized actin. In addition, hectochlorin shows both a unique profile of cytotoxicity by the COMPARE algorithm and potent inhibitory activity toward the fungus Candida albicans. Structurally, hectochlorin resembles dolabellin and the recently reported lyngbyabellin class of compounds.