Marine natural products

Biodiversity, chemical diversity and drug discovery

Drugs developed from microbial natural products are in the fundaments of modern pharmaceutical companies. Despite decades of research, all evidences suggest that there must remain many interesting natural molecules with potential therapeutic application yet to be discovered. Any efforts to successfully exploit the chemical diversity of microbial secondary metabolites need to rely heavily on a good understanding of microbial diversity, being the working hypothesis that maximizing biological diversity is the key strategy to maximizing chemical diversity. This chapter presents an overview of diverse topics related with this basic principle, always in relation with the discovery of novel secondary metabolites. The types of microorganisms more frequently used for natural products discovery are briefly reviewed, as well as the differences between terrestrial and marine habitats as sources of bioactive secondary metabolite producers. The concepts about microbial diversity as applied to prokaryotes have evolved in the last years, but recent data suggest the existence of true biogeographic patterns of bacterial diversity, which are also discussed. Special attention is dedicated to the existing strategies to exploit the microbial diversity that is not easy to tackle by conventional approaches. This refers explicitly to the current attempts to isolate and cultivate the previously uncultured bacteria, including the application of high throughput techniques. Likewise, the advances of microbial molecular biology has allowed the development of metagenomic approaches, i.e., the expression of biosynthetic pathways directly obtained from environmental DNA and cloned in a suitable host, as another way of accessing microbial genetic resources. Also, approaches relying on the genomics of metabolite producers are reviewed.

Survey of estrogenic and androgenic disruption in Swedish coastal waters by the analysis of bile fluid from perch and biomarkers in the three-spined stickleback

The potential for endocrine disruption close to sewage treatment plant and pulp mill effluent discharge points along the Swedish Baltic Sea coast was explored using a dual survey strategy employing two stationary fish species. The levels of vitellogenin and spiggin as biomarkers of endocrine disruption were determined in juvenile three-spined sticklebacks (Gasterosteus aculeatus L.) together with the sex ratios and the presence of intersex. As an indication of exposure, estrogenic and androgenic substances were analysed by GC-MS in bile from perch (Perca fluviatilis L.). Spiggin and vitellogenin levels in juvenile three-spined sticklebacks were generally low, and, for most sampling sites no deviation in gonad type ratios were observed. No remarkable levels of natural or synthetic estrogens or androgens were observed in bile fluid from perch, while bisphenol A and 4-nonylphenol were detected in perch from both reference sites and exposed sites. Taken together, the results did not indicate estrogenic or androgenic disruption in the investigated waters.

Synthesis and antiproliferative activity of benzyl and phenethyl analogs of makaluvamines

Analogs of marine alkaloid, makaluvamine, bearing substituted benzyl and substituted phenethyl side chains have been synthesized and their antiproliferative activities have been evaluated. 4-Methyl, 4-chloro, and 4-fluoro substituted benzyl analogs possessed pronounced antiproliferative effects on the breast cancer cell line, MCF-7 at IC(50) values of 2.3 microM, 1.8 microM, and 2.8 microM, respectively. 4-Methyl, 4-chloro, and 3,4-methylenedioxy derivatives showed the best activity against MCF-7 among the phenethyl analogs with IC(50) values of 2.3 microM, 2.8 microM, and 2.4muM, respectively. In general, methoxy substitutions resulted in slight loss in activity in both benzyl and phenethyl series. Benzyl, 4-fluorobenzyl, 3,4-dimethoxyphenethyl, and 3,4-methylenedioxyphenethyl analogs were tested by NCI in their 60 cell lines in vitro human cancer cell screen. All four compounds showed excellent inhibition against several tested cancer cell lines. Benzyl and 4-fluorobenzyl analogs were relatively more active than 3,4-dimethoxy phenethyl and 3,4-methylenedioxy phenethyl analogs. In NCI assays, the best LogGI(50) values were shown by the fluorobenzyl analog against the renal cancer cell line RXF-393 (<-8.0M) and dimethoxy phenethyl analog against the CNS cancer cell line, SF-268 (<-8.0M). The best LogLC(50) value was shown by the fluorobenzyl analog against the breast cancer cell line MCF-7 (-6.01 M).

Reactive oxygen species mediated apoptosis of esophageal cancer cells induced by marine triprenyl toluquinones and toluhydroquinones

Marine invertebrates, algae, and microorganisms are prolific producers of novel secondary metabolites. Some of these secondary metabolites have the potential to be developed as chemotherapeutic agents for the treatment of a wide variety of diseases, including cancer. We describe here the mechanism leading to apoptosis of esophageal cancer cell lines in the presence of triprenylated toluquinones and toluhydroquinones originally isolated from the Arminacean nudibranch Leminda millecra. Triprenylated toluquinone-induced and toluhydroquinone-induced cell death is mediated via apoptosis after a cell cycle block. Molecular events include production of reactive oxygen species (ROS), followed by induction and activation of c-Jun (AP1) via c-Jun-NH2-kinase-mediated and extracellular signal-regulated kinase-mediated pathways. Partial resistance to these compounds could be conferred by the ROS scavengers Trolox and butylated hydroxyanisol, a c-Jun-NH2-kinase inhibitor, and inhibition of c-Jun with a dominant negative mutant (TAM67). Interestingly, the levels of ROS produced varied between compounds, but was proportional to the ability of each compound to kill cells. Because cancer cells are often more susceptible to ROS, these compounds present a plausible lead for new antiesophageal cancer treatments and show the potential of the South African marine environment to provide new chemical entities with potential clinical significance.

Cultivation of sponge larvae: settlement, survival, and growth of juveniles

The aim of this study was to culture sponge juveniles from larvae. Starting from larvae we expected to enhance the survival and growth, and to decrease the variation in these parameters during the sponge cultures. First, settlement success, morphological changes during metamorphosis, and survival of Dysidea avara, Ircinia oros, Hippospongia communis, under the same culture conditions, were compared. In a second step, we tested the effects of flow and food on survival and growth of juveniles from Dysidea avara and Crambe crambe. Finally, in a third experiment, we monitored survival and growth of juveniles of D. avara and C. crambe transplanted to the sea to compare laboratory and field results. The results altogether indicated that sponge culture from larvae is a promising method for sponge supply and that laboratory culture under controlled conditions is preferred over sea cultures in order to prevent biomass losses during these early life stages.

Sponge-associated microorganisms: evolution, ecology, and biotechnological potential

Marine sponges often contain diverse and abundant microbial communities, including bacteria, archaea, microalgae, and fungi. In some cases, these microbial associates comprise as much as 40% of the sponge volume and can contribute significantly to host metabolism (e.g., via photosynthesis or nitrogen fixation). We review in detail the diversity of microbes associated with sponges, including extensive 16S rRNA-based phylogenetic analyses which support the previously suggested existence of a sponge-specific microbiota. These analyses provide a suitable vantage point from which to consider the potential evolutionary and ecological ramifications of these widespread, sponge-specific microorganisms. Subsequently, we examine the ecology of sponge-microbe associations, including the establishment and maintenance of these sometimes intimate partnerships, the varied nature of the interactions (ranging from mutualism to host-pathogen relationships), and the broad-scale patterns of symbiont distribution. The ecological and evolutionary importance of sponge-microbe associations is mirrored by their enormous biotechnological potential: marine sponges are among the animal kingdom's most prolific producers of bioactive metabolites, and in at least some cases, the compounds are of microbial rather than sponge origin. We review the status of this important field, outlining the various approaches (e.g., cultivation, cell separation, and metagenomics) which have been employed to access the chemical wealth of sponge-microbe associations.

Callophycoic acids and callophycols from the Fijian red alga Callophycus serratus

Callophycoic acids A-H (1-8) and callophycols A and B (9 and 10) were isolated from extracts of the Fijian red alga Callophycus serratus, and identified by NMR, X-ray, and mass spectral analyses. These natural products represent four novel carbon skeletons, providing the first examples of diterpene-benzoic acids and diterpene-phenols in macroalgae. Compounds 1-10 exhibited antibacterial, antimalarial, and anticancer activity, although they are less bioactive than diterpene-benzoate macrolides previously isolated from this red alga.

Total Syntheses of Brominated Marine Sponge Alkaloids

Total syntheses of six brominated marine sponge bis(indole) alkaloids of the hamacanthin, spongotine, and topsentin classes are described. Retrosynthetic analysis shows that their structures all include the 1-(6'-bromoindol-3'-yl)-1,2-diaminoethane unit 13a. This key moiety has been prepared from brominated indolic N-hydroxylamine 5b via synthetic intermediate 8b.

Synthesis of sporiolide B from d-glucal

A total synthesis of the 12-membered ring natural macrolide, sporiolide B, was achieved from D-glucal in 17 steps with 4.8% overall yield. The required stereochemical configuration at C-3 and C-5 in sporiolide B was easily introduced by applying a Mitsunobu reaction on the chiral template D-glucal. Yamaguchi esterification and ring closing metathesis greatly improved the access to the target compound.

Sponge disease: a global threat?

Sponges are the most simple and primitive metazoans, yet they have various biological and ecological properties that make them an influential component of coral-reef ecosystems. Marine sponges provide refuge for many small invertebrates and are critical to benthic-pelagic coupling across a wide range of habitats. Reports of sponge disease have increased dramatically in recent years with sponge populations decimated throughout the Mediterranean and Caribbean. Reports also suggest an increased prevalence of sponge disease in Papua New Guinea, the Great Barrier Reef and in the reefs of Cozumel, Mexico. These epidemics can have severe impacts on the survival of sponge populations, the ecology of the reef and the fate of associated marine invertebrates. Despite the ecological and commercial importance of sponges, the understanding of sponge disease is limited. There has generally been a failure to isolate and identify the causative agents of sponge disease, with only one case confirming Koch's postulates and identifying a novel Alphaproteobacteria strain as the primary pathogen. Other potential disease agents include fungi, viruses, cyanobacteria and bacterial strains within the Bacillus and Pseudomonas genera. There is some evidence for correlations between sponge disease and environmental factors such as climate change and urban/agricultural runoff. This review summarizes the occurrence of sponge disease, describes the syndromes identified thus far, explores potential linkages with environmental change and proposes a strategy for future research towards better management of sponge disease outbreaks.

Nine acetylenic alcohols isolated from the Okinawan marine sponge of the genus Petrosia ( Strongylophora )

Nine new acetylenic alcohols 1-9 were isolated from a marine sponge belonging to the genus Petrosia (Strongylophora). The structures were elucidated mainly based on the analysis of one-and two-dimensional NMR spectral data. To determine the position of the central double bonds in 1-8, each compound was cleaved with OsO(4) and HIO(4), and the resulting aldehyde was converted to the corresponding 2,4-dinitrophenylhydrazone. Analysis of the high-resolution mass and (13)C NMR spectral data of each 2,4-dinitrophenylhydrazone clarified the position of the central double bonds in 1-8.

A functional approach to transcriptome profiling: linking gene expression patterns to metabolites that matter

Secondary metabolites or natural products have been isolated from many marine organisms. These metabolites often have important bioactive functions; however, very little information is available regarding the biosynthesis and regulation of many secondary metabolites. At a time when use of marine-derived metabolites is rapidly expanding in industry and pharmacological fields, a better understanding of the genetic mechanisms controlling secondary metabolite production is necessary. We review the recent development of a novel transcriptome profiling methodology that allows for rapid and high-throughput screening of changes in mRNA sequence pools. The application of genomics-based techniques and the integration of both biochemical and molecular data sets in marine organisms complement ongoing drug discovery efforts.

Cephalosporolides H and I, two novel lactones from a marine-derived fungus, penicillium sp

Two novel lactones, Cephalosporolides H (1) and 1 (2), were isolated from the lyophilized culture broth of the marine-derived fungus, Penicillium sp. The structures were elucidated on the basis of extensive 1D- and 2D-NMR, as well as HRESI-MS spectroscopic analyses. The relative stereochemistries of the compounds were assessed by comparison of the NOESY analysis and spectral data with those in the literature.

Metabolites from algae with economical impact

In order to survive in a highly competitive environment, freshwater or marine algae have to develop defense strategies that result in a tremendous diversity of compounds from different metabolic pathways. Recent trends in drug research from natural sources have shown that algae are promising organisms to furnish novel biochemically active compounds. The current review describes the main substances biosynthesized by algae with potential economic impact in food science, pharmaceutical industry and public health. Emphasis is given to fatty acids, steroids, carotenoids, polysaccharides, lectins, mycosporine-like amino acids, halogenated compounds, polyketides and toxins.

Antibacterial Bromophenol from the Marine Red Alga Pterosiphonia complanata

The dichloromethane/methanol extract of the red alga Pterosiphonia complanata exhibited antibacterial activity against many potentially pathogenic Gram (+) and Gram (-) bacteria. The compound responsible for this activity was isolated and identified, mainly on the basis of 1H and 13C NMR experiments, as the known 3,4,6-tribromo-5-methoxymethyl-benzene-1,2-diol. Its minimum inhibitory concentration against Staphylococcus aureus was 2.8 μg/mL (7 nM).

Antimitotic activity of methoxyconidiol, a meroterpene isolated from an ascidian

Methoxyconidiol is a meroterpene previously extracted from the ascidian Aplidium aff. densum [A. Simon-Levert, A. Arrault, N. Bontemps-Subielos, C. Canal, B. Banaigs. Meroterpenes from the ascidian Aplidium aff. densum, J. Nat. Prod. 68 (2005) 1412-1415]. In the present work we investigated its antimitotic effect on eukaryotic cells by using a bioassay based on the sea urchin early embryo. This bioassay has been successfully used to evaluate the efficacy of antiproliferative agents and to rapidly determine the affected cell cycle phase. We demonstrated that methoxyconidiol inhibits the cleavages of sea urchin Sphaerechinus granularis and Paracentrotus lividus fertilized eggs. This meroterpene disrupts M-phase progression and completely blocks cytokinesis without having any effect on DNA replication. The treatment severely disturbs the establishment of a mitotic spindle, most likely by affecting microtubule dynamics. Moreover, while the cell cycle regulatory kinase cyclin B/CDK1 is activated, cyclin B proteolysis is inhibited, impeding the output of M-phase. This characteristic cell cycle arrest induced by methoxyconidiol in sea urchin eggs emphasizes the interest for this drug as a putative antiproliferative agent for tumor cells.

Carbonarones A and B, new bioactive gamma-Pyrone and alpha-Pyridone derivatives from the marine-derived fungus Aspergillus carbonarius

Two new secondary metabolites, carbonarones A (1) and B (2), were obtained from the culture of the marine-derived fungus Aspergillus carbonarius isolated from the marine sediment collected at Weizhou island of China. Based on ESIMS, 1D and 2D NMR data, and the X-ray crystallographic analysis, their structures were elucidated as 6-benzyl-4-oxo-4H-pyran-3-carboxamide and 6-benzyl-4-hydroxy-2-oxo-1, 2-dihydropyridine-3-carbaldehyde, respectively. 1 and 2 showed moderate cytotoxicity against K562 cells with IC(50) values of 56.0 and 27.8 mug/ml, respectively.

Analogs of the marine alkaloid makaluvamines: synthesis, topoisomerase II inhibition, and anticancer activity

Twelve analogs of makaluvamines have been synthesized. These compounds were evaluated for their ability to inhibit the enzyme topoisomerase II. Five compounds were shown to inhibit topoisomerase catalytic activity comparable to two known topoisomerase II targeting control drugs, etoposide and m-AMSA. Their cytotoxicity against human colon cancer cell line HCT-116 and human breast cancer cell lines MCF-7 and MDA-MB-468 has been evaluated. Four makaluvamine analogs exhibited better IC(50) values against HCT-116 as compared to control drug etoposide. One analog exhibited better IC(50) value against HCT-116 as compared to m-AMSA. All 12 of the makaluvamine analogs exhibited better IC(50) values against MCF-7 and MDA-MB-468 as compared to etoposide as well as m-AMSA.

Cluster analysis as selection and dereplication tool for the identification of new natural compounds from large sample sets

Cluster analysis of gas-chromatographic (GC) data of ca. 500 bacterial isolates was used as an aid in detection and identification of new natural compounds. This approach reduces the number of GC/MS analysis (dereplication) and concomitantly improves the selection of samples with high probability to contain unknown natural products. Lipophilic bacterial extracts were derivatized and analyzed by GC under standardized conditions. A program was developed to convert chromatographic data into a two-dimensional matrix. Based on the results of hierarchical cluster analysis samples were selected for further investigation by GC/MS and NMR. This approach avoided unnecessary analysis of similar samples. By this method, the unusual oligoprenylsesquiterpenes 1 and 2 as well as new aromatic amides 7 and 8 were identified.

Total Synthesis of Marine Sponge Bis(indole) Alkaloids of the Topsentin Class

The synthesis of four natural bis(indole) alkaloids of topsentin class 1 and 2 is described. Their bis(indole) alpha-carbonylimidazoline and subsequently bis(indole) alpha-carbonylimidazole moieties have been built via the condensation between indolic alpha-ketothioimidate salts 4 and 1-(indol-3'-yl)-1,2-diaminoethane 3. This compound results from the beta-amino indolic hydroxylamine 5 by a two-step sequence. This is the first total synthesis of compounds 1d, 2a, and 2b.

Effect of culture conditions on antifouling compound production of a sponge-associated fungus

Microorganisms associated with invertebrate hosts have long been suggested to be a source for bioactive metabolites. In this study, we reported that a sponge-associated fungus, Letendraea helminthicola, produced two antifouling compounds: 3-methyl-N-(2-phenylethyl) butanamide and cyclo(D-Pro-D-Phe). To optimize the production of these antifouling compounds, we then examined the production of compounds under different culture conditions (temperature, salinity, pH, and carbon and nitrogen sources). This fungus grew well and produced more compounds at temperatures between 18 and 30 degrees C; the fungus grew well at 75 parts per thousand (ppt) salinity but produced the highest amount of antifouling compounds at 30 and 45 ppt. The optimal initial pH value for mycelial growth was 5.5 to 6.5, whereas the production of the antifouling compounds was maximized at pH 3.5 and 4.5. Glucose and xylose (as carbon sources) increased the production of antifouling compounds. Yeast extract and peptone (as nitrogen sources) maximized the production of mycelial biomass and antifouling compounds. Our results indicate that culture conditions greatly affect the production of bioactive compounds from mycelial fungal cultures as exemplified by strain L. helminthicola and that the conditions favorable for fungal growth may not be the best conditions for bioactive compound production.

Penisporolides A and B, Two New Spiral Lactones from the Marine-derived Fungus Penicillium sp

In our continued screening on bioactive constituents from marine-derived fungi, two novel compounds containing a rare spiral-lactone skeleton were isolated from lyophilized culture broth of the marine-derived fungus Penicillium sp. The structures of penisporolides A and B were elucidated on the basis of extensive 1D and 2D NMR as well as HRESI-MS spectroscopic data analysis. The relative stereochemistries of the compounds were assessed by analysis of NOESY data together with the comparison with data from previous literatures.

Bromomyrothenone B and botrytinone, cyclopentenone derivatives from a marine isolate of the fungus botrytis

New cyclopentenones, bromomyrothenone B (1) and botrytinone (2), and the known cyclonerodiol (3) were isolated from the marine algicolous fungus of the genus Botrytis. The absolute stereostructures of compounds 1 and 2 were elucidated on the basis of chemical and physicochemical evidence including quantum chemistry calculation, X-ray analysis, and CD exciton chirality method.

Marine natural products

This review covers the literature published in 2005 for marine natural products, with 704 citations (493 for the period January to December 2005) referring to compounds isolated from marine microorganisms and phytoplankton, green algae, brown algae, red algae, sponges, coelenterates, bryozoans, molluscs, tunicates and echinoderms. The emphasis is on new compounds (812 for 2005), together with their 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.

Marine natural products: synthetic aspects

An overview of marine natural products synthesis during 2005 is provided. In a similar vein to earlier installments in this series, the emphasis is on total syntheses of molecules of contemporary interest, new total syntheses, and syntheses that have resulted in structure confirmation or stereochemical assignments.

Recent heterocyclic compounds from marine invertebrates: Structure and synthesis

A large variety of unique heterocyclic natural marine products, without terrestrial counterparts, have been isolated from marine invertebrates, mainly sponges, ascidians, and soft corals. Many of these compounds display interesting biological activity. In this review, we report our recent studies on nitrogen-containing heterocyclic compounds ("alkaloids"), as well as some containing sulfur and oxygen, which have been isolated from Red Sea and Indo-Pacific organisms, and discuss progress on the synthesis of these natural products and structural analogs.

Progress toward a total synthesis of spirastrellolide A

Progress toward a total synthesis of spirastrellolide A, a 38-membered marine macrolide, is reported. Syntheses of two diastereomers of the C1-C25 region, and an evolving Sharpless dihydroxylation strategy toward a C26-C40 fragment, are described. The syntheses exploit boron-mediated aldol chemistry to install key stereocenters, and feature late-stage thermodynamically controlled spiroacetalizations.

Synthesis of macrocyclic shellfish toxins containing spiroimine moieties

An overview of the structure and biological activity of macrocyclic polyketides derived from dinoflagellates that contain unusual cyclic imine units is provided. The total and partial syntheses of these molecules are discussed with an emphasis on the construction of the spiroimine functionality thought to be the key pharmacophore of these fact-acting shellfish toxins.

Marine biotechnology for production of food ingredients

The marine world represents a largely untapped reservoir of bioactive ingredients that can be applied to numerous aspects of food processing, storage, and fortification. Due to the wide range of environments they survive in, marine organisms have developed unique properties and bioactive compounds that, in some cases, are unparalleled by their terrestrial counterparts. Enzymes extracted from fish and marine microorganisms can provide numerous advantages over traditional enzymes used in food processing due to their ability to function at extremes of temperature and pH. Fish proteins such as collagens and their gelatin derivatives operate at relatively low temperatures and can be used in heat-sensitive processes such as gelling and clarifying. Polysaccharides derived from algae, including algins, carrageenans, and agar, are widely used for their ability to form gels and act as thickeners and stabilizers in a variety of foods. Besides applications in food processing, a number of marine-derived compounds, such as omega-3 polyunsaturated fatty acids and photosynthetic pigments, are important to the nutraceutical industry. These bioactive ingredients provide a myriad of health benefits, including reduction of coronary heart disease, anticarcinogenic and anti-inflammatory activity. Despite the vast possibilities for the use of marine organisms in the food industry, tools of biotechnology are required for successful cultivation and isolation of these unique bioactive compounds. In this chapter, recent developments and upcoming areas of research that utilize advances in biotechnology in the production of food ingredients from marine sources are introduced and discussed.

A distinctive structural twist in the aminoimidazole alkaloids from a calcareous marine sponge: isolation and characterization of leucosolenamines A and B

Bioassay-guided fractionation of Papua New Guinea collections of Leucosolenia sp. resulted in the isolation of the novel compounds leucosolenamines A (5) and B (6) and the known compound thymidine (7). Compound 5 contains a 2-aminoimidazole core substituted at C-4 and C-5 by an N,N-dimethyl-5,6-diaminopyrimidine-2,4-dione and a benzyl group, respectively. Compound 6 retains the same core structure; however C-4 is substituted by a 5,6-diamino-1,3-dimethyl-4-(methylimino)-3,4-dihydropyrimidin-2(1H)-one moiety. This substitution pattern is unique and has never been observed in calcareous imidazole alkaloid chemistry. Leucosolenamine A (5) was mildly cytotoxic against the murine colon adenocarcinoma C-38 cell line.

Characterization and online detection of aromatic alkaloids in the ascidian Lissoclinum cf. badium by liquid chromatography/UV detection mass spectrometry

A detection method based on high-performance liquid chromatography coupled with ultraviolet diode-array detection and electrospray ionization ion trap tandem mass spectrometry (HPLC-UV-ESI-MS/MS) was developed to investigate the total alkaloids prepared from the ascidian Lissoclinum cf. badium. The aromatic alkaloids possessing polysulfide structures are the major bioactive constituents isolated from ascidians of the genera Lissoclinum, Eudistoma, and Polycitor. These compounds presented various important biological activities. The ESI-MS fragmentation behavior of this kind of alkaloids was studied, and the fragmentation was characterized by elimination of the NH(CH(3))(2) moiety. The use of reversed-phase HPLC/UV-ESI-MS allowed the online separation and detection of 25 aromatic alkaloids. This approach provided data that can be used for detection of biologically active aromatic alkaloids from marine organisms.

Purification and in vitro cultivation of archaeocytes (stem cells) of the marine sponge Hymeniacidon perleve (Demospongiae)

Marine sponges (Porifera) are the best source of marine bioactive metabolites for drug discovery and development, although the sustainable production of most sponge-derived metabolites remains a difficult task. In vitro cultivation of sponge cells in bioreactors has been proposed as a promising technology. However, no continuous cell line has as yet been developed. Archaeocytes are considered to be toti/multipotent stem cells in sponges and, when purified, may allow the development of continuous sponge cell lines. As a prerequisite, we have developed a novel four-step protocol for the purification of archaeocytes from a marine sponge, Hymeniacidon perleve: (1) differential centrifugation to separate large sponge cells including archaeocytes; (2) selective agglomeration in low-Ca(2+)/Mg(2+) artificial seawater in which living archaeocytes form small loose aggregates with some pinacocytes and collencytes; (3) differential adherence to remove anchorage-dependent pinacocytes, collencytes and other mesohyl cells; (4) Ficoll-Vrografin density gradient centrifugation to purify archaeocytes. The final purity of archaeocytes is greater than 80%. The proliferation potential of the archaeocytes has been demonstrated by high levels of BrdU incorporation, PCNA expression and telomerase activity. In 4-day primary cultures, the purified archaeocytes show a 2.5-fold increase in total cell number. This study opens an important avenue towards developing sponge cell cultures for the commercial exploitation of sponge-derived drugs.

The Marine Natural Product Adociasulfate-2 as a Tool To Identify the MT-Binding Region of Kinesins

Kinesins are molecular motors that transport cargo along microtubules (MTs). To move forward the motor must attach to the MT in a defined orientation and detach from it in a process that is driven by ATP hydrolysis. The knowledge of the motor-MT interface is essential for a detailed understanding of how kinesins move along MTs and how they are related to other molecular motors such as myosins or dyneins. We have used the marine natural product adociasulfate-2 (AS-2), previously identified as a MT-competitive inhibitor of conventional kinesin, to infer the secondary structure elements forming the MT interface of two human mitotic kinesins, namely, CENP-E and Eg5. AS-2 inhibits both basal and MT-stimulated ATPase activities of CENP-E (IC50 of 8.6 and 1.3 microM, respectively) and Eg5 (IC50 of 3.5 and 5.3 microM, respectively) and is a MT-competitive inhibitor of CENP-E with a Ki of 0.35 microM. Binding of AS-2 to CENP-E also stimulates the ADP release from the nucleotide-binding pocket. AS-2 is a nonspecific kinesin inhibitor targeting several superfamily members including KHC, MPP1, MKLP1, RabK6, KIFC1, KIFC3, CENP-E, and Eg5. By measuring hydrogen/deuterium exchange with mass spectrometry we have shown that the formation of the CENP-E/AS-2 complex decreases the solvent accessibility of three neighboring peptides on the same face of CENP-E. We deduce that this is the site of MT attachment and conclude that loop L11, helix alpha4, loop L12, helix alpha5, loop L8, and strand beta5 constitute the main MT interface of the CENP-E motor domain. Similarly for Eg5/AS-2, a region of increased solvent accessibility locates the MT interface of Eg5.

26,27-cyclosterols and other polyoxygenated sterols from a marine sponge Topsentia sp

Thirty sterols (1-30) were isolated from bioactive fractions of a marine sponge Topsentia sp., of which 16 were new (1, 2, 8, 10-14, 16, 17, 19, 21, 24, 25, 27, and 30). They were characterized as sterols with 10 different side chains and as having various functionalities including 5alpha,8alpha-epidioxy (1-9), 5alpha,6alpha-epoxy-7-ol (10-15), 5,8-dien-7-one (24-28), 5-en-3beta-ol (29), and 1(10-->6)abeo-5,7,9-triene-3alpha,11alpha-diol (30) units and included polyoxygenated sterols (16-23). One of the key features of these new sterols is the presence of the (24R,25R,27R)-26,27-cyclo-24,27-dimethylcholestane side chain, whose absolute stereochemistry was defined by an acid-catalyzed ring-opening method and by comparison with the four synthetic isomers of known absolute stereochemistry. The occurrence of several known fungal sterols and relevant new sterols in this sponge suggested their possible origin from symbiotic fungi. Selected compounds were tested against a panel of five human solid tumor cell lines and displayed moderate to marginal cytotoxicity.

Griseusin C, and novel quinone derivative from a marine-derived fungusPenicillium sp

A novel quinone derivative, Griseusin C (1), along with a known quinone, Naphthoquinone C (2), was isolated from the lyophilized culture broth of the marine-derived fungus Penicillium sp. The structures were elucidated on the basis of extensive 1 D- and 2D-NMR, as well as HRESI-MS, spectroscopic analysis. The relative stereochemistries of the compounds were assessed by NOESY analysis.

Crassolides A-F, cembranoids with a trans-fused lactone from the soft coral Sarcophyton crassocaule

Six new polyoxygenated cembrane-based diterpenoids possessing a trans-fused alpha-methylene-gamma-lactone, crassocolides A-F (1-6), have been isolated along with the known compound 7 from the ethyl acetate extract of a Taiwanese soft coral, Sarcophyton crassocaule. The structures of 1-6 have been established by detailed spectroscopic analysis, including 2D NMR (1H-1H COSY, HMQC, HMBC, and NOESY) spectroscopy, while their absolute configurations were determined using a modified Mosher's method for 1. The structure of 5 was further proven by X-ray diffraction analysis. The full assignment of NMR data of 7 is reported herein for the first time. The cytotoxicity of crassocolides 1-4, 6, and 7 against a limited panel of cancer cells was also determined.

The first total synthesis of sporiolide A

The first total synthesis of the natural cytotoxic agent sporiolide A has been accomplished from D-glucal in 16 steps with 6.1% overall yield. Carbohydrates were applied as the chiral templates to manipulate the absolute configuration during the synthesis. Pyridinium chlorochromate (PCC)-promoted transformation of the cyclic enol-ether to lactone, followed by Yamaguchi esterification and intramolecular ring closure metathesis, greatly facilitates synthesis of the target compound.

Glycerolipids from a Sarcotragus species sponge

One known and two new glycerolipids have been isolated from a Sarcotragus sp. marine sponge. The gross structures were established based on NMR and MS analysis.

Recent progress on the total synthesis of natural products in China

An overview of natural products synthesis in Mainland China during the past 10 years is provided. This review only emphasizes the first total synthesis of molecules of contemporary interest and syntheses that helped to correct structures. In addition, some significant results on the novel synthesis and structure-activity relationship (SAR) studies of several natural products are introduced.

Antineoplastic diterpene-benzoate macrolides from the Fijian red alga Callophycus serratus

[structures: see text] Three diterpene-benzoate natural products, with novel carbon skeletons and an unusual proposed biosynthesis, were isolated from extracts of the Fijian red alga Callophycus serratus and identified by a combination of X-ray crystallographic, NMR, and mass spectral analyses. Bromophycolide A (1) displayed cytotoxicity against several human tumor cell lines via specific apoptotic cell death. This represents the first discovery of natural products incorporating a diterpene and benzoate skeleton into a macrolide system.

Temporal Variation in the Production of Four Secondary Metabolites in a Colonial Ascidian

The ecological and applied importance of ascidian secondary metabolites is well reported, but little is known about temporal variation in the production of these compounds. Here, we examined seasonal variation in the production of the four main pyridoacridine alkaloids (shermilamine B, kuanoniamine D, and their deacetylated forms) of the purple morph of the ascidian Cystodytes sp. Five replicate samples were taken monthly from July 2004 to February 2006, and analyzed by high-performance liquid chromatography. Our results showed a high degree of intercolony variability in secondary metabolite concentration and a lack of statistically significant seasonal variation in the production of the four compounds. Minimum values, however, were consistently recorded over the studied years in late summer, after the reproductive period. These minima may be attributable to sexual exhaustion and seasonally varying biotic interactions or abiotic parameters.