Marine natural products

Preliminary molecular characterization of a proinflammatory and nociceptive molecule from the Echinometra lucunter spines extracts

Background

Sea urchins are animals commonly found on the Brazilian shoreline, being Echinometra lucunter the most abundant species. Accidents caused by E. lucunter have been reported as one of the most frequent in Brazil, and are characterized by intense pain and inflammation, consequence of spine puncture in the skin. In order to characterize such toxic effects, we isolated one molecule that caused inflammatory and nociceptive effects.

Methods

E. lucunter specimens were collected without gender distinction. Spines were removed and molecules were extracted, fractionated by RP-HPLC and assayed for inflammatory and nociceptive activity, in a biological-driven fractionation way, until the obtainment of one active molecule and its subsequent analysis by mass spectrometry (MS and MS/MS). For inflammation, intravital microscopy was performed on the mouse cremaster muscle, in order to evaluate rolled, adherent and migrating leukocytes. Paw edema was also evaluated. For the nociceptive activity, the paw pressure test was performed in rats.

Results

One molecule could be isolated and related to the inflammatory and nociceptive activity. Regarding inflammation, increase in adherent and migrating cells was observed in the cremaster muscle after the administration of the molecule. Corroborating the inflammatory response, paw edema was also observed, although only in 20% of controls and 20 min after injection. Additionally, this molecule was able to decrease significantly the pain threshold, characterizing hyperalgesia. This molecule was analyzed by mass spectrometry, and according to the exact molecular mass, isotopic distribution and fragmentation profile, it was possible to propose the molecular formula C₂₉H₄₈N₃O₁₀.

Conclusions

One isolated molecule from the spine extract of E. lucunter is able to elicit inflammation and hypernociception in animal models, which is in agreement with the effects observed in sea urchin accidents.

Three new sesquiterpene aminoquinones from a Vietnamese Spongia sp. and their biological activities

Sesquiterpenoid quinones with remarkable properties, such as anti-inflammatory, antibacterial, antiviral, antitumor, antiangiogenic, and differentiation-inducing activities, have reportedly been isolated from the marine sponge genera Dysidea, Spongia, and Dactylospongia. In our continuing search for bioactive compounds from marine sponges, three new sesquiterpenoid quinones, langcoquinones D-F (1-3), were isolated from the ethyl acetate extract of Spongia sp. collected from Vietnam. Their chemical structures were elucidated on the basis of extensive spectroscopic analyses. The newly isolated compounds 1-3 were assessed for their antibacterial activities against Gram-positive bacteria, Bacillus subtilis and Staphylococcus aureus, and Gram-negative bacteria, Klebsiella pneumoniae and Escherichia coli, as well as their cytotoxic activities against three human cancer cell lines (A549, lung cancer; MCF7, breast cancer; HeLa, cervical cancer) and a human normal cell line (WI-38 fibroblast). All compounds were inactive against the Gram-negative bacteria. Furthermore, langcoquinones E (2) and F (3) lacked antibacterial activities against the Gram-positive bacteria and cytotoxic activities against the tested cell lines. However, langcoquinone D (1) exhibited good antibacterial activities against Bacillus subtilis and Staphylococcus aureus, with MIC values of 12.5 and 25.0 µM, respectively. Furthermore, 1 exhibited significant cytotoxic activities against three human cancer cell lines (A549, lung cancer; MCF7, breast cancer; HeLa, cervical cancer) and a human normal cell line (WI-38 fibroblast).

Palladium-Catalyzed Dehydrogenative Coupling: An Efficient Synthetic Strategy for the Construction of the Quinoline Core

Palladium-catalyzed dehydrogenative coupling is an efficient synthetic strategy for the construction of quinoline scaffolds, a privileged structure and prevalent motif in many natural and biologically active products, in particular in marine alkaloids. Thus, quinolines and 1,2-dihydroquinolines can be selectively obtained in moderate-to-good yields via intramolecular C–H alkenylation reactions, by choosing the reaction conditions. This methodology provides a direct method for the construction of this type of quinoline through an efficient and atom economical procedure, and constitutes significant advance over the existing procedures that require preactivated reaction partners.

Marine microorganisms as a promising and sustainable source of bioactive molecules

There is an urgent need to discover new drug entities due to the increased incidence of severe diseases as cancer and neurodegenerative pathologies, and reducing efficacy of existing antibiotics. Recently, there is a renewed interest in exploring the marine habitat for new pharmaceuticals also thanks to the advancement in cultivation technologies and in molecular biology techniques. Microorganisms represent a still poorly explored resource for drug discovery. The possibility of obtaining a continuous source of bioactives from marine microorganisms, more amenable to culturing compared to macro-organisms, may be able to meet the challenging demands of pharmaceutical industries. This would enable a more environmentally-friendly approach to drug discovery and overcome the over-utilization of marine resources and the use of destructive collection practices. The importance of the topic is underlined by the number of EU projects funded aimed at improving the exploitation of marine organisms for drug discovery.

Beyond the beaten path: improving natural products bioprospecting using an eco-evolutionary framework - the case of the octocorals

Marine natural products (NPs) represent an impressive source of novel bioactive molecules with major biotechnological applications. Nevertheless, the usual chemical and applied perspective leading most of bioprospecting projects come along with various limitations blurring our understanding of the extensive marine chemical diversity. Here, we propose several guidelines: (i) to optimize bioprospecting and (ii) to refine our knowledge on marine chemical ecology focusing on octocorals, one of the most promising sources of marine NPs. We identified a significant phylogenetic bias in the octocoral bioprospecting, which calls for the development of a concerted discovery strategy. Given the gap existing between the number of isolated NPs and the knowledge regarding their functions, we provide an ecologically centered workflow prioritizing biological function ahead of chemical identification. Furthermore, we illustrate how -omic technologies should rapidly increase our knowledge on solving different aspects of the ecology and evolution of marine NPs.

Marine Rare Actinobacteria: Isolation, Characterization, and Strategies for Harnessing Bioactive Compounds

Actinobacteria are prolific producers of thousands of biologically active natural compounds with diverse activities. More than half of these bioactive compounds have been isolated from members belonging to actinobacteria. Recently, rare actinobacteria existing at different environmental settings such as high altitudes, volcanic areas, and marine environment have attracted attention. It has been speculated that physiological or biochemical pressures under such harsh environmental conditions can lead to the production of diversified natural compounds. Hence, marine environment has been focused for the discovery of novel natural products with biological potency. Many novel and promising bioactive compounds with versatile medicinal, industrial, or agricultural uses have been isolated and characterized. The natural compounds cannot be directly used as drug or other purposes, so they are structurally modified and diversified to ameliorate their biological or chemical properties. Versatile synthetic biological tools, metabolic engineering techniques, and chemical synthesis platform can be used to assist such structural modification. This review summarizes the latest studies on marine rare actinobacteria and their natural products with focus on recent approaches for structural and functional diversification of such microbial chemicals for attaining better applications.

Marine Sponges and Bacteria as Challenging Sources of Enzyme Inhibitors for Pharmacological Applications

Enzymes play key roles in different cellular processes, for example, in signal transduction, cell differentiation and proliferation, metabolic processes, DNA damage repair, apoptosis, and response to stress. A deregulation of enzymes has been considered one of the first causes of several diseases, including cancers. In the last several years, enzyme inhibitors, being good candidates as drugs in the pathogenic processes, have received an increasing amount of attention for their potential application in pharmacology. The marine environment is considered a challenging source of enzyme inhibitors for pharmacological applications. In this review, we report on secondary metabolites with enzyme inhibitory activity, focusing our attention on marine sponges and bacteria as promising sources. In the case of sponges, we only reported the kinase inhibitors, because this class was the most representative isolated so far from these marine organisms.

Chemical constituents and biological activities of two Iranian Cystoseira species

The marine environment represents approximately half of the global biodiversity and could provide unlimited biological resources for the production of therapeutic drugs. Marine seaweeds comprise few thousands of species representing a considerable part of the littoral biomass. Extracts of the Cystoseira indica and Cystoseira merica were subjected to phytochemical and cytotoxicity evaluation. The amount of total phenol was determined with Folin-Ciocalteu reagent. Cytotoxicity was characterized by IC₅₀ of human cancer cell lines including MCF-7 (human breast adenocarcinoma), HeLa (cervical carcinoma), and HT-29 (human colon adenocarcinoma) using Sulforhodamin assay. Antioxidant activities were evaluated using 2,2-diphenylpicrylhydrazyl (DPPH) method. The analysis revealed that tannins, saponins, sterols and triterpenes were the most abundant constituents in these Cystoseira species while cyanogenic and cardiac glycosides were the least ones. C. indica had the higher content of total phenolics and also showed higher antioxidant activity. Cytotoxic results showed that both species inhibited cell growth effectively, especially against MCF-7 cell line. The present findings suggest potential pharmacological applications of selected seaweeds but require further investigation and identification of their bioactive principles.

Cytotoxic, antioxidant and phytochemical analysis of Gracilaria species from Persian Gulf

BACKGROUND

Marine algae, also called seaweeds, are abundantly present in the coastal area of Iran, especially in Persian Gulf. These plants contain important phytochemical constituents and have potential biological activities. The present study investigated the presence of phytochemical constituents and total phenolic quantification of the seaweeds Gracilaria salicornia and Gracilaria corticata. Cytotoxicity of seaweeds was tested against HT-29, HeLa, and MCF-7 cell lines. Antioxidant potential of these two Gracilaria species was also analyzed.

MATERIALS AND METHODS

Extracts of G. salicornia and G. corticata were subjected to phytochemical and cytotoxicity tests. Phytochemical screenings were employed to identify the chemical constituents and total phenolic content. Cytotoxicity was characterized by IC50 of human cancer cell lines (MCF-7, HeLa, and HT-29) using sulforhodamine assay. Antioxidant activities were evaluated using 2,2-diphenyl-1-picrylhydrazyl.

RESULTS

The analysis revealed that tannins were the most abundant compounds in G. corticata while sterols and triterpenes were the most abundant ones in G. salicornia, but the total phenolic content of the two seaweeds was similar. Cytotoxic results showed that both species could inhibit cell growth effectively, especially against HT-29 cell line.

CONCLUSION

Considerable phytochemicals, high antioxidant potential, and moderate cytotoxic activity of G. salicornia and G. corticata make them appropriate candidates for further studies and identification of their bioactive principles.

The Potential Role of Seaweeds in the Natural Manipulation of Rumen Fermentation and Methane Production

This study is the first to evaluate the effects of five seaweeds (Ulva sp., Laminaria ochroleuca, Saccharina latissima, Gigartina sp., and Gracilaria vermiculophylla) on gas and methane production and ruminal fermentation parameters when incubated in vitro with two substrates (meadow hay and corn silage) for 24 h. Seaweeds led to lower gas production, with Gigartina sp. presenting the lowest value. When incubated with meadow hay, Ulva sp., Gigartina sp. and G. vermiculophylla decreased methane production, but with corn silage, methane production was only decreased by G. vermiculophylla. With meadow hay, L. ochroleuca and S. latissima promoted similar methane production as the control, but with corn silage, L. ochroleuca increased it. With the exception of S. latissima, all seaweeds promoted similar levels of total volatile fatty acid production. The highest proportion of acetic acid was produced with Ulva sp., G. vermiculophylla, and S. latissima; the highest proportion of butyric acid with the control and L. ochroleuca; and the highest proportion of iso-valeric acid with Gigartina sp. These results reveal the potential of seaweeds to mitigate ruminal methane production and the importance of the basal diet. To efficiently use seaweeds as feed ingredients with nutritional and environmental benefits, more research is required to determine the mechanisms underlying seaweed and substrate interactions.

Cp2ZrMeCl: A Reagent for Asymmetric Methyl Addition

The use of Cp2ZrMeCl is described as a source of nucleophilic methyl in asymmetric catalysis. This easily prepared reagent is bench stable, weighable in air, and generally useful in highly enantioselective copper-catalyzed addition reactions at room temperature. Methyl is successfully (generally >90% ee) added in 1,4-additions to cyclic and acyclic α,β-unsaturated ketones to provide tertiary and quaternary centers. Examples of catalyst controlled diastereoselective 1,6-addition and dynamic kinetic asymmetric allylic alkylation reactions are also reported. The reagent is used in the catalytic asymmetric synthesis of naturally occurring fragrance (R)-(-)-muscone (82% yield, 91% ee).

Metal-Catalyzed Cyclization Reactions of 2,3,4-Trien-1-ols: A Joint Experimental-Computational Study

Controlled preparation of tri- and tetrasubstituted furans, as well as carbazoles has been achieved through chemo- and regioselective metal-catalyzed cyclization reactions of cumulenic alcohols. The gold- and palladium-catalyzed cycloisomerization reactions of cumulenols, including indole-tethered 2,3,4-trien-1-ols, to trisubstituted furans was effective, due to a 5-endo-dig oxycyclization by attack of the hydroxy group onto the central cumulene double bond. In contrast, palladium-catalyzed heterocyclization/coupling reactions with 3-bromoprop-1-enes furnished tetrasubstituted furans. Also studied was the palladium-catalyzed cyclization/coupling sequence involving protected indole-tethered 2,3,4-trien-1-ols and 3-bromoprop-1-enes that exclusively generated trisubstituted carbazole derivatives. These results could be explained through a selective 6-endo-dig cumulenic hydroarylation, followed by aromatization. DFT calculations were carried out to understand this difference in reactivity.

Polycyclic Guanidine Alkaloids from Poecilosclerida Marine Sponges

Sessile marine sponges provide an abundance of unique and diversified scaffolds. In particular, marine guanidine alkaloids display a very wide range of biological applications. A large number of cyclic guanidine alkaloids, including crambines, crambescins, crambescidins, batzelladines or netamins have been isolated from Poecilosclerida marine sponges. In this review, we will explore the chemodiversity of tri- and pentacyclic guanidine alkaloids. NMR and MS data tools will also be provided, and an overview of the wide range of bioactivities of crambescidins and batzelladines derivatives will be given.

Nitric Oxide Production Inhibition and Anti-Mycobacterial Activity of Extracts and Halogenated Sesquiterpenes from the Brazilian Red Alga Laurencia Dendroidea J. Agardh

Background:

Red algae of the genus Laurencia J. V. Lamouroux are a rich source of secondary metabolites with important pharmacological activities such as anti-tumoral, anti-inflammatory, anti-fungal, anti-viral, anti-leishmanial, anti-helminthic, anti-malarial, anti-trypanosomal, anti-microbial as well as anti-bacterial against Mycobacterium tuberculosis.

Objective:

In the present study, we evaluated the inhibition of nitric oxide (NO) and tumor necrosis factor-α production and the anti-mycobacterial activity of crude extracts from the red Alga Laurencia dendroidea (from the South-Eastern coast of Brazil). Halogenated sesquiterpenes elatol (1), obtusol (2) and cartilagineol (3), previously isolated from this Alga by our group, were also studied.

Materials and Methods:

The lipopolysaccharide-activated macrophage cells (RAW 264.7) were used as inflammation model. Cytotoxic effect was determined using a commercial lactate dehydrogenase (LDH) kit and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The growing Mycobacterium inhibition was verified against Mycobacterium bovis Bacillus Calmette–Guérin and M. tuberculosis H₃₇ Rv strains.

Results:

The crude extract from Alga collected at Angra dos Reis, RJ, Brazil, was the most active inhibitor of both mycobacterial growth (half maximal inhibitory concentration [IC₅₀] 8.7 ± 1.4 μg/mL) and NO production by activated macrophages (IC₅₀ 5.3 ± 1.3 μg/mL). The assays with isolated compounds revealed the anti-mycobacterial activity of obtusol (2), whereas (-)-elatol (1) inhibited the release of inflammatory mediators, especially NO. To our knowledge, this is the first report describing an anti-mycobacterial effect of L. dendroidea extract and demonstrating the association of this activity with obtusol (2).

Conclusion:

The described effects of active compounds from L. dendroidea are promising for the control of inflammation in infectious diseases and specifically, against mycobacterial infections associated with exacerbated inflammation.

SUMMARY

Inflammation is strongly involved in the pathogenesis of most infectious diseases, including TB. The treatment of TB is based on the use of anti mycobacterial drugs, however the most severe forms of TB, require additional anti inflammatory therapy to prevent excessive inflammation. A combination of these properties in one compound could provide additional therapeutic benefits. In this work, we studied L. dendroidea extracts and purified compounds and demonstrated that the LDA extract and (-)-elatol (1) were potent in inhibiting NO production by macrophages through the specific inhibition of iNOS expression. The LDA and LDM extracts and obtusol (2) were active against virulent strain of M. tuberculosis. This is the first report demonstrating that the anti-inflammatory activities of L. dendroidea were associated with the presence of (-)-elatol (1), whereas anti-mycobacterial activities of L. dendroidea extracts were associated with obtusol (2).

Coral-Associated Actinobacteria: Diversity, Abundance, and Biotechnological Potentials

Marine Actinobacteria, particularly coral-associated Actinobacteria, have attracted attention recently. In this study, the abundance and diversity of Actinobacteria associated with three types of coral thriving in a thermally stressed coral reef system north of the Arabian Gulf were investigated. Coscinaraea columna, Platygyra daedalea and Porites harrisoni have been found to harbor equivalent numbers of culturable Actinobacteria in their tissues but not in their mucus. However, different culturable actinobacterial communities have been found to be associated with different coral hosts. Differences in the abundance and diversity of Actinobacteria were detected between the mucus and tissue of the same coral host. In addition, temporal and spatial variations in the abundance and diversity of the cultivable actinobacterial communities were detected. In total, 19 different actinobacterial genera, namely Micrococcus, Brachybacterium, Brevibacterium, Streptomyces, Micromonospora, Renibacterium, Nocardia, Microbacterium, Dietzia, Cellulomonas, Ornithinimicrobium, Rhodococcus, Agrococcus, Kineococcus, Dermacoccus, Devriesea, Kocuria, Marmoricola, and Arthrobacter, were isolated from the coral tissue and mucus samples. Furthermore, 82 isolates related to Micromonospora, Brachybacterium, Nocardia, Micrococcus, Arthrobacter, Rhodococcus, and Streptomyces showed antimicrobial activities against representative Gram-positive and/or Gram-negative bacteria. Even though Brevibacterium and Kocuria were the most dominant actinobacterial isolates, they failed to show any antimicrobial activity, whereas less dominant genera, such as Streptomyces, did show antimicrobial activity. Focusing on the diversity of coral-associated Actinobacteria may help to understand how corals thrive under harsh environmental conditions and may lead to the discovery of novel antimicrobial metabolites with potential biotechnological applications.

Larvicidal Potential of the Halogenated Sesquiterpene (+)-Obtusol, Isolated from the Alga Laurencia dendroidea J. Agardh (Ceramiales: Rhodomelaceae), against the Dengue Vector Mosquito Aedes aegypti (Linnaeus) (Diptera: Culicidae)

Dengue is considered a serious public health problem in many tropical regions of the world including Brazil. At the moment, there is no viable alternative to reduce dengue infections other than controlling the insect vector, Aedes aegypti Linnaeus. In the continuing search for new sources of chemicals targeted at vector control, natural products are a promising alternative to synthetic pesticides. In our work, we investigated the toxicity of a bioactive compound extracted from the red alga Laurencia dendroidea J. Agardh. The initial results demonstrated that crude extracts, at a concentration of 5 ppm, caused pronounced mortality of second instar A. aegypti larvae. Two molecules, identified as (−)-elatol and (+)-obtusol were subsequently isolated from crude extract and further evaluated. Assays with (−)-elatol showed moderate larvicidal activity, whereas (+)-obtusol presented higher toxic activity than (−)-elatol, with a LC₅₀ value of 3.5 ppm. Histological analysis of the larvae exposed to (+)-obtusol revealed damage to the intestinal epithelium. Moreover, (+)-obtusol-treated larvae incubated with 2 µM CM-H₂DCFDA showed the presence of reactive oxygen species, leading us to suggest that epithelial damage might be related to redox imbalance. These results demonstrate the potential of (+)-obtusol as a larvicide for use against A. aegypti and the possible mode of action of this compound.

New marine natural products from sponges (Porifera) of the order Dictyoceratida (2001 to 2012); a promising source for drug discovery, exploration and future prospects

The discovery of new drugs can no longer rely primarily on terrestrial resources, as they have been heavily exploited for over a century. During the last few decades marine sources, particularly sponges, have proven to be a most promising source of new natural products for drug discovery. This review considers the order Dictyoceratida in the Phylum Porifera from which the largest number of new marine natural products have been reported over the period 2001-2012. This paper examines all the sponges from the order Dictyoceratida that were reported as new compounds during the time period in a comprehensive manner. The distinctive physical characteristics and the geographical distribution of the different families are presented. The wide structural diversity of the compounds produced and the variety of biological activities they exhibited is highlighted. As a representative of sponges, insights into this order and avenues for future effective natural product discovery are presented. The research institutions associated with the various studies are also highlighted with the aim of facilitating collaborative relationships, as well as to acknowledge the major international contributors to the discovery of novel sponge metabolites. The order Dictyoceratida is a valuable source of novel chemical structures which will continue to contribute to a new era of drug discovery.

Using Molecular Networking for Microbial Secondary Metabolite Bioprospecting

The oceans represent an understudied resource for the isolation of bacteria with the potential to produce novel secondary metabolites. In particular, actinomyces are well known to produce chemically diverse metabolites with a wide range of biological activities. This study characterised spore-forming bacteria from both Scottish and Antarctic sediments to assess the influence of isolation location on secondary metabolite production. Due to the selective isolation method used, all 85 isolates belonged to the phyla Firmicutes and Actinobacteria, with the majority of isolates belonging to the genera Bacillus and Streptomyces. Based on morphology, thirty-eight isolates were chosen for chemical investigation. Molecular networking based on chemical profiles (HR-MS/MS) of fermentation extracts was used to compare complex metabolite extracts. The results revealed 40% and 42% of parent ions were produced by Antarctic and Scottish isolated bacteria, respectively, and only 8% of networked metabolites were shared between these locations, implying a high degree of biogeographic influence upon secondary metabolite production. The resulting molecular network contained over 3500 parent ions with a mass range of m/z 149–2558 illustrating the wealth of metabolites produced. Furthermore, seven fermentation extracts showed bioactivity against epithelial colon adenocarcinoma cells, demonstrating the potential for the discovery of novel bioactive compounds from these understudied locations.

Biodegradable siderophores: survey on their production, chelating and complexing properties

The academic and industrial research on the interactions of complexing agents with the environment has received more attention for more than half a century ago and has always been concerned with the applications of chelating agents in the environment. In contrast, in recent years, an increasing scholarly interest has been demonstrated in the chemical and biological degradation of chelating agents. This is reflected by the increasing number of chelating agents-related publications between 1950 and middle of 2016. Consequently, the discovery of new green biodegradable chelating agents is of great importance and has an impact in the non-biodegradable chelating agent’s replacement with their green chemistry analogs. To acquire iron, many bacteria growing aerobically, including marine species, produce siderophores, which are low-molecular-weight compounds produced to facilitate acquisition of iron. To date and to the best of our knowledge, this is a concise and complete review article of the current and previous relevant studies conducted in the field of production, purification of siderophore compounds and their metal complexes, and their roles in biology and medicine.

Three new cytotoxic isomalabaricane triterpenes from the marine sponge Stelletta tenuis

Three new isomalabaricane-type triterpenes named stellettins N (1), O (2) and P (3), together with four known compounds (4–7),were isolated from the CCl4 extract of the marine sponge Stelletta tenuis Lindgren. Compound 4 was reported as a natural α-pyrone for the first time, which had been synthesized from gibepyrone B, while 5 was found in the genus Stelletta for the first time. The structures of the new compounds were established on the basis of extensive spectroscopic data analysis including IR, MS, 1D and 2D NMR. The inhibitory activities of compounds 1–3 against three human cancer cell lines (A549, AGS and U-251MG) were evaluated and all the tested compounds exhibited significant cytotoxicity to AGS cells, with IC50 values of 4.52, 9.61 and 7.44 μM, respectively.

Significance of investigating allelopathic interactions of marine organisms in the discovery and development of cytotoxic compounds

Marine sessile organisms often inhabit rocky substrata, which are crowded by other sessile organisms. They acquire living space via growth interactions and/or by allelopathy. They are known to secrete toxic compounds having multiple roles. These compounds have been explored for their possible applications in cancer chemotherapy, because of their ability to kill rapidly dividing cells of competitor organisms. As compared to the therapeutic applications of these compounds, their possible ecological role in competition for space has received little attention. To select the potential candidate organisms for the isolation of lead cytotoxic molecules, it is important to understand their chemical ecology with special emphasis on their allelopathic interactions with their competitors. Knowledge of the ecological role of allelopathic compounds will contribute significantly to an understanding of their natural variability and help us to plan effective and sustainable wild harvests to obtain novel cytotoxic chemicals. This review highlights the significance of studying allelopathic interactions of marine invertebrates in the discovery of cytotoxic compounds, by selecting sponge as a model organism.

Diversity of Marine-Derived Fungal Cultures Exposed by DNA Barcodes: The Algorithm Matters

Marine fungi are an understudied group of eukaryotic microorganisms characterized by unresolved genealogies and unstable classification. Whereas DNA barcoding via the nuclear ribosomal internal transcribed spacer (ITS) provides a robust and rapid tool for fungal species delineation, accurate classification of fungi is often arduous given the large number of partial or unknown barcodes and misidentified isolates deposited in public databases. This situation is perpetuated by a paucity of cultivable fungal strains available for phylogenetic research linked to these data sets. We analyze ITS barcodes produced from a subsample (290) of 1781 cultured isolates of marine-derived fungi in the Bioresources Library located at the Australian Institute of Marine Science (AIMS). Our analysis revealed high levels of under-explored fungal diversity. The majority of isolates were ascomycetes including representatives of the subclasses Eurotiomycetidae, Hypocreomycetidae, Sordariomycetidae, Pleosporomycetidae, Dothideomycetidae, Xylariomycetidae and Saccharomycetidae. The phylum Basidiomycota was represented by isolates affiliated with the genera Tritirachium and Tilletiopsis. BLAST searches revealed 26 unknown OTUs and 50 isolates corresponding to previously uncultured, unidentified fungal clones. This study makes a significant addition to the availability of barcoded, culturable marine-derived fungi for detailed future genomic and physiological studies. We also demonstrate the influence of commonly used alignment algorithms and genetic distance measures on the accuracy and comparability of estimating Operational Taxonomic Units (OTUs) by the automatic barcode gap finder (ABGD) method. Large scale biodiversity screening programs that combine datasets using algorithmic OTU delineation pipelines need to ensure compatible algorithms have been used because the algorithm matters.

Psychrophilic fungi from the world's roof

During a survey of cold-adapted fungi in alpine glaciers on the Qinghai-Tibet Plateau, 1 428 fungal isolates were obtained of which 150 species were preliminary identified. Phoma sclerotioides and Pseudogymnoascus pannorum were the most dominant species. Psychrotolerant species in Helotiales (Leotiomycetes, Ascomycota) were studied in more detail as they represented the most commonly encountered group during this investigation. Two phylogenetic trees were constructed based on the partial large subunit nrDNA (LSU) to infer the taxonomic placements of these strains. Our strains nested in two well-supported major clades, which represented Tetracladium and a previously unknown lineage. The unknown lineage is distant to any other currently known genera in Helotiales. Psychrophila gen. nov. was therefore established to accommodate these strains which are characterised by globose or subglobose conidia formed from phialides on short or reduced conidiophores. Our analysis also showed that an LSU-based phylogeny is insufficient in differentiating strains at species level. Additional analyses using combined sequences of ITS+TEF1+TUB regions were employed to further investigate the phylogenetic relationships of these strains. Together with the recognisable morphological distinctions, six new species (i.e. P. antarctica, P. lutea, P. olivacea, T. ellipsoideum, T. globosum and T. psychrophilum) were described. Our preliminary investigation indicates a high diversity of cold-adapted species in nature, and many of them may represent unknown species.

Alternative and efficient extraction methods for marine-derived compounds

Marine ecosystems cover more than 70% of the globe’s surface. These habitats are occupied by a great diversity of marine organisms that produce highly structural diverse metabolites as a defense mechanism. In the last decades, these metabolites have been extracted and isolated in order to test them in different bioassays and assess their potential to fight human diseases. Since traditional extraction techniques are both solvent- and time-consuming, this review emphasizes alternative extraction techniques, such as supercritical fluid extraction, pressurized solvent extraction, microwave-assisted extraction, ultrasound-assisted extraction, pulsed electric field-assisted extraction, enzyme-assisted extraction, and extraction with switchable solvents and ionic liquids, applied in the search for marine compounds. Only studies published in the 21st century are considered.

Tropicihabitans flavus gen. nov., sp. nov., a new member of the family Cellulomonadaceae

Two novel Gram-stain positive actinobacteria, designated PS-14-16(T) and RS-7-1, were isolated from the rhizosphere of a mangrove and sea sediment, respectively, and their taxonomic positions were investigated by a polyphasic approach. Both strains were observed to form vegetative hyphae in the early phase of growth but the hyphae eventually fragment into short rods to coccoid cells. The peptidoglycan type of both strains was found to be A4α. Their predominant menaquinone was identified as MK-9(H4) and the major fatty acid as anteiso-C(15:0). The DNA G+C content was determined to be 68.4-68.5 mol%. 16S rRNA gene sequencing revealed that strains PS-14-16(T) and RS-7-1 were related to members of the family Cellulomonadaceae. Their nearest phylogenetic neighbour was found to be Sediminihabitans luteus, which is currently the only species of the genus Sediminihabitans, with a similarity of 97.94%. However, strains PS-14-16(T) and RS-7-1 were distinguishable from the members of the genus Sediminihabitans and the other genera within the family Cellulomonadaceae in terms of chemotaxonomic characteristics and phylogenetic relationship. The results of DNA-DNA hybridization experiments indicated that strains PS-14-16(T) and RS-7-1 belong to the same species. Strains PS-14-16(T) and RS-7-1 are concluded to represent a novel genus and species of the family Cellulomonadaceae, for which the name Tropicihabitans flavus gen. nov., sp. nov. is proposed. The type strain of T. flavus is PS-14-16(T) (=NBRC 110109(T) = IanCC A 516(T)). [corrected].

Statistical research on the bioactivity of new marine natural products discovered during the 28 years from 1985 to 2012

Every year, hundreds of new compounds are discovered from the metabolites of marine organisms. Finding new and useful compounds is one of the crucial drivers for this field of research. Here we describe the statistics of bioactive compounds discovered from marine organisms from 1985 to 2012. This work is based on our database, which contains information on more than 15,000 chemical substances including 4196 bioactive marine natural products. We performed a comprehensive statistical analysis to understand the characteristics of the novel bioactive compounds and detail temporal trends, chemical structures, species distribution, and research progress. We hope this meta-analysis will provide useful information for research into the bioactivity of marine natural products and drug development.

LC-MS-based metabolomics study of marine bacterial secondary metabolite and antibiotic production in Salinispora arenicola

An LC-MS-based metabolomics approach was used to characterise the variation in secondary metabolite production due to changes in the salt content of the growth media as well as across different growth periods (incubation times). We used metabolomics as a tool to investigate the production of rifamycins (antibiotics) and other secondary metabolites in the obligate marine actinobacterial species Salinispora arenicola, isolated from Great Barrier Reef (GBR) sponges, at two defined salt concentrations and over three different incubation periods. The results indicated that a 14 day incubation period is optimal for the maximum production of rifamycin B, whereas rifamycin S and W achieve their maximum concentration at 29 days. A "chemical profile" link between the days of incubation and the salt concentration of the growth medium was shown to exist and reliably represents a critical point for selection of growth medium and harvest time.

Bioactive chemical constituents from the brown alga Homoeostrichus formosana

A new chromene derivative, 2-(4',8'-dimethylnona-3'E,7'-dienyl)-8-hydroxy-2,6-dimethyl-2H-chromene (1) together with four known natural products, methylfarnesylquinone (2), isololiolide (3), pheophytin a (4), and β-carotene (5) were isolated from the brown alga Homoeostrichus formosana. The structure of 1 was determined by extensive 1D and 2D spectroscopic analyses. Acetylation of 1 yielded the monoacetylated derivative 2-(4',8'-dimethylnona-3'E,7'-dienyl)-8-acetyl-2,6-dimethyl-2H-chromene (6). Compounds 1-6 exhibited various levels of cytotoxic, antibacterial, and anti-inflammatory activities. Compound 2 was found to display potent in vitro anti-inflammatory activity by inhibiting the generation of superoxide anion (IC50 0.22 ± 0.03 μg/mL) and elastase release (IC50 0.48 ± 0.11 μg/mL) in FMLP/CB-induced human neutrophils.

Advances in algal drug research with emphasis on enzyme inhibitors

Enzyme inhibitors are now included in all kinds of drugs essential to treat most of the human diseases including communicable, metabolic, cardiovascular, neurological diseases and cancer. Numerous marine algae have been reported to be a potential source of novel enzyme inhibitors with various pharmaceutical values. Thus, the purpose of this review is to brief the enzyme inhibitors from marine algae of therapeutic potential to treat common diseases. As per our knowledge this is the first review for the potential enzyme inhibitors from marine origin. This review contains 86 algal enzyme inhibitors reported during 1989-2013 and commercial enzyme inhibitors available in the market. Compounds in the review are grouped according to the disease conditions in which they are involved; diabetes, obesity, dementia, inflammation, melanogenesis, AIDS, hypertension and other viral diseases. The structure-activity relationship of most of the compounds are also discussed. In addition, the drug likeness properties of algal inhibitors were evaluated using Lipinski's 'Rule of Five'.

In vitro screening of antifungal activity of marine sponge extracts against five phytopathogenic fungi

The aim of our research is the screening of extracts of marine sponges for their antifungal activity against phytopathogenic fungi. The in vitro screening of hydroalcoholic and organic extracts of ten marine sponges from Atlantic coast of Morocco against five phytopathogenic fungi (Fusarium oxysporum f.sp. melonis, Fusarium oxysporum f.sp. radicis-lycopersici, Fusarium oxysporum f.sp. ciceris, Botrytis cinerea and Penicillium digitatum) showed that only two sponges (Haliclona viscosa and Cynachirella tarentina) are active against all phytopathogenic fungi studied.

Marine sponge Cribrochalina vasculum compounds activate intrinsic apoptotic signaling and inhibit growth factor signaling cascades in non-small cell lung carcinoma

Marine-derived compounds have been explored and considered as possible antitumor agents. In this study, we analyzed extracts of the sponge Cribrochalina vasculum for their ability to inhibit tumor cell proliferation. Screening identified two acetylenic compounds of similar structure that showed strong tumor-specific toxicity in non-small cell lung carcinoma (NSCLC) cells and small-cell lung carcinoma cells, and less prominent toxicity in ovarian carcinoma, while having no effect on normal cells. These acetylenic compounds were found to cause a time-dependent increase in activation of apoptotic signaling involving cleavage of caspase-9, caspase-3, and PARP, as well as apoptotic cell morphology in NSCLC cells, but not in normal fibroblasts. Further analysis demonstrated that these compounds caused conformational change in Bak and Bax, and resulted in loss of mitochondrial potential and cytochrome c release in NSCLC cells. Moreover, a decreased phosphorylation of the growth factor signaling kinases Akt, mTOR, and ERK was evident and an increased phosphorylation of JNK was observed. Thus, these acetylenic compounds hold potential as novel therapeutic agents that should be further explored for NSCLC and other tumor malignancies.

Didemnaketals f and g, new bioactive spiroketals from a red sea ascidian didemnum species

In continuation of our ongoing efforts to identify bioactive compounds from Red Sea marine organisms, a new collection of the ascidian Didemnum species was investigated. Chromatographic fractionation and HPLC purification of the CH₂Cl₂ fraction of an organic extract of the ascidian resulted in the identification of two new spiroketals, didemnaketals F (1) and G (2). The structure determination of the compounds was completed by extensive study of 1D (¹H, ¹³C, and DEPT) and 2D (COSY, HSQC, and HMBC) NMR experiments in addition to high-resolution mass spectral data. Didemnaketal F (1) and G (2) differ from the previously reported compounds of this class by the lack the terminal methyl ester at C-1 and the methyl functionality at C-2. Instead, 1 and 2 possess a methyl ketone moiety instead of the terminal ester. Furthermore, didemnaketal F possesses a disubstituted double bond between C-2 and C-3, while the double bond was replaced by a secondary alcohol at C-3 in didemnaketal G. In addition, they possess the unique spiroketal/hemiketal functionality which was previously reported in didemnaketal E. Didemnaketals F (1) and G (2) displayed moderate activity against HeLa cells with of IC_50s of 49.9 and 14.0 µM, respectively. In addition, didemnaketal F (1) displayed potent antimicrobial activity against E. coli and C. albicans. These findings provide further insight into the biosynthetic capabilities of this ascidian and the chemical diversity as well as the biological activity of this class of compounds.

Synthesis and antiproliferative activity of some steroidal thiosemicarbazones, semicarbazones and hydrozones

Steroidal thiosemicarbazones, semicarbazones and hydrazones have received extensive attention of scientists recently because they exhibit some biological activities such as antibacterial, antiviral and anticancer. Using different steroids as starting materials, through different chemical methods, 24 steroidal compounds with thiosemicarbazone, semicarbazone or hydrazone groups in their structures, were synthesized, characterized by IR, NMR and MS. The antiproliferative activity of the compounds was evaluated against human gastric cancer (SGC-7901) and human liver cancer (Bel-7404) cells. The structure-activity relationship of these compounds was discussed. The results showed that compound 3 and 12a-12c exhibited significant inhibitory activity to Bel-7404 cells, and IC50 values of them were 4.2, 11.0, 7.4 and 15.0μM respectively (Cisplatin, IC50: 11.6μM).

Marine sponge derived natural products between 2001 and 2010: trends and opportunities for discovery of bioactives

Marine sponges belonging to the phylum Porifera (Metazoa), evolutionarily the oldest animals are the single best source of marine natural products. The present review presents a comprehensive overview of the source, taxonomy, country of origin or geographical position, chemical class, and biological activity of sponge-derived new natural products discovered between 2001 and 2010. The data has been analyzed with a view to gaining an outlook on the future trends and opportunities in the search for new compounds and their sources from marine sponges.

Novel and highly potent antitumour natural products from cnidarians of marine origin

This article covers the 2003-2012 literature published for marine natural products from the phylum Cnidaria. The focus is on new and highly potent antitumour substances, together with details related to the organism sourced. It describes 12 promising bioactives isolated from 7 species.

Cytotoxic neviotane triterpene-type from the red sea sponge Siphonochalina siphonella

Background:

Siphonochalina siphonella is a marine sponge collected from saudi Red Sea water and scare study from this region.

Objective:

To isolate the anticancer triterpenes with potent cytotoxicity from marine sponge, Siphonochalina siphonella and state the mode of action in cancer cell lines.

Materials and Methods:

The sponge material was collected, extracted with organic solvent, and fractionated on different adsorbents. The structure of the pure metabolites were elucidated employing different spectroscopic techniques including 1D (¹H and ¹³C) and 2D (COSY, HMQC and HMBC) NMR, and MS spectroscopy.

Results:

A new Neviotine-C (1) was obtained, along with four known metabolites (2-5). All compounds, except 5, were tested towards MCF-7, PC-3 and A549 and showed effects with IC₅₀ in range 7.9-87 μM, whilst, 3 showed potent anti-proliferative activity against PC-3 and A549 with IC₅₀ = 7.9 ± 0.120 and 8.9 ± 0.010 μM, respectively.

Conclusion:

Compounds (1-4) showed significant cytotoxic activities, while 3 showed potent effect. The antiproliferative of 3 was attributed to significant S-phase cell cycle arrest.

Marine actinobacteria: an important source of bioactive natural products

Marine environment is largely an untapped source for deriving actinobacteria, having potential to produce novel, bioactive natural products. Actinobacteria are the prolific producers of pharmaceutically active secondary metabolites, accounting for about 70% of the naturally derived compounds that are currently in clinical use. Among the various actinobacterial genera, Actinomadura, Actinoplanes, Amycolatopsis, Marinispora, Micromonospora, Nocardiopsis, Saccharopolyspora, Salinispora, Streptomyces and Verrucosispora are the major potential producers of commercially important bioactive natural products. In this respect, Streptomyces ranks first with a large number of bioactive natural products. Marine actinobacteria are unique enhancing quite different biological properties including antimicrobial, anticancer, antiviral, insecticidal and enzyme inhibitory activities. They have attracted global in the last ten years for their ability to produce pharmaceutically active compounds. In this review, we have focused attention on the bioactive natural products isolated from marine actinobacteria, possessing unique chemical structures that may form the basis for synthesis of novel drugs that could be used to combat resistant pathogenic microorganisms.

In vitro and in silico studies on the anticancer and apoptosis-inducing activities of the sterols identified from the soft coral, subergorgia reticulata

BACKGROUND

Gorgonians and other octocorals are known to possess a huge array of secondary metabolites in which sterols are the major group of secondary metabolites apart from sesquiterpenes and diterpenes, and the bioactive metabolites could show marked biomedical potential for future drug discovery.

OBJECTIVE

This study was intended for the isolation and identification of sterols from the octocoral Subergorgia reticulata and to evaluate the anticancer and apoptosis-inducing activities of the identified sterols through in vitro and in silico approach.

MATERIALS AND METHODS

The organism was collected from Lakshadweep Island. The isolated sterols were identified using Gas chromatography-mass spectrometry (GC-MS). The structure was confirmed by using comparison of their spectra those in National Institute of Standard Technology (NIST) library. The apoptosis inducing effect of identified sterols were determined by PASS online prediction. In vitro cytotoxity studies were carried out using Dalton's lymphoma ascites cells (DLA) and the cell viability was determined by trypan blue exclusion method.

RESULTS

Six sterols were identified from the soft coral S. reticulata. They are Cholesta-5,22-diene-3ol (3β), Ergosta-5-22-dien-3ol (3β,22E 24S), Cholesterol, 26,26-Dimethyl-5,24(28)-ergostadien-3β-ol. β-sitosterol, and Fucosterol. In silico predictions showed that the identified sterols exhibited remarkable apoptosis agonist activity. The probability of apoptosis agonist activity were found maximum for 26,26-Dimethyl-5,24 (28)-S. reticulata sterol fractions isolated were found to be having anticancer activity.

CONCLUSIONS

These findings suggest that S. reticulata contained biologically active sterol compounds that may be useful in the treatment of cancer.