New Discorhabdin B Dimers with Anticancer Activity from the Antarctic Deep-Sea Sponge Latrunculia biformis

Latrunculia sponges represent a rich source of discorhabdin-type pyrroloiminoquinone alkaloids, a few of which comprise a dimeric structure. The anticancer-activity-guided isolation of the n-hexane subextract of the Antarctic deep-sea sponge Latrunculia biformis yielded the known compound (−)-(1R,2R,6R,8S,6'S)-discorhabdin B dimer (1) and two new derivatives, (−)-(1S,2R,6R,8S,6'S)-discorhabdin B dimer (2) and (−)-(1R,2R,6R,8S,6'S)-16',17'-dehydrodiscorhabdin B dimer (3). The chemical structures of compounds 1–3 were elucidated by means of HR-ESIMS, NMR, [], ECD spectroscopy, and a comparison with the previously reported discorhabdin analogs. Compounds 1 and 2 showed significant in vitro anticancer activity against the human colon cancer cell line (HCT-116), with IC50 values of 0.16 and 2.01 µM, respectively. Compared to monomeric discorhabdins, dimeric discorhabdins are very rare in Nature. This study adds two new discorhabdin dimers (2 and 3) to this small pyrroloiminoquinone subfamily. This is also the first report of compound 1 as a natural product and the first assessment of its in vitro anticancer activity

Macroscopic characteristics facilitate identification of common Antarctic glass sponges (Porifera, Hexactinellida, Rossellidae)

Glass sponges (Porifera, Hexactinellida) are conspicuous habitat-forming members of many Antarctic shelf communities. Despite their ecological importance, in-situ species identification remains problematic as it is traditionally based on micro- scopic analysis of spicules. External morphological features, in contrast, have largely been disregarded, so that different species have been mislabeled or lumped together when their identification was based on image material. In this paper, we provide a straight-forward guideline for in-situ identification of the most common rossellid sponges of the Antarctic shelf based on macroscopic characteristics. To determine diagnostic macroscopic characteristics of Anoxycalyx (Scolymastra) joubini and eight Rossella species, we combined examination of trawl-collected specimens, previous species descriptions and in-situ image material from the eastern Weddell Sea. Our study revealed that the smooth-walled species A. joubini, R. nuda and R. vanhoeffeni, previously often mixed up, can be distinguished by the form of their basal spicule tuft, their surface structure and their overall body form. The previously synonymized species R. racovitzae and R. podagrosa can be distinguished by their markedly different habitus. Based on our results, the so-called ‘R. racovitzae budding type’ in fact refers to R. podagrosa which occurs regularly in the eastern Weddell Sea. The species R. villosa, R. levis, R. fibulata and R. antarctica can be distinguished by the appearance of their conules, protruding spicules and overall body form. We conclude that macroscopic characteristics are helpful means for identification of Antarctic rossellid sponge species. This approach enables species-specific quantitative studies of Antarctic glass sponge grounds based on increasingly used non-invasive imaging technology

Hexactinellida (Porifera) from the Drake Passage (Southern Ocean) with a description of three new species

Goodwin, Claire E., Berman, Jade, Janussen, Dorte, Göcke, Christian, Hendry, Katharine R. (2016): Hexactinellida (Porifera) from the Drake Passage (Southern Ocean) with a description of three new species. Zootaxa 4126 (2): 207-220, DOI: http://doi.org/10.11646/zootaxa.4126.2.

New Discorhabdin Alkaloids from the Antarctic Deep-Sea Sponge Latrunculia biformis

The sponge genus Latrunculia is a prolific source of discorhabdin type pyrroloiminoquinone alkaloids. In the continuation of our research interest into this genus, we studied the Antarctic deep-sea sponge Latrunculia biformis that showed potent in vitro anticancer activity. A targeted isolation process guided by bioactivity and molecular networking-based metabolomics yielded three known discorhabdins, (−)-discorhabdin L (1), (+)-discorhabdin A (2), (+)-discorhabdin Q (3), and three new discorhabdin analogs (−)-2-bromo-discorhabdin D (4), (−)-1-acetyl-discorhabdin L (5), and (+)-1-octacosatrienoyl-discorhabdin L (6) from the MeOH-soluble portion of the organic extract. The chemical structures of 1–6 were elucidated by extensive NMR, HR-ESIMS, FT-IR, [α]D, and ECD (Electronic Circular Dichroism) spectroscopy analyses. Compounds 1, 5, and 6 showed promising anticancer activity with IC50 values of 0.94, 2.71, and 34.0 µM, respectively. Compounds 1–6 and the enantiomer of 1 ((+)-discorhabdin L, 1e) were docked to the active sites of two anticancer targets, topoisomerase I-II and indoleamine 2,3-dioxygenase (IDO1), to reveal, for the first time, the binding potential of discorhabdins to these proteins. Compounds 5 and 6 are the first discorhabdin analogs with an ester function at C-1 and 6 is the first discorhabdin bearing a long-chain fatty acid at this position. This study confirms Latrunculia sponges to be excellent sources of chemically diverse discorhabdin alkaloids

Biological activities of ethanolic extracts from deep-sea antarctic marine sponges

We report on the screening of ethanolic extracts from 33 deep-sea Antarctic marine sponges for different biological activities. We monitored hemolysis, inhibition of acetylcholinesterase, cytotoxicity towards normal and transformed cells and growth inhibition of laboratory, commensal and clinically and ecologically relevant bacteria. The most prominent activities were associated with the extracts from sponges belonging to the genus Latrunculia, which show all of these activities. While most of these activities are associated to already known secondary metabolites, the extremely strong acetylcholinesterase inhibitory potential appears to be related to a compound unknown to date. Extracts from Tetilla leptoderma, Bathydorus cf. spinosus, Xestospongia sp., Rossella sp., Rossella cf. racovitzae and Halichondria osculum were hemolytic, with the last two also showing moderate cytotoxic potential. The antibacterial tests showed significantly greater activities of the extracts of these Antarctic sponges towards ecologically relevant bacteria from sea water and from Arctic ice. This indicates their ecological relevance for inhibition of bacterial microfouling

Targeted Isolation of Tsitsikammamines from the Antarctic Deep-Sea Sponge Latrunculia biformis by Molecular Networking and Anticancer Activity

The Antarctic deep-sea sponge Latrunculia (Latrunculia) biformis Kirkpatrick, 1908 (Class Demospongiae Sollas, Order Poecilosclerida Topsent, Latrunculiidae Topsent) was selected for chemical analyses due to its potent anticancer activity. Metabolomic analysis of its crude extract by HRMS/MS-based molecular networking showed the presence of several clusters of pyrroloiminoquinone alkaloids, i.e., discorhabdin and epinardin-type brominated pyridopyrroloquinolines and tsitsikammamines, the non-brominated bis-pyrroloiminoquinones. Molecular networking approach combined with a bioactivity-guided isolation led to the targeted isolation of the known pyrroloiminoquinone tsitsikammamine A (1) and its new analog 16,17-dehydrotsitsikammamine A (2). The chemical structures of the compounds 1 and 2 were elucidated by spectroscopic analysis (one-dimensional (1D) and two-dimensional (2D) NMR, HR-ESIMS). Due to minute amounts, molecular modeling and docking was used to assess potential affinities to potential targets of the isolated compounds, including DNA intercalation, topoisomerase I-II, and indoleamine 2,3-dioxygenase enzymes. Tsitsikammamines represent a small class of pyrroloiminoquinone alkaloids that have only previously been reported from the South African sponge genus Tsitsikamma Samaai & Kelly and an Australian species of the sponge genus Zyzzya de Laubenfels. This is the first report of tsitsikammamines from the genus Latrunculia du Bocage and the successful application of molecular networking in the identification of comprehensive chemical inventory of L.biformis followed by targeted isolation of new molecules. This study highlights the high productivity of secondary metabolites of Latrunculia sponges and may shed new light on their biosynthetic origin and chemotaxonom

Nanostructural organization of naturally occurring composites - part II: silica-chitin-based biocomposites

Investigations of the micro- and nanostructures and chemical composition of the sponge skeletons as examples for natural structural biocomposites are of fundamental scientific relevance. Recently, we show that some demosponges (Verongula gigantea, Aplysina sp.) and glass sponges (Farrea occa, Euplectella aspergillum) possess chitin as a component of their skeletons. The main practical approach we used for chitin isolation was based on alkali treatment of corresponding external layers of spicules sponge material with the aim of obtaining alkali-resistant compounds for detailed analysis. Here, we present a detailed study of the structural and physicochemical properties of spicules of the glass sponge Rossella fibulata. The structural similarity of chitin derived from this sponge to invertebrate alpha chitin has been confirmed by us unambiguously using physicochemical and biochemical methods. This is the first report of a silica-chitin composite biomaterial found in Rossella species. Finally, the present work includes a discussion related to strategies for the practical application of silica-chitin-based composites as biomaterials

Host-specific assembly of sponge-associated prokaryotes at high taxonomic ranks

Sponges (Porifera) are abundant and diverse members of benthic filter feeding communities in most marine ecosystems, from the deep sea to tropical reefs. A characteristic feature is the associated dense and diverse prokaryotic community present within the sponge mesohyl. Previous molecular genetic studies revealed the importance of host identity for the community composition of the sponge-associated microbiota. However, little is known whether sponge host-specific prokaryotic community patterns observed at 97% 16S rRNA gene sequence similarity are consistent at high taxonomic ranks (from genus to phylum level). In the present study, we investigated the prokaryotic community structure and variation of 24 sponge specimens (seven taxa) and three seawater samples from Sweden. Results show that the resemblance of prokaryotic communities at different taxonomic ranks is consistent with patterns present at 97% operational taxonomic unit level

Prokaryotic Diversity and Community Patterns in Antarctic Continental Shelf Sponges

Marine sponges (Phylum Porifera) are globally distributed within marine and freshwater ecosystems. In addition, sponges host dense and diverse prokaryotic communities, which are potential sources of novel bioactive metabolites and other complex compounds. Those sponge-derived natural products can span a broad spectrum of bioactivities, from antibacterial and antifungal to antitumor and antiviral compounds. However, most analyses concerning sponge-associated prokaryotes have mainly focused on conveniently accessible relatively shallow sampling locations for sponges. Hence, knowledge of community composition, host-relatedness and biotechnological potential of prokaryotic associations in temperate and cold-water sponges from greater depths (mesophotic to mesopelagic zones) is still scarce. Therefore, we analyzed the prokaryotic community diversity of four phylogenetically divergent sponge taxa from mesophotic to mesopelagic depths of Antarctic shelf at different depths and locations in the region of the South Shetland Islands using 16S rRNA gene amplicon-based sequencing. In addition, we predicted functional profiles applying Tax4Fun from metagenomic 16S rRNA gene data to estimate their biotechnological capability and possible roles as sources of novel bioactive compounds. We found indications that cold and deep-water sponges exhibit host-specific prokaryotic communities, despite different sampling sites and depths. Functional prediction analysis suggests that the associated prokaryotes may enhance the roles of sponges in biodegradation processes of xenobiotics and their involvement in the biosynthesis of secondary metabolites

Schwämme am Meeresboden im Südpolarmeer

Die obere Wasserschicht des Südpolarmeers ist reich an Pflanzennährstoffen wie Nitrat und Phosphat, trotzdem ist die biologische Produktion in großen Teilen des Südozeans relativ gering, denn es mangelt am Spurennährstoff Eisen. Die Tiere am Meeresboden sind auf Nahrung in Form von organischen Partikeln angewiesen, die von oben in die Tiefe absinken. Welche Nahrung und wie viel davon steht den Tiefseeorganismen hier überhaupt zur Verfügung? Welche Tiere – insbesondere welche Schwämme – kommen mit diesen Bedingungen gut zurecht? Darüber sollte eine Polarstern-Expedition Aufschluss gebe