Covering the literature on cold-water marine natural products from 2006 to 2016.This is an update report on marine natural products isolated from cold-water organisms in the last decade, following the previous review that covered the literature up to 2005. Emphasis is given to the biological activities as well as the spectroscopic methods used for the structure elucidation of the new metabolites isolated from cold-water habitats.

The present study examines aspects of palatability and chemical defense in the early life history stages of 7 common species of shallow-water antarctic marine invertebrates with contrasting modes of reproduction. These included the spawned eggs and larvae of a sea urchin and the intraovanan eggs of a sea star, both with planktotrophic larvae, and the lecithotrophic embryos and larvae of 3 sea stars with elther brooding 01-broadcast~ng modes of reproduction. In addition, a sponge and a nudibranch with brooded lecithotrophic embryos and e g g nbbons, respectively, were investigated. Ovaries containing eggs, spawned eggs, and developing embryos or larvae were tested for their palatability against 3 common sympatric predators representing widely disparate feeding patterns: the sea star Odontaster vahdus [ d benthic scavenger), the sea anemone Isotealia aritarctlca (a benthic filter feeder and opportunistic carnivore) and the amphipod Paramoera walkeri (a benthic and water column scavenger). Alginate feeding pellets containing hydrophilic and lipophilic extracts of spawned eggs of the broadcasting planktotrophic sea urchin Sterechinus neumayeri and ovaries containing developing eggs of the broadcasting planktotrophic sea star 0. validus were readily consumed by all 3 predators. Pellets containing hydrophilic and lipophilic extracts of 4-armed echinoplutei larvae of S. neumayeri offered to the sea anemone I. antarctica were also consumed, indicating a lack of chemical defense. In contrast, a t least 1 of the 3 predators demonstrated feeding inhibition to eggs, embryos, larvae or their hydrophilic or lipophilic extracts in the remaining 5 lecithotrophic species. In the lecithotrophic sea star Diplasteria brucei w e demonstrate that the basis of rejection is chemically mediated. It is likely that rejection among the other 4 lecithotrophic species is also chemically based a s eggs, embryos and larvae are conspicuous and high in energy content, lack morphological defenses, and are immobile or sluggish swimmers Our findings Indicate predators display species-specific feeding deterrent responses and support observations that lecithotrophic embryos or larvae may be particularly well suited to chemical defenses. Chemical defense in early life history stages may be especially important in shallow antarctic seas where species with lecithotrophic development patterns are relatively common, and where conspicuous yolky embryos or larvae may spend a considerable period of time developing in benthic or pelagic environments prior to recruitment.

Polar marine ecosystems hold the potential for bioactive compound biodiscovery, based on their untapped macro- and microorganism diversity. Characterization of polar benthic marine invertebrate-associated microbiomes is limited to few studies. This study was motivated by our interest in better understanding the microbiome structure and composition of the ascidian, Synoicum adareanum, in which palmerolide A (PalA), a bioactive macrolide with specificity against melanoma, was isolated. PalA bears structural resemblance to a hybrid nonribosomal peptide-polyketide that has similarities to microbially-produced macrolides. We conducted a spatial survey to assess both PalA levels and microbiome composition in S. adareanum in a region of the Antarctic Peninsula near Anvers Island (64°46′ S, 64°03′ W). PalA was ubiquitous and abundant across a collection of 21 ascidians (3 subsamples each) sampled from seven sites across the Anvers Island Archipelago. The microbiome composition (V3–V4 16S rRNA gene sequence variants) of these 63 samples revealed a core suite of 21 bacterial amplicon sequence variants (ASVs)—20 of which were distinct from regional bacterioplankton. ASV co-occurrence analysis across all 63 samples yielded subgroups of taxa that may be interacting biologically (interacting subsystems) and, although the levels of PalA detected were not found to correlate with specific sequence variants, the core members appeared to occur in a preferred optimum and tolerance range of PalA levels. These results, together with an analysis of the biosynthetic potential of related microbiome taxa, describe a conserved, high-latitude core microbiome with unique composition and substantial promise for natural product biosynthesis that likely influences the ecology of the holobiont.

From the CH 2 Cl 2 extract of the Antarctic sponge Dendrilla antarctica we found spongian diterpenes, including previously reported aplysulphurin (1), tetrahydroaplysulphurin-1 (2), membranolide (3), and darwinolide (4), utilizing a CH 2 Cl 2 / MeOH extraction scheme. However, the extracts also yielded diterpenes bearing one or more methyl acetal functionalities (5−9), two of which are previously unreported, while others are revised here. Further investigation of diterpene reactivity led to additional new metabolites (10−12), which identified them as well as the methyl acetals as artifacts from methanolysis of aplysulphurin. The bioactivity of the methanolysis products, membranoids A−H (5−12), as well as natural products 1−4, were assessed for activity against Leishmania donovani-infected J774A.1 macrophages, revealing insights into their structure/activity relationships. Four diterpenes, tetrahydroaplysulphurin-1 (2) as well as membranoids B (6), D (8), and G (11), displayed low micromolar activity against L. donovani with no discernible cytotoxicity against uninfected J774A.1 cells. Leishmaniasis is a neglected tropical disease that affects one million people every year and can be fatal if left untreated.