Current Organic Chemistry - Volume 21, Issue 5, 2017

Marine organisms represent an enormous reservoir of compounds with many potential applications. Microbes, vegetals and animals from the sea have been exploited for numerous purposes. From seaweeds, in particular, many active compounds can be obtained, such as three important phycocolloids: agar, carrageenan and algin. In this report, an overview is given about biological characteristics, cultivation, agar and bioactive molecules content of the Rhodophyta Gracilaria gracilis; also, agar extraction processes and its traditional and innovative applications are discussed. Cultivation of G. gracilis is subject of several studies and experiments, because there is still much to understand for improving productivity and biomass yield. G. gracilis is one of the best candidates for cultivation and consequent agar extraction, thanks to: fast growth rate, ease of vegetative reproduction, good resistance to salinity and temperature oscillation, good agar qualities. The possibility of farming G. gracilis opens positive perspectives if some factors are taken into account: constant availability of raw material for agar extraction and preservation of ecological balances in natural environments. Agar extraction methods have been also reviewed in terms of improvement related to both agar yield and agar gel strength. As widely acknowledged, the main uses of agar are related to formation of thermoreversible gels at low concentrations in water. It exhibits also many beneficial biological activities including anticoagulant, antiviral, antioxidative, anticancer and immune- modulating activities. Newest applications of agar in pharmaceutical, medical, engineering and other fields are of great interest and are the topic of current and future studies.

This paper reviews several scientific articles regarding levels of organic and inorganic contaminants in a variety of marine species coming from two Sicilian protected areas: the Strait of Messina and Cape Peloro lakes (Ganzirri and Faro). Moreover, different analytical techniques for the determinations of organic and inorganic contaminants, and the procedures adopted for the analyses, are summarized. Quantitative and qualitative determination of organic pollutants was performed by High Resolution Gas Chromatography-Electron Capture Detection and confirmed by Gas Chromatography-Mass Spectrometry. The concentrations of inorganic elements were determined by Atomic Absorption Spectrophotometry, derivative Stripping Chronopotentiometry, Inductively Coupled Plasma-Optical Emission Spectrometry and Inductively Coupled Plasma -Mass Spectrometry. Results provide evidence that organic and inorganic residues found in some of the examined samples were mostly below the Maximum Residue Levels (MRLs). In conclusion, species analyzed in these studies were safe for human consumption and, consequently the investigated environments were estimated as free from toxicological risk.

Sponges are known to be a rich source of structurally diverse bioactive natural products, accounting for approximately one third of the 25,000 novel marine natural products discovered to date. The advancement of molecular techniques, especially next generation sequencing, has revealed a highly diverse and complex microbial consortia associated with sponges. Currently, research is on-going to investigate the role of these microorganisms in symbiosis and in the production of these sponge-associated secondary metabolites. It is hypothesised that adaptations to extreme temperatures and oxygen levels in the Antarctic may result in novel microbial strains with unprecedented bioactive metabolites. Although ecological and environmental factors are believed to play a crucial role in the expression of microbial bioactive secondary metabolites, underpinning the ecological function of microorganism- sponge interactions within Antarctica is poorly understood, despite mounting evidence that these metabolites play an important role in chemical defence and microbial community structure. The importance of the Antarctic ecosystem as a research resource will be underpinned by future global change; therefore it will be vital for ecological approaches to be addressed in addition to these biomedical functions. This review collates studies that assess the biomedical activity of secondary metabolites produced by Antarctic sponge associated microorganisms, which may stimulate the ecological function to be addressed by the community.

A growing percentage of aquatic production worldwide is derived from aquaculture, whose importance is increasing due to commercial overfishing and a rising consumer demand for seafood. This has led to an increased interest in quality improvement and certification of seafood products to guarantee their safety, quality, authenticity, and nutritional benefits. In this context, proteomics has arisen as a promising tool for unravelling the biological, physiological and ecological traits of seafood products, thus improving cost-effectiveness and sustainability of aquaculture. As one of the fastest growing segments of global seafood production, shellfish farming can directly benefit from the application of these high-throughput technologies in search for biomarkers for the detection of shellfish contamination, health, quality, safety and nutritional value. With this in mind, the goal of this review is to highlight the potential of advanced and high-throughput proteomic tools for the evaluation of environmental toxicity and assessment of quality and safety in shellfish species, relevant both as bioindicators and as seafood products. An overview of the different proteomic approaches will be presented, outlining the main advantages, disadvantages and challenges intrinsic to these techniques. Furthermore, several studies where proteomic techniques were applied for a better understanding of the mechanisms underlying alterations in shellfish proteomes are also described.

Marine sponges represent a prolific and chemically diverse source of secondary metabolites, some of which feature hitherto unprecedented carbon skeletons that continue to attract the interest of natural product researchers. The novel chemistry of these metabolites is often accompanied by exceptional bioactivity profiles suggesting these compounds to be potential leads for drug discovery. In recent years, advances in chromatographic and spectroscopic techniques have allowed the identification of structurally complex natural products, even at nanomolar concentrations, thus uncovering the vast potential of marine sponges as sources of novel bioactive compounds. In this review, we present an overview on selected natural products reported from marine sponges from 2010 to 2016. In total, 182 different compounds belonging mainly to the groups of alkaloids, peptides, terpenoids, or polyketides are highlighted based on their unique structural features as well as on their reported bioactivities, which are primarily in the fields of anticancer agents, antibiotics, anti-inflammatory compounds, and neuroprotective agents.

Mechanically interlocked molecules have attracted the attention of scientists widely. With the functionalization of supramolecular systems novel strategies and approaches were used to construct mechanically interlocked molecules. Currently, the mechanically interlocked molecules have been installed on photochromic molecules to design novel photochromic materials. In the recent years, mechanically interlocked molecules-based photochromic materials have received the interest of scientists due to their potential applications in many fields, and many types of functionalized molecular machines were constructed, such as molecular switches and selfassembly systems. In this review, we summarize the recent progress of photochromism in mechanically interlocked molecules.

Background: Over the past decade, simple 1-deoxysphingoid bases with a saturated hydrocarbon sidechain such as spisulosine, xestoaminol C, 3-epi-xestoaminol C, clavaminol A have attracted considerable attention from synthetic organic chemists because of their impressive cytotoxic/antiproliferative properties as well as the unique structures possessing a variously configured vicinal amino alcohol motif. Results: The stereoselective total synthesis of two deoxysphingosines ent-homospisulosine and N,Odiacetylhomoclavaminol A has been accomplished via a common approach. The key steps were a substrate controlled aza-Claisen rearrangement to install the C-N bond together with the required erythro arrangement of the neighbouring amino and hydroxyl functionalities. Further, the spontaneous intramolecular addition to the –NCS moiety proceeded regioselectively to form the requisite oxazolidine-2-thione skeleton. The employed Wittig olefination then completed the carbon backbone of the target molecules. Conclusions: Several newly prepared compounds was assessed for their antiproliferative/cytotoxic activity against six cancer cell lines (Jurkat, HeLa, MDA-MB-231, MCF-7, HTC-116 and Caco-2) using the MTT assay. On the basis of the observed potency, three structures were taken up for further investigation.