Search

NPY is among the most abundant neuropeptides in vertebrate brain and is primarily involved in the regulation of food intake. The NPY system is also associated with the aging process showing beneficial effects on neuronal survival via autophagy modulation. Here, we explore the age-related regulation of NPY in the brain and foregut of the shortest- and longest-lived fish species, Nothobranchius furzeri and Danio rerio, respectively. These two research models, despite some similarities, display profound biological differences making them attractive vertebrates to elucidate the mechanisms underlying the regulation of neuropeptide synthesis and function. It is noteworthy that in both fish species only Npya has been identified, while in the other teleosts two classes of NPY (Npya and Npyb) have been annotated. Our findings document that in both species: (i) NPY is centrally regulated; (ii) NPY levels increase in the brain during aging; (iii) NPY is localized in the enteroendocrine cells as well as in the myenteric plexus and drastically decreases in old animals. According to our data, the age-related regulation in the gut resembles that described in other vertebrate species while the increased levels in the brain offer the unique possibility to explore the role of NPY in model organisms to develop future experimental and translatable approaches.

The identification of novel strategies to control Helicobacter pylori (Hp)-associated chronic inflammation is, at present, a considerable challenge. Here, we attempt to combat this issue by modulating the innate immune response, targeting formyl peptide receptors (FPRs), G-protein coupled receptors that play key roles in both the regulation and the resolution of the innate inflammatory response. Specifically, we investigated, in vitro, whether Caulerpin—a bis-indole alkaloid isolated from algae of the genus Caulerpa—could act as a molecular antagonist scaffold of FPRs. We showed that Caulerpin significantly reduces the immune response against Hp culture filtrate, by reverting the FPR2-related signaling cascade and thus counteracting the inflammatory reaction triggered by Hp peptide Hp(2–20). Our study suggests Caulerpin to be a promising therapeutic or adjuvant agent for the attenuation of inflammation triggered by Hp infection, as well as its related adverse clinical outcomes.

A new bis-gamma-pyrone polypropionate, 4,16-di-epi-onchidiol (1), along with three known related compounds (2-4) were isolated from the marine pulmonate mollusk Onchidium sp. The structure of compound 1 was elucidated by extensive spectroscopic analysis and by comparison the NMR data with its stereoisomers 2-4, whereas its absolute configuration was determined by the combination of X-ray diffraction analysis and TDDFT-ECD calculation. In bioassay, the isolated compounds exhibited broad cytotoxicity against several cancer cell lines with IC50 values ranging from 24.6 to 88.5?M.

Terpene content of two distinct collections of the nudibranch Phyllidia coelestis from the South China Sea has been chemically analyzed. A series of amphilectene diterpenes, most likely of dietary origin, with isocyano and formamido functionalities have been isolated from both collections and spectroscopically characterized by an exhaustive nuclear magnetic resonance (NMR) analysis. Interestingly, the structural architecture of compounds 5&ndash, 7 and 9 with both 8,13-cis and 12,13-cis ring junctions is unprecedented in the amphilectene skeleton. Metabolite 3, which was the most abundant in the nudibranch&rsquo, s mantle, has been shown to deter feeding by a generalist predator, supporting its involvement in chemical defense.

Heterobranchs are a fascinating group of marine mollusks that are recognized as an important source of bioactive natural products. Often, these molecules, which are either selected from the diet or de novo biosynthesized by the mollusks, play a fundamental role for their survival being utilized as defensive chemicals against predators. A summary of the studies carried out by our group, in the last decade, on heterobranchs is presented here. A number of new compounds exhibiting different molecular architectures have been chemically characterized. Some of them have also shown an interesting pharmacological potential. Some ecological studies that we conducted on selected species of heterobranchs are also reviewed.

The biological invasion of the green algae Caulerpa cylindracea represents a serious scientific and public issue in the Mediterranean Sea, essentially due to strong modifications both to habitat structure and native benthic communities. Although alterations in health status and changes in flesh quality of some marine species (dietary exposed to C. cylindracea) have been observed, no studies on cause-effect relationships have been carried out. Here, for the first time, through a controlled feeding experiment followed by 1H NMR Spectroscopy and multivariate analysis (PCA, OPLS-DA), we showed that caulerpin taken with diet is directly responsible of changes observed in metabolic profile of fish flesh, including alteration of lipid metabolism, in particular with a reduction of &omega, 3 PUFA content. The potential of caulerpin to directly modulate lipid metabolism opens up new questions about causal mechanism triggered by algal metabolite also in view of a possible exploitation in the nutraceutical/medical field.

Although the chemical warfare between invasive and native species has become a central problem in invasion biology, the molecular mechanisms by which bioactive metabolites from invasive pests influence local communities remain poorly characterized. This study demonstrates that the alkaloid caulerpin (CAU)&mdash, a bioactive component of the green alga Caulerpa cylindracea that has invaded the entire Mediterranean basin&mdash, is an agonist of peroxisome proliferator-activated receptors (PPARs). Our interdisciplinary study started with the in silico prediction of the ligand-protein interaction, which was then validated by in vivo, ex vivo and in vitro assays. On the basis of these results, we candidate CAU as a causal factor of the metabolic and behavioural disorders observed in Diplodus sargus, a native edible fish of high ecological and commercial relevance, feeding on C. cylindracea. Moreover, given the considerable interest in PPAR activators for the treatment of relevant human diseases, our findings are also discussed in terms of a possible nutraceutical/pharmacological valorisation of the invasive algal biomasses, supporting an innovative strategy for conserving biodiversity as an alternative to unrealistic campaigns for the eradication of invasive pests.

Multitargeting or polypharmacological approaches, looking for single chemical entities retaining the ability to bind two or more molecular targets, are a potentially powerful strategy to fight complex, multifactorial pathologies. Unfortunately, the search for multiligand agents is challenging because only a small subset of molecules contained in molecular databases are bioactive and even fewer are active on a preselected set of multiple targets. However, collections of natural compounds feature a significantly higher fraction of bioactive molecules than synthetic ones. In this view, we searched our library of 1175 natural compounds from marine sources for molecules including a 2-aminoimidazole+aromatic group motif, found in known compounds active on single relevant targets for Alzheimer's disease (AD). This identified two molecules, a pseudozoanthoxanthin (1) and a bromo-pyrrole alkaloid (2), which were predicted by a computational approach to possess interesting multitarget profiles on AD target proteins. Biochemical assays experimentally confirmed their biological activities. The two compounds inhibit acetylcholinesterase, butyrylcholinesterase, and beta-secretase enzymes in high-to submicromolar range. They are also able to prevent and revert beta-amyloid (A beta) aggregation of both A beta(1-40) and A beta(1-42) peptides, with 1 being more active than 2. Preliminary in vivo studies suggest that compound 1 is able to restore cholinergic corticohippocampal functional connectivity.

The green alga Caulerpa cylindracea is a non-autochthonous and invasive species that is severely affecting the native communities in the Mediterranean Sea. Recent researches show that the native edible fish Diplodus sargus actively feeds on this alga and cellular and physiological alterations have been related to the novel alimentary habits. The complex effects of such a trophic exposure to the invasive pest are still poorly understood. Here we report on the metabolic profiles of plasma from D. sargus individuals exposed to C. cylindracea along the southern Italian coast, using 1H NMR spectroscopy and multivariate analysis (Principal Component Analysis, PCA, Orthogonal Partial Least Square, PLS, and Orthogonal Partial Least Square Discriminant Analysis, OPLS-DA). Fish were sampled in two seasonal periods from three different locations, each characterized by a different degree of algal abundance. The levels of the algal bisindole alkaloid caulerpin, which is accumulated in the fish tissues, was used as an indicator of the trophic exposure to the seaweed and related to the plasma metabolic profiles. The profiles appeared clearly influenced by the sampling period beside the content of caulerpin, while the analyses also supported a moderate alteration of lipid and choline metabolism related to the Caulerpa-based diet.

Olfaction is considered a distance sense; hence, aquatic olfaction is thought to be mediated only by molecules dissolved in water. Here, we challenge this view by showing that shrimp and fish can recognize the presence of hydrophobic olfactory cues by a “tactile” form of chemoreception. We found that odiferous furanosesquiter- penes protect both the Mediterranean octocoral Maasella edwardsi and its specialist predator, the nudibranch gastropod Tritonia striata, from potential predators. Food treated with the terpenes elicited avoidance responses in the cooccurring shrimp Palaemon elegans. Rejection was also induced in the shrimp by the memory recall of postingestive aversive effects (vomiting), evoked by repeatedly touching the food with chemosensory mouthparts. Consistent with their emetic properties once ingested, the compounds were highly toxic to brine shrimp. Further experiments on the zebrafish showed that this vertebrate aquatic model also avoids food treated with one of the terpenes, after having experienced gastrointestinal malaise. The fish refused the food after repeatedly touching it with their mouths. The compounds studied thus act simultaneously as (i) toxins, (ii) avoidance-learning inducers, and (iii) aposematic odorant cues. Although they produce a characteristic smell when exposed to air, the compounds are detected by direct contact with the emitter in aquatic environments and are perceived at high doses that are not compatible with their transport in water. The mouthparts of both the shrimp and the fish have thus been shown to act as “aquatic noses,” supporting a substantial revision of the current definition of the chemical senses based upon spatial criteria.

Four new uncommon nitrogenous eudesmane-type sesquiterpenes, axiriabilines A-D (1-4), and two known related ones (5 and 6), were isolated from the Hainan sponge Axinyssa variabilis. The structures of the new compounds were elucidated on the basis of extensive spectroscopic analysis and by comparison of their NMR data with those reported in the literature. The absolute configurations of compounds 1 and 4 were determined by TDDFT ECD calculations. All the new compounds were found to exhibit no cytotoxicity against several cancer cells. (C) 2017 Elsevier Ltd. All rights reserved.

Covering: up to 2017 The review summarizes results up to 2017 on chemosensory cues occurring in both aquatic and terrestrial environments. The chemicals are grouped by their physicochemical properties to compare their potential mobility in the different media. In contrast to what is widely asserted in the literature, the report emphasizes that living organisms encounter and sense molecules of various degrees of solubility and volatility both on land and in aquatic environments. The picture that emerges from the review suggests a substantial revision of the traditional definitions of the chemical senses based on their spatial range, which is currently orienting the literature on chemosensory signaling, in favor of a new vision based on the natural products that are the actual mediators of the chemosensory perceptions. According to this perspective, natural product chemistry is a powerful tool with which to explore the evolutionary history of the chemical senses.

Natural products play a key role in the process of chemosensory signalling during an early stage outside the cells, when they bind to molecular sensors (receptors), either 1) after being transported via fluid media (air or water), or 2) after coming in direct tactile contact with the receptors. This first stage is only part of the path that leads to the final interpretation of the chemical signal, involving neuroanatomical and physiological aspects, but it is certainly an ancient part, already developed in very simple forms of aquatic life devoid of complex neurophysiological systems. In spite of this, the current definitions of the chemical senses (olfaction and gustation) are mainly based on the spatial range of the senses, and only take into account the molecular, neurophysiological, and anatomical sensors involved, regardless of the natural products that are the first and essential actors in chemosensory perception. Remarkably, a vast literature entirely ignores the information provided by natural product chemists about the chemical cues available to the different sensors in both aquatic and terrestrial organisms. For example, it is widely believed that aquatic animals do not encounter volatile compounds that are insoluble in water. Surprisingly, this assumption - which is patently wrong through the eyes of a chemist who has isolated many volatile and hydrophobic natural products from marine organisms - pervades the major literature on the neuroanatomy and physiology of the sensory organs of fish and crustaceans and represents one of the most serious obstacles to an effective debate on the evolutionary history of the chemical senses. Recent publications, however, have underlined that many chemosensory cues have been instead conserved during the evolutionary transition from aquatic to terrestrial life, and that aquatic animals can recognize the presence of hydrophobic olfactory cues by a "tactile" form of chemoreception.1-3 Such arguments will be discussed here to emphasize that the information provided by marine natural product chemistry, if adequately decompartmentalized, could become a powerful tool toward a more accurate historical narrative on chemoreception and could lead to a future redefinition of the chemical senses. [1] E. Mollo, A. Fontana, V. Roussis, G. Polese, P. Amodeo, M. T. Ghiselin, Front Chem, 2014, 2, 92. [2] G. Giordano, M. Carbone, M. L. Ciavatta, E. Silvano, M. Gavagnin, M. J. Garson, K. L. Cheney, I. W. Mudianta, G. F. Russo, G. Villani, L. Magliozzi, G. Polese, C. Zidorn, A. Cutignano, A. Fontana, M. T. Ghiselin, E. Mollo, Proc Natl Acad Sci USA, 2017, 114, 3451-3456. [3] E. Mollo, M. J. Garson, G. Polese, P. Amodeo, M. T. Ghiselin, Nat Prod Rep, 2017, 34, 496-513.

Recent studies have shown that the Mediterranean white sea bream Diplodus sargus includes the invasive green alga Caulerpa cylindracea in its diet, with consequent metabolic and enzymatic alterations. As a result of this novel alimentary habit, the bioactive algal red pigment caulerpin has been detected in its tissues. However, this may not be an isolated case: other fish species have also been reported to feed on C. cylindracea, although the possible accumulation of caulerpin in their tissues has not yet been investigated. In this report, we analysed stomach con- tents and caulerpin levels in the native sparid species Spondyliosoma cantharus, Sarpa salpa, and Diplodus vulgaris, and in the scarid Sparisoma cretense, along with the Lessepsian siganid Siganus luridus. C. cylindracea was found in the stomachs of all but one fish species, the exception being S. cretense, in which prey items could not be determined due to the high degree of diges- tion. Chemical analysis of fish tissues revealed that only S. cantharus and S. salpa accumulated caulerpin, while no traces of the compound were detected in the other species. Despite intense research efforts on natural products obtained from C. cylindracea, a complete picture of the impacts caused by fish including this alga in their diet has not been elucidated. The identification of caulerpin in other Mediterranean native fish suggests a need for further research in order to assess the possible transfer of such molecules to humans through seafood consumption.

Natural products play a key role in the process of chemosensory signaling, either after being transported via fluid media (air or water), or after coming in direct contact with molecular sensors (receptors). In spite of this, the current definitions of olfaction (the sense of smell) and gustation (the sense of taste) are mainly based on the spatial range of action of the two chemical senses. Accordingly, olfaction is traditionally regarded as a "distance sense", while gustation is considered a "contact sense". This view has led to the belief that "odors" for aquatic animals are molecules in solution, just because in aquatic environments solubility, rather than volatility, is required for the long-distance transport of biomolecules. However, novel perspectives recognize a major source of bias in the above traditional differentiation between taste and smell (1,2), developing the insight that odorant compounds can also be detected by means of "tactile" forms of olfaction in aquatic environments. This thesis has been proved by exploring the defensive role of terpenes isolated from aquatic invertebrates, which act both as defensive toxic weapons and as olfactory signals (3). The obtained results will be discussed here to undermine some of the major obstacles for an effective debate on the evolutionary history of chemical communication. References 1.Mollo, E.; Fontana, A.; Roussis, V.; Polese G.; Amodeo, P.; Ghiselin, M. T. Front. Chem. 2014, 2, 92. 2.Mollo, E.; Garson, M. J.; Polese, G.; Amodeo, P.; Ghiselin, M. T. Nat. Prod. Rep. 2017, 34, 496-513. 3.Giordano, G.; Carbone, M.; Ciavatta, M. L.; Silvano, E.; Gavagnin, M.; Garson, M. J.; Cheney, K. L.; Mudianta, I. W.; Russo, G. F.; Villani, G.; Magliozzi, L.; Polese, G.; Zidorn, C.; Cutignano, A.; Fontana, A.; Ghiselin, M. T.; Mollo, E. Proc. Natl. Acad. Sci. USA 2017, 114, 3451-3456.

The red pigment caulerpin, a secondary metabolite from the marine invasive green algae Caulerpa cylindracea can be accumulated and transferred along the trophic chain, with detrimental consequences on biodiversity and ecosystem functioning. Despite increasing research efforts to understand how caulerpin modifies fish physiology, little is known on the effects of algal metabolites on mammalian cells. Here we report for the first time the mitochondrial targeting activity of both caulerpin, and its closely related derivative caulerpinic acid, by using as experimental model rat liver mitochondria, a system in which bioenergetics mechanisms are not altered. Mitochondrial function was tested by polarographic and spectrophotometric methods. Both compounds were found to selectively inhibit respiratory complex II activity, while complexes I, III, and IV remained functional. These results led us to hypothesize that both algal metabolites could be used as antitumor agents in cell lines with defects in mitochondrial complex I. Ovarian cancer cisplatin-resistant cells are a good example of cell lines with a defective complex I function on which these molecules seem to have a toxic effect on proliferation. This provided novel insight toward the potential use of metabolites from invasive Caulerpa species for the treatment of human ovarian carcinoma cisplatin-resistant cells.

Marine sponges of the Irciniidae family contain both bioactive furanosesterterpene tetronic acids (FTAs) and prenylated hydroquinones (PHQs). Both classes of compounds are known for their anti-inflammatory, antioxidant, and antimicrobial properties and known to display growth inhibitory effects against various human tumor cell lines. However, the different experimental conditions of the reported in vitro bioassays, carried out on different cancer cell lines within separate studies, prevent realistic actual discrimination between the two classes of compounds from being carried out in terms of growth inhibitory effects. In the present work, a chemical investigation of irciniid sponges from Tunisian coasts led to the purification of three known FTAs and three known PHQs. The in vitro growth inhibitory properties of the six purified compounds have been evaluated in the same experiment in a panel of five human and one murine cancer cell lines displaying various levels of sensitivity to proapoptotic stimuli. Surprisingly, FTAs and PHQs elicited distinct profiles of growth inhibitory-responses, differing by one to two orders of magnitude in favor of the PHQs in all cell lines. The obtained comparative results are discussed in the light of a better selection of drug candidates from natural sources., SCOPUS: ar.j, info:eu-repo/semantics/published

Five new isocyano/isothiocyanato sesquiterpenes (1-5) with tri- or bicyclic carbon skeletons have been characterized from Australian specimens of the nudibranch Phyllidia ocellata. Spectroscopic analyses at 900 MHz were informed by DFT calculations. The 1S, 5S, 8R configuration of 2-isocyanoclovene (1) was determined by X-ray crystallographic analysis of formamide 6. A biosynthetic pathway to clovanes 1 and 2 from epicaryolane precursors is proposed. Isocyanides 1, 2, and 4 showed activity against Plasmodium falciparum (IC50 0.26-0.30 ?M), while isothiocyanate 3 and formamide 6 had IC50 values of >10 ?M.

Among natural products there are molecules well known to influence the abundance and distribution of marine organisms and to play important roles in their interactions with one another. Recently, chemical ecologists have also started to consider how research on natural products might be useful in understanding marine biological invasions, assessing their impact in the invaded areas, and considering how to deal with them. Their efforts especially focused on the Mediterranean Sea, which is one of the major hotspots of marine biological invasions on earth, showing in what way marine natural products (MNPs) may influence (1) the ability of exotic marine organisms to invade and to get established, (2) how they affect the invaded biota, and (3) public health and the economy. In all cases, the study of such chemical warfare between alien and native species started with the isolation of the pure chemicals required for chemical structure elucidation and subsequent biological testing, implying a central role of natural product chemistry in approaching critical issues in invasion biology. In this position paper we also introduce a theme of possible interest for managing marine invasive species, based on the exploitation of available chemical and biological information on MNPs. We show how a kind of chemical data originally gathered for other objectives--such as obtaining drugs from the sea--might also offer valid alternatives to unrealistic eradication campaigns, becoming the basis for a desirable commercial use of the bioactive compounds obtainable from marine pests, thus paving the way for making the control of invasions profitable. The pests might then be harvested, reducing their impact on marine ecosystems.

The chemical investigation of the marine pulmonate Onchidium sp. and of its defensive mucous secretion led us to the isolation of a novel polypropionate, onchidione (4), containing two g-pyrone rings. The structure of 4 was elucidated by spectroscopic methods, mainly NMR techniques, and secured by X-ray analysis on a single crystal.

Biological invasions are deemed as one of the most severe threats to biodiversity and can result in huge economic impacts on natural resources. Many studies have assessed structural changes caused by the introduction of nonindigenous species, but urgent questions remain to be answered about the complex indirect effects of invasive pests on marine biodiversity at the species and ecosystem level. Previous investigations focusing on the biological invasion by Caulerpa racemosa in the Mediterranean indicated that the lipophilic algal metabolite caulerpin accumulates in the tissues of the native edible white sea bream Diplodus sargus feeding on the exotic alga. The level of caulerpin in D. sargus has been thus used as an indicator of the trophic exposure of the fish to the seaweed and related with adverse effects on the fish health. In the present study, we show that the C. racemosa-based diet can also alter muscle fatty acids composition in the white sea bream by reducing the percentage of polyunsaturated fatty acids of the n-3 and n-6 series, such as eicosapentaenoic (C20:5), docosahexaenoic (C22:6) and arachidonic acids (C20:4). This represents both a real threat to the health of fish unable to biosynthesize these essential fatty acids and an impoverishment of an important source of essential fatty acids for human nutrition, which helps to prevent cardiovascular diseases, diabetes, hepatic steatosis, cancer and neurological disorders. On the whole, this work sheds light on an unexplored and critical aspect of biological invasions with implication on the health of both humans and the environment. © 2014 Springer-Verlag Berlin Heidelberg.

In the Mediterranean Sea, the biological invasion by the green algae Caulerpa racemosa var. cylindracea is maybe the most striking marine sea-bottom landscape change of the last decades. In this paper, we have synthesized the results of 5 years of studies about the C. cylindracea effects on fish of ecological and economic importance, such as the white sea bream Diplodus sargus. We found that a secondary metabolite of C. cylindracea has the potential to enter in trophic chains and accumulate in fish tissues. Ecotoxicological analyses made on tissues of the D. sargus specimens showed alterations of some of main antioxidant systems, such as catalase, glutathione peroxidases and total glutathione, and a significant induction of P450 biotransformation system. We found also that the C. cylindracea based-diet can alter muscle fatty acids composition in the white sea bream by reducing the percentage of polyunsaturated fatty acids (PUFA) of the n-3 and n-6 series, such as eicosapentaenoic (EPA, C20:5), docosahexaenoic (DHA, C22:6) and arachidonic acids (AA, C20:4). On the whole, this work sheds light on an unexplored and critical aspect of biological invasions with implication on the health of both humans and the environment.

The re-investigation of the Mediterranean opisthobranch Thuridilla hopei resulted in the isolation and chemical characterization of three novel nor-diterpene aldehydes, nor-thuridillonals 2-4, structurally related to co-occurring already reported thuridillins. Analogous with the thuridillins, the new molecules were thought to derive from the same dietary precursor epoxylactone 1. © 2014 Elsevier Ltd. All rights reserved.

The green alga Caulerpa racemosa is a non-native, invasive species in the Mediterranean, and an important stressor for several native organisms. The algal capacity to produce secondary metabolites has been suggested to modulate success of the C. racemosa invasion, although many of potentially involved biological pathways still remain unexplored. In this respect, the aim of the present study was to investigate some molecular and cellular effects in the white seabream Diplodus sargus , an ecologically key species, which included the alien C. racemosa in its diet. Organisms were sampled in 2 seasonal periods from 3 locations of Southern Italy, each characterized by different levels of algal abundance. The level of caulerpin, one of the main secondary algal metabolites, in fish tissues has been used as an indicator of the trophic exposure to the seaweed and related with molecular and cellular responses. Chemical analyses indicated that fish from invaded sites can accumulate caulerpin, with liver concentrations ranging from a few up to hundreds of μg/g. Biomarkers analyses revealed only limited alterations of the main antioxidant defences, such as glutathione reductase and levels of glutathione; on the other hand, increased enzymatic activities of cytochrome P450, glutathione S-transferases and acyl CoA oxidase, as well as enhanced gene transcription for peroxisome proliferator-activated receptor alpha, cytochrome P4501A and vitellogenin 1 were observed in fish more exposed to C. racemosa as indicated by liver concentrations of caulerpin higher than 50 μg/g. Despite a direct molecular relationship with this algal metabolite could not be established, our results suggest that a C. racemosa enriched diet can modulate biotransformation and fatty acids metabolism of D. sargus. Assessing whether similar effects represent short- or long-term effects will be of crucial importance to understand consequences on the general health status and reproductive performance of exposed key fish species in the Mediterranean region.

BackgroundStorage of secondary metabolites with a putative defensive role occurs in the so-called mantle dermal formations (MDFs) that are located in the more exposed parts of the body of most and very likely all members of an entire family of marine mollusks, the chromodorid nudibranchs (Gastropoda: Opisthobranchia). Given that these structures usually lack a duct system, the mechanism for exudation of their contents remains unclear, as does their adaptive significance. One possible explanation could be that they are adapted so as to be preferentially attacked by predators. The nudibranchs might offer packages containing highly repugnant chemicals along with parts of their bodies to the predators, as a defensive variant of the strategic theme of the Trojan horse.Methodology and principal findingsWe detected, by quantitative (1)H-NMR, extremely high local concentrations of secondary metabolites in the MDFs of six species belonging to five chromodorid genera. The compounds were purified by chromatographic methods and subsequently evaluated for their feeding deterrent properties, obtaining dose-response curves. We found that only distasteful compounds are accumulated in the reservoirs at concentrations that far exceed the values corresponding to maximum deterrent activity in the feeding assays. Other basic evidence, both field and experimental, has been acquired to elucidate the kind of damage that the predators can produce on both the nudibranchs' mantles and the MDFs.SignificanceAs a result of a long evolutionary process that has progressively led to the accumulation of defensive chemical weapons in localized anatomical structures, the extant chromodorid nudibranchs remain in place when molested, retracting respiratory and chemosensory organs, but offering readily accessible parts of their body to predators. When these parts are masticated or wounded by predators, breakage of the MDFs results in the release of distasteful compounds at extremely high concentration in a way that maximizes their repugnant impact.

The isolation and structure elucidation of 10 unreported polypropionate metabolites (compounds 6-15), structurally related to either ilikonapyrone (1) or onchidione (3), from two onchidiid pulmonate mollusk species are discussed. Structure elucidation was achieved by NMR spectroscopy and chemical correlation with model compounds. Evaluation of in vitro growth-inhibitory properties in human cancer cells was also carried out on some of the isolated polypropionates including previously reported onchidione metabolites.

Three new sulfated meroterpenoids containing sesquiterpene and hydroquinone moieties, namely siphonodictyal A sulfate (1), akadisulfate A (2) and akadisulfate B (3), along with the known siphonodictyal B3 and bis(sulfato)-cyclosiphonodictyol A were isolated from the sponge Aka coralliphaga. Their structures were elucidated on the basis of spectroscopic data. Akadisulfate B and siphonodictyal B3 showed a radical-scavenging activity comparable with that of the known lipophylic antioxidant BHT.

Marine invasive species are having a tremendous impact on the Mediterranean biota, which is losing its biological distinctiveness under the continuous pressure of biological invasions. The new scenario calls for a better understanding of the factors that affect marine biological invasions, and for the development of effective and knowledge-based strategies to face this relevant threat to local biodiversity. Moving in this direction, recent research on selected key cases underlines the importance of natural product-based tools to study poorly characterized biological processes associated to marine invasions (Raniello et al. 2007; Mollo et al. 2008; Terlizzi et al. 2011; Felline et al. 2012). These studies stemmed from a growing interest in the use of natural products as probes to appreciate the remarkable complexity of biological systems. Small organic molecules, in fact, interact with biological targets/macromolecules with high affinity and selectivity, acting as mediators of evolutionarily significant biological phenomena. This is the long-term result of selective pressures, including competition, predation, food resources, and successful reproduction. However, when non-indigenous species invade a new environment, in the absence of past co-evolutionary processes (rapid evolution), their bioactive compounds may start exerting unexpected and dramatic effects on the native communities, playing a critical role in the behaviour, spread, and impact of the invaders. A holistic and decompartmentalized approach to biological invasions, aimed at considering and evaluating the often neglected effects of well-defined chemical entities through progressively higher levels of biological complexity, is proposed here for a better appreciation, monitoring, and management of marine biological invasions. References Raniello R, Mollo E, Lorenti M, Gavagnin M, Buia MC (2007) Biological Invasions 9 : 361-8. Mollo E, Gavagnin M, Carbone M, Castelluccio F, Pozone F, Roussis V, Templado J, Ghiselin MT, Cimino G (2008) Proceedings of the National Academy of Sciences USA 105:4582-6 Terlizzi A, Felline S, Lionetto MG, Caricato R, Perfetti V, Cutignano A, Mollo E (2011) Aquatic Biology 12: 109-17 Felline S, Caricato R, Cutignano A, Gorbi S, Lionetto MG, Mollo E, Regoli F, Terlizzi A (2012) PloS ONE 7(6):e38763.

In this communication, selected results obtained in the course of a 10-year Sino-Italian collaborative project are presented. During this collaboration, several studies on marine organisms collected in the South China Sea have been conducted, resulting in the characterization of a large number of novel natural products. The main interest has been focused on sponges, cnidarians, and molluscs. Here, the recent research, including some not yet published studies, on cnidarians and molluscs, in particular, opisthobranchs and pulmonates, will be briefly described. The study of cnidarians and pulmonates led to isolate molecules, in particular, biscembranoids and polypropionates, displaying carbon skeletons already described in previous papers. Our studies resulted in their complete structural characterization including the absolute stereochemistry that was clarified by coupling X-ray diffraction to circular dichroism (CD) spectra analysis. Some unique nitrogenous molecules containing either an isonitrile function or an 1,2,4-oxadiazole moiety, this latter found for the first time in a marine organism, as well as known sesterterpenoids and diterpenoids were isolated from opisthobranchs. Owing to their anatomical location, these metabolites should play a relevant role in the protection of the molluscs. Finally, a series of alkaloids structurally related to known anticancer agents were also characterized.

The first chemical study of the Indo-Pacific dorid nudibranch Aldisa andersoni resulted in the isolation of five chlorinated phenyl-pyrrolyloxazoles belonging to the phorbazole series. Two new molecules, 9-chloro-phorbazole D and N1-methyl-phorbazole A, co-occurring with known phorbazoles A, B and D, have been characterized. Phorbazoles were found to be present mainly in the external part of the mollusc. The structures of the new compounds were determined by interpretation of spectroscopic data, mainly NMR and mass spectrometry and by comparison with the literature data. Evaluation of feeding-deterrence activity as well as in vitro growth inhibitory properties in human cancer cells was also carried out. © 2012 by the authors; licensee MDPI., SCOPUS: ar.j, info:eu-repo/semantics/published

The green alga Caulerpa racemosa var. cylindracea has invaded Mediterranean seabed including marine reserves, modifying the structure of habitats and altering the distributional patterns of associated organisms. However, the understanding of how such invasion can potentially affect functional properties of Mediterranean subtidal systems is yet to be determined. In this study, we show that C. racemosa changes foraging habit of the native white seabream, Diplodus sargus. In invaded areas, we found a high frequency of occurrence of C. racemosa in the stomach contents of this omnivorous fish (72.7 and 85.7%), while the alga was not detected in fish from a control area. We also found a significant accumulation of caulerpin, one of the main secondary metabolites of C. racemosa, in fish tissues. The level of caulerpin in fish tissues was used here as an indicator of the trophic exposure to the invasive pest and related with observed cellular and physiological alterations. Such effects included activation of some enzymatic pathways (catalase, glutathione peroxidases, glutathione S-transferases, total glutathione and the total oxyradical scavenging capacity, 7-ethoxy resorufin O-deethylase), the inhibition of others (acetylcholinesterase and acylCoA oxidase), an increase of hepatosomatic index and decrease of gonadosomatic index. The observed alterations might lead to a detrimental health status and altered behaviours, potentially preventing the reproductive success of fish populations. Results of this study revealed that the entering of alien species in subtidal systems can alter trophic webs and can represent an important, indirect mechanism which might contribute to influence fluctuations of fish stocks and, also, the effectiveness of protection regimes.

Two indole alkaloids, phidianidines A (1) and B (2), exhibiting an uncommon 1,2,4-oxadiazole ring linked to the indole system, have been isolated from the marine opisthobranch mollusk Phidiana militaris. The structures of the two metabolites have been elucidated by spectroscopic techniques. Phidianidines exhibit high cytotoxicity against tumor and nontumor mammalian cell lines in in vitro assays.

Natural products possess an extraordinary pharmacological effectiveness and specificity compared to artificially designed molecules because evolutionary selection has been the "nature's own high-throughput screening" process for the optimization of biologically active compounds [1,2]. In the case of marine environments, ecological pressures, including competition for space, the fouling of the surface, predation, and successfully reproducing have led to the evolution of unique secondary metabolites with various biological activities. As a result, a broad range of bioactivities has been found within the increasing number of novel secondary metabolites isolated from the under-explored marine sources [3]. This suggests that a better understanding of the ecological role of marine natural products should efficiently contribute to the selection of promising candidates in drug discovery. The purpose of this practical experience is to provide students with opportunities to examine how: (i) chemosensation is essential to food recognition, (ii) chemical stimuli can supply different information depending from the receptor organisms, and (iii) natural products contribute to chemical defense of sessile or slow-moving marine organisms in a structure- and dose-dependent manner. After a preliminary discussion introducing the students to methods used in chemical ecology studies, the work session focuses on the ability of selected metabolites, previously isolated from molluscs and/or sponges, to deter the generalist Mediterranean shrimp Palaemon elegans from feeding (as shown in figure below). This pratical experience follows a recently proposed technique to assay the effects of marine natural products on food palatability [4,5]. Control or treated pellets, prepared by the students themselves, will be presented to shrimps in series of independent replicates. The activity includes both the statistical evaluation of the results to test whether the differences between the treatments and controls are significant, and the graphic representation of the results. References 1. Paterson I., Anderson E.A., 2005. The renaissance of natural products as drug candidates. Science, 310: 451-453. 2. Clardy J., Walsh C. (2004) Lessons from natural molecules. Nature, 432: 829-837. 3. Donia M., Hamman M.T., 2003. Marine natural products and their potential applications as anti-infective agents. Lancet Infect. Dis., 3: 338-48. 4. Mollo E., Gavagnin M., Carbone M., Castelluccio F., Pozone F., Roussis V., Templado J., Ghiselin M.T., Cimino G., 2008. Factors promoting marine invasions: A chemoecological approach. PNAS, 105: 4582-4586. 5. Haber, M., Cerfeda S., Carbone M., Calado G., Gaspar H., Neves R., Maharajan V. , Cimino G., Gavagnin M., Ghiselin M.T., Mollo E., 2010. Coloration and defense in the nudibranch gastropod Hypselodoris fontandraui. Biol. Bull., 218: 181-188.

The flavonoid fraction from the butanol extract of a Mediterranean sample of the seagrass Halophila stipulacea was chemically analyzed. A new malonylated flavone glucoside, genkwanin- 40-O-(6"-malonyl-glucopyranoside) (3), was isolated together with known flavone glucosides 4-9, previously reported only from terrestrial sources. The structure of 3 was established by means of spectroscopic techniques, mainly NMR methods.