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Polyaxibetaines A-C, three unique amino acids derivatives isolated from the marine sponge Axinella polypoides.
No full textBetaines and similar zwitterionic compounds are widely distributed in terrestrial plants and algae, as well as in marine invertebrates. In biological systems, these highly soluble dipolar molecules serve as organic osmolytes (osmoprotectants), namely substances synthesized or taken up from the environment by cells for protection against osmotic stress. Osmoprotectants can stabilize proteins and membranes when salt levels or temperatures are unfavourable; therefore, they could play important roles in the adaption of cells of marine invertebrates to various adverse environmental conditions.
Examples of betaines isolated from marine invertebrates are homarine,1 trigonelline,2 taurines, baikiain betaine,3 β-stachydrine, 4 nor- and aminozooanemonin, 5 pyridinebetaines A and B.5 Most of these compounds are amphoteric low-molecular weight quaternary ammonium compounds deriving from proteinogenic or non- proteinogenic amino acids in which the nitrogen atom if fully methylated. Within a recent investigation of alkaloids from Axinella sponges, we have examined specimens of Axinella polypoides collected along Sardinian coasts and we have isolated three novel unique compounds, polyaxibetaines A-C (1-3), whose structure elucidations are the subject of this paper.Polyaxibetaines A-C extend the structural variety of the so far known betaines; in compounds 1 and 2, indeed, the nitrogen atom of the -amino group of phenylalanine and tyrosine, respectively, is comprised in a piperidine ring and further methylated, while compound 3 is a pyridine derivative sharing the nitrogen atom with the alfa-amino group of a tyrosine residue
Study about stereochemistry of Turbinamide, a strong cytotoxic agent from marine ascidian Sidnyum turbinatum
No full textConisulfamines A-C, novel unique alkyl sulfoxides from the Mediterranean ascidian Aplidium conicum
No full textAscidians belonging to the Aplidium genus are characterized by a great chemiodiversity that includes nitrogenous and non-nitrogenous metabolites, this latter group being dominated by prenyl quinones/hydroquinones, linear or cyclic derivatives1. These compounds are generally known as meroterpenes. Recently, we analyzed a sample of Aplidium conicum collected in the Bay of Naples and, surprisingly, the pattern of its secondary metabolites resulted very different from that of other samples of A. conicum previously investigated. In fact, the ascidian is completely lacking in meroterpenoids, whilst the main components of its methanolic extract are a new class of molecules, unsaturated linear alkylsulfoxides, whose major constituents are Conisulfamines A, B, and C. The structures of the new compounds have been elucidated through an extensive application of MS, 1H, 13C and 2D homo-and heteronuclear-NMR techniques. The stereochemical analysis of Conisulfamine A has been carried out in a three stages–approach, relying on the combination of NMR spectroscopy and computational methods
Polysubstituted alkyl sulfates with antiproliferative activity from different species of Mediterranean ascidians
No full textComplex polysubstituted alkyl sulfates have been isolated from ascidians; a remarkable example is turbinamide, a bioactive metabolite isolated in our laboratory from Sidnyum turbinatum. This molecule demonstrated a strong and selective cytotoxic effect against neuronal rather than immune system cells. We have indeed isolated two new sulphated compounds (1 and 2) from another collection of S. turbinatum; as well as two new molecules (3 and 4) from two different Mediterranean ascidians (Sidnyum elegans and Ciona edwardsii). Their structural analogy with turbinamide allowed evaluating the influence of slight structural modifications on the activity
Conithiaquinones A and B, tetracyclic cytotoxic meroterpenes from the Mediterranean ascidian Aplidium conicum
No full textChemical investigation of the Mediterranean ascidian A.conicum resulted in the isolation of two new meroterpenes, the conithiaquinones A (1) and B (2), in addition to two previously reported chromenols (3 and 4) and conicaquinones (5 and 6). The structures of conithiaquinones A and B were determined by interpretation of spectroscopic data, and regiochemical and stereochemical assignments were achieved with the aid of computational methods, including the recently developed DP4 NMR spectral prediction method. Both conithiaquinones A and B showed significant effects on the growth and viability of cells, with 1 showing interesting cytotoxicity against human breast cancer cells
Aplisulfamines, Unique Natural Sulfoxides from Aplidium sp.: Assignment of Sulfur and Carbons Absolute Configuration through an Unprecedented Combination of Spectroscopic and Computational Methods
No full textThe occurrence of sulfoxides in nature is limited, being confined mostly to peptide derivatives containing methionine- or b,b-dimethylmethionine S-oxides, podolactones, metabolites from onions and from other Allium species as well as from a few marine organisms. In the frame of a research project devoted to the study of secondary metabolites of Mediterranean tunicates, we have isolated two novel natural sulfoxides, aplisulfamines A e B (1 and 2), from an Aplidium sp. collected in the Bay of Naples. In the present communication we report about the isolation and structure determination of these two unique compounds. The assignment of absolute configuration of chiral sulfur and carbon atoms present in the molecules 1 and 2 was achieved by an unprecedented approach based on a combination of NMR experiments and CD studies assisted by computational methods
New natural sulfoxides from a Mediterranean Aplidium sp : absolute configuration assignment through combination of spectroscopic and computational methods
No full textAscidians belonging to the genus Aplidium of the Polyclinidae family are renowned for the variability of their metabolic content. A great chemiodiversity is devised from non-nitrogenous metabolites, mainly prenyl quinones or hydroquinones, to a vast array of nitrogenous metabolites. Within a research project directed to the study of the chemistry of marine ascidians from the Mediterranean sea we have investigated an Aplidium sp. collected in the Bay of Naples. It revealed a very unusual metabolic content, since it was completely lacking in meroterpenes, whilst the major component of its methanol extract was shown to be a group of unique alkyl sulfoxides.
The structures of the novel metabolites have been elucidated through extensive spectroscopic analysis and their stereochemical analysis has been carried out in a three stages-approach, relying on the combination of NMR spectroscopy, CD studies, and computational method
Marine natural meroterpenes from Aplidium conicum: structures, synthesis and pharmacology
No full textMeroterpenes are compounds of mixed biosynthesis, mostly quinones or hydroquinones bonded with a terpenoid portion. In the marine environment, these secondary metabolites are isolated mainly from brown algae, but other sources include microorganisms, soft corals and invertebrates. Among marine ascidians, they have been found almost exclusively in species belonging to the genus Aplidium, which have been the source of a vast array of prenyl-quinone, -hydroquinone, -chromene, and/or -chromane derivatives, either linear or cyclic, originated from intra- and inter-molecular cyclizations and/or rearrangements, thus giving macrocyclic or policyclic skeletons, often linked to amino acids or taurine residues. We have isolated from several collections of A. conicum a large group of unique meroterpenes. One of these compound has been used as model compound for the synthesis of synthetic analogues in which the prenyl chain is replaced by other alkyl chains; both the synthetic analogues and the natural metabolite were subjected to pharmacological screenings and were shown to possess interesting biological effects, depending on the nature and the length of side chain linked to the benzoquinone ring and, mainly, on its position respect to the dioxothiazine ring. Our studies revealed exemplify the potential of a natural product to qualify as lead structure for medicinal chemistry campaigns, affording simplified analogues with better bioactivity and easier to synthesize
Chemical Diversity of the Mediterranean sponge Axinella polypoides
No full textAmong the multitude of marine organisms, some of them appear to possess a much more efficient synthetic potential. This capacity doesn’t represent the attribute of a single species, but it is shared by a number of other sponges, tunicates, bryozoans or molluscs. The consequent uncommon chemodiversity of these invertebrates is a resource to be adequately exploited. The extremely rich secondary metabolism of some marine invertebrates can be illustrated through the case of the sponge Axinella polypoides, whose chemical analysis, revealed an incredible variety and abundance of secondary metabolites, some of them being new molecues. The structures of all the isolated metabolites have been elucidated mainly by spectroscopic methods (HRESIMS, 2DNMR, ECD) with the support of computational methods
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