The chemical investigation of the Caribbean sponge Agelas citrina revealed four new pyrrole–imidazole alkaloids (PIAs), the citrinamines A–D (1–4) and the bromopyrrole alkaloid N-methylagelongine (5). All citrinamines are dimers of hymenidin (6) which was also isolated from this sponge as the major metabolite. Citrinamines A (1) and B (2) are derivatives of the PIA dimer mauritiamine (7), whereas citrinamine C (3) is derived from the PIA dimer nagelamide B (8). Citrinamine D (4) shows an uncommon linkage between the imidazole rings of both monomeric units as it is only observed in the benzocyclobutane ring moiety of benzosceptrins A–C (9–11). Compound 5 is the N-methyl derivative of agelongine (12) which consist of a pyridinium ring and an ester linkage instead of the aminoimidazole moiety and the common amide bond in PIAs.

Four new diterpenes (1–4) together with six known members of this family were isolated from the brown alga Bifurcaria bifurcata collected off the coast near Roscoff, France. The structures of the new compounds were established in a comprehensive study on the basis of 1D and 2D NMR spectroscopic and mass spectrometric (ESI-MS) analyses. Our assignment is supported by a comparison of the 13C NMR chemical shifts to known compounds and predicted values. The new diterpenes are derivatives of the diterpene eleganolone (5). The structural relation and hypothetical metabolic pathway of the new diterpenes (1–4) with the co-isolated known diterpenes are discussed.

The chemistry of the burrowing sponge Aka coralliphagum was investigated to identify chemically labile secondary metabolites. The HPLC-MS analysis of the two growth forms typica and incrustans revealed different metabolites. The previously unknown sulfated compounds siphonodictyals B1 to B3 (6-8), corallidictyals C (9) and D (10), and siphonodictyal G (11) were isolated, and their structures were elucidated by NMR and MS experiments. The compounds were tested in a DPPH assay, in antimicrobial assays against bacteria, yeasts, and fungi, and in antiproliferation assays using cultures of mouse fibroblasts. The biological activity was linked to the presence of the ortho-hydroquinone moiety.

Two new bromopyrrole alkaloids were isolated from the Caribbean sponge Stylissa caribica. The new natural products, 4-bromopyrrole-2-carboxyargi nine (1) and 4-bromopyrrole-2-carboxy-N(epsilon)-lysine (2), are derivatives of amino acids linked with a 4-bromopyrrole-2-carboxylic acid. The structures were elucidated on the basis of NMR and MS/MS data and their absolute configurations assigned via synthesis.

Previous studies have indicated that Caribbean reef sponges of the common genus Agelas are chemically defended from fish predators by brominated pyrrole alkaloids: Agelas clathrodes and A. wiedenmayeri by 4,5-dibromopyrrole-2-carboxylic acid (1) and oroidin (2), A. conifera by sceptrin (3). In this study, we expand our understanding of chemical defense in this sponge genus to include an extensive HPLC quantification analysis of the defensive metabolites in tissues of A. cerebrum, A. cervicornis, A. dilatata, A. dispar and A. sceptrum. A. cervicornis and A. dispar contained the same two major metabolites as A. clathrodes and A. wiedenmayeri, while A. cerebrum, A. dilatata and A. sceptrum contained a mixture of dimeric bromopyrrole alkaloids dominated by sceptrin, similar to A. conifera. At natural volumetric concentrations, both crude extracts and purified compounds from each species were unpalatable to a common generalist reef fish, Thalassoma bifasciatum, in aquarium assays, and inhibited attachment of the marine bacterium Vibrio harveyi in surface fouling assays. Brominated pyrrole alkaloids may play multiple ecological roles in protecting sponges of the genus Agelas.

There are a large number of studies on sponges from warm or tropical waters, whereas little is known about the chemistry of sponges from Arctic waters. Here, we describe the isolation and structure elucidation of two new 3-alkyltetrahydropyridine alkaloids (haliclamines C and D) from the Arctic sponge Haliclona viscosa. MS and 2D NMR spectroscopy were used to analyse the structure of the two new compounds. Since the haliclamines consist of long alkyl chains, MS/MS methods were necessary for the unambiguous assignment of the constitution of the new alkaloids. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004).

Previous studies have indicated that Caribbean reef sponges of the common genus Agelas are chemically defended from fish predators by brominated pyrrole alkaloids: Agelas clathrodes and A. wiedenmayeri by 4,5-dibromopyrrole-2-carboxylic acid (1) and oroidin (2), A. conifera by sceptrin (3). In this study, we expand our understanding of chemical defense in this sponge genus to include an extensive HPLC quantification analysis of the defensive metabolites in tissues of A. cerebrum, A. cervicornis, A. dilatata, A. dispar and A. sceptrum. A. cervicornis and A. dispar contained the same two major metabolites as A. clathrodes and A. wiedenmayeri, while A. cerebrum, A. dilatata and A. sceptrum contained a mixture of dimeric bromopyrrole alkaloids dominated by sceptrin, similar to A. conifera. At natural volumetric concentrations, both crude extracts and purified compounds from each species were unpalatable to a common generalist reef fish, Thalassoma bifasciatum, in aquarium assays, and inhibited attachment of the marine bacterium Vibrio harveyi in surface fouling assays. Brominated pyrrole alkaloids may play multiple ecological roles in protecting sponges of the genus Agelas.

Previous studies have determined that Caribbean reef sponges of the genus Agelas are chemically defended from fish predation by brominated pyrrole alkaloids, and that the compounds responsible for this defense have been elucidated for 1 species, A. clathrodes. In this study, we expand our understanding of chemical defense in this common sponge genus to include the characterization of defensive metabolites in the tissues of A. wiedenmayeri and A. conifera. Bioassay-directed isolation of defensive metabolites was undertaken using fish feeding assays carried out in laboratory aquaria and in the field. A. wiedenmayeri contained the same 2 major metabolites as A. clathrodes, 4,5-dibromopyrrole-2-carboxylic acid (1), and oroidin (2), in addition to a small amount of bromoageliferin (7). The 2 major metabolites were present at higher concentrations in samples of A. wiedenmayeri than in A. clathrodes, and their relative concentrations were reversed, with A. wiedenmayeri on average containing more 4, 5-dibromopyrrole-2-carboxylic acid (1) (2.0 mg ml(-1)) than oroidin (2) (0.8 mg ml(-1)). A. conifera contained a mixture of dimeric bromopyrrole alkaloids dominated by sceptrin (3), with <10% each of dibromosceptrin (5), bromoageliferin (7), dibromoageliferin (8), ageliferin (6), and bromosceptrin (4). Mean concentration of sceptrin (3) in sponge tissue was 5.3 mg ml(-1); this compound deterred feeding of reef fish in aquarium assays at 1.0 mg ml(-1), the lowest concentration assayed. Sceptrin (3) concentrations were higher in sponges collected in the southern Bahama Islands than in those collected in the middle Bahamas, but the reasons for this variation remain unclear. The structure-activity relationship of the pyrrole group was investigated by assaying derivatives of the active metabolites. Feeding deterrent activity of the molecule was enhanced by the addition of bromine to the pyrrole group, but not affected by exchange of the heteroatom from N to O or S. Combining an understanding of the structure-activity relationship of Agelas metabolites with an understanding of the variation in these metabolites across the genus may provide insight into the evolution of defensive chemistry in this highly successful taxa of pan-tropical sponges.

A detailed analysis of the chemical constituents of a specimen of Agelas wiedenmayeri (Alcolado, 1984) was performed. Four brominated alkaloids (1−4) were isolated and one was identified as a new bromopyrrole metabolite. The structure of the new compound, 1, was assigned using spectroscopic methods. Compounds 2 and 3, which are the major brominated metabolites, have been previously described from other Agelas sponges. The new compound, 1, may be a biosynthetic precursor for oroidin-like derivatives.

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Peptides from small combinatorial libraries, covalently attached to polymeric TentaGel beads, can be directly sequenced using amino acid analysis. For libraries with restricted diversity, generated by the split-mix synthesis method, the amino acids on a selected single bead identified by pre-column derivatization with o-phthaldialdehyde (OPA) correlate directly with the sequence of a given peptide. This is shown on a tripeptide (343 different compounds) and a tetrapeptide (4096 different compounds) library. This method allows for rapid peptide sequence determination without relying on complex encoding strategies.