Marine Terpenoid Diacylguanidines: Structure, Synthesis, and Biological Evaluation of Naturally Occurring Actinofide and Synthetic Analogues.

A new diacylguanidine, actinofide (1), has been isolated from the marine mollusk Actinocyclus papillatus. The structure, exhibiting a guanidine moiety acylated by two terpenoid acid units, has been established by spectroscopic methods and secured by synthesis. Following this, a series of structural analogues have been synthesized using the same procedure. All of the compounds have been evaluated in vitro for the growth inhibitory activity against a variety of cancer cell lines.

Exploring the Bioactive Terpenoid Content of an Algerian Plant of the Genus Pulicaria: The ent-Series of Asteriscunolides.

Chemical analysis of the chloroform extract of the aerial parts of the Algerian plant Pulicaria undulata exhibiting anti-inflammatory activity resulted in the isolation of 10 new humulene sesquiterpenoids, 1-10, belonging to the asteriscunolide family of compounds. The structure and relative configuration have been defined by NMR data, whereas the absolute configuration has been established by ECD analysis. Compounds 1-10 include enantiomers of the known asteriscunolides A-D and tetrahydroasteriscunolide previously reported from the genera Asteriscus and Nauplius. Compounds 1 and 10 showed in vitro anti-inflammatory activity by inhibiting heat-induced albumin denaturation with IC50 values of 23.76 and 220.42 µM.

Sequestered fulvinol-related polyacetylenes in Peltodoris atromaculata.

The Mediterranean dorid nudibranch Peltodoris atromaculata that had been collected while feeding on Haliclona fulva was shown to sequester long-chain fulvinol-like polyacetylene metabolites (compounds 2-5) from the prey. They were isolated along with previously reported bromorenierins from the diethyl ether extracts of both the mollusk and the sponge. Their structures were elucidated by NMR spectroscopy and tandem FABMS analysis. Compound 5 exhibited in vitro growth inhibitory effects against the SKMEL-28 melanoma cell line.

Occurrence of a taurine derivative in an antarctic glass sponge.

The n-butanol extract of an Antarctic hexactinellid sponge, Anoxycalyx (Scolymastra) joubini, was found to contain a taurine-conjugated anthranilic acid, never reported so far either as a natural product or by synthesis. The compound was inactive against human cancer cells in an in vitro growth inhibitory test, and also showed no antibacterial activity.

Extending the record of bis-γ-pyrone polypropionates from marine pulmonate mollusks.

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.

Bioactive terpenes from Spongia officinalis.

The terpene metabolite pattern of Mediterranean Spongia officinalis was chemically investigated. This study resulted in the isolation of a series of sesterterpenes and C21 furanoterpenes, according to the literature data on this sponge. Four new oxidized minor metabolites (compounds 1, 2, 3, and 4) were isolated along with six known compounds of the furospongin series (compounds 5-8, 9, and 10) and three scalarane sesterterpenes (compounds 11-13). Interestingly, tetrahydrofurospongin-2 (6) and dihydrofurospongin-2 (7), which were among the main metabolites, induced biofilm formation by Escherichia coli. All compounds isolated were also assayed for antibacterial and antifungal properties.

Aromatic cyclic peroxides and related keto-compounds from the Plakortis sp. component of a sponge consortium.

Six unreported aromatic compounds, 1-6, were isolated, along with the known compounds dehydrocurcuphenol and manoalide, from a sample of Plakortis sp., which was the main component of a Pacific sponge consortium. The new molecules were chemically characterized by spectroscopic methods. Compounds 1-4 contain a six-membered cyclic peroxide, whereas 5 and 6 display a terminal methyl ketone. The new metabolites were tested for antifungal and antibacterial properties. Compounds 1 and 4 were weakly active against S. aureus.

Chemistry of Glossodoris nudibranchs: specific occurrence of 12-keto scalaranes.

With the aim of establishing whether the oxidation of the tricyclic carbon skeleton of scalaradial (1) is specific to Glossodoris mollusks, the chemical investigation of specimens of Glossodoris pallida from two distinct geographical areas (China and Guam) and of Glossodoris vespa and Glossodoris averni from Eastern Australia was performed. 12-Deacetoxy-12-oxo-scalaradial (4), recently reported from another Glossodoris nudibranch, was the main metabolite of G. pallida from China, G. vespa, and G. averni. A series of scalarane compounds 3 and 5-11, including the unprecedented 12,16-deacetoxy-12-oxo-scalarafuran 5, was isolated from the mollusks. Interestingly, a population of G. pallida from Guam displayed a different scalarane pattern that was characterized by scalaradial (1), deacetyl scalaradial (2), and deoxoscalarin (3), thus confirming previous reports. The specific occurrence of 12-keto-derivatives in some nudibranchs of the genus Glossodoris is discussed.

New caulerpenyne-derived metabolites of an Elysia sacoglossan from the South Indian coast.

Chemical analysis of the secondary metabolite pattern of the sacoglossan mollusc Elysia cf. expansa, collected along South Indian coasts, showed the presence of the typical Caulerpa-derived sesquiterpene caulerpenyne (1) and two new minor co- occurring metabolites, the compounds dihydrocaulerpenyne (4) and expansinol (5). The chemical characterization of these molecules, structurally related to 1, is reported.

Isocyanide terpene metabolites of Phyllidiella pustulosa, a nudibranch from the South China Sea.

A series of isocyanides, compounds 4-11, including diterpenes never before found in Phyllidiid nudibranchs, have been isolated from a Chinese population of the nudibranch Phyllidiella pustulosa. Three new sesquiterpenes (8, 10, and 11), with eudesmane, guaiane, and bisabolane skeletons, respectively, have been characterized by spectral methods and chemical comparison with known related molecules. The absolute stereochemistry of the major metabolite, the isocyanide 8, an enantiomer of the known sponge metabolite stylotelline (12), has also been determined.