Carexanes: prenyl stilbenoid derivatives from Carex distachya

Metabolites with a new molecular skeleton, named carexane, have been isolated from the leaves of Carex distachya. The structures have been determined on the basis of the spectroscopic characteristics of the compounds. Bidimensional NMR has furnished important data useful for the characterization and the stereochemistry of the molecules. The compounds have a tetracyclic skeleton derived from the coupling of the prenyl moiety on a stilbenoid structure.     

Structural elucidation and bioactivity of novel secondary metabolites from Carex distachya

Four new carexanes and a new seco-derivative metabolite have been isolated and characterized from the herbaceous plant Carex distachya Desf. All of the structures have been elucidated on the basis of spectroscopic data. These compounds derive from the cyclization of prenylate stylbenoid precursors. The seco-carexane is formed by a further oxidative cleavage of the C-7-C-8 bond. The absolute configurations have been determined by Mosher's method using appropriate chemical correlations. All of the carexanes A-H have been tested for their phytotoxicity against Lactuca sativa. The bioassays showed an inhibitory effect on seed germination for all compounds described in this report.     

Glandulaurencianols A–C,brominated diterpenes from the red alga, Laurencia glandulifera and the sea hare, Aplysia punctata

Glandulaurencianols A and B were isolated from the organic extract of the red alga, Laurencia glandulifera, collected from the island of Crete in South Greece. Investigation of the mollusk, Aplysia punctata, collected from the coast of Nea Makri, Central Greece, resulted in the isolation of glandulaurencianols A and C. The structures of the new metabolites, as well as their relative configurations, were established on the basis of thorough analyses of their spectroscopic data.     

Calyciphylline G, a novel alkaloid with an unprecedented fused-hexacyclic skeleton from Daphniphyllum calycinum

Calyciphylline G (1), a novel Daphniphyllum alkaloid with an unprecedented fused-hexacyclic skeleton containing a 5-azatricyclo[6.2.1.0^1,5]undecane ring, has been isolated from the stem of Daphniphyllum calycinum (Daphniphyllaceae), and the structure and relative stereochemistry were elucidated on the basis of spectroscopic data.     

New dimeric phenanthrenoids from the rhizomes of Juncus acutus. Structure determination and antialgal activity

In a study of the allelochemical interactions between the wetland plant Juncus acutus and microalgae some dimeric dihydrophenanthrenoids have been isolated. The structures have been determined on the basis of their spectroscopic properties and their phytotoxicity was evaluated on Selenastrum capricornutum.     

Amarantholidols and amarantholidosides: new nerolidol derivatives from the weed Amaranthus retroflexus

Seven new sesquiterpenes, with nerolidol skeleton, have been isolated and characterized from the plant Amaranthus retroflexus, one of the major weeds of the world. The structures have been elucidated on the basis of spectroscopic data. The compounds have been characterized by the presence of hydroxyl groups or a glucopyranosyl moiety in the molecules. The configurations have been determined using Mosher's method. The compounds have been tested for their phytotoxicity on the test species Lactuca sativa. The bioassays showed an inhibitory effect on seed germination for all of compounds at the lowest concentrations.     

Antioxidant benzylidene 2-aminoimidazolones from the Mediterranean sponge Phorbas topsenti

Three new benzylidene 2-aminoimidazolones, named phorbatopsins A-C, have been isolated from the Mediterranean marine sponge Phorbas topsenti, in addition to the known astaxanthin, adonirubin, taurine, and taurobetain. Their structures were elucidated through mass spectrometric and detailed 1D and 2D NMR spectroscopic data. The relative configuration of the molecules was determined on the basis of ¹H and ¹³C chemical shifts and proton-proton coupling constants. The absolute configuration of the chiral carbon C-6 of phorbatopsin B was determined by modified Mosher's method. The antioxidant activity, evaluated through the Oxygen Radical Absorbance Capacity (ORAC) assay, was also reported for the seven isolated compounds and structure-activity relationships are discussed. Phorbatopsin A appeared as the most active with an ORAC value of 0.88. Further investigations to support the promising antioxidant activity of phorbatopsin A will be followed.     

Nitrogenous sesquiterpenes from the Thai marine sponge Halichondria sp.

Five nitrogenous sesquiterpenes having an isonitrile [(−)-axisonitrile-3], a formamide [(+)-axamide-3, axamide-2 and (3S^*,5R^*,6R^*,9R^*)-3-formamido-1(10)-cadinene], and an amine [(−)-halichamine] functionality were isolated from the Thai marine sponge Halichondria sp., together with two steroids, ergosterol and ergosterol peroxide. (−)-Axisonitrile-3 was isolated from the natural source for the first time, while (+)-axamide-3 and (−)-halichamine were new metabolites. The structures of these compounds were elucidated on the basis of their spectroscopic data and by chemical transformations. All sesquiterpenes were tested for their cytotoxic activity against six cancer cell lines (HeLa, HuCCA-1, A549, MOLT-3, HepG2, MDA-MB231). Only (−)-axisonitrile-3 showed strong activity to the HepG2 cell line with an IC₅₀ value of 1.3 μM.     

Lansai A-D, secondary metabolites from Streptomyces sp. SUC1

Streptomyces sp. SUC1, endophytic on the aerial roots of Ficus benjamina was isolated and characterized on the basis of its morphology, amino acid composition of the whole-cell extract, and genomic DNA. Four novel secondary metabolites, lansai A-D, were isolated from the culture of this endophyte. The structures were identified by spectroscopic data. The compounds were tested for anticancer and antifungal activities.     

Sinularianins A and B, novel sesquiterpenoids from the Formosan soft coral Sinularia sp.

Two novel sesquiterpenoids, sinularianins A and B (1 and 2), have been isolated from the Formosan coral Sinularia sp. The skeleton of sinularianins A (1), namely sinulariolane, was found to be unprecedented. Sinularianin B (2), with a novel spiro-butenolide moiety, possesses a valerenane skeleton, which had been reported mostly from the plant. The structures of both metabolites were established by extensive analysis of spectroscopic data.     

Acremines A-F, novel secondary metabolites produced by a strain of an endophytic Acremonium, isolated from sporangiophores of Plasmopara viticola in grapevine leaves

Six novel metabolites, acremines A-F have been isolated from agar cultures of a strain of Acremonium sp. Their structures and stereochemistry were elucidated using a combination of ¹³C and ¹H homo and heteronuclear 2D NMR experiments and X-ray analysis. Acremines A-D inhibited the germination of sporangia of Plasmopara viticola.     

Acremines H-N, novel prenylated polyketide metabolites produced by a strain of Acremonium byssoides

Five novel metabolites, acremines H-N, have been isolated from malt extract-peptone-glucose agar cultures of a strain of Acremonium byssoides. Their structures and stereochemistry were elucidated using a combination of ¹³C and ¹H homo and heteronuclear 2D NMR experiments. Acremines H-N inhibited the germination of sporangia of Plasmopara viticola.     

Calyciphyllines E and F, novel hepta- and pentacyclic alkaloids from Daphniphyllum calycinum

Two new Daphniphyllum alkaloids, calyciphyllines E (1) and F (2), have been isolated from the leaves of Daphniphyllum calycinum (Daphniphyllaceae), and the structures and relative stereochemistry were elucidated on the basis of spectroscopic data.     

Daphniglaucin C, a novel tetracyclic alkaloid from Daphniphyllum glaucescens

A novel Daphniphyllum alkaloid with an unprecedented tetracyclic ring system consisting of an octahydroindole and a hexahydroazulene rings, daphniglaucin C (1), has been isolated from the leaves of Daphniphyllum glaucescens and the structure and relative stereochemistry were elucidated on the basis of spectroscopic data. Daphniglaucin C (1) inhibited the polymerization of tubulin.     

Minor cacospongionolide derivatives from the sponge Fasciospongia cavernosa

Together with the known cacospongionolide, three new related sesterterpenes have been isolated from the sponge Fasciospongia cavernosa, collected from the Northern Adriatic Sea. The structures of the new compounds were proposed on the basis of spectroscopic data.     

Five novel norcembranoids from Sinularia leptoclados and S. parva

Three new norcembrane-based diterpenoids, leptocladolides A (1), B (4) and C (5), along with five known metabolites 6-10, have been isolated from the dichloromethane extract of a Taiwanese soft coral Sinularia leptoclados. Furthermore, a chemical investigation on the dichloromethane extract of S. parva has resulted in the isolation of two new related isomers, 1-epi-leptocladolide A (2) and 7E-leptocladolide A (3), in addition to 1 and 7. The structures of new metabolites 1-5 were elucidated on the basis of extensive spectroscopic analyses and their relative stereochemistries were determined by NOESY experiments. The new metabolites 1 and 3 have been shown to exhibit significant cytotoxic activity against KB and Hepa59T/VGH cancer cell lines.     

Thiazo rifamycins—I : Structure and synthesis of rifamycins p,q and verde,novel metabolites from mutants of nocardia mediterranea

Structures 1, 2 and 3 have been assigned to rifamycins P, Q and Verde, novel metabolites isolated from a mutant strain of Nocardia mediterranea both on the basis of spectroscopic evidence (UV, IR, MS, ¹H and ¹³C NMR) in comparison with the model compounds rifamycin S (4), rifampicin (5) and 4-dimethylamino-4-deoxy-rifamycin SV (6), and of an unambiguous synthesis from rifamycin S (4).     

Notoamide E: Biosynthetic incorporation into notoamides C and D in cultures of Aspergillus versicolor NRRL 35600

Notoamide E, a short-lived secondary metabolite, has been proposed as a biosynthetic intermediate to several advanced metabolites isolated from Aspergillus versicolor. In order to verify the role of this indole alkaloid along the biosynthetic pathway, synthetic doubly ¹³C-labeled notoamide E was fed to Aspergillus versicolor. Analysis of the metabolites showed significant incorporation of notoamide E into the natural products notoamides C and D.     

Structural revision of clusianone and 7-epi-clusianone and anti-HIV activity of polyisoprenylated benzophenones

For the first time, the tautomeric pairs of clusianone and 7-epi-clusianone were isolated from the same source, Clusia torresii fruits. An extensive NMR spectroscopic study is described to establish ¹H and ¹³C chemical shift assignments and the C-7 relative configuration of these epimers and to clarify contradictory NMR spectroscopic data previously reported. Quantum mechanical computations than pointed out the relationship between indirect coupling constants and the equilibrium between the B-ring chair and twist-boat forms of the bicyclo-[3.3.1.]-nonane system. Clusianone, 7-epi-clusianone and polyisoprenylated benzophenones 18,19-dihydroxyclusianone, propolone A and nemorosone were screened for their activity against HIV infection in C8166 cells. All compounds inhibited infection with selectivity index values ranging from 2.25 to 15.6. Only clusianone derivatives inhibited infection by binding to viral protein gp120 and prevented its interaction with cellular receptor CD4 as detected by ELISA using recombinant proteins.     

Novel alkaloids of the aaptamine class from an Indonesian marine sponge of the genus Xestospongia

Four novel alkaloids of the aaptamine class have been isolated in addition to the known aaptamine, isoaaptamine, demethyl(oxy)aaptamine and its dimethylketal from an unidentified species of Indonesian marine sponge of the genus Xestospongia. Their structures were elucidated on the basis of detailed 1D and 2D NMR spectroscopic data. Their antimicrobial activity was tested towards Gram (+) (S. aureus), Gram (−) (E. coli, V. anguillarum) bacterial strains, a fungus (C. tropicalis); their cytotoxic activity was evaluated against KB cells.