Dactylomelane Diterpenes from the Sea Hare <i>Aplysia depilans</i>

A chemical investigation of the organic extract of the sea hare <i>Aplysia depilans</i>, collected off Skyros Island, Greece, yielded eight new brominated diterpenes (<b>1</b>–<b>8</b>), featuring the rare dactylomelane skeleton, together with the previously reported luzodiol (<b>9</b>). The structure elucidation and the assignment of the relative configurations of the new natural products were based on extensive NMR spectroscopic and MS spectrometric analyses. Compounds <b>1</b>–<b>9</b> were evaluated for their cytotoxic activities against five human tumor cell lines, but were proven inactive

Metabolites from the Sea Hare <i>Aplysia fasciata</i>

Examination of the digestive and hermaphroditic glands’ organic extract of the sea hare Aplysia fasciata yielded 16 metabolites, including eight sesquiterpenes, three diterpenes, and five C15-acetogenins. Among them, three sesquiterpenes, 6-hydroxy-1-brasilene (1), epibrasilenol acetate (2), and 6-epi-β-snyderol (3), one acetogenin, (3Z,9Z)-7-chloro-6-hydroxy-12-oxo-pentadeca-3,9-dien-1-yne (4), and one diterpene, 16-acetoxy-15-bromo-7-hydroxy-9(11)-parguerene (5), are new natural products. The structure elucidation and the assignment of the relative configurations of the isolated natural products were established on the basis of extensive analyses of their spectroscopic data (NMR, MS, IR)

Brasilane-Type Sesquiterpenoids from <i>Laurencia </i><i>o</i><i>btusa</i>

Three novel halogenated rearranged sesquiterpenes (1−3) have been isolated along with brasilenol (4) and epibrasilenol (5) from the organic extract of the red alga Laurencia obtusa, collected at Symi island in the Aegean Sea, Greece. The new metabolites possess the unusual skeleton of brasilane and contain the unprecedented 1,6-epoxy moiety. The structures of the new natural products, as well as their relative stereochemistry, were established by means of spectral data analyses, including two-dimensional NMR experiments along with molecular calculations

Novel Cytotoxic Brominated Diterpenes from the Red Alga <i>Laurencia </i><i>o</i><i>btusa</i>

Five new brominated diterpenes, along with two known, have been isolated from the organic extract of the red alga Laurencia obtusa, collected from the coastal rocks of Preveza in the Ionean Sea, Greece. The novel metabolites prevezols B−E possess two new carbon skeletons, to the best of our knowledge, unprecedented in the literature. The structures and the relative stereochemistry of the new natural products were established by means of spectral data analyses. The new metabolites were tested for their cytotoxic activity against five human cell lines. Two metabolites have exhibited significant cytotoxicity

Pharmacophore Modeling for Qualitative Prediction of Antiestrogenic Activity

A ligand-based pharmacophore approach for the prediction of antiestrogenic activity to be used as an in silico screening tool for bioactive compounds including natural products was developed using Catalyst HypoGen. The generated pharmacophore hypothesis (HYPO-7) consisted of five features, namely, one hydrophobic (HY1), two hydrophobic aromatic (HY2), one hydrogen-bond acceptor (HBA), and one hydrogen-bond donor (HBD). HYPO-7 successfully predicted the lack of cytotoxicity of a number of new metabolites isolated from the red alga Laurencia glandulifera. Furthermore, a screening of the Asinex Gold Collection database was performed by coupling HYPO-7 with a docking filtration, which resulted in a restricted set of 12 new scaffolds to be investigated as potential SERMs. The inhibitory activity of these compounds was evaluated in vitro using MCF7 human breast adenocarcinoma cell line. Ten out of the twelve compounds exhibited inhibitory activity with IC50 values between 26 and 188 μM. This result shows that application of HYPO-7 could assist in the selection of potentially active compounds, thus expediting the hit discovery process

Parnapimarol and Nepetaparnone from <i>Nepeta parnassica</i>

Parnapimarol (1), a new pimarane diterpene, along with nepetaparnone (2) and nepetanudone (3), one new and one previously reported nepetalactone dimer, respectively, were isolated from the dichloromethane extract of the aerial parts of Nepeta parnassica, collected on Mt. Parnassos, Greece. The structures and relative configurations of 1–3 were determined on the basis of their spectroscopic characteristics (1D and 2D NMR, IR, MS). The structure of 2 was confirmed by single-crystal X-ray diffraction analysis. The insecticidal activity of 1−3 against ants and mosquito larvae was also evaluated

Dolabellanes with Antibacterial Activity from the Brown Alga <i>Dilophus spiralis</i>

Seventeen diterpenes featuring the dolabellane skeleton (1−17) were isolated from the organic extracts of the brown alga Dilophus spiralis. Seven compounds are new natural products (1, 3, 5, 6, 11, 14, 15) and eight are structurally revised (2, 4, 7−10, 12, 13), among which three are reported for the first time from a natural source (4, 9, 10). The structure elucidation and the assignment of the relative configurations of the isolated natural products were based on detailed analyses of their spectroscopic data. The structure of metabolite 10 was confirmed by single-crystal X-ray diffraction analysis, whereas the absolute configurations of compounds 2, 4−10, 12, and 13 were determined using the modified Mosher’s method on the semisynthetic product 18 and chemical interconversions. The antibacterial activities of compounds 1−18 were evaluated against six strains of Staphylococcus aureus, including multidrug- and methicillin-resistant variants

Dolabellanes with Antibacterial Activity from the Brown Alga <i>Dilophus spiralis</i>

Seventeen diterpenes featuring the dolabellane skeleton (1−17) were isolated from the organic extracts of the brown alga Dilophus spiralis. Seven compounds are new natural products (1, 3, 5, 6, 11, 14, 15) and eight are structurally revised (2, 4, 7−10, 12, 13), among which three are reported for the first time from a natural source (4, 9, 10). The structure elucidation and the assignment of the relative configurations of the isolated natural products were based on detailed analyses of their spectroscopic data. The structure of metabolite 10 was confirmed by single-crystal X-ray diffraction analysis, whereas the absolute configurations of compounds 2, 4−10, 12, and 13 were determined using the modified Mosher’s method on the semisynthetic product 18 and chemical interconversions. The antibacterial activities of compounds 1−18 were evaluated against six strains of Staphylococcus aureus, including multidrug- and methicillin-resistant variants

Structure and Absolute Stereochemistry of Syphonoside, a Unique Macrocyclic Glycoterpenoid from Marine Organisms

The glycoterpenoid syphonoside (1) is the main secondary metabolite of both the marine mollusk Syphonota geographica and the sea-grass Halophila stipulacea, two Indo-Pacific species migrated to the Mediterranean Sea through the Suez Canal. The structure and the absolute stereochemistry of 1, which displays unique structural features, has been accomplished by using a combination of spectroscopic techniques, degradation reactions, and conformational analysis methods. Compound 1 was able to inhibit high density induced apoptosis in a number of human and murine carcinoma cell lines