Neopetromin, a Cyclic Tripeptide with a C-N Cross-Link, from the Marine Sponge Neopetrosia sp., That Causes Vacuole Fragmentation in Tobacco BY-2 Cells.

HPLC-MS analysis revealed the presence of an unreported peptide in the extract of the marine sponge Neopetrosia sp. Its structure was determined as a tripeptide, named neopetromin (1), composed of two tyrosine and one tryptophan residues with a heteroaromatic C-N cross-link between side chains. The absolute configuration of amino acids was determined using Marfey's method after ozonolysis and hydrolysis of 1. Compound 1 promoted vacuole fragmentation in an actin-independent manner in tobacco BY-2 cells.

Aaptocarbamates A-G, chlorinated terpene carbamates with antiosteoclastogenic activities from the marine sponge Aaptos sp.

Six undescribed chlorinated sesquiterpene carbamates, aaptocarbamates A-F, and a chlorinated tris-norsesquiterpene carbamate, aaptocarbamate G, were isolated from the marine sponge Aaptos sp. collected in Indonesia. Aaptocarbamates D-F and G possess tetrahydrofurans and a tetrahydrofuranone, respectively. The relative configurations of the tetrahydrofuran units were determined by the NOE correlations and DFT-based calculation of the 13C chemical shifts. This is the first time that chlorinated terpene carbamates have been reported from natural sources. Various aaptamine derivatives have been reported from the Aaptos sponges so far, the isolation of chlorinated terpene carbamates is very rare. Aaptocarbamates A, B, and D showed 60% inhibition of the RANKL-induced formation of multinucleated osteoclasts in RAW264 macrophages at 20 µM.

Cyclopsammocinamides A and B, Enantiomeric Cyclic Peptides of Cyclocinamide A, from the Marine Sponge Psammocinia sp.

LC-MS and molecular networking analyses of the extract of the marine sponge Psammocinia sp. indicated the presence of two new compounds with multiple halogens. LC-MS-guided isolation yielded cyclic peptides, cyclopsammocinamides A (1) and B (2), in an enantiomeric relationship to cyclocinamide A (3). Planar structures of 1 and 2 were elucidated by NMR and mass spectroscopic analyses and the absolute configurations of the amino acid residues were determined using Marfey's method with their acid hydrolysates. The sponge extract exhibited cytotoxicity and the bioassay-guided isolation afforded a dimeric dilactone macrolide, swinholide A, as the cytotoxic compound.

Halichonic Acid B, a Rearranged Nitrogenous Bisabolene-Type Sesquiterpene from a Marine Sponge Axinyssa sp.

A new rearranged nitrogenous bisabolone-type sesquiterpene, halichonic acid B (1), was isolated from a marine sponge Axinyssa sp. together with halichonic acid (2) and (6R,7S)-7-amino-7,8-dihydro-α-bisabolene (3). The structure of 1 was determined by extensive NMR and MS analyses, revealing an unprecedented carbon framework, and its absolute configuration was elucidated by time-dependent density-functional theory (TDDFT)-based electronic circular dichroism (ECD) spectrum calculation. We propose that 1 and 2 may be biosynthesized in the same pathway, involving the reaction between farnesyl pyrophosphate and glycine, followed by cyclization.

Fluorescent image-based high-content screening of extracts of natural resources for cell cycle inhibitors and identification of a new sesquiterpene quinone from the sponge, Dactylospongia metachromia.

Natural products are important sources for drug development. Discovery of natural products that inhibit cell cycle progression significantly contributes to the progress of cancer biology and the development of new antitumor agents. In this study, cell cycle inhibitory activity was evaluated with our extract library of natural resources, including marine invertebrates, fungi, and bacteria, using HeLa/Fucci2 cells which allow classification of the cell cycle phases of living cells. Screening of the extract library revealed that the extract of the marine sponge Dactylospongia metachromia inhibited cell cycle progression at S/G2/M phases. Bioassay-guided fractionation afforded a new sesquiterpene quinone, neoisosmenospongine (1), and four known compounds, nakijiquinone I, N, and Q (2-4) and (-)-dictyoceratin-C (5). The chemical structure of 1 was elucidated by interpretating the NMR and mass spectroscopic data, and the absolute configuration was determined by comparison of the experimental and calculated ECD spectra. Fluorescent imaging of HeLa/Fucci2 cells revealed that 1-4 inhibited the cell cycle progression at S/G2/M phases. This study demonstrated that fluorescent image-based high-content screening using HeLa/Fucci2 cells is an effective approach for isolating cell cycle inhibitors from natural resources.

Tetradehydrohalicyclamine B, a new proteasome inhibitor from the marine sponge Acanthostrongylophora ingens.

A new halicyclamine derivative, tetradehydrohalicyclamine B (1), was isolated from the marine sponge Acanthostrongylophora ingens, along with halicyclamine B (2) as proteasome inhibitors. Compound 1 is the second example found to have a pyridinium ring in the halicyclamine family. Although the relative configuration of 2 was previously determined by X-ray crystallographic analysis, here we determined the absolute configuration of 2 by ECD experiment. Compounds 1 and 2 inhibited the constitutive proteasome as well as the immunoproteasome. The inhibitory activities of 2 were 4- to 10-fold more potent than those of 1.

New geranyl flavonoids from the leaves of Artocarpus communis.

Four new geranyl flavonoids 1-4 and four known flavonoids 5-8 were obtained from the leaves of Artocarpus communis collected in Indonesia. The planar structures of flavonoids were elucidated by analyses of MS and NMR spectroscopic data. Absolute configurations of 1 and 2 were determined by ECD spectroscopy. Analyses by HPLC with a chiral-phase column and ECD spectra confirmed that 3 and 4 were stereoisomeric mixtures and 7 and 8 were racemic mixtures. The compounds obtained in this study inhibited the enzymatic activities of ubiquitin-specific protease 7 (USP7) and the chymotrypsin-like activity of the proteasome. Among the geranyl flavonoids tested in this experiment, the USP7 inhibitory activity of 6 (IC50 value, 0.094 µM) was 55 times more potent than the commercially available positive control, P5091 (IC50 value, 5.2 µM).

Lamellodysidines A and B, Sesquiterpenes Isolated from the Marine Sponge Lamellodysidea herbacea.

Four new sesquiterpenes, lamellodysidines A and B, O,O-dimethyllingshuiolide A, and 11-epi-O,O-dimethyllingshuiolide A (1-4), were obtained from the marine sponge, Lamellodysidea herbacea, collected in Indonesia. Their planar structures were elucidated by analysis of spectroscopic data. The absolute configurations of the new compounds were determined by the calculated ECD spectra. Compound 1 has a unique carbon framework, and 2 is a new nitrogenous sesquiterpene.

Sulawesins A-C, Furanosesterterpene Tetronic Acids That Inhibit USP7, from a Psammocinia sp. Marine Sponge.

Three new furanosesterterpene tetronic acids, sulawesins A-C (1-3), were isolated from a Psammocinia sp. marine sponge, along with the known compounds ircinins-1 (4) and -2 (5). Although ircinins-1 and -2 were previously isolated as (+)- or (-)-enantiomers from marine sponges, we isolated them as enantiomeric mixtures. Sulawesins A and B possess a new carbon skeleton with a 5-(furan-3-yl)-4-hydroxycyclopent-2-enone moiety and were also found to be diastereomeric mixtures of four isomers by an HPLC analysis with a chiral-phase column. Sulawesin C has a dimeric structure of ircinin-1 and is the first dimer in this family. USP7, a deubiquitinating enzyme, is an emergent target of cancer therapy, and the isolated compounds inhibited USP7 with IC50 values in the range of 2.7-4.6 µM.

Ceylonins A-F, Spongian Diterpene Derivatives That Inhibit RANKL-Induced Formation of Multinuclear Osteoclasts, from the Marine Sponge Spongia ceylonensis.

Six new spongian diterpene derivatives, ceylonins A-F (1-6), were isolated from the Indonesian marine sponge Spongia ceylonensis along with spongia-13(16),14-dien-19-oic acid (7). They contained three additional carbons in ring D to supply an ether-bridged bicyclic ring system. Their structures were elucidated by analyzing NMR spectroscopic data and calculated ECD spectra in comparison to experimental ECD spectra. The bicyclic ring system may be derived from the major metabolite 7 and a C3 unit (an acrylic acid equivalent) through an intermolecular Diels-Alder reaction, which was experimentally supported by the formation of 1-6 from 7 and acrylic acid. The inhibitory effects of the isolated compounds on the RANKL-induced formation of multinuclear osteoclasts in RAW264 macrophages were examined.

Ceylonamides A-F, Nitrogenous Spongian Diterpenes That Inhibit RANKL-Induced Osteoclastogenesis, from the Marine Sponge Spongia ceylonensis.

Seven new spongian diterpenes, ceylonamides A-F (1-6) and 15α,16-dimethoxyspongi-13-en-19-oic acid (7), were isolated from the Indonesian marine sponge Spongia ceylonensis along with eight known spongian diterpenes, 8-15. Compounds 1-6 were determined to be nitrogenous spongian diterpenes. The isolated compounds were examined for the inhibition of RANKL-induced osteoclastogenesis in RAW264 macrophages. Ceylonamide A (1) exhibited the most potent inhibitory activity with an IC50 value of 13 µM, followed by ceylonamide B (2) (IC50, 18 µM). An examination of the structure-activity relationships of the isolated compounds revealed that the position of the carbonyl group of the γ-lactam ring and bulkiness of the substituent at its nitrogen atom were important for inhibitory activity.

Bastadins, brominated-tyrosine derivatives, suppress accumulation of cholesterol ester in macrophages.

The formation of foam cells in macrophages has been suggested to play an essential role in the progression of early atherosclerotic lesions in vivo and, thus, its suppression is considered to be one of the major approaches for the treatment of atherosclerosis. We isolated eight brominated-tyrosine derivatives, bastadins, from the EtOH extract of the marine sponge Ianthella vasta as inhibitors of the formation of foam cells induced by acetylated low-density lipoproteins in human monocyte-derived macrophages. Bastadin 6 was the strongest inhibitor of foam cell formation due to its suppression of acyl-coenzyme A:cholesterol acyltransferase.

Verruculides A and B, two new protein tyrosine phosphatase 1B inhibitors from an Indonesian ascidian-derived Penicillium verruculosum.

Two new merosesquiterpenes, verruculides A (1) and B (2), were isolated from a culture broth of the Indonesian ascidian-derived Penicillium verruculosum TPU1311, together with three known congeners, chrodrimanins A (3), B (4), and H (5). The structures of 1 and 2 were assigned on the basis of their spectroscopic data (1D and 2D NMR, HRMS, UV, CD, and IR). Compound 2 had a linear sesquiterpene moiety and was considered to be the derivative of the biosynthetic precursor for 1 and 3-5. Compounds 1, 3, and 5 inhibited the activity of protein tyrosine phosphatase 1B (PTP1B) with IC50 values of 8.4, 8.5, and 14.9 µM, respectively. Compound 2 showed 40% inhibition at 23.1 µM, while 4 was not active at 20.7 µM.

Manadodioxans A-E: polyketide endoperoxides from the marine sponge Plakortis bergquistae.

Five new polyketide endoperoxides, manadodioxans A-E, were isolated from the marine sponge Plakortis bergquistae. Manadodioxan E showed antimicrobial activity against Escherichia coli at 10 µg/disk, while its oxo congener, manadodioxan D, was inactive.

Strongylophorines, meroditerpenoids from the marine sponge Petrosia corticata, function as proteasome inhibitors.

Two new strongylophorine derivatives, along with six known strongylophorines, were isolated from the marine sponge Petrosia corticata as proteasome inhibitors. Of these, a hemiacetal mixture of strongylophorines-13/-14 was the strongest inhibitor of the proteasome with an IC50 of 2.1µM.

Two new protein tyrosine phosphatase 1B inhibitors, hyattellactones A and B, from the Indonesian marine sponge Hyattella sp.

Two unique sesterterpenes, hyattellactones A (1) and B (2), together with two known sesterterpenes, phyllofolactones F (3) and G (4), were isolated from the Indonesian marine sponge Hyattella sp. The structures of the two new compounds, 1 and 2 were assigned based on their spectroscopic data. Hyattellactone A (1) was a scalarane sesterterpene with an α,ß-unsaturated-γ-lactone ring and C-ethyl group, while B (2) was an epimer of 1 at the C-24 position. Compounds 1 and 3 inhibited PTP1B activity with IC50 values of 7.45 and 7.47µM, respectively. On the other hand, compounds 2 and 4 (24S-isomers of 1 and 3, respectively) showed much reduced activity than the 24R-isomers.

Halenaquinone inhibits RANKL-induced osteoclastogenesis.

Halenaquinone was isolated from the marine sponge Petrosia alfiani as an inhibitor of osteoclastogenic differentiation of murine RAW264 cells. It inhibited the RANKL (receptor activator of nuclear factor-κB ligand)-induced upregulation of TRAP (tartrate-resistant acid phosphatase) activity as well as the formation of multinuclear osteoclasts. In addition, halenaquinone substantially suppressed RANKL-induced IκB degradation and Akt phosphorylation. Thus, these results suggest that halenaquinone inhibits RANKL-induced osteoclastogenesis at least by suppressing the NF-κB and Akt signaling pathways.

Combined effect of papuamine and doxorubicin in human breast cancer MCF-7 cells.

Our previous study reported that an extract of an Indonesian marine sponge, Haliclona sp., showed potent cytotoxicity and induced apoptosis. The major cytotoxic chemical compound was identified as papuamine, which caused reduction of cell survival through activation of c-Jun N-terminal kinase (JNK) in human breast cancer MCF-7 cells. Doxorubicin (DOX), a Streptomyces metabolite, is used in chemotherapy against a wide range of cancers, including breast cancer. The present study examined the combined effect of papuamine and DOX on MCF-7 cells. The effect of these reagents on cell growth was assessed by a colony formation assay. Incubation with either of the reagents alone resulted in concentration-dependent decreases in the colony formation of the MCF-7 cells. Incubation with the reagents together at sub-cytotoxic concentrations resulted in significant decreases in colony formation. The phosphorylation of JNK, the activated form of the protein, was elevated in a concentration-dependent manner upon co-incubation with papuamine and DOX. Fluorescence intensity analysis demonstrated that papuamine caused a small, but non-significant, decrease in cellular accumulation of DOX. These results indicate that the combinatory effect of papuamine and DOX is not associated with changes in the cellular accumulation of DOX, and may instead reflect additive effects on JNK activation. This study indicates that papuamine may represent a novel type of modulator for DOX chemotherapy.

Acanthomanzamines A-E with new manzamine frameworks from the marine sponge Acanthostrongylophora ingens.

Five new manzamine alkaloids, acanthomanzamines A-E, were isolated from the marine sponge Acanthostrongylophora ingens. Acanthomanzamines A and B are the first examples, containing a tetrahydroisoquinoline instead of a ß-carboline in manzamine-related alkaloids. Acanthomanzamine C contains a hexahydrocyclopenta[b]pyrrol-4(2H)-one ring that may be converted from an eight-membered ring in manzamine A. Acanthomanzamines D and E have an additional oxazolidine and 2-methyloxazolidine rings, respectively, which fuse to the manzamine skeleton.

Acantholactam and pre-neo-kauluamine, manzamine-related alkaloids from the Indonesian marine sponge Acanthostrongylophora ingens.

Two new manzamine alkaloids, acantholactam (3) and pre-neo-kauluamine (4), were isolated from the marine sponge Acanthostrongylophora ingens along with manzamine A (1) and neo-kauluamine (2). Acantholactam contains a γ-lactam ring N-substituted with a (Z)-2-hexenoic acid moiety and is proposed to be biosynthetically derived from manzamine A by oxidative cleavage of the eight-membered ring. Compound 4 was converted to the dimer 2 during storage, suggesting nonenzymatic dimer formation. Among the four isolated compounds, 1, 2, and 4 showed proteasome inhibitory activity.