Petrosaspongiolides M-R: new potent and selective phospholipase A2 inhibitors from the New Caledonian marine sponge Petrosaspongia nigra.

Five new bioactive sesterterpenes (1-5) have been isolated from the New Caledonian marine sponge Petrosaspongia nigra Bergquist and named petrosaspongiolides M-R. Their chemical structures were determined from 1D and 2D NMR studies and MS data. All compounds inhibited different preparations of phospholipase A2 (PLA2) by irreversibly blocking these enzymes (particularly human synovial and bee venom, see Table 3), with IC50 values in the micromolar range. Interestingly, these compounds displayed a much lower activity (or no activity at all) toward porcine pancreas and Naja naja venom PLA2 enzymes. The most potent compound, 1 (IC50 1.6 and 0.6 microM for human synovial and bee venom PLA2 enzymes, respectively), was slightly more active than manoalide (6) (IC50 3.9 and 7.5 microM) under our experimental conditions. Compound 3 is more selective, inhibiting human synovial PLA2 to a greater extent than bee venom PLA2.

Isolation, structure elucidation, and biological activity of the steroid oligoglycosides and polyhydroxysteroids from the Antarctic starfish Acodontaster conspicuus.

A total of 19 steroids, of which 13 steroidal oligoglycosides (nine new and four known) and six polyhydroxylated steroids (four new and two known), has been isolated from the Antarctic starfish Acodontaster conspicuus. The mixture is dominated by glycosides composed of steroidal aglycons having the hydroxyl groups typically disposed on one side of the tetracyclic nucleus, i.e., 3 beta,4 beta,6 alpha,8,15 beta-, with some having a sulfate at C-6, and differing in the side chains and/or in the disaccharide moieties that are usually attached at C-26, with some at C-28 and C-29. Those compounds are accompanied by minute amounts of glycosides with a delta 8(14)-double bond in the steroid, which is a structural feature not previously found among polyhydroxysteroids derived from starfish. Small amounts of six related unglycosidated polyhydroxysteroids and three higher-molecular-weight asterosaponins complete the composition of the mixture. The structures of the new compounds were determined by interpretation of their spectral data and by comparison with spectral data of known compounds. Eighteen of these compounds were evaluated for their ability to inhibit growth in Antarctic marine bacteria isolated from either the water column or the surfaces of benthic marine invertebrates. Of these compounds, 50% were active against at least one Antarctic marine bacterium. This suggests that these compounds may play an important role in deterring microbial fouling.

Microfilament depletion and circumvention of multiple drug resistance by sphinxolides.

Sphinxolides, a newly described family of cytotoxins from the New Caledonian sponge Neosiphonia superstes, bear structural resemblance to scytophycins. We now demonstrate that the cytotoxicity of sphinxolides is associated with cell cycle arrest in G2-M and induction of apoptosis. Like scytophycins and cytochalasins, sphinxolides caused rapid loss of microfilaments in cultured cells, without affecting microtubule organization. Microfilament reassembly was very slow after removal of the sphinxolide, consistent with the slow recovery of cellular proliferation. Sphinxolides potently inhibited actin polymerization in vitro and the microfilament-dependent ATPase activity of purified actomyosin, indicating a direct effect on actin. Importantly, sphinxolides were equally cytotoxic toward MCF-7 human breast carcinoma cells and a subline which overexpresses P-glycoprotein (MCF-7/ADR). Similarly, overexpression of the multidrug resistance-associated protein MRP by HL-60 cells did not confer resistance to the sphinxolides. These studies demonstrate that sphinxolides are potent new antimicrofilament compounds that circumvent multidrug resistance mediated by overexpression of either P-glycoprotein or MRP. Therefore, these agents may be useful in the treatment of drug-resistant tumors.

Isolation of 20 glycosides from the starfish Henricia downeyae, collected in the Gulf of Mexico.

Thirteen new (1-13) and seven known (14-20) steroid glycosides were isolated from Henricia downeyae, collected from the offshore waters of the northern Gulf of Mexico. Ethanolic extracts of these starfish caused growth inhibition in bacteria and fungi, potent antifouling activity against barnacle and bryozoan larvae, and feeding deterrent activity against a marine fish. The known compounds are typical glycosides found in several species of the family Echinasteridae, i.e., Echinaster sp. and Henricia laeviuscola. One of the new compounds belongs to this group, whereas the remaining 12 new compounds represent a novel series of steroid glycosides which have aglycons with structural similarities to the "asterosaponins". They possess a delta 9(11) 3 beta, 6 alpha-dihydroxysteroidal aglycon with 23-oxo or 22,23-epoxy functionalities and often a 20-hydroxyl group in the side chain. The sulfate is located at C-6 and the saccharide moiety at C-3, in contrast with the asterosaponins which have the sulfate at C-3 and the oligosaccaride moiety at C-6. All the new compounds contain a glucuronic acid unit, which is uncommon among steroid glycosides from echinoderms. The structures of the new compounds, isolated in amounts ranging from 3.4 to 0.9 mg, were determined by interpretation of their spectral data and by comparison with spectral data of known compounds.

Steroid and triterpenoid oligoglycosides of marine origin.

Saponins have been considered for a long time typical metabolites of plant origin. It has been only in the last two decades that the world-wide investigation of marine organisms as sources of new bioactive metabolites disclosed the wide distribution of these molecules also among marine animals. Today saponins are recognized as the most common characteristic metabolites in two classes of the phylum Echinodermata (Holothuroidea and Asteroidea). Furthermore, several steroid and triterpenoid oligoglycosides have been isolated from different species of marine sponges, more rarely Anthozoans, and also from fishes of the genus Pardachirus, where they have been shown to act as shark repellents. This communication offers a general view of the distribution of steroid and triterpenoid oligoglycosides among marine organisms and focuses on a number of recent examples to discuss structural characteristics, biological activities, and methods of investigation.

Chemical and biological investigation of the polar constituents of the starfish Luidia clathrata, collected in the Gulf of Mexico.

Ten new [1-10] and three known [11-13] polyhydroxysteroids were isolated, along with four known asterosaponins [14-17], from the starfish Luidia clathrata, collected from the offshore waters of the northern Gulf of Mexico. The EtOH extracts of this starfish showed feeding-deterrent properties against marine fish, and inhibited the settlement of larvae of barnacles and bryozoans, as well as the growth of several bacteria. The structures of the new compounds were determined by interpretation of their nmr spectral data and by comparison with the spectral data of known compounds. The assignment of the configurations of the side-chain stereogenic centers of compounds 1 and 3-10 were based on the comparison of their nmr data with those of the stereoisomeric model compounds after derivatization with the chiral auxiliary MTPA reagent. Larval settlement assays conducted on ten isolated compounds revealed they are all potent inhibitors of settlement. Two of these isolated compounds inhibited the growth of several bacteria.

Starfish saponins, Part 53. A reinvestigation of the polar steroids from the starfish Oreaster reticulatus: isolation of sixteen steroidal oligoglycosides and six polyhydroxysteroids.

A reinvestigation of the starfish Oreaster reticulatus has led to the isolation of sixteen steroidal oligoglycosides and six polyhydroxysteroids. One steroidal monoglycoside has been identified as asterosaponin-1 [5], previously isolated from the same organism, and one pentaglycoside steroidal sulfate has been identified with the known ophidianoside F [1], previously isolated from starfish species of the family Ophidiasteridae. The novel pentaglycoside steroidal sulfates reticulatosides A [3] and B [4] represent the second examples of asterosaponins containing the 5 alpha-cholesta-9(11)-en-3 beta,6 alpha,20,22-tetraol aglycone. Of the remaining new steroidal oligoglycosides, the majority are characterized by the common (24S)-5 alpha-cholesta-3 beta,6 alpha,8,15 alpha,24-pentaol aglycone, with some having a sulfate group at C-6, and differing in the sugar moiety. Compounds 11, 12, 15, and 16 represent major departures from the more common structural features encountered in steroidal glycosides from starfish with the presence in 11 and 12 of a rare 5-O-methylgalactofuranosyl unit and in 15 and 16 of a 3-O-methyl-2-O-sulfate-xylopyranosyl unit. The latter was shown by nmr data combined with molecular dynamics calculations to exist in an 8:2 equilibrium mixture of the 1C4 and 4C1 conformations.

Neosiphoniamolide A, a novel cyclodepsipeptide, with antifungal activity from the marine sponge Neosiphonia superstes.

A novel cyclodepsipeptide, neosiphoniamolide A [1], has been isolated from the sponge Neosiphonia superstes. The structure of 1, which contains a 12-carbon hydroxy acid, glycine, valine, and a halogenated tyrosine residue in an 18-membered ring, is related to jaspamide and the geodiamolides, previously isolated from sponges. The structure was solved by spectroscopic analysis.

A novel cytotoxic macrolide, superstolide B, related to superstolide A, from the New Caledonian marine sponge Neosiphonia superstes.

The structure of a new cytotoxic macrolide, superstolide B [1], isolated from the deep water sponge Neosiphonia superstes, collected off New Caledonia, was elucidated mainly on the basis of nmr data. Compound 1 is closely related to superstolide A [2], a major cytotoxic component isolated from that organism, but lacks the 25-hydroxyl group found in 2 and has a C-24 (C-25)-double bond.

Four new dimeric peptide alkaloids, anchinopeptolides B-D, and cycloanchinopeptolide C, congeners of anchinopeptolide A, from the Mediterranean marine sponge Anchinoe tenacior.

Following the characterization of anchinopeptolide A[1], three new congeneric dimeric peptide alkaloids, named anchinopeptolides B [2], C[3], and D[4], have been isolated from the Mediterranean sponge Anchinoe tenacior. A fourth compound, cycloanchinopeptolide C[5], which is related to anchinopeptolide C[3] by a head-to-head intramolecular [2+2] cyclo-addition reaction, has also been isolated. The structures of these peptide alkaloids have been elucidated on the basis of spectral evidence. Anchinopeptolides bind to the somatostatin, human B2 bradykinin, and neuropeptide Y receptors.

(+/-)-Gelliusines A and B, two diastereomeric brominated tris-indole alkaloids from a deep water new caledonian marine sponge (Gellius or Orina sp.).

Two new diastereomeric brominated tris-indole alkaloids occurring as enantiomeric pairs, (+/-)-gelliusines A [1] and B [2], have been isolated from a deep water New Caledonian sponge (Gellius or Orina sp.), whose crude extract exhibited cytotoxicity against KB cells. Their structures were elucidated by spectroscopic methods including one- and two-dimensional nmr spectroscopy. The major compound, (+/-) gelliusine A [1], which showed very weak cytotoxicity, proved to be active at the serotonin receptor.

Starfish saponins, Part 2. Steroidal oligoglycosides from the starfish Cosmasterias lurida.

Four new sulfated asterosaponins, designated as cosmasterosides A [1], B [2], C [4], and D [5], have been isolated from the Atlantic starfish Cosmasterias lurida along with large amounts of the pentaglycoside ophidianoside F [3] and the minor component forbeside H [6], previously isolated from Ophidiaster ophidianus and Asterias forbesi, respectively. Cosmasteroside A [1] contains the same oligosaccharide chain as ophidianoside F [3] and a (20S)-5 alpha-cholesta-9(11),24-diene-3 beta,6 alpha,20-triol-3 beta-sulfated aglycone. Cosmasterosides B [2], C [4], and D [5] are based on the known aglycone, thornasterol A, and differ in the number and type of monosaccharide components of the carbohydrate chain. Cosmasteroside B [2] contains a novel oligosaccharide chain that differs from that of ophidianoside F [3] by the replacement of the quinovose unit attached to C-6 of the steroidal aglycone by glucose. The tetraglycosides cosmasterosides C [4] and D [5] are structurally related to ophidianoside F [3] and cosmasteroside B [2], respectively, by the loss of a terminal fucose unit.

HIV-inhibitory natural products. 11. Comparative studies of sulfated sterols from marine invertebrates.

A total of 22 sulfated sterols isolated from marine sponges, ophiuroids (brittle stars), and asteroids (sea stars) were comparatively evaluated for their antiviral activity against HIV-1 and HIV-2. In general, sterols with sulfate groups at position 2, 3, or 6 were the most active, with EC50 values of 3-13 microM against HIV-1 (RF) and 2-8 microM against HIV-2 (CBL20). Those compounds which were sulfated on the sterol D ring were completely inactive against both HIV-1 and HIV-2. Overall, sulfated sterols active against HIV-1 were also active against HIV-2.

Novel HIV-inhibitory halistanol sulfates F-H from a marine sponge, Pseudoaxinissa digitata.

Three new steroid sulfates 2-4 related to halistanol sulfate [1] were isolated along with the known halistanol sulfate C [5] from the marine sponge Pseudoaxinissa digitata. Halistanol sulfates F [2] and G [3] proved to be cytoprotective against HIV.

Starfish saponins, 52. Chemical constituents from the starfish Echinaster brasiliensis.

This paper reports an analysis of the chemical constituents from the Caribbean starfish Echinaster brasiliensis collected at Grand Bahama Island. This species is completely devoid of cyclic steroidal glycosides, previously isolated from two species of the genus Echinaster in place of the more common penta- and hexa-glycoside steroidal sulfates ("asterosaponins"). Two typical "asterosaponins" and ten glycosides of polyhydroxysteroids were instead isolated in relatively large amounts from E. brasiliensis. The asterosaponins include the known marthasteroside A1 [1] and the new brasiliensoside [2], while the glycosides of polyhydroxysteroids include seven new compounds (six monoglycosides and one diglycoside). The known echinasteroside A, previously found in Echinaster sepositus and in the related Henricia laeviuscula (both belonging to the family Echinasteridae), and laeviusculosides C and I from H. laeviuscula were also isolated. Most of the glycosides from E. brasiliensis are 3-O-beta-xylopyranosides of delta 4-3 beta,6 beta,8,15 alpha,16 beta pentahydroxysteroid aglycones, having different side chains and sometimes a sulfate group at C-15, structural features which are typical of steroidal glycosides from starfishes of the family Echinasteridae. Continuing the analysis of the constituents of E. brasiliensis, we have also isolated a series of anthraquinones, known animal pigments found only in echinoderms and particularly in Crinoidea and in the Echinasteridae family of Asteroidea.

Starfish saponins, Part 51. Steroidal oligoglycosides from the starfish Distolasterias nipon.

A reinvestigation of the extracts from the starfish Distolasterias nipon, collected at Mutsu Bay, Japan, has led to the isolation of six glycosides of polyhydroxysteroids and six asterosaponins. Four steroidal glycosides have been identified as distolasterosides D1 [1] and D2 [2] (previously isolated from the same organism), and pycnopodioside C [5] and pisasteroside A [6], previously found in the related species Pycnopodia helianthoides and Pisaster ochraceus (family Asteridae), respectively. Two asterosaponins have been identified as the common versicoside A [7] and thornasteroside A [7a]. The two remaining glycosides of polyhydroxysteroids, named distolasterosides D4 [3] and D5 [4], and four asterosaponins designated nipoglycosides A [8], B [9], C [10], and D [11] are new compounds, and their structures have been elucidated mainly by interpretation of spectral data and comparison with known compounds.

Starfish saponins, Part 50. Steroidal glycosides from the Okinawan starfish Nardoa tuberculata.

This paper describes a complete analysis of the glycoside and polyhydroxysteroid constituents of the starfish Nardoa tuberculata, collected at Zampa, Okinawa, Japan. Besides a group of known non-sulfated steroidal diglycosides, halitylosides A [5], B [6], D [7], E [8], and F [9], and two known polyhydroxysteroids 10 and 11, N. tuberculata also contains four new sulfated steroidal glycosides 1-4 closely related to the previous halitylosides. The antifungal activities and the effects on the development of fertilized sea urchin eggs of some steroid components from this starfish were examined.

Paniceins and related sesquiterpenoids from the Mediterranean sponge Reniera fulva.

Two novel sesquiterpenes, fulvanin 1 [1] and fulvanin 2 [2], have been isolated from the Mediterranean sponge Reniera fulva. Compound 2 is a sesquiterpenoid linked to a hydroquinone. Also found in Reniera fulva are four known paniceins, a group of aromatic sesquiterpenoids linked to a quinol, isolated previously from Halichondria panicea. The total assignments of 13C-nmr spectra of paniceins have been made with the aid of 2D1H-13C correlation techniques, confirming their structures. The paniceins were tested in the in vitro disease-oriented primary antitumor screen at NCI, Bethesda. Paniceins C and B3 showed cytotoxicity against NCI-H522 non-small lung cancer cells and CCRF-CEM leukemia cells, while panicein A hydroquinone revealed more selective cytotoxicity against the latter ones.

Starfish saponins, part 49. New cytotoxic steroidal glycosides from the starfish Fromia monilis.

Nine new cytotoxic steroidal glycosides 1-9 have been isolated from the starfish Fromia monilis collected off New Caledonia. Structures of these compounds, which include four mono-(1-4), two di-(5,6), and three glycosides (7-9), were elucidated through spectral interpretation. Monilosides G [7], H [8], and I [9] are the first tri-glycosides to be found among the group of glycosides of polyhydroxilated steroids from starfishes.