New cytotoxic peroxylactones from the marine sponge, Plakinastrella onkodes.

Three new peroxylactones, plakortolides B [6], C [7], and D [8], and a new peroxy ester, epiplakinic acid E methyl ester [9], were isolated and characterized from a previously unstudied marine sponge, Plakinastrella onkodes. A mixture of steroidal peroxides was also found in this organism. Plakortolides B [6] and D [8], and epiplakinic acid E methyl ester [9], were evaluated for biological activity and found to show cytotoxicity against the A549 human lung carcinoma and P388 murine leukemia cell lines, and to effect adhesion in an assay employing the EL-4.IL-2 cell line, which correlates with signal transduction activity.

Staurosporine aglycone (K252-c) and arcyriaflavin A from the marine ascidian, Eudistoma sp.

Staurosporine aglycone (K252-c) (compound 1) and arcyriaflavin A (2) were isolated from a specimen of the marine ascidian, Eudistoma sp., collected off the coast of West Africa. In addition to expressing micromolar and submicromolar inhibition of enzyme activity against seven protein kinase C isoenzymes and inhibition of proliferation of the human lung cancer A549 and P388 murine leukemia cell lines, 1 also inhibited cell adhesion of the EL-4.IL-2 cell line and expressed activity in the K562 bleb and neutrophil assays.

Analogues of the marine immunosuppressant microcolin A: preparation and biological activity.

A series of analogs of the immunosuppressive lipopeptide microcolin A has been prepared and evaluated for in vitro activity in the human and murine two-way mixed lymphocyte reaction. The compounds tested were obtained by semisynthetic modification and chemical degradation of the natural product. The relative potencies of these analogs suggest that the hydroxyproline and 5-methyl-3-pyrrolin-2-one portion of the molecule are important for immunosuppressive activity and that other structural elements may play an ancillary role. Methanolysis of microcolin A also led to a novel immunosuppressive lactone analog.

Evaluation of marine sponge metabolites for cytotoxicity and signal transduction activity.

Twenty-four metabolites derived from marine sponges were evaluated for their cytotoxicities against two human tumor cell lines, non-small cell lung carcinoma A549 and colon adenocarcinoma HT-29, and against one murine leukemia cell line, P-388, and evaluated for their ability to effect signal transduction in a newly developed cell adhesion assay using an EL-4 cell line. The compounds included latrunculin A [1], batzelline A [2], chondrillin [3], aureol [4], epihippuristanol, theonellamine B, discorhabdins A and C, kabiramide C, dercitin, meridine, manzamines A, B, and C, 8,15-diisocyano-11(20)-amphilectene and the corresponding C-15 formamide, a 20-carbon acetylenic alcohol, 4,5-dihydro-6"-deoxybromotopsentin, epispongiadiol, isospongiadiol, puupehenone, reiswigin A, and demethyl- and demethyloxyaaptamine. Latrunculin A [1], batzelline A [2], chondrillin [3], and aureol [4] expressed the desired profile of a greater than five-fold level of cytotoxicity against A549 relative to P-388, and an effect in the cell adhesion assay. In this group of compounds, cytotoxicity toward A549 was equal to or more pronounced than against HT-29. Latrunculin A was evaluated in an sc-implanted human A549 lung tumor xenograft mouse model and yielded a T/C of 146%. Batzelline A was evaluated in the cancer cell line panel at the National Cancer Institute and found to express selective cytotoxicity against several melanoma cancer cell lines.

Isometachromin, a new cytotoxic sesquiterpenoid from a deep water sponge of the family Spongiidae.

Isometachromin (1), a new sesquiterpene-quinone that is related structurally to metachromin C (2), and the known compounds ilimaquinone (3) and 5-epi-ilimaquinone (4), were isolated from a deep water sponge in the family Spongiidae; the structure of isometachromin was elucidated by spectral methods. Isometachromin exhibits in vitro cytotoxicity against the human lung cancer cell line A549 (IC50 = 2.6 micrograms/ml), but not against P388 murine leukemia (IC 50 > or equal to 10 micrograms/ml) and also exhibits antimicrobial activity.

Antifouling agents against the benthic marine diatom,Navicula salinicola Homarine from the gorgoniansLeptogorgia virgulata andL. setacea and analogs.

At concentrations found in the gorgonian corals,Leptogorgia virgulata (L.) andL. setacea (L.), homarine (N-methyl-2-carboxypyridine) and water-soluble extracts from the gorgonians that contained homarine inhibited the growth of the potential fouling diatom.Navicula salinicola Hust., by 50-60%. Homarine comprised 0.3 and 0.25% of the fresh weight ofL. virgulata andL. setacea, respectively, and the water-soluble extracts comprised 4.0 and 3.0% of the fresh weight of the gorgonians, respectively. Three compounds structurally related to homarine including, in order of most to least active, nicotinic acid, picolinic acid, and pyridine, also reduced growth ofN. salinicola. The activity of these compounds in the diatom assay suggests that the carboxyl group at the 2 position of the pyridine ring is important for activity and thatN-methylation is not important. We conclude that chemical defense against fouling is operative inLeptogorgia species. Evidence from the literature for combined chemical and mechanical defenses byLeptogorgia and other organisms against fouling is presented.

Detection of secondary metabolites in marine macroalgae using the marsh periwinkle,Littorina irrorata say, as an indicator organism.

Twenty-four chemically profiled organic macroalgal extracts and seven purified natural products were bioassayed using the mesogastropodLittorina irrorata Say to determine if the presence of secondary metabolites in crude algal extracts could be correlated with the activity of the snail. Avoidance behavior by snails in the assay was highly correlated with the presence of secondary metabolites in the macrophyte extracts.

Effects of secondary metabolites from marine algae on feeding by the sea urchin,Lytechinus variegatus.

A bioassay was developed to test the hypothesis that secondary metabolites from marine algae affect feeding by sea urchins. During experiments measuring chemoreception and gustation, feeding by the regular sea urchin,Lytechinus variegatus (Lamarck), was inhibited by extracts from the green marine alga,Caulerpa prolifera (Forsskal) Lamouroux andCymopolia barbata (Linneaus) Lamouroux. Cymopol, a monoterpene-bromohydroquinone component ofC. barbata, was partially responsible for the inhibited feeding observed in tests of theCymopolia crude extract. Caulerpenyne, an oxygenated sesquiterpene fromC. prolifera, was responsible for all of the urchin feeding inhibition observed in tests of theC. prolifera crude extract. Feeding was not affected by: (1) extracts from several otherCaulerpa species includingC. mexicana (Sonder) J. Agardh,C. ashmaedii Harvey,C. racemosa v.macrophysa (Kutzing) Taylor, andC. racemosa v.laetevirens (Montagne) Weber-van Bosse; (2) caulerpin, an indole-containing pigment isolated from all of theCaulerpa species exceptC. mexicana; and (3) an extract from the red marine alga,Gracilaria foliifera v.angustissima (Harvey) Taylor, which has no known secondary metabolites. Feeding inhibition was independent of the test diameter which correlated with the reproductive state of the urchins. Feeding inhibition was also independent of the starvation periods between experiments, and the temperature and salinity in ranges tolerated byL. variegatus obtained from the Florida Gulf Coast. The data strongly suggest that at least one alga,Caulerpa prolifera, is chemically defended against a dominant omnivore in its community.

Polyphenols in brown algaeFucus vesiculosus andAscophyllum nodosum: Chemical defenses against the marine herbivorous snail,Littorina littorea.

Polyphenols from two brown algae,Fucus vesiculosus (L.) andAscophyllum nodosum (L.) Le Jolis, inhibited feeding by the herbivorous snail,Littorina littorea. The active compounds were characterized as phloroglucinol polymers with a wide molecular weight range (mol wt <30,000 to >300,000) by spectroscopic, Ultrafiltration, thin-layer chromatographic, and chemical degradation data. As little as 1% (dry wt) polyphenol in food reduced feeding by more than 50%, and polyphenolic extracts inhibited feeding entirely when present in concentrations of 2-5% (dry wt). Commercially available phloroglucinol dihydrate and gallotannin, which are known herbivore feeding deterrents in terrestrial plants, inhibitedL. littorea feeding when added to food media in concentrations similar to those above. We conclude that polyphenols inF. vesiculosus andA. nodosum are functionally similar to terrestrial plant polyphenols (tannins) in providing chemical defenses against herbivores. This research is the first demonstration that chemical compounds defend these two dominant, perennial marine algae from the major herbivore found in their community.