Ryan M. Van Wagoner

Mirabamides E-H, HIV-inhibitory depsipeptides from the sponge Stelletta clavosa.

Four new depsipeptides, mirabamides E-H (1-4), and the known depsipeptide mirabamide C (5) have been isolated from the sponge Stelletta clavosa, collected from the Torres Strait. The planar structures were determined on the basis of extensive 1D and 2D NMR and HRESIMS. The absolute configurations were established by the advanced Marfeys method, NMR, and GC-MS. The four new compounds all showed strong inhibition of HIV-1 in a neutralization assay with IC(50) values of 121, 62, 68, and 41 nM, respectively.

Structure and Biosynthesis of Amphidinol 17, a Hemolytic Compound from Amphidinium carterae

Amphidinol 17 (AM17; 1), a novel amphidinol, has been isolated from a Bahamas strain of Amphidinium carterae. This new congener contains the signature hairpin region and a Delta(6) polyene arm, whereas the polyol arm is distinct from those of other amphidinols. The pattern of acetate incorporation in 1 was directly determined by feeding a single labeled substrate, [2-(13)C]acetate. While the highly conserved regions within the amphidinol family of AM17 have exhibited identical occurrences of cleaved acetates to other amphidinols for which the biosynthesis has been explored, the polyol arm for AM17 displays a higher degree of nascent chain processing that shows similarities to amphidinolide biosynthesis. AM17 exhibited an EC(50) of 4.9 microM in a hemolytic assay using human red blood cells but displayed no detectable antifungal activity.

Further Studies on the Chemistry of the Flustra Alkaloids from the Bryozoan Flustra foliacea

Since 1980, over a dozen novel brominated alkaloids, named flustramines, have been isolated from Scandinavian and Canadian collections of the marine bryozoan Flustra foliacea. This paper describes the reisolation of the known compound dihydroflustramine C (1) and the isolation of 11 new flustramines (2-4, 6-13), including two dimers (12, 13) that may be isolation artifacts. Together these compounds, some with an unexpected aryl substitution pattern, reveal an intricate network of metabolites present in the extracts of the bryozoan. The structures of these metabolites were solved using a variety of spectroscopic techniques and chemical derivatization and modification. This work also led to the recognition of an unusual rearrangement reaction that occurred slowly over a number of years.

Thiazoline Peptides and a Tris-Phenethyl Urea from Didemnum molle with Anti-HIV Activity

As part of our screening for anti-HIV agents from marine invertebrates, the MeOH extract of Didemnum molle was tested and showed moderate in vitro anti-HIV activity. Bioassay-guided fractionation of a large-scale extract allowed the identification of two new cyclopeptides, mollamides E and F (1 and 2), and one new tris-phenethyl urea, molleurea A (3). The absolute configurations were established using the advanced Marfeys method. The three compounds were evaluated for anti-HIV activity in both an HIV integrase inhibition assay and a cytoprotective cell-based assay. Compound 2 was active in both assays with IC(50) values of 39 and 78 μM, respectively. Compound 3 was active only in the cytoprotective cell-based assay, with an IC(50) value of 60 μM.

Strongylophorine-8, a pro-electrophilic compound from the marine sponge Petrosia (Strongylophora) corticata, provides neuroprotection through Nrf2/ARE pathway.

Green plant-origin electrophilic compounds are a newly-recognized class of neuroprotective compounds that provide neuroprotection through activation of the Nrf2/ARE pathway. Electrophilic hydroquinones are of particular interest due to their ability to become electrophilic quinones upon auto-oxidation. Although marine organisms frequently produce a variety of electrophilic compounds, the detailed mechanisms of action of these compounds remain unknown. Here, we focused on the neuroprotective effects of strongylophorine-8 (STR8), a para-hydroquinone-type pro-electrophilic compound from the sponge Petrosia (Strongylophora) corticata. STR8 activated the Nrf2/ARE pathway, induced phase 2 enzymes, and increased glutathione, thus protecting neuronal cells from oxidative stress. Microarray analysis indicated that STR8 induced a large number of phase 2 genes, the regulation of which is controlled by the Nrf2/ARE pathway. STR8 is the first example of a neuroprotective pro-electrophilic compound from marine organisms.

Araiosamines A-D: tris-bromoindole cyclic guanidine alkaloids from the marine sponge Clathria (Thalysias) araiosa.

Four new tris-bromoindole cyclic guanidine alkaloids, araiosamines A-D, were isolated from the methanol extract of a marine sponge, Clathria (Thalysias) araiosa, collected from Vanuatu. Their carbon skeletons delineate a new class of indole alkaloids apparently derived from a linear polymerization process involving a carbon-carbon bond formation. Comparison of the structures including the relative configurations suggests a common intermediate containing a dihydroaminopyrimidine moiety capable of undergoing various modalities of conjugate addition to yield unprecedented ring systems.

4-quinolone alkaloids from melochia odorata

The methanol extract of Melochia odorata yielded three 4-quinolone alkaloids including waltherione A (1) and two new alkaloids, waltherione C (2) and waltherione D (3). Waltheriones A and C showed significant activities in an in vitro anti-HIV cytoprotection assay at concentrations of 56.2 and 0.84 μM and inhibition of HIV P24 formation of more than 50% at 1.7 and 0.95 μM, respectively. The structures of the alkaloids were established by spectroscopic data interpretation.

Biosynthesis of scorpinone, a 2-azaanthraquinone from Amorosia littoralis, a fungus from marine sediment.

The biogenetic origin of the carbon atoms in the 2-azaanthraquinone scorpinone ( 1), produced by the rare fungus Amorosia littoralis isolated from marine sediment, was explored through isotopic enrichment studies utilizing [2- (13)C]-acetate and [1,2- (13)C]-acetate. The labeling results reveal a heptaketide precursor is involved in the biosynthesis of 1, as has been found for the structurally related naphthoquinone dihydrofusarubin. The previously identified naphthoquinone herbarin ( 2) was also isolated and appears to bear the same biogenetic relationship to 1 as the fusarubins do to the fungal 2-azaanthraquinone bostrycoidins.

Juxtaposition of Chemical and Mutation-Induced Developmental Defects in Zebrafish Reveal a Copper-Chelating Activity for Kalihinol F

A major hurdle in using complex systems for drug screening is the difficulty of defining the mechanistic targets of small molecules. The zebrafish provides an excellent model system for juxtaposing developmental phenotypes with mechanism discovery using organism genetics. We carried out a phenotype-based screen of uncharacterized small molecules in zebrafish that produced a variety of chemically induced phenotypes with potential genetic parallels. Specifically, kalihinol F caused an undulated notochord, defects in pigment formation, hematopoiesis, and neural development. These phenotypes were strikingly similar to the zebrafish mutant, calamity, an established model of copper deficiency. Further studies into the mechanism of action of kalihinol F revealed a copper-chelating activity. Our data support this mechanism of action for kalihinol F and the utility of zebrafish as an effective system for identifying therapeutic and target pathways.

Single-molecule inhibition of human kinesin by adociasulfate-13 and -14 from the sponge Cladocroce aculeata

Significance Kinesin motor proteins are central to cellular processes and considered good drug targets, but very few reported kinesin inhibitors exhibit potential as drugs. Adociasulfates uniquely inhibit kinesins by competing with microtubules for binding. A declining interest in these compounds resulted from a report of large aggregates of adociasulfate-2 responsible for kinesin inhibition, poor cell permeability, and broad kinesin inhibition, limiting potential therapeutic applications. In this study, we show that kinesin inhibition is likely a 1:1 interaction and does not involve aggregates. We suggest a means by which cell permeability may be improved and show that adociasulfates inhibit kinesin-1 and -5 families of motors to a significantly different extent. These results collectively bring adociasulfates back to the foreground of chemical biology. Two merotriterpenoid hydroquinone sulfates designated adociasulfate-13 (1) and adociasulfate-14 (2) were purified from Cladocroce aculeata (Chalinidae) along with adociasulfate-8. All three compounds were found to inhibit microtubule-stimulated ATPase activity of kinesin at 15 µM by blocking both the binding of microtubules and the processive motion of kinesin along microtubules. These findings directly show that substitution of the 5′-sulfate in 1 for a glycolic acid moiety in 2 maintains kinesin inhibition. Nomarski imaging and bead diffusion assays in the presence of adociasulfates showed no signs of either free-floating or bead-bound adociasulfate aggregates. Single-molecule biophysical experiments also suggest that inhibition of kinesin activity does not involve adociasulfate aggregation. Furthermore, both mitotic and nonmitotic kinesins are inhibited by adociasulfates to a significantly different extent. We also report evidence that microtubule binding of nonkinesin microtubule binding domains may be affected by adociasulfates.