Adociasulfate 10, A New Merohexaprenoid Sulfate from the Sponge Haliclona (aka Adocia) sp

Biogenetic Relationships of Bioactive Sponge Merotriterpenoids

Hydroquinone meroterpenoids, especially those derived from marine sponges, display a wide range of biological activities. However, use of these compounds is limited by their inaccessibility; there is no sustainable supply of these compounds. Furthermore, our knowledge of their metabolic origin remains completely unstudied. In this review, an in depth structural analysis of sponge merotriterpenoids, including the adociasulfate family of kinesin motor protein inhibitors, provides insight into their biosynthesis. Several key structural features provide clues to the relationships between compounds. All adociasulfates appear to be derived from only four different hydroquinone hexaprenyl diphosphate precursors, each varying in the number and position of epoxidations. Proton-initiated cyclization of these precursors can lead to all carbon skeletons observed amongst sponge merotriterpenoids. Consideration of the enzymes involved in the proposed biosynthetic route suggests a bacterial source, and a hypothetical gene cluster was constructed that may facilitate discovery of the authentic pathway from the sponge metagenome. A similar rationale can be extended to other sponge meroterpenoids, for which no biosynthetic pathways have yet been identified.

Marine natural products that interfere with multiple cytoskeletal protein interactions

Various marine natural products that target cytoskeletal proteins have been discovered. A few of these compounds have recently been shown to induce or inhibit protein-protein interactions. Lobophorolide, an actin filament-disrupting macrolide, binds to actin with a unique 2 : 2 stoichiometry in which two lobophorolide molecules cooperate to stabilize an actin dimer. Adociasulfates, merotriterpenoid derivatives, inhibit microtubule-stimulated ATPase activity of a motor protein kinesin by blocking both the binding of microtubules and the processive motion of kinesin along microtubules. The antitumor macrolide aplyronine A synergistically binds to tubulin in association with actin, and prevents spindle formation and mitosis. In this highlight, we address recent chemical biology studies on these mechanistically-attractive marine natural products. These findings may be useful for the design and development of new pharmacological tools and therapeutic agents.

Pd-catalyzed steroid reactions

We review the most important achievements of the last decade in the field of steroid synthesis in the presence of palladium catalysts. Various palladium-catalyzed cross-coupling reactions, including Heck, Suzuki, Stille, Sonogashira, Negishi and others, are exemplified with steroid transformations.

Unusual cyclic terpenoids with terminal pendant prenyl moieties: from occurrence to synthesis

The paper reviews the known examples of cyclic terpenoids produced from open chain polyenic precursors by an "unusual" biosynthetic pathway, involving selective electrophilic attack on an internal double bond followed by cyclization. The resulting compounds possess cyclic backbones with pendant terminal prenyl groups. Synthetic approaches applied for the synthesis of such specifically functionalized compounds are also discussed, as well as biological activity of reported representatives.

Antibiotic activity and microbial community of the temperate sponge, Haliclona sp

AIMS

Sessile marine invertebrates engage in a diverse array of beneficial interactions with bacterial symbionts. One feature of some of these relationships is the presence of bioactive natural products that can defend the holobiont from predation, competition or disease. In this study, we investigated the antimicrobial activity and microbial community of a common temperate sponge from coastal North Carolina.

METHODS AND RESULTS

The sponge was identified as a member of the genus Haliclona, a prolific source of bioactive natural products, based on its 18S rRNA gene sequence. The crude chemical extract and methanol partition had broad activity against the assayed Gram-negative and Gram-positive pathogenic bacteria. Further fractionation resulted in two groups of compounds with differing antimicrobial activity, primarily against Gram-positive test organisms. There was, however, notable activity against the Gram-negative marine pathogen, Vibrio parahaemolyticus. Microbial community analysis of the sponge and surrounding sea water via denaturing gradient gel electrophoresis (DGGE) indicates that it harbours a distinct group of bacterial associates.

CONCLUSIONS

The common temperate sponge, Haliclona sp., is a source of multiple antimicrobial compounds and has some consistent microbial community members that may play a role in secondary metabolite production.

SIGNIFICANCE AND IMPACT OF THE STUDY

These data suggest that common temperate sponges can be a source of bioactive chemical and microbial diversity. Further studies may reveal the importance of the microbial associates to the sponge and natural product biosynthesis.

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

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.

Meroterpenes from marine invertebrates: structures, occurrence, and ecological implications

Meroterpenes are widely distributed among marine organisms; they are particularly abundant within brown algae, but other important sources include microorganisms and invertebrates. In the present review the structures and bioactivities of meroterpenes from marine invertebrates, mainly sponges and tunicates, are summarized. More than 300 molecules, often complex and with unique skeletons originating from intra- and inter-molecular cyclizations, and/or rearrangements, are illustrated. The reported syntheses are mentioned. The issue of a potential microbial link to their biosynthesis is also shortly outlined.

Halicloic acids A and B isolated from the marine sponge Haliclona sp. collected in the Philippines inhibit indoleamine 2,3-dioxygenase

Two new merohexaprenoids, halicloic acids A (1) and B (2), have been isolated from the marine sponge Haliclona (Halichoclona) sp. collected in the Philippines. The glycolic acids 1 and 2 slowly decomposed during acquisition of NMR data to aldehydes 3 and 4, respectively, via an oxidative decarboxylation. Halicloic acid B (2) has the new rearranged "haliclane" meroterpenoid carbon skeleton. The halicloic acids 1 and 2 are indoleamine 2,3-dioxygenase inhibitors that are significantly more active than the decomposition products 3 and 4.

Elucidating the functionality of kinesins: an overview of small molecule inhibitors

Kinesin motor proteins are ubiquitously involved in multiple fundamental cellular processes, coordinating transport and mediating changes to cellular architecture. Thus, specific small molecule kinesin inhibitors can shed new light on the functions of kinesins and the dynamic roles in which they participate. Here we review the range of known inhibitors, their key characteristics, and specificity, and discuss their potential suitability for chemical genetics as starting points to further investigate complex kinesin-mediated processes.

Sulfated meroterpenoids from the Brazilian sponge Callyspongia sp. are inhibitors of the antileishmaniasis target adenosine phosphoribosyl transferase

Three new disulfated meroterpenoids, ilhabelanol (1), ilhabrene (2), and isoakaterpin (3), have been isolated from extracts of the Brazilian marine sponge Callyspongia sp. Isoakaterpin (3) inhibits Leishmania spp. adenosine phosphoribosyl transferase with an IC50 of 1.05 microM. The structures of 1, 2, and 3 were elucidated by analysis of one- and two-dimensional NMR data. Ilhabelanol (1) and ilhabrene (2) both have unprecedented meroterpenoid carbon skeletons.

Heteroareno-annelated estranes by triene cyclization

17-Thienyl-and 17-benzo[b]thienyl-3-hydroxyestra-1,3,5(10),16-tetraenes were synthesized by either sequential or one-pot Suzuki cross-coupling and Wittig olefination reactions. At 160 °C, heteroaryl substituted steroids were observed to undergo thermal intramolecular cyclization to produce E-ring heteroareno-annelated estranes.

Inhibition of Kinesin Motor Proteins by Adociasulfate-2

Kinesin motor proteins are involved in cell division and intracellular transport of vesicles and organelles, and as such, they play a role in neurological disease, cancer, and developmental disorders. Inhibitors of kinesin would be valuable as probes of cell physiology and as potential therapeutics. Adociasulfate-2 (AS-2) is the only known natural product inhibitor of kinesins, but its mechanism of action is unknown. We utilized kinetic studies, dynamic light scattering, and transmission electron microscopy to investigate the inhibitory action of AS-2. Our data suggest that AS-2 is not a classical 1:1 inhibitor. Instead, a rodlike aggregate that mimics microtubules is complexed with kinesin and inhibits its ATPase activity. An intriguing implication of this hypothesis is that aggregates of a chiral natural product can have interesting and biologically relevant properties. This mode of action might represent one way in which a small molecule can disrupt a protein-protein interaction.

Hexaprenoid hydroquinones from the sponge Haliclona (aka Adocia) sp

Three new hexaprenoid hydroquinones, adociaquinol (1), adociasulfate 11 (2), and adociasulfate 12 (3), together with the known adociasulfates 2, 4, and 6, were isolated from the marine sponge Haliclona (aka Adocia) sp. The structures of these compounds were elucidated by interpretation of spectroscopic data.