Alfonso Mangoni

Dispacamides, anti-histamine alkaloids from Caribbean Agelas sponges

Abstract Dispacamide 1 and its monobromo derivative 2 , are novel bromopyrrole alkaloids containing an aminoimidazolone moiety. They were isolated from four Caribbean Agelas sponges ( A. conifera, A. longissima, A. clathrodes, A. dispar ), and their structures elucidated on the basis of spectroscopic data. Compounds 1 and 2 exhibit remarkably selective antihistamine activity, tested on the guinea pig ileum.

The hoiamides, structurally intriguing neurotoxic lipopeptides from Papua New Guinea marine cyanobacteria.

Two related peptide metabolites, one a cyclic depsipeptide, hoiamide B (2), and the other a linear lipopeptide, hoiamide C (3), were isolated from two different collections of marine cyanobacteria obtained in Papua New Guinea. Their structures were elucidated by combining various techniques in spectroscopy, chromatography, and synthetic chemistry. Both metabolites belong to the unique hoiamide structural class, characterized by possessing an acetate extended and S-adenosyl methionine modified isoleucine unit, a central triheterocyclic system comprised of two alpha-methylated thiazolines and one thiazole, and a highly oxygenated and methylated C-15 polyketide unit. In neocortical neurons, the cyclic depsipeptide 2 stimulated sodium influx and suppressed spontaneous Ca(2+) oscillations with EC(50) values of 3.9 microM and 79.8 nM, respectively, while 3 had no significant effects in these assays.

Glycolipids from sponges. IV. Immunomodulating glycosyl ceramides from the marine sponge agelas dispar.

The GSL composition of the marine sponge Agelas dispar was investigated. In addition to four GSLs previously isolated from Agelas clathrodes (2 and 4), Agelas conifera (3), and Agelas longissima (5), the novel triglycosylceramide 1a was isolated as a major component of the GSL mixture. All the isolated GSLs were tested using the MLR assay, and only some of them were shown to be immunoactivating agents, suggesting a possible structure-activity relationship.

Longamide and 3,7-dimethylisoguanine, two novel alkaloids from the marine sponge Agelas longissima

Abstract A purine derivative. 3,7-dimethylisoguanine ( 1 ), and a novel alkaloid with the unusual pyrrolopiperazine nucleus, longamide ( 2 ), were isolated from the sponge Agelas longissima , and their structures established on the basis of spectroscopic data. In addition, 2 exhibited a mild antibacterial activity.

The Molecular Basis for the Evolution of the Metazoan Bodyplan: Extracellular Matrix-Mediated Morphogenesis in Marine Demosponges

Molecular data on development/differentiation and on comparative genomics allow insights into the genetic basis of the evolution of a bodyplan. Sponges (phylum Porifera) are animals that are the (still extant) stem group with the hypothetical Urmetazoa as the earliest common ancestor of all metazoans; they possess the basic features of the characteristic metazoan bodyplan also valid for the animals of the crown taxa. Here we describe three homeobox genes from the demosponge Suberites domuncula whose deduced proteins (HOXa1_SUBDO, HOXb1_SUBDO, HOXc1_SUBDO) are to be grouped with the Antennapedia class of homeoproteins (subclasses TIx-Hox11 and NK-2). In addition, a cDNA encoding a LIM/homeobox protein has been isolated which comprises high sequence similarity to the related LIM homeodomain (HD) proteins in its LIM as well as in its HD domains. To elucidate the potential function of these proteins in the sponge a new in vitro system was developed. Primmorphs which are formed from dissociated cells were grown on a homologous galectin matrix. This galectin cDNA was cloned and the recombinant protein was used for the preparation of the matrix. The galectin/polylysine matrix induced in primmorphs the formation of channels, one major morphogenetic process in sponges. Under such conditions the expression of the gene encoding the LIM/homeobox protein is strongly upregulated, while the expression of the other homeobox genes remains unchanged or is even downregulated. Competition experiments with galactosylceramides isolated from S.domuncula were performed. They revealed that a β-galactosylceramide, named Sdgal-1, prevented the expression of the LIM gene on the galectin matrix, while Sdgal-2, a diglycosylceramide having a terminal α-glycosidically linked galactose, caused no effect on the formation of channels in primmorphs or on LIM expression. This study demonstrates for the first time that an extracellular matrix molecule, galectin, induces a morphogenetic process in sponges which is very likely caused by a LIM/homeobox protein. Furthermore, a new model is introduced (galectin-caused channel formation in sponge primmorphs) to investigate basic pathways, thus allowing new insights into the functional molecular evolution of Metazoa.

Genome mining reveals trans-AT polyketide synthase directed antibiotic biosynthesis in the bacterial phylum bacteroidetes.

Complex polyketides such as erythromycin, epothilone, and FK506 greatly contribute to human health. Bacteria synthesize these natural products through large, multifunctional enzymes called modular polyketide synthases (PKSs), which use many catalytic domains in sequence to generate polyketide chains in an assembly-line-like process. Because there is usually a strict correlation between the enzymatic architecture and the structure of the metabolite, it is often possible to predict the biosynthetic product from a PKS gene sequence. This feature has been successfully exploited for natural product discovery through bioinformatic analysis of bacterial DNA sequences. Considering the impressive recent developments in the field of sequencing technologies and the concomitant explosion in genomic data, it is anticipated that genome mining will play a key role in future drug discovery programs. A crucial prerequisite for the success of this strategy is for predictions to be made at a high level of confidence for a wide range of pathways. A recent unexpected discovery by our research group and others is the presence of a novel and evolutionarily distinct group of modular PKSs. These enzymes use free-standing acyltransferases (AT) to select polyketide building blocks and to attach them to the multifunctional PKS in trans, as opposed to cis-acting textbook PKSs that carry integrated AT domains. Such trans-AT PKSs have long been overlooked, as they are rare in actinomycetes that served as initial model organisms to study polyketide biosynthesis. However, a wide range of bioactive polyketides from diverse bacteria, including the clinically used antibiotics of the mupirocin and streptogramin series, are now known to be products of trans-AT PKSs. Trans-AT pathways represent highly interesting targets for natural product discovery for two reasons: they often occur in bacteria that have not been well studied in pharmacological screening programs, and the PKSs exhibit a remarkable array of unusual enzymatic features, such as new catalytic domains, unprecedented module architectures, and non-canonical biosynthetic transformations, which often translate into unusual chemistry. Another consequence of these peculiarities is that textbook collinearity rules cannot be applied to deduce structures from DNA data. However, on the basis of functional and phylogenetic studies, we recently developed a novel predictive approach that allows the assignment of polyketides to transAT PKS sequences with high confidence. This method is based on the observation that the substrate specificity of ketosynthase (KS) domains, which catalyze polyketide chain extensions in a Claisen-condensation-like reaction, correlates with its evolution. Thus, if the position of a particular KS in a phylogenetic tree is known, it can often be predicted whether its substrate carries a b-hydroxy group, an a,b-double bond, an a,breduced moiety, or an aor b-carbon branch. In this way, structural information for an entire polyketide chain can be obtained by combining the information of all KSs present in a PKS. The utility of these trans-AT collinearity rules was demonstrated by the isolation of novel thailandamide polyketides by genome mining of Burkholderia thailandensis. Since then, it was shown that the predictive power can be continuously increased by refining the phylogenetic analysis with KSs of newly sequenced gene clusters. In this work, we demonstrate the utility of trans-AT genome mining by assigning a PKS of Chitinophaga pinensis DSM 2588, a member of the chemically poorly studied bacterial phylum Bacteroidetes, to the biosynthesis of elansolids, antibacterial and cytotoxic agents that arise from an unusual series of post-PKS modifications. The genome of C. pinensis DSM 2588, a heterotrophic gliding bacterium consisting of long unicellular filaments, was found to contain two large gene clusters that encode a hybrid non-ribosomal peptide synthetase-PKS and a trans-AT PKS system (the latter termed els PKS). Intrigued by the fact that only few compounds have been previously reported from the genus Chitinophaga, we were interested in the product of the els pathway. The cluster (Table 1) spans 75.1 kb and contains 18 genes, of which six (elsIJNOPQ) encode multimodular PKS proteins, none of which harbors AT domains. Instead, elsA and elsB exhibit similarities to free-standing AT genes of transAT PKSs. ElsA also contains an additional C-terminal oxidoreductase domain that was recently shown to catalyze enoyl reductions in trans. The els polyketide was therefore expected to contain at least one reduced moiety. Several putative proteins (ElsDEKLM) were identified that are usually involved in the generation of b-carbon branches at the growing polyketide chain. 14] Further gene products resemble 4-hydroxybenzoate synthases (ElsH), cytochromes P450 (ElsF), methyltransferases (ElsR), and proteins with unknown function (ElsC and ElsG). The six large PKS proteins contain a total of 15 modules. The N terminus of ElsI harbors a module that consists of [a] Dr. R. Teta , E. J. N. Helfrich, S. K nne, A. Schneider, Prof. Dr. J. Piel Kekul Institute of Organic Chemistry and Biochemistry University of Bonn, Gerhard-Domagk-Strasse 1, 53121 Bonn (Germany) Fax: (+ 49) 228-739712 E-mail : joern.piel@uni-bonn.de [b] Dr. M. Gurgui, Dr. G. Van Echten-Deckert Kekul Institute LIMES Membrane Biology and Lipid Biochemistry University of Bonn, Gerhard-Domagk-Strasse 1, 53121 Bonn (Germany) [c] Dr. R. Teta , Prof. Dr. A. Mangoni Dipartimento di Chimica delle Sostanze Naturali Universit di Napoli “Federico II” Via D. Montesano 49, 80131 Napoli (Italy) Supporting information for this article is available on the WWW under http ://dx.doi.org/10.1002/cbic.201000542.

Glycolipids from sponges. VII.1 simplexides, novel immunosuppressive glycolipids from the caribbean sponge Plakortis simplex

The new glycolipids simplexides (1) have been isolated from the marine sponge Plakortis simplex, and their structure determined by spectroscopic data and microgram-scale chemical degradation. Simplexides are composed of long-chain secondary alcohols glycosylated by a disaccharide chain, and represent a new structural kind of glycolipids. Simplexides strongly inhibit proliferation of activated T-cells by a non-cytotoxic mechanism and can be regarded as simple model molecules for designing immunosuppressive drugs.

Okadaic acid in mussels of Adriatic Sea

Abstract The diarrethic shellfish poisoning from mussels, collected in the main producing areas in the seawater off the coast of Emilia-Romagna (Italy), has been investigated. The ether soluble material from hepatopancreas of highly toxic mussels (Mytilus galloprovincialis) was partitioned between n-hexane and methanol-water 9:1. The hydromethanolic phase was successively subjected to repeated chromatographic separations (SiO2, Sephadex LH-20 and reversed-phase HPLC). Following the toxicity of each fraction by mouse lethality test, the presence of okadaic acid has been evidenced through 1H NMR spectroscopy. The investigation of two further toxic fractions is still in progress. The obtained results represent an initial contribution to current Italian legislation and to future health measures to be defined at European Community level.

A mild and easy one-pot procedure for the synthesis of 2-deoxysugars from glycals

Abstract Glycals can be converted into the corresponding 2-deoxysugars in good yields by treatment with N-iodosuccinimide in CH3CN–H2O 95:5 and removal of the iodide group using Na2S2O4 in DMF/H2O at room temperature. This method is easy to apply, sufficiently mild to allow the survival of acid-sensitive groups such as silyl and trityl ethers and less harmful to the environment than metal-based reactions.

New 9,11-secosterols from gorgonia Subergorgia suberosa of the Indian Ocean

Three new 9,11-secosterols, 3 beta,6 alpha,11-trihydroxy-9,11-seco-5 alpha-cholest-7-ene-9-one (1), 24S- (2a), and 24R-methyl-3 beta,6 alpha, 11-trihydroxy-9,11-seco-5 alpha-cholest-7,22E-diene-9-one (2b), were isolated from the Indian Ocean gorgonia, Subergorgia suberosa. Their structures were established by spectroscopic data.