| Name | Valeria |
| Surname | Costantino |
| Institution | University of Naples – Federico II |
| valeria.costantino@unina.it | |
| Address | Dipartimento di Farmacia, Università degli Studi di Napoli Federico II, via Domenico Montesano 49, 80131 Napoli, Italy |
| Resume | Download |
Electrospray ionization (ESI) and liquid secondary ionization (LSI) mass spectrometry were applied for characterization of glycosphingolipids (GSLs) isolated in their peracetylated form from four Agelas marine sponge species. Since peracetylated glycosphingolipids are not soluble in solvents traditionally used for ESI, lithium chloride was added to the samples in order to obtain lithium cationized molecules. Although the preferred fragmentation seems to be the sequential loss of acetic acid molecules, it was found that tandem mass spectra obtained from peracetylated diglycosyl ceramides might provide direct information about the structure of the long-chain base (formation of W''/Z0 fragments). The utility of ESI and LSI in the analysis of these compounds has also been compared. It was found that the tandem mass spectra obtained by LSI-MS/MS experiments could provide information about the chain-length (carbon atom number) variations within a certain ceramide mass. Thus, from one of our samples, 25 different ceramide compositions have been identified from 8 precursor (Z0) ions. Comparison of the two ionization modes (LSI and ESI) highlights the fact that molecular mass distributions obtained by LSI-MS, especially the presence of unsaturated species, have to be interpreted carefully. For the first time a direct high-performance liquid chromatography (HPLC)/ESI-MS method was used for characterization of complex mixtures of peracetylated GSLs. The results demonstrate that HPLC/ESI-MS is able to analyze mono- and diglycosylated GSLs, and other kinds of glycolipids that are actually present in the sample.
In addition to the previously reported crasserides (1a-m), marine sponges contain smaller amounts of the isomeric isocrasserides (3a-m). The structures of these new glycoglycerolipid analogues were determined by NMR analysis and chemical degradation. Crasserides and isocrasserides were present in all the species of marine sponges we analyzed and therefore appear to be characteristic of the phylum Porifera.
The sterol composition of the Caribbean sponge Iotrochota birotulata was investigated. Structure of a new ecdysteroid 2beta,3beta,14alpha, 20beta-tetrahydroxy-22alpha-(2-hydroxyacetiloxy)-5b eta-colest-7-en-6- one (1) was assigned on the basis of spectroscopic and chemical evidence and molecular mechanics calculations. Isolation of the widespread ecdysteroids 2-5 is also reported.
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.
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.
The sterol composition of the Caribbean sponge Neofibularia nolitangere has been investigated. In addition to usual sterols this sponge elaborates comparable amounts of 24-methylene-4 alpha-methyl-5 alpha-cholest-8-en-3 beta-ol (1), which is very unusual among sponge sterols, and lesser quantities of two new polyoxygenated sterols, (24S)-24-ethyl-5 alpha-cholest-8-ene-5,6 beta,7 alpha-triol (2) and (24S)-24-ethyl-5 alpha-cholest-8(14)-ene-5,6 beta,7 alpha-triol (3).
The Senegalese sponge Microscleroderma spirophora has been found to produce exclusively very unusual 3 beta-methoxysteroids in place of the common 3 beta-hydroxysteroids. Six different methoxysteroids (three of which are novel compounds) have been isolated and identified by spectroscopic means (MS, IR, 1H and 13C NMR), and their taxonomic significance discussed. A new method for the determination of the configuration at C-24 in saturated 24-ethyl side chains is also proposed.