Maurice Aknin

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.

Four new cytotoxic cyclic hexa- and heptapeptides from the marine ascidian Didemnum molle

Abstract Two novel cyclic hexapeptides, comoramides A and B and two new cyclic heptapeptides, mayotamides A and B were isolated, separately, from two collections of the compound ascidian Didemnum molle collected at two spots of the lagoon of Mayotte. The structure of all four peptides, including the absolute configuration of all amino acids, was elucidated by spectroscopic analysis, mainly NMR data, and degradation experiments. All four compounds exhibit mild cytotoxicity against several tumor cells. Obtaining four new cyclic peptides from two D. molle collections, which add to the two earlier reported cyclic peptides from an Australian and Philippine D. molle , supports the notion that these compounds originate from prokaryotic algal symbionts.

New Lobane and Cembrane Diterpenes from Two Comorian Soft Corals

Preliminary biological investigation of a collection of Comorian soft corals resulted in the selection of two specimens, one of Sarcophyton and the other of Lobophytum, on the basis of their toxicity on larvae of the brine shrimp (Artemia salina) and inhibition of acetylcholinesterase, respectively. Bioassay-guided fractionations provided a known antitumor promoter cembrane diterpenoid, (+)-sarcophytol-A (1), along with a new lobane diterpenoid, carbomethoxyfuscol (2), from Sarcophyton sp., and a new cembranoid, crassumolide E (3), from Lobophytum sp. The structures of compounds 1–3 were determined by spectroscopic analysis and by comparison of the spectral data with previously reported values. The cembranoid 3 was found to exhibit a moderate inhibitory effect on acetylcholinesterase.

Trikentramine, an unusual pyrrole derivative from the sponge trikentrion loeve carter

Abstract Trikentramine, an unusual pyrrole, has been isolated from the Senegalese sponge Trikentrion loeve and characterized by spectroscopic and X-ray diffraction techniques.

Saldedines A and B, dibromo proaporphine alkaloids from a Madagascan tunicate.

Two new dibromo proaporphine alkaloids, designated saldedines A (1) and B (2), were isolated from an unidentified tunicate collected at Salary Bay, Madagascar. Saldedines A and B are the first marine proaporphine alkaloids. Their structures were elucidated by extensive spectroscopic means, and the structure of 1 was confirmed by single-crystal X-ray diffraction analysis. Both saldedines A and B were tested for toxicity to brine shrimp and showed moderate activity.

Novel 3-β-methoxysteroids from the senegalse sponge Microscleroderma spirophora

Abstract The Senegalse sponge Microscleroderma spirophora has been found to produce exclusively very unusual 3β-methoxysteroids in place of the common 3β-hydroxysteroids. Six different methoxysteroids (three of which are novel compounds) have been isolated and identified by spectroscopic means (MS, IR, 1 H and 13 C 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 propose.

Netamines H-N, tricyclic alkaloids from the marine sponge Biemna laboutei and their antimalarial activity.

Chemical examination of the CH2Cl2-MeOH (1:1) extract of the Madagascar sponge Biemna laboutei resulted in the isolation of seven new tricyclic alkaloids, netamines H-N (1-7), along with the known netamine G and mirabilins A, C, and F. Their structures were elucidated by interpretation of 1D and 2D NMR spectra and HRESIMS data. All compounds were evaluated for their cytotoxicity against KB cells and their antiplasmodial activity. Netamine M (6) was found to be cytotoxic, with an IC50 value in the micromolar range, and netamine K (4) exhibited activity against Plasmodium falciparum with an IC50 value of 2.4 μM.

24-O-Ethylmanoalide, a Manoalide-related Sesterterpene from the Marine sponge Luffariella cf. variabilis

A new manoalide-related sesterterpene, 24-O-ethylmanoalide (3), was isolated from the Indian Ocean sponge Luffariella cf. variabilis, together with the known compounds manoalide (1), seco-manoalide, manoalide monoacetate and 24-O-methyl-manoalide (2). The structure of compound 3 was elucidated by interpretation of its spectroscopic data.

Isohalitulin and haliclorensins B and C, three marine alkaloids from Haliclona tulearensis.

Three new alkaloids, designated isohalitulin (4), haliclorensin B (5), and haliclorensin C (6), were isolated from two specimens of the Madagascan sponge Haliclona tulearensis, collected at two locations in Salary Bay, north of Tulear. Their structures were elucidated by extensive spectroscopic means. Alkaloids 4-6 exhibited mild toxicity in the brine shrimp test.

A new alkaloid from the purple Indian Ocean tunicate Eudistoma bituminis

A new alkaloid, segoline C 1 possessing the benzo 1,6-diazaphenanthroline ring system has been isolated from the Indian Ocean tunicate Eudistoma bituminis with the known segoline A 2 isolated from the Red Sea tunicate Eudistoma sp. The structure of all compounds was elucidated on the basis of spectroscopic data. The relative configuration of the chiral compound 1 is proposed on the basis of comparative circular dichroism (CD) measurements of segolines A 2 and B 3.