New lipids from the tunicate Cystodytes cf. dellechiajei, as PLA2 inhibitors

Chemical and Pharmacological Prospection of the Ascidian Cystodytes dellechiajei

Marine invertebrates are a traditional source of natural products with relevant biological properties. Tunicates are soft-bodied, solitary or colonial, sessile organisms that provide compounds unique in their structure and activity. The aim of this work was to investigate the chemical composition of the ascidian Cystodytes dellechiajei, selected on the basis of a positive result in biological screening for ligands of relevant receptors of the innate immune system, including TLR2, TLR4, dectin-1b, and TREM2. Bioassay-guided screening of this tunicate extract yielded two known pyridoacridine alkaloids, shermilamine B (1) and N-deacetylshermilamine B (2), and a family of methyl-branched cerebrosides (3). Compounds 2 and 3 showed selective binding to TREM2 in a dose-dependent manner. N-deacetylshermilamine B (2), together with its acetylated analogue, shermilamine B (1), was also strongly cytotoxic against multiple myeloma cell lines. TREM2 is involved in immunomodulatory processes and neurodegenerative diseases. N-deacetylshermilamine B (2) is the first example of a polycyclic alkaloid to show an affinity for this receptor.

Mechanism of action of antiepileptic ceramide from Red Sea soft coral Sarcophyton auritum

Chemical investigation of the Red Sea soft coral Sarcophyton auritum led to the isolation and structure elucidation of a new ceramide N-((2S,3R,4E,6E)-1,3-dihydroxyhenicosa-4,6-dien-2-yl)tridecanamide (1). Structure elucidation was achieved using spectroscopic techniques, including 1D and 2D NMR and HRMS. The anticonvulsant activity of the isolated ceramide was measured in vivo using the pentylenetetrazole (PTZ)-induced seizure model, where it successfully antagonized the lethality of pentylenetetrazole in mice. In addition, the isolated ceramide showed good anxiolytic activity when used in the light–dark transition box and the elevated plus maze compared to diazepam. The molecular modeling studies for the antiepileptic and antianxiety mechanism of the isolated ceramide suggested a CNS depressing activity possibly through GABA and serotonin receptors modulation. The pharmacological activity of the ceramide involved agonistic activity on GABA-A receptors but not 5HT3 receptors.

Endozoicomonas Are Specific, Facultative Symbionts of Sea Squirts

Ascidians are marine filter feeders and harbor diverse microbiota that can exhibit a high degree of host-specificity. Pharyngeal samples of Scandinavian and Mediterranean ascidians were screened for consistently associated bacteria by culture-dependent and -independent approaches. Representatives of the Endozoicomonas (Gammaproteobacteria, Hahellaceae) clade were detected in the ascidian species Ascidiella aspersa, Ascidiella scabra, Botryllus schlosseri, Ciona intestinalis, Styela clava, and multiple Ascidia/Ascidiella spp. In total, Endozoicomonas was detected in more than half of all specimens screened, and in 25-100% of the specimens for each species. The retrieved Endozoicomonas 16S rRNA gene sequences formed an ascidian-specific subclade, whose members were detected by fluorescence in situ hybridization (FISH) as extracellular microcolonies in the pharynx. Two strains of the ascidian-specific Endozoicomonas subclade were isolated in pure culture and characterized. Both strains are chemoorganoheterotrophs and grow on mucin (a mucus glycoprotein). The strains tested negative for cytotoxic or antibacterial activity. Based on these observations, we propose ascidian-associated Endozoicomonas to be commensals, living off the mucus continuously secreted into the pharynx. Members of the ascidian-specific Endozoicomonas subclade were also detected in seawater from the Scandinavian sampling site, which suggests acquisition of the symbionts by horizontal transmission. The combined results indicate a host-specific, yet facultative symbiosis between ascidians and Endozoicomonas.

Anti-choline esterase activity of ceramides from the Red Sea marine sponge Mycale euplectellioides

New ceramides were isolated, and structurally elucidated, from the marine sponge Mycale euplectellioides. The isolated compounds showed moderate anti-choline esterase activity in vitro and tight binding to AChE as confirmed through a docking study.

Structural Analysis of the Minor Cerebrosides from a Glass Sponge Aulosaccus sp

The minor cerebrosides from a Far-Eastern glass sponge Aulosaccus sp. were analyzed as constituents of some multi-component RP-HPLC fractions. The structures of eighteen new and one known cerebrosides were elucidated on the basis of NMR spectroscopy, mass spectrometry, optical rotation data and chemical transformations. These β-D-glucopyranosyl-(1→1)-ceramides contain sphingoid bases N-acylated with straight-chain (2R)-2-hydroxy fatty acids, namely, (2S,3S,4R,11Z)-2-aminoeicos-11-ene-1,3,4-triol, acylated with 15E-22:1, 16Z-21:1, 15Z-21:1, 15Z-20:1, 15E-20:1, 19:0, 18:0 acids, (2S,3S,4R)-2-amino-13-methyltetradecane-1,3,4-triol--with 19Z-26:1, 16Z-23:1, 23:0, 22:0 acids, (2S,3S,4R)-2-amino-14-methylpentadecane-1,3,4-triol--with 16Z-23:1, 16E-23:1, 15Z-22:1, 22:0 acids, (2S,3S,4R)-2-amino-14-methylhexadecane-1,3,4-triol, linked to 16Z-23:1, 15Z-22:1 acids, (2S,3S,4R)-2-amino-9-methylhexadecane-1,3,4-triol--to 16Z-23:1 acid, and (2S,3S,4R)-2-aminohexadecane-1,3,4-triol, attached to 15Z-22:1 acid. The 13-methyl and 9-methyl-branched trihydroxy sphingoid base backbones (C15 and C17, respectively) have not been found previously in sphingolipids. The ceramide parts, containing other backbones, present new variants of N-acylation of the marine sphingoid bases with the 2-hydroxy fatty acids. The combination of the instrumental and chemical methods used in this study improved the efficiency of the structural analysis of such complex cerebroside mixtures that gave more detailed information on glycosphingolipid metabolism of the organism.

Cytotoxic effects of three new metabolites from Red Sea marine sponge, Petrosia sp

Marine sponges represent an affluent source of biogenetically unprecedented array of biologically active compounds. This study revealed the isolation of ten compounds from marine sponge of Petrosia sp. Their chemical structures were determined by using 1D and 2D NMR, UV, IR and MS measurements. A polyoxygenated steroid (3β,7β,9α-trihydroxycholest-5-en (1), a purine-derivative (3,7-dimethyl-2-(methylamino)-3H-purin-6(7H)-one (2) and a sphingolipid (N-((3S,E)-1,3-dihydroxytetracos-4-en-2-yl)stearamide (3) proved to be new compounds. Meanwhile, seven known compounds; (4-10) were also identified. The cytotoxicity of the total extract and the isolated compounds were subjected to cytotoxicity evaluation employing two cancer cell lines; HepG2 and MCF-7. All tested compounds exhibited cytotoxic effect on both cancer cell lines with IC(50) in range of 20-500 μM. The proposed mechanism of cytotoxic activities was examined through its molecular affinity to the DNA. Compound 5 showed the highest affinity to the DNA with IC(50) 30 μg/mL.

Neritinaceramides A-E, new ceramides from the marine bryozoan Bugula neritina inhabiting South China Sea and their cytotoxicity

Five new ceramides, neritinaceramides A (1), B (2), C (3), D (4) and E (5), together with six known ceramides (6–11), two known alkyl glycerylethers (12 and 13) and a known nucleoside (14), were isolated from marine bryozoan Bugula neritina, which inhabits the South China Sea. The structures of the new compounds were elucidated as (2S,3R,3′S,4E,8E,10E)-2-(hexadecanoylamino)-4,8,10-octadecatriene-l,3,3′-triol (1), (2S,3R,2′R,4E,8E,10E)-2-(hexadecanoylamino)-4,8,10-octadecatriene-l,3,2′-triol (2), (2S,3R,2′R,4E,8E,10E)-2-(octadecanoylamino)-4,8,10-octadecatriene-l,3,2′-triol (3), (2S,3R,3′S,4E,8E)-2-(hexadecanoylamino)-4,8-octadecadiene-l,3,3′-triol (4) and (2S,3R,3′S,4E)-2-(hexadecanoylamino)-4-octadecene-l,3,3′-triol (5) on the basis of extensive spectral analysis and chemical evidences. The characteristic C-3′S hydroxyl group in the fatty acid moiety in compounds 1, 4 and 5, was a novel structural feature of ceramides. The rare 4E,8E,10E-triene structure in the sphingoid base of compounds 1–3, was found from marine bryozoans for the first time. The new ceramides 1–5 were evaluated for their cytotoxicity against HepG2, NCI-H460 and SGC7901 tumor cell lines, and all of them exhibited selective cytotoxicity against HepG2 and SGC7901 cells with a range of IC₅₀ values from 47.3 μM to 58.1 μM. These chemical and cytotoxic studies on the new neritinaceramides A–E (1–5) added to the chemical diversity of B. neritina and expanded our knowledge of the chemical modifications and biological activity of ceramides.

Phytoceramides and acylated phytosterol glucosides from Pterospermum acerifolium Willd. seed coat and their osteogenic activity

Phytochemical investigation of seed coats of Pterospermum acerifolium afforded two phytoceramides (1, 2) and two acylated phytosterol glucosides (3, 4) together with five known compounds (5-9). Their structures were elucidated on the basis of extensive spectroscopic analysis using 1D, 2D NMR and Mass spectrometry. Compounds 1, 2, 3, and 4 were assessed for their osteogenic activity using primary cultures of osteoblasts harvested from neonatal rat calvaria. Among these compounds, 1 and 2 markedly stimulated osteoblast differentiation assessed by alkaline phosphatase production and osteoblast mineralization by alizarin red-S staining.

Bioactive lipids from the sponge Spirastrella abata

Three sphingosine 4-sulfates (1-3) and a lysophosphatidylglycerol (4) were isolated from the Korean sponge Spirastrella abata. The structures of these compounds were determined based on the combined results of spectroscopic analyses. Based on the results of combined synthesis and comparison of specific rotation and circular dichroism, the absolute configurations of 1-3 were found to be enantiomeric to the previously isolated metabolites. The configurations of 4 were also partially determined by similar chemical and spectroscopic methods. The compounds exhibited significant cytotoxicity and weak antimicrobial activity (1), as well as weak-to-moderate inhibitory activity against isocitrate lyase and Na(+)/K(+)-ATPase. A structure-activity relationship was found for the sphingosine 4-sulfates.

Saturated Ceramides from the Sponge Dysidea Robusta

Chemical investigation of the crude extract of a marine sponge Dysidea robusta led to the isolation of an inseparable mixture of saturated ceramides. These were identified from spectroscopic data as well as by hydrolysis followed by LC-MS analysis of the sphingosine moieties.

Antiepileptic ceramides from the Red Sea sponge Negombata corticata

A new antiepileptic ceramide mixture 1 was isolated from the Red Sea sponge Negombata corticata. The structures of the metabolites were determined by extensive spectroscopic analysis. The anticonvulsant activity of 1 was measured in vivo using the pentylenetetrazole-induced seizure model. This finding has important implications for biological studies with this class of compounds.

Ergosterol peroxides as phospholipase A(2) inhibitors from the fungus Lactarius hatsudake

Four ergosterol derivatives (1-4) have been isolated for the first time from the fruiting bodies of a basidiomycete fungus, Lactarius hatsudake, through activity-guided fractionation. Their structures were determined, using spectroscopic analysis, as: (22E,24R)-ergosta-5,7,22-dien-3beta-ol (ergosterol, 1); 5alpha,8alpha-epidioxy-(22E,24R)-ergosta-6,22-dien-3beta-ol (ergosterol peroxide, 2); 5alpha,8alpha-epidioxy-(24S)-ergosta-6-en-3beta-ol (3); and (22E,24R)-ergosta-7,22-dien-3beta,5alpha,6beta-triol (cerevisterol, 4). Compounds 2 and 3 showed selective inhibitory activity against Crotalus adamenteus venom phospholipase A(2) (PLA(2)) enzyme, but not against Apis mellifcra bee venom PLA(2). The antiphospholipase A(2) activity of compounds 2 and 3 are reported here for the first time.

Sphingolipids with neuritogenic activity from Euphorbia sororia

Two groups of sphingolipids 1 and 2 were isolated from the aerial parts of Euphorbia sororia. On the basis of spectroscopic data, chemical methods and GC-MS analysis, the structures of 1 and 2 were characterized as 1-O-beta-D-glucopyranosyl-(2S,3S,4R,8Z)-2-[(2'R)-2'-hydroxydocosanoyl approximately hexacosanoyl, octacosanoyl amino]-1,3,4-octadecanetriol-8-ene and (2S,3S,4R,8E)-2-[(2'R)-2'-hydroxyeicosanoyl approximately hexacosanoyl amino]-1,3,4-octadecanetriol-8-ene, respectively. Both of them exhibited marked neuritogenic activity on the rat pheochromocytoma PC12 cell line.

Cytotoxicity of the ascidian Cystodytes dellechiajei against tumor cells and study of the involvement of associated microbiota in the production of cytotoxic compounds

Many cytotoxic compounds of therapeutic interest have been isolated from marine invertebrates, and some of them have been reported to be of microbial origin. Pyridoacridine alkaloids are the main compounds extracted from the ascidian Cystodytes dellechiajei. Here we describe the in vitro antiproliferative activity against different tumor cell lines of the ascidian extracts and provide some insights on the role of the microbial community associated with the tunicate in the production of these compounds. C. dellechiajei extracts showed remarkably high antiproliferative activity (IC₅₀ ≤5 μg/mL) in human lung carcinoma A-549, colon adenocarcinoma H-116, pancreatic adenocarcinoma PSN-1 and breast carcinoma SKBR3 cell lines. Moreover, we found that the maximum activity was located in the tunic tissue of the colony, which harbours a microbial community. In order to ascertain the involvement of this community in the synthesis of the bioactive compounds different approachs that included culture and culture independent methods were carried out. We undertook a screening for antiproliferative activities of the bacterial isolates from the ascidian, as well as a comprative analysis of the cytotoxic activities and the microbial communities from two color morphs of the ascidian, green and blue. In addition, the changes of the antiproliferative activities and the composition of the microbial communities were studied from ascidians kept in aquaria and treated with antibiotics for one month. Our data obtained from the different experiments did not point out to bacteria as the source of the cytotoxic compounds, suggesting thus an ascidian origin.

Immunosuppressive diacetylenes, ceramides and cerebrosides from Hydrocotyle leucocephala

Three C-17 diacetylenic compounds (1-3), one monoterpenoid (4), seven ceramides (leucoceramides A-G, 5a-g), six cerebrosides (leucocerebrosides A-F, 6a-f) and nine known compounds were isolated from the methanolic extract of Hydrocotyle leucocephala. Their structures were established by spectroscopic methods. The isolated compounds 1-3, 5a-g, 6a-f and 7 were shown to be active in the lipopolysaccharide (LPS) induced cytokine production assay for IL-10, IL-12, and TNF-alpha.

Anti-inflammatory activity of a new sphingosine derivative and cembrenoid diterpene (lobohedleolide) isolated from marine soft corals of Sinularia crassa TIXIER-DURIVAULT and Lobophytum species of the Andaman and Nicobar Islands

The aim of this study is to determine the anti-inflammatory activity of a new sphingosine derivative (1) and cembrenoid diterpene (lobohedleolide) (2) isolated from the soft corals of Sinularia crassa and Lobophytum species respectively, collected on the coasts of Andaman and Nicobar Islands. The anti-inflammatory activity was evaluated using carrageenin-induced rat hind paw edema model for acute inflammation and cotton pellet granuloma model for chronic inflammation. Indomethacin was used as a standard drug in this study. Both the sphingosine derivative (1) and the cembrenoid diterpene (2) produced the maximum effect at a dose of 10 mg/kg and this is comparable to that of indomethacin (2 mg/kg, p<0.001). The observed anti-inflammatory activity is almost identical in both the types of experimental inflammation.

New ceramides from Rantherium suaveolens

A mixture of five new ceramides was isolated from the aerial parts of Rantherium suaveolens and characterized by spectroscopic and chemical methods. Their structures were elucidated by spectroscopic and chemical methods as (2S,3S, 4R,2'R, 14E)-2-(2'-hydroxydocosanoylamino) - 14 - octadecene -1,3,4-triol (1), (2S,3S,4R,2'R, 14E)-2-(2'-hydroxytricosanoylamino)-14-octadecene-1,3,4-triol (2), (2S,3S,4R,2'R, 14E)-2-(2'-hydroxytetracosanoylamino)- 14 - octadecene - 1,3,4 - triol (3), (2S, 3S,4R,2'R, 14E) - 2 - (2'- hydroxypentacosanoylamino) - 14 - octadecene - 1,3,4-triol (4), and (2S,3S,4R,2'R,14E)-2-(2'-hydroxyhexacosanoylamino)-14-octadecene-1,3,4-triol (5).

[Chemo-pharmaceutical studies on the glycosphingolipid constituents from echinoderm, sea cucumbers, as the medicinal materials]

Glycosphingolipids (GSLs), together with glycopeptides, are typical constitutents of various cell membranes in a wide variety of organisms. In particular, it is known that GSLs have numerous physiological functions due to variations in the sugar chain, in spite of the very small quantity of constituents. Those are classified into cerebrosides, sulfatides, ceramide oligohexosides, globosides, and gangliosides based on the constituent sugars. Gangliosides, sialic acid-containing GSLs, are especially enriched in the brain and nervous tissues and are involved in the regulation of many cellular events. Recently, a number of GSLs have been isolated from marine invertebrates such as echinoderms, poriferans, and mollusks. We have also been researching biologically active GSLs from echinoderms to elucidate the structure-function relationships of GSLs and to develop novel medicinal resources. This review summarizes the structures and biological activities of GSLs from sea cucumbers. This study showed that the characteristics of GSLs and structure-activity relationships had neuritogenic activity toward the rat pheochromocytoma cell line PC12. That is, most of the cerebroside constituents of the sea cucumber are same glucocerebrosides as in other animals, except for some constituents, while the ganglioside constituents were unique in that a sialic acid directly binds to the glucose of cerebroside, they are mutually connected in tandem, and some are located in the internal parts of the sugar chain. It also became apparent that sialic acid is indispensable for the neuritogenic activities.