Cerebrosides from a Far-Eastern Glass Sponge Aulosaccus sp

Phytoceramides from the Marine Sponge Monanchora clathrata: Structural Analysis and Cytoprotective Effects

In our research on sphingolipids from marine invertebrates, a mixture of phytoceramides was isolated from the sponge Monanchora clathrata (Western Australia). Total ceramide, ceramide molecular species (obtained by RP-HPLC, high-performance liquid chromatography on reversed-phase column) and their sphingoid/fatty acid components were analyzed by NMR (nuclear magnetic resonance) spectroscopy and mass spectrometry. Sixteen new (1b, 3a, 3c, 3d, 3f, 3g, 5c, 5d, 5f, 5g, 6b-g) and twelve known (2b, 2e, 2f, 3b, 3e, 4a-c, 4e, 4f, 5b, 5e) compounds were shown to contain phytosphingosine-type backbones i-t17:0 (1), n-t17:0 (2), i-t18:0 (3), n-t18:0 (4), i-t19:0 (5), or ai-t19:0 (6), N-acylated with saturated (2R)-2-hydroxy C21 (a), C22 (b), C23 (c), i-C23 (d), C24 (e), C25 (f), or C26 (g) acids. The used combination of the instrumental and chemical methods permitted the more detailed investigation of the sponge ceramides than previously reported. It was found that the cytotoxic effect of crambescidin 359 (alkaloid from M. clathrata) and cisplatin decreased after pre-incubation of MDA-MB-231 and HL-60 cells with the investigated phytoceramides. In an in vitro paraquat model of Parkinson's disease, the phytoceramides decreased the neurodegenerative effect and ROS (reactive oxygen species) formation induced by paraquat in neuroblastoma cells. In general, the preliminary treatment (for 24 or 48 h) of the cells with the phytoceramides of M. clathrata was necessary for their cytoprotective functions, otherwise the additive damaging effect of these sphingolipids and cytotoxic compounds (crambescidin 359, cisplatin or paraquat) was observed.

The Structural Diversity of Natural Glycosphingolipids (GSLs)

Glycosphingolipids (GSLs) are a subclass of glycolipids made of a glycan and a ceramide that, in turn, is composed of a sphingoid base moiety and a fatty acyl group. GSLs represent the vast majority of glycolipids in eukaryotes, and as an essential component of the cell membrane, they play an important role in many biological and pathological processes. Therefore, they are useful targets for the development of novel diagnostic and therapeutic methods for human diseases. Since sphingosine was first described by J. L. Thudichum in 1884, several hundred GSL species, not including their diverse lipid forms that can further amplify the number of individual GSLs by many folds, have been isolated from natural sources and structurally characterized. This review tries to provide a comprehensive survey of the major GSL species, especially those with distinct glycan structures and modification patterns, and the ceramides with unique modifications of the lipid chains, that have been discovered to date. In particular, this review is focused on GSLs from eukaryotic species. This review has listed 251 GSL glycans with different linkages, 127 glycans with unique modifications, 46 sphingoids, and 43 fatty acyl groups. It should be helpful for scientists who are interested in GSLs, from isolation and structural analyses to chemical and enzymatic syntheses, as well as their biological studies and applications.

Structural Analysis of Oxidized Cerebrosides from the Extract of Deep-Sea Sponge Aulosaccus sp.: Occurrence of Amide-Linked Allylically Oxygenated Fatty Acids

The structural elucidation of primary and secondary peroxidation products, formed from complex lipids, is a challenge in lipid analysis. In the present study, rare minor oxidized cerebrosides, isolated from the extract of a far eastern deep-sea glass sponge, Aulosaccus sp., were analyzed as constituents of a multi-component RP-HPLC (high-performance liquid chromatography on reversed-phase column) fraction using NMR (nuclear magnetic resonance) spectroscopy, mass spectrometry, GC (gas chromatography), and chemical transformations (including hydrogenation or derivatization with dimethyl disulfide before hydrolysis). Eighteen previously unknown β-D-glucopyranosyl-(1→1)-ceramides (1a-a//, 1b-b//, 2a-a//, 2b-b//, 3c-c//, 3d-d//) were shown to contain phytosphingosine-type backbones (2S,3S,4R,11Z)-2-aminoeicos-11-ene-1,3,4-triol (in 1), (2S,3S,4R,13Z)-2-aminoeicos-13-ene-1,3,4-triol (in 2), and (13S*,14R*)-2-amino-13,14-methylene-eicosane-1,3,4-triol (in 3). These backbones were N-acylated with straight-chain monoenoic (2R)-2-hydroxy acids that had allylic hydroperoxy/hydroxy/keto groups on C-17/ in the 15/E-23:1 chain (a-a//), C-16/ in the 17/E-23:1 (b-b//) and 14/E-22:1 (c-c//) chains, and C-15/ in the 16/E-22:1 chain (d-d//). Utilizing complementary instrumental and chemical methods allowed for the first detailed structural analysis of a complex mixture of glycosphingolipids, containing allylically oxygenated monoenoic acyl chains.

Analysis of the Configuration of an Isolated Double Bond in Some Lipids by Selective Homonuclear Decoupling

The purpose of this report is to demonstrate that selective homonuclear decoupling can be used as an alternative for 13C NMR method for identifying configuration of an isolated (mid-chain) double bond in some lipids. Using homodecoupling of allylic protons, the coupling constants Jcis or Jtrans between the olefinic protons of some fatty acid methyl esters and related compounds with ( n–7) and ( n–9) terminal structures were evaluated. The optimal conditions of the homodecoupling experiments on these compounds were examined. Empirical rules were proposed to predict the results of homodecoupling experiments on lipid with an isolated double bond.

Marine natural products

Covering: 2015. Previous review: Nat. Prod. Rep., 2016, 33, 382-431This review covers the literature published in 2015 for marine natural products (MNPs), with 1220 citations (792 for the period January to December 2015) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1340 in 429 papers for 2015), together with the relevant biological activities, source organisms and country of origin. Reviews, biosynthetic studies, first syntheses, and syntheses that lead to the revision of structures or stereochemistries, have been included.

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.