Renierosides, cerebrosides from a marine sponge Haliclona (Reniera) sp

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.

Identifying the specific-targeted marine cerebrosides against SARS-CoV-2: an integrated computational approach

Cerebrosides are a group of metabolites belonging to the glycosphingolipids class of natural products. So far, 167 cerebrosides, compounds 1-167, have been isolated from diverse marine organisms or microorganisms. The as yet smaller number of compounds that have been studied more in depth proves a potential against challenging diseases, such as cancer, a range of viral and bacterial diseases, as well as inflammation. This review provides a comprehensive summary on this so far under-explored class of compounds, their chemical structures, bioactivities, and their marine sources, with a full coverage to the end of 2020. Today, the global pandemic concern, COVID-19, has claimed millions of death cases around the world, making the development of anti-SARS-CoV-2 drugs urgently needed for such a battle. Accordingly, selected examples from all subclasses of cerebrosides were virtually screened for potential inhibition of SARS-CoV-2 proteins that are crucially involved in the viral-host interaction, viral replication, or in disease progression. The results highlight five cerebrosides that could preferentially bind to the hACE2 protein, with binding scores between -7.1 and -7.6 kcal mol^-1 and with the docking poses determined underneath the first α₁-helix of the protein. Moreover, the molecular interaction determined by molecular dynamic (MD) simulation revealed that renieroside C1 (60) is more conveniently involved in key hydrophobic interactions with the best stability, least deviation, least ΔG (-6.9 kcal mol^-1) and an RMSD value of 3.6 Å. Thus, the structural insights assure better binding affinity and favorable molecular interaction of renieroside C1 (60) towards the hACE2 protein, which plays a crucial role in the biology and pathogenesis of SARS-CoV-2.

Sphingolipids of Asteroidea and Holothuroidea: Structures and Biological Activities

Sphingolipids are complex lipids widespread in nature as structural components of biomembranes. Commonly, the sphingolipids of marine organisms differ from those of terrestrial animals and plants. The gangliosides are the most complex sphingolipids characteristic of vertebrates that have been found in only the Echinodermata (echinoderms) phylum of invertebrates. Sphingolipids of the representatives of the Asteroidea and Holothuroidea classes are the most studied among all echinoderms. In this review, we have summarized the data on sphingolipids of these two classes of marine invertebrates over the past two decades. Recently established structures, properties, and peculiarities of biogenesis of ceramides, cerebrosides, and gangliosides from starfishes and holothurians are discussed. The purpose of this review is to provide the most complete information on the chemical structures, structural features, and biological activities of sphingolipids of the Asteroidea and Holothuroidea classes.

Natural Products from the Marine Sponge Subgenus Reniera

Marine sponges are one of the prolific producers of bioactive natural products with therapeutic potential. As an important subgenus of Haliclona, Reniera sponges are mainly distributed in the Mediterranean Sea and Atlantic area, and had been chemically investigated for over four decades. By an extensive literature search, this review first makes a comprehensive summary of all natural products from Reniera sponges and their endozoic microbes, as well as biological properties. Perspectives on strengthening the chemical study of Reniera sponges for new drug-lead discovery are provided in this work.

Marine Carbohydrate-Based Compounds with Medicinal Properties

The oceans harbor a great diversity of organisms, and have been recognized as an important source of new compounds with nutritional and therapeutic potential. Among these compounds, carbohydrate-based compounds are of particular interest because they exhibit numerous biological functions associated with their chemical diversity. This gives rise to new substances for the development of bioactive products. Many are the known applications of substances with glycosidic domains obtained from marine species. This review covers the structural properties and the current findings on the antioxidant, anti-inflammatory, anticoagulant, antitumor and antimicrobial activities of medium and high molecular-weight carbohydrates or glycosylated compounds extracted from various marine organisms.

Sponge chemical defenses are a possible mechanism for increasing sponge abundance on reefs in Zanzibar

Coral reefs are experiencing increasing anthropogenic impacts that result in substantial declines of reef-building corals and a change of community structure towards other benthic invertebrates or macroalgae. Reefs around Zanzibar are exposed to untreated sewage and runoff from the main city Stonetown. At many of these sites, sponge cover has increased over the last years. Sponges are one of the top spatial competitors on reefs worldwide. Their success is, in part, dependent on their strong chemical defenses against predators, microbial attacks and other sessile benthic competitors. This is the first study that investigates the bioactive properties of sponge species in the Western Indian Ocean region. Crude extracts of the ten most dominant sponge species were assessed for their chemical defenses against 35 bacterial strains (nine known as marine pathogens) using disc diffusion assays and general cytotoxic activities were assessed with brine shrimp lethality assays. The three chemically most active sponge species were additionally tested for their allelopathic properties against the scleractinian coral competitor Porites sp.. The antimicrobial assays revealed that all tested sponge extracts had strong antimicrobial properties and that the majority (80%) of the tested sponges were equally defended against pathogenic and environmental bacterial strains. Additionally, seven out of ten sponge species exhibited cytotoxic activities in the brine shrimp assay. Moreover, we could also show that the three most bioactive sponge species were able to decrease the photosynthetic performance of the coral symbionts and thus were likely to impair the coral physiology.

A new cerebroside from the twigs of Lindera glauca (Sieb. et Zucc.) Blume

Lindera glauca (Sieb. et Zucc.) Blume (Lauraceae) has been used to treat rheumatic arthritis, stroke, and cardiac pain. Phytochemical investigation of twigs of L. glauca (Sieb. et Zucc.) Blume resulted in the isolation and identification of a new cerebroside, glaucerebroside (1). The structure of 1 was elucidated by a combination of extensive spectroscopic analyses, including extensive 2D NMR, HR-MS, chemical reactions, and LC/MS analysis. Compound 1 is a relatively rare cerebroside with l-threo-configuration of the sphingosine part. This is the second example of identification of a cerebroside from the family Lauraceae. Compound 1 significantly inhibited nitric oxide (NO) production in lipopolysaccharide (LPS)-stimulated BV-2 cells, with an IC₅₀ value of 23.84μM without inducing cell toxicity. This study suggests that glaucerebroside (1) can be an excellent candidate for development of novel anti-neuroinflammatory agents.

Anti-inflammatory Cerebrosides from Cultivated Cordyceps militaris

Cordyceps militaris (bei-chong-chaw, northern worm grass) is a precious and edible entomopathogenic fungus, which is widely used in traditional Chinese medicine (TCM) as a general booster for the nervous system, metabolism, and immunity. Saccharides, nucleosides, mannitol, and sterols were isolated from this fungus. The biological activity of C. militaris was attributed to the saccharide and nucleoside contents. In this study, the aqueous methanolic fraction of C. militaris fruiting bodies exhibited a significant anti-inflammatory activity. Bioactivity-guided fractionation of the active fraction led to the isolation of eight compounds, including one new and two known cerebrosides (ceramide derivatives), two nucleosides, and three sterols. Cordycerebroside A (1), the new cerebroside, along with soyacerebroside I (2) and glucocerebroside (3) inhibited the accumulation of pro-inflammatory iNOS protein and reduced the expression of COX-2 protein in LPS-stimulated RAW264.7 macrophages. This is the first study on the isolation of cerebrosides with anti-inflammatory activity from this TCM.

Cytotoxic glucosphingolipid from Celtis Africana

Background:

Literature survey proved the use of the powdered sun-dried bark and roots of Celtis africana for the treatment of cancer in South Africa.

Objective:

The aim of this study was to do further isolation work on the ethyl acetate fraction and to investigate the cytotoxic activities of the various fractions and isolated compound.

Materials and Methods:

Cytotoxicity of petroleum ether, chloroform, ethyl acetate, n-butanol fractions and compound 1 were tested on mouse lymphoma cell line L5178Y using the microculture tetrazolium assay.

Results:

One new glucosphingolipid 1 was isolated from the aerial parts of C. africana. The structure of the new compound was determined by extensive analysis by one-dimensional and two-dimensional nuclear magnetic resonance spectroscopy and mass spectrometry. The ethyl acetate fraction and compound 1 showed strong cytotoxic activity with an EC₅₀ value of 8.3 μg/mL and 7.8 μg/mL, respectively, compared with Kahalalide F positive control (6.3 μg/mL).

Conclusion:

This is the first report of the occurrence of a cytotoxic glucosphingolipid in family Ulmaceae.

Antimicrobial gageomacrolactins characterized from the fermentation of the marine-derived bacterium Bacillus subtilis under optimum growth conditions

Marine bacteria are a potential source of structurally diversified bioactive secondary metabolites that are not found in terrestrial sources. In our continuous effort to search for new antimicrobial agents from marine-derived bacteria, we isolated bacterial strain 109GGC020 from a marine sediment sample collected from Gageocho, Republic of Korea. The strain was identified as Bacillus subtilis based on a 16s rRNA sequence analysis. After a 7-day fermentation of the B. subtilis strain under optimum growth conditions three new and four known secondary metabolites were discovered using chromatographic procedures, and their biological activities were evaluated against both bacteria and crop-devastating fungi. The discovered metabolites were confirmed by extensive 2D NMR and high-resolution ESI-MS data analyses to have the structures of new macrolactin derivatives gageomacrolactins 1-3 and known macrolactins A (4), B (5), F (6), and W (7). The stereoconfigurations of 1-3 were assigned based on coupling constant values, chemical derivatization studies, and a literature review. The coupling constants were very crucial to determine the relative geometries of olefins in 1-3 because of overlap of the ¹H NMR signals. The NMR data of these compounds were recorded in different solvents to overcome this problem and obtain accurate coupling constant values. The new macrolactin derivatives 1-3 displayed good antibiotic properties against both Gram-positive (S. aureus, B. subtilis, and B. cereus) and Gram-negative (E. coli, S. typhi, and P. aeruginosa) bacteria with minimum inhibitory concentration (MIC) values of 0.02-0.05 μM. Additionally, the antifungal activities of 1-7 were evaluated against pathogenic fungi and found to inhibit mycelial growth of A. niger, B. cinerea, C. acutatum, C. albicans, and R. solani with MIC values of 0.04-0.3 μM, demonstrating that these compounds were good fungicides.

Ieodoglucomides A and B from a marine-derived bacterium Bacillus licheniformis

Ieodoglucomides A (1) and B (2), unique glycolipopeptides consisting of an amino acid, a new fatty acid, a succinic acid, and a sugar, were isolated from a Marine-derived bacterium Bacillus licheniformis. The absolute stereochemistry of 1 and 2 was determined by deploying coupling constants, Marfey's and Mosher's methods, and literature reviews. Compounds 1 and 2 displayed moderate in vitro antimicrobial activity. Furthermore, ieodoglucomide B (2) exhibited cytotoxic activity against lung cancer and stomach cancer cell lines with GI(50) values of 25.18 and 17.78 μg/mL, respectively.

Flavusides A and B, antibacterial cerebrosides from the marine-derived fungus Aspergillus flavus

Flavusides A (1) and B (2), two new antibacterial cerebroside derivatives, and the previously described phomaligol A (3), kojic acid (4), methyl kojic acid (5), and dimethyl kojic acid (6) have been isolated from the extract of a marine isolate of the fungus Aspergillus flavus. The structure and absolute stereochemistry of two cerebrosides were assigned on the basis of NMR and Tandem FAB-MS/MS experiments. Compounds 1, 2, and 3 exhibited a mild antibacterial activity against Staphylococcus aureus, methicillin-resistant S. aureus, and multidrug-resistant S. aureus. The minimum inhibitory concentration (MIC) values for each strain are as follows: compounds 1 and 2 showed 15.6 μg/ml for S. aureus and 31.2 μg/ml for methicillin-resistant S. aureus and multidrug-resistant S. aureus, and compound 3 exhibited 31.2 μg/ml for S. aureus and methicillin-resistant S. aureus and 62.5 μg/ml for multidrug-resistant S. aureus.

Kinase Inhibitory, Haemolytic and Cytotoxic Activity of Three Deep-water Sponges from North Western Australia and their Fatty Acid Composition

The cAMP dependent protein kinase (PKA) inhibition, haemolytic activity, and cytoxicity of 21 extracts obtained from North Western Australian sponges collected from depths of 84-135 m were investigated. Hexane extracts from Ircinia/Sarcotragus sp. and Geodia sp. displayed PKA inhibitory activities of 100 and 97% respectively (at 100 μg/mL), while aq. methanol extracts from Haliclona sp. exhibited potent haemolytic activity (75%) and hexane extracts from Geodia sp. were highly toxic (88%) to the brine shrimp Artemia franciscana. As the non-polar extracts gave the greatest PKA inhibition, these were further analysed by GCMS and 29 fatty acids were identified in the highest proportions in Ircinia/Sarcotragus sp. > Haliclona sp. > Geodia sp. In contrast to shallow-water sponges that are dominated by polyunsaturated fatty acids with a high percentage of long chain fatty acids, LCFAs (C24-C30), the deep-sea sponges investigated herein were all found to be rich in saturated fatty acids, in particular C14-C20 fatty acids, including odd and branched chain fatty acids, with only low levels (0-10%) of LCFAs. Screening of the PKA inhibitory activity of a series of commercially available fatty acids identified C14-C18 fatty acids as possessing significant PKA inhibitory activity that may contribute to the activity observed in the sponges studied.

Cytotoxicity on human cancer cells of ophidiacerebrosides isolated from the African starfish Narcissia canariensis

The starfish Narcissia canariensis harvested from the coasts off Dakar, Senegal, was investigated for glycolipids (GL). This report deals with the isolation, characterization and biological activity of a fraction F13-3 separated from the GL mixture and selected according to its ability to inhibit KB cell proliferation after 72 hours of treatment. Firstly, a GL mixture F13 was obtained that accounted for 1.36% of starfish biomass (dry weight) and 0.36% of total lipids. The fraction F13-3 obtained from F13 contained three homologous GL identified as peracetylated derivatives on the basis of chemical and spectroscopic evidence. These contained a β-glucopyranoside as sugar head, a 9-methyl-branched 4,8,10-triunsaturated long-chain aminoalcohol as sphingoid base and amide-linked 2-hydroxy fatty acid chains. The majority (63%) had an amide-linked 2-hydroxydocosanoic acid chain and was identified as the ophidiacerebroside-C, firstly isolated from the starfish Ophidiaster ophidiamus. The minor components of F13-3 differed by one more or one less methylene group, and corresponded to ophidiacerebroside-B and -D. We found that F13-3 displayed an interesting cytotoxic activity over 24 hours on various adherent human cancerous cell lines (multiple myeloma, colorectal adenocarcinoma and glioblastoma multiforme) with an IC₅₀ of around 20 μM.

Novel ceramides from aerial parts of Saussurea involucrata Kar. et. Kir

Novel ceramides, together with nine known compounds were isolated from aerial parts of the Saussurea involucrata Kar. et. Kir. The novel structures were determined by spectroscopic methods and microscale chemical degradation. The ceramides showed appreciable cytotoxicity against three human tumor cell lines including human promyelocytic leukemia (HL-60), human melanoma (A375-S2) and human cervical carcinoma (HeLa) cell lines. The results suggested that this class of ceramides may have potential as an antitumor agent.

Langmur monolayers of cerebroside with different head groups originated from sea cucumber: binary systems with dipalmitoylphosphatidylcholine (DPPC)

Surface properties (Langmuir monolayer) of two different cerebrosides which are extracted from the sea cucumber (Bohadschia argus) were investigated. A main difference in chemical structure of cerebroside between BAC-2a and BAC-4 is their head groups (glucose and galactose, respectively). Furthermore, miscibility and interaction between dipalmitoylphosphatidylcholine (DPPC) and cerebrosides (BAC-2a and BAC-4) in the monolayer have been systematically examined. The surface pressure (pi)-area (A), the surface potential (Delta V)-A, and the dipole moment (mu(perpendicular))-A isotherms for monolayers of DPPC, cerebrosides, and their binary combinations have been measured using the Wilhelmy method and the ionizing electrode method. BAC-4 forms a stable liquid-expanded (LE) monolayer, whereas BAC-2a has a first-order phase transition from the LE phase to the liquid-condensed (LC) state on 0.15 M NaCl at 298.2 K. The fundamental properties for each cerebroside monolayer were elucidated in terms of the surface dipole moment based on the three-layer model [R.J. Demchak, T. Fort Jr., J. Colloid Interface Sci. 46 (1974) 191-202] for both cerebrosides and the apparent molar quantity change (Delta s(gamma), Delta h(gamma), and Delta u(gamma)) for BAC-2a. In addition, their miscibility with DPPC was examined by the variation of the molecular areas and the surface potentials as a function of cerebroside mole fractions, the additivity rule. The miscibility was also confirmed by constructing the two-dimensional phase diagrams. The phase diagrams for the both binary systems were of negative azeotropic type. That is, the two-component DPPC/BAC-2a and DPPC/BAC-4 monolayers are miscible. Furthermore, the Joos equation for the analysis of the collapse pressure of binary monolayers allowed calculation of the interaction parameter and the interaction energy between the DPPC and cerebroside monolayers. The miscibility in the monolayer state was also confirmed by the morphological observation with Brewster angle microscopy (BAM), fluorescence microscopy (FM), and atomic force microscopy (AFM).

New cerebrosides from a marine sponge Haliclona (Reniera) sp

A chemical investigation of the MeOH extract of a marine sponge Haliclona (Reniera) sp., collected off the coast of Ulleung Island, Korea, led to the isolation of thirteen new cerebrosides (1--3, 5--14), along with a known analogue (4). Their structures were elucidated on the basis of 1D and 2D NMR spectroscopy, MS spectrometry, and chemical method. The major new features of these glucocerebrosides are C15 and C19 acyl chains, long (C24-C28) acyl chains, or the S-configuration of the acyl chains. It is noteworthy that both R- and S-configurations of the acyl chains were observed in the same specimen.

Ceramide and cerebrosides from the octocoral Sarcophyton ehrenbergi

Chemical investigation of the octocoral Sarcophyton ehrenbergi, collected at the Dongsha Islands, Taiwan, has led to the isolation of a known ceramide (1) and two new cerebrosides, sarcoehrenosides A (2) and B (4), along with three known cerebrosides (3, 5, and 6). The structures of the new compounds were established by spectroscopic and chemical methods. Sarcoehrenoside A (2) differs from previously known marine cerebrosides in that it possesses a rare alpha-glucose moiety. Compounds 1-6 were evaluated for antimicrobial activity against a small panel of bacteria and for anti-inflammatory activity using RAW 264.7 macrophages.

Marine natural products

This review covers the literature published in 2007 for marine natural products, with 948 citations(627 for the period January to December 2007) referring to compounds isolated from marine microorganisms and phytoplankton, green algae, brown algae, red algae, sponges, cnidarians,bryozoans, molluscs, tunicates, echinoderms and true mangrove plants. The emphasis is on new compounds (961 for 2007), together with the relevant biological activities, source organisms and country of origin. Biosynthetic studies, first syntheses, and syntheses that lead to the revision of structures or stereochemistries, have been included.1 Introduction, 2 Reviews, 3 Marine microorganisms and phytoplankton, 4 Green algae, 5 Brown algae, 6 Red algae, 7 Sponges, 8 Cnidarians, 9 Bryozoans, 10 Molluscs, 11 Tunicates (ascidians),12 Echinoderms, 13 Miscellaneous, 14 Conclusion, 15 References.

Cytotoxic constituents from the bark of Salix hulteni

Eight compounds were isolated from the bark of Salix hulteni. Based on spectral data, the isolated compounds were identified as 4-hydroxyacetophenone (1), naringenin (2), aromadendrin (3), catechin (4), picein (5), sachaliside 1 (6), 1-p-coumaroyl-beta-D-glucoside (7), and dihydromyricetin (8). Their cytotoxic activities against brine shrimp and a human lung cancer cell line (H1299) were evaluated.

Furan metabolites from the sponge-derived yeast Pichia membranifaciens

Five new compounds, pichiafurans A-C (1-3) and pichiacins A and B (4 and 5), along with five known compounds (6-10), have been isolated from the yeast Pichia membranifaciens derived from a marine sponge Petrosia sp. Their structures were elucidated by 1D and 2D NMR and mass spectrometry techniques. Pichiafurans are rare examples of monofurano metabolites isolated from yeast.