Regulosides A–C: Glycosphingolipids from the StarfishPentaceraster regulus

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.

Polyhydroxylated steroid derivatives from the starfish Pentaceraster regulus

A new polyhydroxysteroid glycoside, regulusoside D (1), and a new polyhydroxylated steroid, (24S)-cholestane-3β,5,6β,8,15α,24-hexol (2), together with seven known compounds were purified from the starfish Pentaceraster regulus collected near Con Co Islands, Vietnam. The structure elucidation was confirmed by extensive analysis of their NMR and HR-QTOF mass experiments. Among isolated compounds, regulusoside D (1), (24S)-cholestane-3β,5,6β,8,15α,24-hexol (2), granulatoside A (4), 5α-cholestane-3β,6β,7α,15α,16β,26-hexol (6), 5α-cholestane-3β,6β,7α,8β,15α,16β,26-heptol (7) and 5α-cholestane-3β,6α,8,15α,16β,26-hexol (8) exhibited strong inhibitory effects on LPS-induced NO production in RAW264.7 cells with IC₅₀ values of 9.13 ± 1.17, 9.19 ± 0.77, 8.63 ± 3.31, 12.61 ± 0.51, 14.83 ± 3.02 and 10.98 ± 1.22 µM, respectively.

Regulusosides A, B, and C, Three New Polyhydroxysteroid Glycosides from the Starfish Pentaceraster regulus

Three new polyhydroxysteroid glycosides, regulusosides A-C (1-3) along with the previously known five steroid compounds (4-8) were isolated from the tropical starfish Pentaceraster regulus. The structures of compounds 1-3 were established by extensive NMR and ESI-MS techniques. New glycosides have the same aglycon, (24 S)-5α-cholestane-3β,5,6β,8,15α,24-hexol, and various disaccharide moieties: β-D-xylopyranosyl-(1→2)-3- O-methyl-α-L-arabinofuranosyl (1), β-D-xylopyranosyl-(1→2)-α-L-arabinofuranosyl (2), and 2- O-methyl-β-D-xylopyranosyl-(1→2)-3- O-methyl-α-L-arabinofuranosyl (3), attached at C-24 of the side chain. Compounds 1, 2 and 6 exhibit potential immunomodulatory properties, inducing intracellular ROS (reactive oxygen species) formation in the RAW 264.7 murine macrophage cells.

Chemical constituents and bioactivities of starfish

Starfish have been the research topic in many chemical and pharmacological laboratories due to their complex secondary metabolites and diverse bioactivities. The aim of this review is to provide an up-to-date review on the chemistry and bioactivity of compounds isolated from all kinds of starfish to illustrate the chemodiversity and biological significance of these constituents, along with their geographical distribution where it is discernible.

Astonishing diversity of natural surfactants: 4. Fatty acid amide glycosides, their analogs and derivatives

FA amide glycosides are of great interest, especially for the medicinal and pharmaceutical industries. These biologically active natural surfactants are good prospects for future chemical preparation of compounds useful as antibiotics, anticancer agents, or for industry. More than 200 unusual and interesting natural surfactants, including their chemical structures and biological activities, are described in this review article.

Molecular species of ceramides from the ascomycete truffle Tuber indicum

The ceramide fractions were isolated from the chloroform/methanolic extractable of the fruiting bodies of Tuber indicum and separated into three kinds of molecular species TI-1, TI-2, and TI-3 by normal and reverse phase silica gel-column chromatography. By means of (1)H NMR and (13)C NMR spectroscopy, fast atom bombardment mass spectrometry (FAB-MS), and chemical degradation experiment, their component sphingoid base for TI-1 and TI-2 was uniformly (2S,3S,4R)-2-amino-1,3,4-octadecantriol, while the sphingoid of TI-3 was d-erythro-sphingosine, and their structures have been determined unequivocally to be (2S,2'R,3S,4R)-2-(2'-d-hydroxyalkanoylamino) octadecane-1,3,4-triol, the fatty acid composition of which consists of 2-hydroxydocosanoic, 2-hydroxytetracosanoic, and 2-hydroxytricosanoic acids (from major to minor); (2S,3S,4R)-2-(alkanoylamino)octadecane-1,3,4-triol, the fatty acid composition of which is unusual and consists of docosanoic, hexadecanoic, tricosanoic, octadecanoic and nonadecanoic acids (from major to minor); and (2S,3R,4E)-2-(alkanoylamino)-4-octadecene-1,3-diol, the component fatty acids of which were hexadecanoic (predominant) and octadecanoic acids, respectively.

Two novel glucosylceramides from gonads and body walls of the Patagonian starfish Allostichaster inaequalis

From the water-insoluble lipid fraction of the chloroform/methanol/water extract of the gonads and body walls of the Patagonian starfish Allostichaster inaequalis, two new glucosylceramides (4 and 7) were isolated together with the known phalluside-1 (1) and two glucosylceramides (2 and 3) previously isolated from the starfish Cosmasterias lurida. The new compounds were characterized as (2S,3R,4E,8E,10E)-1-(beta-D-glucopyranosyloxy)-3-hydroxy-2-[(R)-2-hydroxy-15-tetracosenoyl] amino-4,8,10-octadecatriene (4) and (2S,3R,4E,15Z)-1-(beta-D-glucopyranosyloxy)-3-hydroxy-2-[(R)-2-hydroxyhexadecanoyl] amino-4,15-docosadiene (7) by means of spectroscopic and chemical methods.

Isolation and structure of glucosylceramides from the starfish Cosmasterias lurida

From the water-insoluble lipid fraction of the methylene chloride/methanol extract of the starfish Cosmasterias lurida, two new glucosylceramides together with a known glucosylceramide, ophidiacerebroside E, were isolated by chromatographic procedures and characterized by spectroscopic (1H and 13C nuclear magnetic resonance, mass spectrometry) methods. The new compounds were identified as (2S,3R,4E,8E,10E)-1-(beta-D-glucopyranosyloxy)-3 -hydroxy-2-[(R)-2-hydroxyheptadecanoyl)amino]-9-methyl-4,8,10-o ctadecatriene (3) and (2S,3R,4E,8E,10E)-1-(beta-D-glucopyranosyloxy)-3 -hydroxy-2-[(R)-2-hydroxyoctadecanoyl)amino]-9-methyl-4,8,10-oc tadecatriene (4).