Kurilosides A1, A2, C1, D, E and F—Triterpene Glycosides from the Far Eastern Sea Cucumber Thyonidium (= Duasmodactyla) kurilensis (Levin): Structures with Unusual Non-Holostane Aglycones and Cytotoxicities

Six new monosulfated triterpene tetra-, penta- and hexaosides, namely, the kurilosides A1 (1), A2 (2), C1 (3), D (4), E (5) and F (6), as well as the known earlier kuriloside A (7), having unusual non-holostane aglycones without lactone, have been isolated from the sea cucumber Thyonidium (= Duasmodactyla) kurilensis (Levin) (Cucumariidae, Dendrochirotida), collected in the Sea of Okhotsk near Onekotan Island from a depth of 100 m. Structures of the glycosides were established by 2D NMR spectroscopy and HR-ESI mass spectrometry. Kurilosides of the groups A and E contain carbohydrate moieties with a rare architecture (a pentasaccharide branched by C(4) Xyl1), differing from each other in the second monosaccharide residue (quinovose or glucose, correspondingly); kurilosides of the group C are characterized by a unique tetrasaccharide branched by a C(4) Xyl1 sugar chain; and kurilosides of the groups D and F are hexaosides differing from each other in the presence of an O-methyl group in the fourth (terminal) sugar unit. All these glycosides contain a sulfate group at C-6 of the glucose residue attached to C-4 Xyl1 and the non-holostane aglycones have a 9(11) double bond and lack γ-lactone. The cytotoxic activities of compounds 1–7 against mouse neuroblastoma Neuro 2a, normal epithelial JB-6 cells and erythrocytes were studied. Kuriloside A1 (1) was the most active compound in the series, demonstrating strong cytotoxicity against the erythrocytes and JB-6 cells and a moderate effect against Neuro 2a cells.

The answer lies in the energy: how simple atomistic molecular dynamics simulations may hold the key to epitope prediction on the fully glycosylated SARS-CoV-2 spike protein

Betacoronavirus SARS-CoV-2 is posing a major threat to human health and its diffusion around the world is having dire socioeconomical consequences. Thanks to the scientific community’s unprecedented efforts, the atomic structure of several viral proteins has been promptly resolved. As the crucial mediator of host cell infection, the heavily glycosylated trimeric viral Spike protein (S) has been attracting the most attention and is at the center of efforts to develop antivirals, vaccines, and diagnostic solutions.Herein, we use an energy-decomposition approach to identify antigenic domains and antibody binding sites on the fully glycosylated S protein. Crucially, all that is required by our method are unbiased atomistic molecular dynamics simulations; no prior knowledge of binding properties or ad hoc combinations of parameters/measures extracted from simulations is needed. Our method simply exploits the analysis of energy interactions between all intra-protomer aminoacid and monosaccharide residue pairs, and cross-compares them with structural information (i.e., residueresidue proximity), identifying potential immunogenic regions as those groups of spatially contiguous residues with poor energetic coupling to the rest of the protein.Our results are validated by several experimentally confirmed structures of the S protein in complex with anti- or nanobodies. We identify poorly coupled sub-domains: on the one hand this indicates their role in hosting (several) epitopes, and on the other hand indicates their involvement in large functional conformational transitions. Finally, we detect two distinct behaviors of the glycan shield: glycans with stronger energetic coupling are structurally relevant and protect underlying peptidic epitopes; those with weaker coupling could themselves be poised for antibody recognition. Predicted Immunoreactive regions can be used to develop optimized antigens (recombinant subdomains, synthetic (glyco)peptidomimetics) for therapeutic applications.

Extraction, Characterization, Antitumor and Immunological Activities of Hemicellulose Polysaccharide from Astragalus radix Herb Residue

Astragalus radix (radix) have been frequently used for clinical application in China, and the herb residues of radix turn out to be a waste of resources. To escape from this, the medicine value of radix herb residues is mined in this article. We isolated hemicellulose polysaccharide AX-I-3b from radix herb residues by fractional extraction. Monosaccharide-composition analysis revealed that AX-I-3b consisted of arabinose, xylose, and glucose with a molar ratio of 10.4:79.3:1.1. Methylation, NMR and FT-IR analyses showed that AX-I-3b monosaccharide residue was linked as follows: →2,3,4)-β-d-Xylp-(1→, →4)-β-d-Arap-(1→, →4)-β-d-Glcp-(1→. Then, we found that AX-I-3b exhibited antitumor activity against lung cancer in vitro and vivo through MTT assay and xenograft tumor model. Mechanistically, AX-I-3b induced apoptosis in lung cancer cells and xenograft tumors, which is evidenced by the up-regulation of p53, Bax and cleaved caspase-3, and the down-regulation of Bcl-2. Moreover, AX-I-3b synergistically improved the therapeutic ability of cisplatin in xenograft tumors model. Furthermore, AX-I-3b treatment effectively improved the immune organ index, the percentage of spleen lymphocyte subsets and serum cytokine levels in lung cancer mice, supporting that AX-I-3b showed immunomodulatory activity. In conclusion, our results identified AX-I-3b as an antitumor and immunomodulatory agent, providing a new insight into the reutilization of radix herb residue.

Psolusosides C3 and D2-D5, Five Novel Triterpene Hexaosides From the Sea Cucumber Psolus fabricii (Psolidae, Dendrochirotida): Chemical Structures and Bioactivities

Five new triterpene glycosides, psolusosides C3 (1), D2 (2), D3 (3), D4 (4), and D5 (5), have been isolated from the sea cucumber Psolus fabricii. The structures of these glycosides were elucidated by 2-dimensional nuclear magnetic resonance spectroscopy and high-resolution mass spectrometry. All the compounds contain hexasaccharide carbohydrate chains, differing from each other in the third monosaccharide residue: xylose was found in psolusosides of group C and glucose in group D. Aglycones of the isolated compounds belong to the holostane type, contain 9(11)-double bond and 16-keto-group and have different side chains. The hemolytic activity against mouse erythrocytes and cytotoxic activity against mouse Ehrlich carcinoma cells (ascite form) and neuroblastoma Neuro 2A cells of 1 to 5 as well as the psolusosides isolated by us earlier, C1, C2, and D1, 26-nor-25-oxo-holotoxin A1, and holotoxin A1, have been studied. Psolusosides C2, D1, and D2 (2) having the aglycones without hydroxy group in the side chain showed the strongest hemolytic action in this series. Psolusoside D3 (3) containing a peroxide group in the side chain of its aglycone was surprisingly highly cytotoxic in all the tests.

Psolusosides C1, C2, and D1, Novel Triterpene Hexaosides from the Sea CucumberPsolus fabricii (Psolidae, Dendrochirotida)

Three new triterpene glycosides, psolusosides C1 (1), C2 (2) and D1 (3) have been isolated from the sea cucumber Psolus fabricii collected in the Sea of Okhotsk in the shallow waters of Onekotan Island (Kurile Islands). Five known glycosides: cladolosides B, M1, P2, isolated earlier from the sea cucumbers of genus Cladolabes and holotoxin A1 with 27- nor-25-oxo-holotoxin A1, isolated earlier from Apostichopus japonicus have also been found. The glycoside structures were elucidated by 2D NMR spectroscopy and HR mass-spectrometry. Compounds 1–3 possess hexasaccharide carbohydrate chains, identical for 1 and 2 and different in the third monosaccharide residue for 3. All the glycosides comprise holostane type aglycones with a 9(11)-double bond and a 16-keto-group and differ from each other in the side chains structures.

Colochirosides A1, A2, A3, and D, Four Novel Sulfated Triterpene Glycosides from the Sea Cucumber Colochirus Robustus (Cucumariidae, Dendrochirotida)

Four new triterpene glycosides, colochirosides A1 (1), A2 (2), A3 (3) and D (4), have been isolated from the sea cucumber Colochirus robustus (Cucumariidae, Dendrochirotida). Structures of the glycosides have been elucidated by 2D NMR spectroscopy and mass-spectrometry. Colochiroside D (4) has a new type of carbohydrate chain having the only sulfate group attached to C-6 of the third (glucose) monosaccharide residue. Cytotoxic activities of glycosides 1–4 against the ascite form of mouse Ehrlich carcinoma cells and hemolytic activity against mouse erythrocytes have been studied. Hemolytic activity of the glycosides was higher than cytotoxic. Glycosides 1, 3 and 4 demonstrated strong effects, whereas compound 2 showed only moderate activity.

Cucumarioside E from the Far Eastern Sea Cucumber Cucumaria japonica (Cucumariidae, Dendrochirotida), New Minor Monosulfated Holostane Triterpene Pentaoside with Glucose as the Second Monosaccharide Residue

New minor triterpene glycoside, cucumarioside E (1) has been isolated from the Far Eastern sea cucumber Cucumaria japonica. The structure of the glycoside was elucidated by 2D-NMR specroscopy and mass-spectrometry. The glycoside has glucose instead of quinovose as the second monosaccharide residue and xylose as third monosaccharide residue that is unique structural feature for triterpene glycosides carbohydrate chains from sea cucumbers belonging to the genus Cucumaria.

Structures and Biological Activities of Typicosides A1, A2, B1, C1 and C2, Triterpene Glycosides from the Sea Cucumber Actinocucumis typica

Five new minor triterpene glycosides, typicosides A1 (1), A2 (2), B1 (3), C1 (4) and C2 (5), along with two known glycosides, intercedenside A and holothurin B3, have been isolated from the sea cucumber Actinocucumis typica. Structures of the glycosides were elucidated by 2D NMR spectroscopy and MS. Glycosides 1–5 are linear mono- and disulfated tetraosides differing from each other in both aglycone structures and monosaccharide composition of the carbohydrate chains. Typicosides A1 (1) and A2 (2) have identical monosulfated carbohydrate moieties with a xylose residue as the third monosaccharide unit and differ from each other in aglycon structures. Typicoside B1 (3) has glucose as the third monosaccharide residue. Typicosides C1 (4) and C2 (5) contain the same disulfated carbohydrate chains and differ from each other in structures of aglycone side chains. Antifungal activity of glycosides 1–5 against three species of fungi along with cytotoxic activity against mouse spleen lymphocytes and mouse Ehrlich carcinoma cells (ascite form), as well as hemolytic activities against mouse erythrocytes have been studied. All new glycosides, except for typicoside C1 (4), containing a hydroxy-group in the aglycone side chain, demonstrate rather strong hemolytic and cytotoxic activities.