Triterpene glycosides from the far eastern sea cucumber Pentamera calcigera II: disulfated glycosides

Unusual Structures and Cytotoxicities of Chitonoidosides A, A1, B, C, D, and E, Six Triterpene Glycosides from the Far Eastern Sea Cucumber Psolus chitonoides

Six new triterpene tetra-, penta- and hexaosides, chitonoidosides A (1), A₁ (2), B (3), C (4), D (5), and E (6), containing one or two sulfate groups, have been isolated from the Far-Eastern sea cucumber Psolus chitonoides, collected near Bering Island (Commander Islands) from the depth of 100–150 m. Three of the isolated compounds (1, 3 and 6) are characterized by the unusual aglycone of new type having 18(20)-ether bond and lacking a lactone in contrast with wide spread holostane derivatives. Another unexpected finding is 3-O-methylxylose residue as a terminal unit in the carbohydrate chains of chitonoidosides B (3), C (4), and E (6), which has never been found before in the glycosides from holothurians belonging to the Psolidae family. Moreover, this monosaccharide is sulfated in the compound 4 into unprecedented 3-O-methylxylose 4-O-sulfate residue. Chitonoidoside C (4) is characterized by tetrasaccharide moiety lacking a part of the bottom semi-chain, but having disaccharide fragment attached to C-4 of Xyl1. Such architecture is not common in sea cucumber glycosides. Cytotoxic activities of the compounds 1–5 against mouse and human erythrocytes and human cancer cell lines: adenocarcinoma HeLa, colorectal adenocarcinoma DLD-1, and leukemia promyeloblast HL-60 cells were studied. The cytotoxic effect of chitonoidoside d (5) was the most significant in this series due to the presence of pentasaccharide disulfated sugar chain in combination with holostane aglycone. Surprisingly, the glycosides 1 and 3, comprising the new aglycone without γ-lactone, demonstrated similar activity to the known compounds with holostane aglycones. Chitonoidoside C (4) was less cytotoxic due to the different architecture of the carbohydrate chain compared to the other glycosides and probably due to the presence of a sulfate group at C-4 in 3-O-MeXyl4.

Anti-inflammatory peptides and metabolomics-driven biomarkers discovery from sea cucumber protein hydrolysates

The hydrolysates from Apostichopus japonicus sea cucumber are an important source of nitrogen that may be added to foods. We evaluated the effect of A. japonicus hydrolysates on inflammation-associated leukocyte recruitment. The results revealed that leukocyte migration to the site of injury was significantly blocked by AJH-1 (<10 kDa), suggesting a protective effect against CuSO₄ -induced neuromast damage in a zebrafish model. Based on liquid chromatography/time-of-flight/mass spectrometry, and metabolomic analysis, the nine biomarker candidates in AJH-1 were Val, Ala-Pro-Arg, Gly-Lys, Asp propyl ester, Glu methyl ester, His butyl ester, Ile-Ala-Ala-Lys, Tyr-Lys, and Asn-Pro-Gly-Lys. We used molecular docking to predict the binding affinity and docked position of the peptides onto the angiotensin converting enzyme (ACE). All the identified peptides had adequate binding affinity toward ACE, especially peptides Ala-Pro-Arg and Gly-Lys. These peptides may be used in the development of therapeutic foods. PRACTICAL APPLICATION: The study revealed the anti-inflammatory properties of the fractionated sea cucumber protein hydrolysate (<10 kDa). The characteristic peptides may be used as functional ingredients in nutraceutical foods and beverages.

Non-holostane aglycones of sea cucumber triterpene glycosides. Structure, biosynthesis, evolution

Triterpene glycosides are known as characteristic metabolites of sea cucumbers (class Holothuroidea, phylum Echinodermata). The most of them have lanostane aglycones containing 18(20)-lactone, i.e. belongs to so-called holostane series. However non-holostane glycosides having no lactone (with the both normal and shortened side chains) or containing 18(16)-lactone function were also found in these invertebrates last a few decades. In addition, some very rare findings of the glycosides containing rearranged lanostane skeleton systems were reported. Probably, these natural products are formed in result of intramolecular aldol condensation of 1,6-diketo precursors as well as by Meinwald rearrangement of 1,2-epoxy precursor or pinacol-pinacolone rearrangement of fully substituted 1,2-diol precursor. Structures, biosynthesis and evolution of non-holostane aglycones of sea cucumber triterpene glycosides are discussed. Biological properties of the glycosides with hon-holostane aglycones are also discussed.

Separation, purification, structures and anticoagulant activities of fucosylated chondroitin sulfates from Holothuria scabra

In this study, a new fucosylated chondroitin sulfate (HsG) with an average molecular weight of 69.1 kDa was isolated from sea cucumber Holothuria scabra. We investigated the structure of the HsG by adopting monosaccharide composition analysis, disaccharide composition analysis, IR,¹H and¹³C NMR spectra and methylation analysis. According to methylation results of desulfated/carboxyl-reduced polysaccharides and the analysis of unsaturated disaccharides generated through the enzymolysis of the defucosed polysaccharides, it is shown that each branch is formed by one fucopyranosyl residue, wherein 55.7% of the fucopyranosyl residues are linked to the O-6 position of the N-acetylgalactosamine moiety, 21.2% of the fucopyranosyl residues are linked to the O-3 position of β-d-glucuronic acid, 13.0% of the fucopyranosyl residues are linked to the O-4 positions of the N-acetylgalactosamine moiety, and 10.1% of the fucopyranosyl residues are not linked to sulfate groups on the backbone. The backbone →4)GlcUAβ(1 → 3)GalNAcβ(1→ and sulfated fucose branches were composed of the β-d-glucuronic acid, N-acetyl-β-d- galactosamine, α-l-fucose and sulfate groups by the molar ratio of 1:1.72:2.34:3.29. The anticoagulant activities of the HsG was evaluated and compared with heparin. The result showed that the HsG could prolong the activated partial thromboplastin time.

Sea Cucumber Glycosides: Chemical Structures, Producing Species and Important Biological Properties

Sea cucumbers belonging to echinoderm are traditionally used as tonic food in China and other Asian countries. They produce abundant biologically active triterpene glycosides. More than 300 triterpene glycosides have been isolated and characterized from various species of sea cucumbers, which are classified as holostane and nonholostane depending on the presence or absence of a specific structural unit γ(18,20)-lactone in the aglycone. Triterpene glycosides contain a carbohydrate chain up to six monosaccharide units mainly consisting of d-xylose, 3-O-methy-d-xylose, d-glucose, 3-O-methyl-d-glucose, and d-quinovose. Cytotoxicity is the common biological property of triterpene glycosides isolated from sea cucumbers. Besides cytotoxicity, triterpene glycosides also exhibit antifungal, antiviral and hemolytic activities. This review updates and summarizes our understanding on diverse chemical structures of triterpene glycosides from various species of sea cucumbers and their important biological activities. Mechanisms of action and structural-activity relationships (SARs) of sea cucumber glycosides are also discussed briefly.

Acetylated Triterpene Glycosides and Their Biological Activity from Holothuroidea Reported in the Past Six Decades

Sea cucumbers have been valued for many centuries as a tonic and functional food, dietary delicacies and important ingredients of traditional medicine in many Asian countries. An assortment of bioactive compounds has been described in sea cucumbers. The most important and abundant secondary metabolites from sea cucumbers are triterpene glycosides (saponins). Due to the wide range of their potential biological activities, these natural compounds have gained attention and this has led to their emergence as high value compounds with extended application in nutraceutical, cosmeceutical, medicinal and pharmaceutical products. They are characterized by bearing a wide spectrum of structures, such as sulfated, non-sulfated and acetylated glycosides. Over 700 triterpene glycosides have been reported from the Holothuroidea in which more than 145 are decorated with an acetoxy group having 38 different aglycones. The majority of sea cucumber triterpene glycosides are of the holostane type containing a C18 (20) lactone group and either Δ(7(8)) or Δ(9(11)) double bond in their genins. The acetoxy group is mainly connected to the C-16, C-22, C-23 and/or C-25 of their aglycone. Apparently, the presence of an acetoxy group, particularly at C-16 of the aglycone, plays a significant role in the bioactivity; including induction of caspase, apoptosis, cytotoxicity, anticancer, antifungal and antibacterial activities of these compounds. This manuscript highlights the structure of acetylated saponins, their biological activity, and their structure-activity relationships.

Colochirosides B1, B2, B3 and C, Novel Sulfated Triterpene Glycosides from the Sea Cucumber Colochirus robustus (Cucumariidae, Dendrochirotida)

Four new triterpene glycosides, colochirosides B1 (1), B2 (2), B3 (3) and C (4) have been isolated from the sea cucumber Colochirus robustus (Cucumariidae, Dendrochirotida). Six known earlier glycosides from representatives of two families of the order Dendrochirotida have also been found in C. robustus. Structures of the glycosides have been elucidated by 2D NMR spectroscopy and mass spectrometry. All the glycosides belong to the holostane series and contain tetrasaccharide linear carbohydrate chains with one or two sulfate groups. Cytotoxic activities of glycosides 1-4 against the ascite form of mouse Ehrlich carcinoma cells and hemolytic activities against mouse erythrocytes have been studied. Hemolytic activity of the glycosides was higher than cytotoxic. Glycosides 3 and 4 demonstrated strong effects, whereas compounds 1 and 2 containing the hydroxy-group in the side chains showed moderate hemolytic activity and were not cytotoxic.

Structure elucidation of five novel isomeric saponins from the viscera of the sea cucumber Holothuria lessoni

Sea cucumbers are prolific producers of a wide range of bioactive compounds. This study aimed to purify and characterize one class of compound, the saponins, from the viscera of the Australian sea cucumber Holothuria lessoni. The saponins were obtained by ethanolic extraction of the viscera and enriched by a liquid-liquid partition process and adsorption column chromatography. A high performance centrifugal partition chromatography (HPCPC) was applied to the saponin-enriched mixture to obtain saponins with high purity. The resultant purified saponins were profiled using MALDI-MS/MS and ESI-MS/MS which revealed the structure of isomeric saponins to contain multiple aglycones and/or sugar residues. We have elucidated the structure of five novel saponins, Holothurins D/E and Holothurinosides X/Y/Z, along with seven reported triterpene glycosides, including sulfated and non-sulfated saponins containing a range of aglycones and sugar moieties, from the viscera of H. lessoni. The abundance of novel compounds from this species holds promise for biotechnological applications.

Discovery of novel saponins from the viscera of the sea cucumber Holothuria lessoni

Sea cucumbers, sometimes referred to as marine ginseng, produce numerous compounds with diverse functions and are potential sources of active ingredients for agricultural, nutraceutical, pharmaceutical and cosmeceutical products. We examined the viscera of an Australian sea cucumber Holothuria lessoni Massin et al. 2009, for novel bioactive compounds, with an emphasis on the triterpene glycosides, saponins. The viscera were extracted with 70% ethanol, and this extract was purified by a liquid-liquid partition process and column chromatography, followed by isobutanol extraction. The isobutanol saponin-enriched mixture was further purified by high performance centrifugal partition chromatography (HPCPC) with high purity and recovery. The resultant purified polar samples were analyzed using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS)/MS and electrospray ionization mass spectrometry (ESI-MS)/MS to identify saponins and characterize their molecular structures. As a result, at least 39 new saponins were identified in the viscera of H. lessoni with a high structural diversity, and another 36 reported triterpene glycosides, containing different aglycones and sugar moieties. Viscera samples have provided a higher diversity and yield of compounds than observed from the body wall. The high structural diversity and novelty of saponins from H. lessoni with potential functional activities presents a great opportunity to exploit their applications for industrial, agricultural and pharmaceutical use.

Triterpene Glycosides from the Sea Cucumber Eupentacta Fraudatrix. Structure and Biological Action of Cucumariosides I1, I3, I4, Three New Minor Disulfated Pentaosides

Three new minor triterpene glycosides, cucumariosides I1 (1), I3 (2) and I4 (3) have been isolated from the Far Eastern sea cucumber Eupentacta fraudatrix. Structures of the glycosides were elucidated by 2D NMR spectroscopy and MS. Glycosides 1–3 belong to the group of cucumariosides I, having branched pentasaccharide carbohydrate moieties with two sulfate groups and possessing 3- O-methyl-D-xylose as a terminal monosaccharide unit that is a characteristic feature of all the glycosides isolated from E. fraudatrix. Glycosides 1 and 2 differ from each other by the side chain structures in the holostane aglycone moieties, while cucumarioside I4 (3) has a 23,24,25,26,27-pentanorlanostane aglycone with an 18(16)-lactone. Cytotoxic activities of glycosides 1–3 against mouse spleen lymphocytes and ascite form of mouse Ehrlich carcinoma cells, along with hemolytic activity against mouse erythrocytes and antifungal activity were studied. Glycoside 1, having an aglycone side chain with a 24(25)-double bond, possesses moderate activity in all the tests, while glycoside 2, having 23(24)-double bond and 25-hydroxy group in the side chain, and glycoside 3 with an aglycone with an 18(16)-lactone and shortened side chain have either low activity or are non-active.

Triterpene glycosides from sea cucumbers and their biological activities

Triterpenoid glycosides are abundantly present in sea cucumbers, which are responsible for the toxicity of these echinoderms. More than 100 triterpenoid glycosides have been isolated in the past 20 years and those are grouped into four main structural categories considering their aglycone structure: 3β-hydroxyholost-9(ll)-ene aglycone skeleton, 3β-hydroxyholost-7-ene skeleton, other holostane type aglycones and nonholostane aglycone. Most of the triterpenoid glycosides are found to be possessing potential biological activities. Among the biological activities, anticancer activity and antiviral activity are the most widely studied areas. In this communication, we have presented a general view of the structural characteristics of triterpenoid glycosides and their major biological activities. The structural significance and the application limitations of triterpene glycosides are also discussed.

Structures and cytotoxic properties of cucumariosides H₂, H₃ and H₄ from the sea cucumber Eupentacta fraudatrix

New triterpene glycosides, cucumariosides H₂ (1), H₃ (2) and H₄ (3), have been isolated from the Far Eastern sea cucumber Eupentacta fraudatrix. The structures of 1-3 were elucidated using extensive NMR spectroscopy (¹H- and ¹³C-NMR, DEPT, ¹H-¹H COSY, 1D TOCSY, H2BC, HMBC, heteronuclear single-quantum coherence, and NOESY) and ESI-MS. Glycosides 1-3 are monosulphated branched pentaosides having rare 3-O-methyl-D-xylose as a terminal monosaccharide. Glycosides 1 and 3 contain holostane aglycones, whereas 2 has a 23,24,25,26,27-pentanorlanostane aglycone with an 18(16)-lactone, which is also uncommon for the sea cucumbers. Glycoside 3 contains a very rare ethoxyl radical at C-25 of the aglycone side chain, and it is most probably an artefact that was formed during long storage of the ethanolic extract. Cytotoxic activities of 1-3 against mouse spleen lymphocytes, haemolytic activity against mouse erythrocytes and Ehrlich carcinoma cells have been studied. The presence of 25-hydroxy group in aglycone moiety significantly decreased the activities.

Synaptosides A and A1, triterpene glycosides from the sea cucumber Synapta maculata containing 3-O-methylglucuronic acid and their cytotoxic activity against tumor cells

Two novel triterpene holostane glycosides, synaptosides A ( 1) and A 1 ( 2), have been isolated from the Vietnamese sea cucumber Synapta maculata (Synaptida, Apodida). Their structures were elucidated by spectroscopic methods (NMR and MS) and chemical transformations. Glycosides 1 and 2 have rare branched pentasaccharide carbohydrate chains featuring a 3- O-methylglucuronic acid residue not previously reported in glycosides from sea cucumbers and a 6- O-sulfated glucose. Glycoside 2 has an oxo group at C-7 and a 8(9)-double bond. All these structural features are unknown in glycosides from sea cucumbers. Glycoside 1 has moderate cytotoxic activity (IC 50 8.6 microg/mL) and glycoside 2 is inactive against HeLa tumor cells.