Hillasides A and B, two new cytotoxic triterpene glycosides from the sea cucumber Holothuria hilla Lesson

Biochemical metabolomic profiling of the Crown-of-Thorns Starfish (Acanthaster): New insight into its biology for improved pest management

The Crown-of-Thorns Starfish (COTS), Acanthaster species, is a voracious coral predator that destroys coral reefs when in outbreak status. The baseline metabolite and lipid biomolecules of 10 COTS tissues, including eggs from gravid females, were investigated in this study to provide insight into their biology and identify avenues for control. Targeted and untargeted metabolite- and lipidomics-based mass spectrometry approaches were used to obtain tissue-specific metabolite and lipid profiles. Across all COTS tissues, 410 metabolites and 367 lipids were identified. Most abundant were amino acids and peptides (18.7%) and wax esters (17%). There were 262 metabolites and 192 lipids identified in COTS eggs. Wax esters were more abundant in the eggs (30%) followed by triacylglycerols (TG), amino acids, and peptides. The diversity of asterosaponins in eggs (34) was higher than in tissues (2). Several asterosaponins known to modulate sperm acrosome reaction were putatively identified, including glycoside B, asterosaponin-4 (Co-Aris III), and regularoside B (asterosaponin A). The saponins saponin A, thornasteroside A, hillaside B, and non-saponins dictyol J and axinellamine B which have been shown to possess defensive properties, were found in abundance in gonads, skin, and radial nerve tissues. Inosine and 2-hexyldecanoic acid are the most abundant metabolites in tissues and eggs. As a secondary metabolite of purine degradation, inosine plays an important role in purine biosynthesis, while 2-hexyldecanoic acid is known to suppress side-chain crystallization during the synthesis of amphiphilic macromolecules (i.e., phospholipids). These significant spatial changes in metabolite, lipid, and asterosaponin profiles enabled unique insights into key biological tissue-specific processes that could be manipulated to better control COTS populations. Our findings highlight COTS as a novel source of molecules with therapeutic and cosmetic properties (ceramides, sphingolipids, carnosine, and inosine). These outcomes will be highly relevant for the development of strategies for COTS management including chemotaxis-based biocontrol and exploitation of COTS carcasses for the extraction of commercial molecules.

Saponin and Fatty Acid Profiling of the Sea Cucumber Holothuria atra, α-Glucosidase Inhibitory Activity and the Identification of a Novel Triterpene Glycoside

Saponin-rich sea cucumber extracts have shown antidiabetic effects in a few reports. Although the triterpene glycosides of sea cucumbers are commonly isolated from their Cuvierian tubules, these are absent in Holothuria atra Jaeger. Therefore, this study intended to investigate the saponin profile in the body wall of H. atra, as well as to assess the α-glucosidase inhibitory activity of the H. atra extracts. The chemical profiling of sea cucumber extracts was conducted by UPLC-HRMS analysis. This resulted in the tentative identification of 11 compounds, 7 of which have not been reported in the H. Atra body wall before. Additionally, two triterpene glycosides were purified and their structures were elucidated based on HRMS and NMR data: desholothurin B (1), and a novel epimer, 12-epi-desholothurin B (2). Moreover, the fatty acid profile of the H. atra body wall was investigated by GC-MS. It was found that the Me90 fraction of the H. atra body wall showed the strongest α-glucosidase inhibitory activity (IC₅₀ value 0.158 ± 0.002 mg/mL), thus making it more potent than acarbose (IC₅₀ value 2.340 ± 0.044 mg/mL).

CN-3 increases TMZ sensitivity and induces ROS-dependent apoptosis and autophagy in TMZ-resistance glioblastoma

Many glioma patients develop resistance to temozolomide (TMZ) treatment, resulting in reduced efficacy and survival rates. TMZ-resistant cell lines SHG44R and U87R, which highly express O₆ -methylguanine DNA methyltransferase (MGMT) and P-gp, were established. CN-3, a new asterosaponin, showed cytotoxic effects on TMZ-resistant cells in a dose- and time-dependent manner via reactive oxygen species (ROS)-mediated apoptosis and autophagy. Transmission electron microscopy and monodansylcadaverine (MDC) staining showed turgidity of the mitochondria and autophagosomes in CN-3-treated SHG44R and U87R cells. The autophagy inhibitor 3-methyladenine was used to confirm the important role of autophagy in CN-3 cytotoxicity in TMZ-resistant cells. The ROS scavenger N-acetyl- l-cysteine (NAC) attenuated the levels of ROS induced by CN-3 and, therefore, rescued the CN-3 cytotoxic effect on the viability of SHG44R and U87R cells by Cell Counting Kit-8 assays and JuLI-Stage videos. MDC staining also confirmed that NAC rescued an autophagosome increase in CN-3-treated SHG44R and U87R cells. Western blotting revealed that CN-3 increased Bax, cleaved-caspase 3, cytochrome C, PARP-1, LC3-Ⅱ, and Beclin1, and decreased P-AKT, Bcl-2, and p62. Further rescue experiments revealed that CN-3 induced apoptosis and autophagy through ROS-mediated cytochrome C, cleaved-caspase 3, Bcl-2, P-AKT, PARP-1, and LC3-Ⅱ. In addition, CN-3 promoted SHG44R and U87R cells sensitive to TMZ by reducing the expression of P-gp, MGMT, and nuclear factor kappa B p65, and it had a synergistic cytotoxic effect with TMZ. Moreover, CN-3 disrupted the natural cycle arrest and inhibited the migration of SHG44R and U87R cells by promoting cyclin E1 and D1, and by decreasing P21, P27, N-cadherin, β-catenin, transforming growth factor beta 1, and Smad2.

Fucosylated Chondroitin Sulfates from the Sea Cucumbers Paracaudina chilensis and Holothuria hilla: Structures and Anticoagulant Activity

Fucosylated chondroitin sulfates (FCSs) PC and HH were isolated from the sea cucumbers Paracaudina chilensis and Holothuria hilla, respectively. The purification of the polysaccharides was carried out by anion-exchange chromatography on a DEAE-Sephacel column. The structural characterization of the polysaccharides was performed in terms of monosaccharide and sulfate content, as well as using a series of nondestructive NMR spectroscopic methods. Both polysaccharides were shown to contain a chondroitin core [→3)-β-d-GalNAc (N-acethyl galactosamine)-(1→4)-β-d-GlcA (glucuronic acid)-(1→]_n, bearing sulfated fucosyl branches at O-3 of every GlcA residue in the chain. These fucosyl residues were different in their pattern of sulfation: PC contained Fuc2S4S and Fuc4S in a ratio of 2:1, whereas HH included Fuc2S4S, Fuc3S4S, and Fuc4S in a ratio of 1.5:1:1. Moreover, some GalNAc residues in HH were found to contain an unusual disaccharide branch Fuc4S-(1→2)-Fuc3S4S-(1→ at O-6. Sulfated GalNAc4S6S and GalNAc4S units were found in a ratio of 3:2 in PC and 2:1 in HH. Both polysaccharides demonstrated significant anticoagulant activity in a clotting time assay, which is connected with the ability of these FCSs to potentiate the inhibition of thrombin and factor Xa in the presence of anti-thrombin III (ATIII) and with the direct inhibition of thrombin in the absence of any cofactors.

Reduction of SCUBE3 by a new marine-derived asterosaponin leads to arrest of glioma cells in G1/S

Many saponins are characterized as exhibiting a wide spectrum of antitumor activities at low concentrations. Most of the previous studies that aimed to understand the mechanisms underlying anticancer saponins have focused on numerous classical signaling pathways. However, at the oncogene level, little is known about the action of saponins, especially asterosaponin. In this study, CN-3, a new asterosaponin isolated from the starfish Culcita novaeguineae, decreased the proliferation of U87 and U251 cells at low doses in a dose- and time-dependent manner. Microarray analysis revealed CN-3 significantly induced the differential expression of 661 genes that are related to its antiglioma effect in U251. Nine downregulated genes (SCUBE3, PSD4, PGM2L1, ACSL3, PRICKLE1, ABI3BP, STON1, EDIL3, and KCTD12) were selected, for further verification of their low expression. Then, shRNA transfection and high-content screening were performed and significantly decreased U251 cell proliferation rate was only observed for the SCUBE3 knockdown. qPCR confirmed SCUBE3 was highly expressed in U251 and U87 cells, and had medium expression levels in U373 cells. Real-time cellular analysis using iCELLigence demonstrated that SCUBE3 is an oncogene in U251 and U87 cells, with knockdown of SCUBE3 inhibiting U251 and U87 cell proliferation while, conversely, SCUBE3 overexpression promoted their proliferation. Afterward, SCUBE3 protein was found to have high expression in primary glioma specimens from patients examined by immunohistochemistry but low expression in normal brain. PathScan ELISA analysis in conjunction with TEM observation demonstrated that the effect of SCUBE3 knockdown in U251 does not appear to be related to the induction of apoptosis. Employing CCK-8, iCELLigence, flow cytometry, western blotting, and shRNA transfection (knockdown and overexpression) experiments, we reveal that the reduction of SCUBE3 expression, induced by CN-3, mediated both inhibition and G1/S arrest of U251 via the Akt/p-Akt/p53/p21/p27/E2F1 pathway.

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.

Mechanisms of cancer cell killing by sea cucumber-derived compounds

The aim of cancer therapy is to specifically eradicate tumor cells while causing minimal damage to normal tissues and minimal side-effects. Because of this, the use of natural substances with low toxicity is a good option. Sea cucumbers are one of many potential marine animals that contain valuable nutrients and medicinal properties. The medicinal value of sea cucumbers is attributed to the presence of bioactive agents with promising biological and pharmacological properties that include cytotoxic activity, induction of apoptosis, cell cycle arrest, inhibition of tumor growth, anti-metastatic and anti-angiogenic properties, and inhibition of drug resistance. This review discusses the mechanisms of cancer cell death induced by sea cucumber-derived compounds with regard to exploring the potential use of these marine natural products for cancer therapy.

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.

Anticancer activity of sea cucumber triterpene glycosides

Triterpene glycosides are characteristic secondary metabolites of sea cucumbers (Holothurioidea, Echinodermata). They have hemolytic, cytotoxic, antifungal, and other biological activities caused by membranotropic action. These natural products suppress the proliferation of various human tumor cell lines in vitro and, more importantly, intraperitoneal administration in rodents of solutions of some sea cucumber triterpene glycosides significantly reduces both tumor burden and metastasis. The anticancer molecular mechanisms include the induction of tumor cell apoptosis through the activation of intracellular caspase cell death pathways, arrest of the cell cycle at S or G2/M phases, influence on nuclear factors, NF-κB, and up-down regulation of certain cellular receptors and enzymes participating in cancerogenesis, such as EGFR (epidermal growth factor receptor), Akt (protein kinase B), ERK (extracellular signal-regulated kinases), FAK (focal adhesion kinase), MMP-9 (matrix metalloproteinase-9) and others. Administration of some glycosides leads to a reduction of cancer cell adhesion, suppression of cell migration and tube formation in those cells, suppression of angiogenesis, inhibition of cell proliferation, colony formation and tumor invasion. As a result, marked growth inhibition of tumors occurs in vitro and in vivo. Some holothurian triterpene glycosides have the potential to be used as P-gp mediated MDR reversal agents in combined therapy with standard cytostatics.

New Cytotoxic Triterpene Glycoside from the East China Sea Cucumber Holothuria nobilis

A new cytotoxic triterpene glycoside named nobiliside E (1) has been obtained from the East China Sea cucumber Holothuria nobilis Selenka. Its structure was determined on the basis of NMR spectroscopic and MS analyses, together with chemical evidence. The new compound showed significant cytotoxicity to eight human tumor cell lines with IC50 values in the range of 0.53–4.06 μg/mL.

Structure elucidation of new acetylated saponins, Lessoniosides A, B, C, D, and E, and non-acetylated saponins, Lessoniosides F and G, from the viscera of the sea cucumber Holothuria lessoni

Sea cucumbers produce numerous compounds with a wide range of chemical structural diversity. Among these, saponins are the most diverse and include sulfated, non-sulfated, acetylated and methylated congeners with different aglycone and sugar moieties. In this study, MALDI and ESI tandem mass spectrometry, in the positive ion mode, were used to elucidate the structure of new saponins extracted from the viscera of H. lessoni. Fragmentation of the aglycone provided structural information on the presence of the acetyl group. The presence of the O-acetyl group was confirmed by observing the mass transition of 60 u corresponding to the loss of a molecule of acetic acid. Ion fingerprints from the glycosidic cleavage provided information on the mass of the aglycone (core), and the sequence and type of monosaccharides that constitute the sugar moiety. The tandem mass spectra of the saponin precursor ions [M + Na]⁺ provided a wealth of detailed structural information on the glycosidic bond cleavages. As a result, and in conjunction with existing literature, we characterized the structure of five new acetylated saponins, Lessoniosides A–E, along with two non-acetylated saponins Lessoniosides F and G at m/z 1477.7, which are promising candidates for future drug development. The presented strategy allows a rapid, reliable and complete analysis of native saponins.

Biological and taxonomic perspective of triterpenoid glycosides of sea cucumbers of the family Holothuriidae (Echinodermata, Holothuroidea)

Since the discovery of saponins in sea cucumbers, more than 150 triterpene glycosides have been described for the class Holothuroidea. The family Holothuriidae has been increasingly studied in search for these compounds. With many species awaiting recognition and formal description this family currently consists of five genera and the systematics at the species-level taxonomy is, however, not yet fully understood. We provide a bibliographic review of the triterpene glycosides that has been reported within the Holothuriidae and analyzed the relationship of certain compounds with the presence of Cuvierian tubules. We found 40 species belonging to four genera and 121 compounds. Holothurin A and B are the most common saponins for Actinopyga, Holothuria, and Pearsonothuria. The genus Bohadschia presents mainly bivittoside C and D. Actinopyga has only sulfated saponins mainly oxidized, Bohadschia non-sulfated ones mainly non-oxidized, Holothuria and Pearsonothuria contain both types of compounds, mainly oxidized. Within the genus Holothuria, the subgenus Panningothuria only has non-sulfated saponins. The presence of sulfated and non-sulfated compounds seemingly relates to the expellability or the absence of Cuvierian tubules and the temporal or permanent concealing habits of the species. Our study concludes that better insights into the systematic distribution of saponins in Holothuriidae will only be possible if the identifications of the investigated species are confirmed by a taxonomist, especially in this group wherein cryptic species and variation between life-history stages are common and yet poorly understood. Understanding of saponin distribution within the Holothuriidae would also benefit from a stabilization of triterpene glycoside nomenclature.

High-value components and bioactives from sea cucumbers for functional foods--a review

Sea cucumbers, belonging to the class Holothuroidea, are marine invertebrates, habitually found in the benthic areas and deep seas across the world. They have high commercial value coupled with increasing global production and trade. Sea cucumbers, informally named as bêche-de-mer, or gamat, have long been used for food and folk medicine in the communities of Asia and Middle East. Nutritionally, sea cucumbers have an impressive profile of valuable nutrients such as Vitamin A, Vitamin B1 (thiamine), Vitamin B2 (riboflavin), Vitamin B3 (niacin), and minerals, especially calcium, magnesium, iron and zinc. A number of unique biological and pharmacological activities including anti-angiogenic, anticancer, anticoagulant, anti-hypertension, anti-inflammatory, antimicrobial, antioxidant, antithrombotic, antitumor and wound healing have been ascribed to various species of sea cucumbers. Therapeutic properties and medicinal benefits of sea cucumbers can be linked to the presence of a wide array of bioactives especially triterpene glycosides (saponins), chondroitin sulfates, glycosaminoglycan (GAGs), sulfated polysaccharides, sterols (glycosides and sulfates), phenolics, cerberosides, lectins, peptides, glycoprotein, glycosphingolipids and essential fatty acids. This review is mainly designed to cover the high-value components and bioactives as well as the multiple biological and therapeutic properties of sea cucumbers with regard to exploring their potential uses for functional foods and nutraceuticals.

Triterpenoids

This review covers the isolation and structure determination of triterpenoids including squalene derivatives, protostanes, lanostanes, holostanes, cycloartanes, dammaranes, euphanes, tirucallanes, tetranortriterpenoids, lupanes, oleananes, friedelanes, ursanes, hopanes, isomalabaricanes and saponins; 574 references are cited.

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.