Cytotoxic and antifungal triterpene glycosides from the Patagonian sea cucumber Hemoiedema spectabilis

Triterpene Glycosides from the Viscera of Sea Cucumber Apostichopus japonicus with Embryotoxicity

Sea cucumbers release chemical repellents from their guts when they are in danger from predators or a hostile environment. To investigate the chemical structure of the repellent, we collected and chemically analyzed the viscera of stressed sea cucumbers (Apostichopus japonicus) in the Yellow Sea of China. Two undescribed triterpene glycosides (1 and 2), together with a known cladoloside A (3), were identified and elucidated as 3β-O-{2-O-[β-d-quinovopyranosyl]-4-O-[3-O-methyl-β-d-glucopyranosyl-(1→3)-β-d-glucopyranosyl]-β-d-xylopyranosyl}-holosta-9(11),25(26)-dien-16-one (1), 3β-O-{2-O-[β-d-glucopyranosyl]-4-O-[3-O-methyl-β-d-glucopyranosyl-(1→3)-β-d-glucopyranosyl]-β-d-xylopyranosyl}-holosta-9(11),25(26)-dien-16-one (2), 3β-O-{2-O-[3-O-methyl-β-d-glucopyranosyl-(1→3)-β-d-xylopyranosyl-(1→4)-β-d-quinovopyranosyl]-β-d-xylopyranosyl}-holosta-9(11),25(26)-dien-16-one (3) by spectroscopic analysis, including HR-ESI-MS and NMR spectra. Compounds 1, 2, and 3 display embryonic toxicity, as indicated by their 96-hour post-fertilization lethal concentration (96 hpf-LC50) values of 0.289, 0.536, and 0.091 μM, respectively. Our study discovered a class of triterpene glycoside compounds consisting of an oligosaccharide with four sugar units and a holostane aglycone. These compounds possess embryotoxicity and may serve as chemical defense molecules in marine benthic ecosystems.

Sea Cucumber Viscera Contains Novel Non-Holostane-Type Glycoside Toxins that Possess a Putative Chemical Defense Function

Sea cucumbers frequently expel their guts in response to predators and an aversive environment, a behavior perceived as releasing repellents involved in chemical defense mechanisms. To investigate the chemical nature of the repellent, the viscera of stressed sea cucumbers (Apostichopus japonicus) in the Yellow Sea of China were collected and chemically analyzed. Two novel non-holostane triterpene glycosides were isolated, and the chemical structures were elucidated as 3ꞵ-O-[ꞵ-D-glucopyranosyl-(1→2)-ꞵ-D-xylopyranosyl]-(20S)-hydroxylanosta-7,25-diene-18(16)-lactone (1) and 3ꞵ-O-[ꞵ-D-quinovopyranosyl-(1→2)-ꞵ-D-xylopyranosyl]-(20S)-hydroxylanosta-7,25-diene-18(16)-lactone (2) by spectroscopic and mass-spectrometric analyses, exemplifying a triterpene glycoside constituent of an oligosaccharide containing two sugar-units and a non-holostane aglycone. Zebrafish embryos were exposed to various doses of 1 and 2 from 4 to 96 hpf. Compound 1 exposure showed 96 h-LC50 41.5 µM and an increased zebrafish mortality rates in roughly in a dose- and time-dependent manner. Compound 2, with different sugar substitution, exhibited no mortality and moderate teratogenic toxicity with a 96 h-EC50 of 173.5 µM. Zebrafish embryos exhibited teratogenic effects, such as reduced hatchability and total body length. The study found that triterpene saponin from A. japonicus viscera had acute toxicity in zebrafish embryos, indicating a potential chemical defense role in the marine ecosystem.

Saponins of North Atlantic Sea Cucumber: Chemistry, Health Benefits, and Future Prospectives

Frondosides are the major saponins (triterpene glycosides) of the North Atlantic sea cucumber (Cucumaria frondosa). Frondosides possess amphiphilic characteristics due to the presence of various hydrophilic sugar moieties and hydrophobic genin (sapogenin). Saponins are abundant in holothurians, including in sea cucumbers that are widely distributed across the northern part of the Atlantic Ocean. Over 300 triterpene glycosides have been isolated, identified, and categorized from many species of sea cucumbers. Furthermore, specific saponins from sea cucumbers are broadly classified on the basis of the fron-dosides that have been widely studied. Recent studies have shown that frondoside-containing extracts from C. frondosa exhibit anticancer, anti-obesity, anti-hyperuricemic, anticoagulant, antioxidant, antimicrobial, antiangiogenic, antithrombotic, anti-inflammatory, antitumor, and immunomodulatory activities. However, the exact mechanism(s) of action of biological activities of frondosides is not clearly understood. The function of some frondosides as chemical defense molecules need to be understood. Therefore, this review discusses the different frondosides of C. frondosa and their potential therapeutic activities in relation to the postulated mechanism(s) of action. In addition, recent advances in emerging extraction techniques of frondosides and other saponins and future perspectives are discussed.

Functional foods and bioactive ingredients harnessed from the ocean: current status and future perspectives

With an increase in life expectancy and decrease of quality-of-life couple with the high prevalence of diseases, diet is expected to play a key function in sustaining human health. Nutritionists, food technologists and medical experts are working in synergy to cater for the increasing demand of food with associated therapeutic benefits, commonly known as functional food, that may improve well-being and reduce the risk of diseases. Interestingly, the marine ecosystem, due to its abundant and phenomenal biodiversity of marine organisms, constitutes a vital source of a panoply of healthy foods supply for the thriving functional food industry. Marine organisms such as seaweeds, sea cucumbers, sponges, and mollusks amongst others are sources of thousands of biologically active metabolites with antioxidant, anti-parasitic, antiviral, anti-inflammatory and anticancer properties. Given the growing number of research and interest to probe into the therapeutic roles of marine products, this review was designed to provide a comprehensive summary of the therapeutic properties of marine organisms (macroalgae, sea cucumbers and fish among others) which are consumed worldwide, in addition to their potentials and as sources of functional ingredients for developing novel food and fostering wellness. The gap between research development and actual commercialization, and future prospects of marine-based products also summarized to some extent.

Structures and Bioactivities of Quadrangularisosides A, A1, B, B1, B2, C, C1, D, D1-D4, and E from the Sea Cucumber Colochirus quadrangularis: The First Discovery of the Glycosides, Sulfated by C-4 of the Terminal 3-O-Methylglucose Residue. Synergetic Effect on Colony Formation of Tumor HT-29 Cells of these Glycosides with Radioactive Irradiation

Thirteen new mono-, di-, and trisulfated triterpene glycosides, quadrangularisosides A-D₄ (1-13) have been isolated from the sea cucumber Colochirus quadrangularis, which was collected in Vietnamese waters. The structures of these glycosides were established by 2D NMR spectroscopy and HR-ESI (High Resolution Electrospray Ionization) mass spectrometry. The novel carbohydrate moieties of quadrangularisosides D-D₄ (8-12), belonging to the group D, and quadrangularisoside E (13) contain three sulfate groups, with one of them occupying an unusual position-at C(4) of terminal 3-O-methylglucose residue. Quadrangularisosides A (1) and D₃ (11) as well as quadrangularisosides A₁ (2) and D₄ (12) are characterized by the new aglycones having 25-hydroperoxyl or 24-hydroperoxyl groups in their side chains, respectively. The cytotoxic activities of compounds 1-13 against mouse neuroblastoma Neuro 2a, normal epithelial JB-6 cells, erythrocytes, and human colorectal adenocarcinoma HT-29 cells were studied. All the compounds were rather strong hemolytics. The structural features that most affect the bioactivity of the glycosides are the presence of hydroperoxy groups in the side chains and the quantity of sulfate groups. The membranolytic activity of monosulfated quadrangularisosides of group A (1, 2) against Neuro 2a, JB-6 cells, and erythrocytes was relatively weak due to the availability of the hydroperoxyl group, whereas trisulfated quadrangularisosides D₃ (11) and D₄ (12) with the same aglycones as 1, 2 were the least active compounds in the series due to the combination of these two structural peculiarities. The erythrocytes were more sensitive to the action of the glycosides than Neuro 2a or JB-6 cells, but the structure-activity relationships observed for glycosides 1-13 were similar in the three cell lines investigated. The compounds 3-5, 8, and 9 effectively suppressed the cell viability of HT-29 cells. Quadrangularisosides A₁ (2), C (6), C₁ (7), and E (13) possessed strong inhibitory activity on colony formation in HT-29 cells. Due to the synergic effects of these glycosides (0.02 μM) and radioactive irradiation (1 Gy), a decreasing of number of colonies was detected. Glycosides 1, 3, and 9 enhanced the effect of radiation by about 30%.

Natural Products as Fungicide and Their Role in Crop Protection

Seeking solutions from nature for solving one and all problems is the age-old practice for mankind, and natural products are proved to be the most effective one for keeping up the balance of development as well as the “healthy, wealthy, and well” condition of mother nature. Fungal pathogens are proved to be a common and popular contaminant of agroecosystem that approximately causes 70–80% of total microbial crop loss. To meet the proper global increasing need of food products as a result of population explosion, managing agricultural system in an eco-friendly and profitable manner is the prime target; thus the word “sustainable agriculture” plays it part, and this package is highly effective when coupled with nature-derived fungicidal products that can minimize the event of fungal infections in agrarian ecosystem. Present study enlists the most common and effective natural products that might be of plant or microbial origin, their mode of action, day-by-day development of phytopathogenic resistance against the prevailing fungicides, and also their role in maintenance of sustainability of agricultural practices with special emphasis on their acceptance over the synthetic or chemical one. A large number of bioactive compounds ranging from direct plant (both cryptogams algae and moss and phanerogams)-derived natural extracts, essential oil of aromatic plants, and low-molecular-weight antimicrobial compounds known as phytoalexins to secondary metabolites that are both volatile and nonvolatile organic compounds of microbes (fungal and actinobacterial members) residing inside the host tissue, called endophyte, are widely used as agricultural bioweapons. The rhizospheric partners of plant, mycorrhizae, are also a prime agent of this chemical warfare and protect their green partners from fungal invaders and emphasize the concept of “sustainable agriculture.”

Leishmanicidal, Antifungal, and Cytotoxic Activity of Triterpenoid Glycosides Isolated from the Sea Cucumber Neothyone Gibbosa

Neothyosides A - C, isolated from the body walls of the sea cucumber Neothyone gibbosa Deichmann, and a partially purified mixture of these saponins, were tested in vitro against promastigotes of two strains of Leishmania mexicana and a panel of several fungi using the broth microdilution technique. In addition, the cytotoxicity of these saponins was tested against Artemia salina. The IR, 1H and 13C NMR spectroscopic and FAB MS data of neothyoside C revealed that its structure was identical to that of pervicoside B, isolated from another sea cucumber species, Holothuria pervicax. Neothyoside C was the most active antiparasitic compound, inhibiting 100% of the promastigotes at 5 and 10 μg/mL of both L. mexicana strains. The mixture of saponins and pure neothyoside C showed the best activity against Aspergillus niger strains with MIC values between 15.6 μg/mL and 16.7 μg/mL for the mixture, and 4.65 μg/mL and 7.8 μg/mL for neothyoside C. Assays for cytotoxicity using Artemia salina showed that neothyosides A and C caused 50% brine-shrimp deaths at 130 and 63 μg/mL with this cytotoxicity 4 to 6 times greater than the concentration at which these compounds produce an antimicrobial effect. This is the first report describing the antileishmanial, antifungal, and cytotoxic activity of N. gibbosa saponins.

Saponins from Sea Cucumber and Their Biological Activities

Sea cucumbers, belonging to the phylum Echinodermata, have been valued for centuries as a nutritious and functional food with various bioactivities. Sea cucumbers can produce highly active substances, notably saponins, the main secondary metabolites, which are the basis of their chemical defense. The saponins are mostly triterpene glycosides with triterpenes or steroid in aglycone, which possess multiple biological properties including antitumor, hypolipidemic activity, improvement of nonalcoholic fatty liver, inhibition of fat accumulation, antihyperuricemia, promotion of bone marrow hematopoiesis, antihypertension, etc. Sea cucumber saponins have received attention due to their rich sources, low toxicity, high efficiency, and few side effects. This review summarizes current research on the structure and activities of sea cucumber saponins based on the physiological and pharmacological activities from source, experimental models, efficacy, and mechanisms, which may provide a valuable reference for the development of sea cucumber saponins.

Diversity and antimicrobial potential in sea anemone and holothurian microbiomes

Marine invertebrates, as holobionts, contain symbiotic bacteria that coevolve and develop antimicrobial substances. These symbiotic bacteria are an underexplored source of new bioactive molecules to face the emerging antibiotic resistance in pathogens. Here, we explored the antimicrobial activity of bacteria retrieved from the microbiota of two sea anemones (Anemonia sulcata, Actinia equina) and two holothurians (Holothuria tubulosa, Holothuria forskali). We tested the antimicrobial activity of the isolated bacteria against pathogens with interest for human health, agriculture and aquaculture. We isolated 27 strains with antibacterial activity and 12 of these isolates also showed antifungal activity. We taxonomically identified these strains being Bacillus and Vibrio species the most representative producers of antimicrobial substances. Microbiome species composition of the two sea anemones was similar between them but differed substantially of seawater bacteria. In contrast, microbiome species composition of the two holothurian species was different between them and in comparison with the bacteria in holothurian feces and seawater. In all the holobiont microbiomes Bacteroidetes was the predominant phylum. For each microbiome, we determined diversity and the rank-abundance dominance using five fitted models (null, pre-emption, log-Normal, Zipf and Zipf-Mandelbrot). The models with less evenness (i.e. Zipf and Zipf-Mandelblot) showed the best fits in all the microbiomes. Finally, we tracked (using the V4 hypervariable region of 16S rRNA gene) the relative abundance of these 27 isolates with antibacterial activity in the total pool of sequences obtained for the microbiome of each holobiont. Coincidences, although with extremely low frequencies, were detected only in the microbiome of H. forskali. This fact suggests that these isolated bacteria belong to the long tail of rare symbiotic bacteria. Therefore, more and more sophisticated culture techniques are necessary to explore this apparently vast pool of rare symbiontic bacteria and to determine their biotechnological potentiality.

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.

Scabraside D Extracted from Holothuria scabra Induces Apoptosis and Inhibits Growth of Human Cholangiocarcinoma Xenografts in Mice

Scabraside D, a sulfated triterpene glycoside extract from sea cucumber Holothulia scabra, shows various biological activities, but effects on human cholangiocarcinoma cells have not previously been reported. In the present study, we investigated the activity of scabraside D against human cholangiocarcinoma (HuCCA) both in vitro and for tumor growth inhibition in vivo using a xenograft model in nude mice. Scabraside D (12.5-100 μg/mL) significantly decreased the viability and the migration of the HuCCA cells in a dose-dependent manner, with 50% inhibitory concentration (IC50) of 12.8 ± 0.05 μg/mL at 24 h. It induced signs of apoptotic cells, including shrinkage, pyknosis and karyorrhetic nuclei and DNA fragmentation on agarose gel electrophoresis. Moreover, by quantitative real-time PCR, scabraside D effectively decreased Bcl-2 while increasing Bax and Caspase-3 gene expression levels suggesting that the scabraside D could induce apoptosis in HuCCA cells. In vivo study demonstrated that scabraside D (1 mg/kg/day, i.p. for 21 days) significantly reduced growth of the HuCCA xenografts without adverse effects on the nude mice. Conclusively, scabraside D induced apoptosis in HuCCA cells and reduced the growth of HuCCA xenographs model. Therefore, scabraside D may have potential as a new therapeutic agent for cholangiocarcinoma.

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.

Scabraside D Derived from Sea Cucumber Induces Apoptosis and Inhibits Metastasis via iNOS and STAT-3 Expression in Human Cholangiocarcinoma Xenografts

Scabraside D, a sulfated triterpene glycoside, was extracted from the sea cucumber Holothuria scabra. It shows anti-proliferation in many of cancer cell lines, but the function and mechanisms of action of scabraside D in human cholangiocarcinoma (HuCCA) have not previously determined. In this study, we investigated the activity of scabraside D on HuCCA cell apoptosis, lymphangiogenesis and metastasis in a nude mouse model. Scabraside D induced signs of apoptosis, such as cell shrinkage, nuclear condensation, nuclear fragmentation and DNA fragmentation on TUNEL assays, while effectively decreasing expression of BCl-2 but increasing caspase-3 gene level expression. Immunohistochemistry revealed that scabraside D significantly reduced lymphatic vessel density (LVD). Moreover, scabraside D treatment significantly decreased VEGF-C, MMP-9 and uPA gene expression, which play important roles in the lymphangiogenesis and invasion of cancer cells in metastasis processes. Quantitative real-time PCR showed that scabraside D significantly decreased iNOS and STAT-3 gene expression. This study demonstrated that scabraside D plays a role in activation of HuCCA tumor apoptosis and inhibition of lymphangiogenesis, invasion and metastasis through decreasing BCl-2, MMP-9, uPA and VEGF-C and increasing caspase-3 expression by suppression of iNOS and STAT-3 expression. Therefore, scabraside D could be a promising candidate for cholangiocarcinoma treatment.

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.

Antioxidant, hemolytic, antimicrobial, and cytotoxic activities of the tropical Atlantic marine zoanthid Palythoa caribaeorum

Marine invertebrates are capable of synthesizing bioactive compounds, which may be beneficial to human health. The aim of this study was to evaluate the antioxidant, hemolytic, antimicrobial and cytotoxic activities of crude extract (70% EtOH), and dichloromethane (DCM), ethyl acetate (EtOAc), and aqueous (Aq) fractions of the marine zoanthid Palythoa caribaeorum. The phenolic compound contents of the crude extract, DCM, EtOAc and Aq fractions were 12.33, 18.17, 10.53, and 3.18 mg GAE per gram, respectively. DPPH radical scavenging activity showed slight variation. IC50 of crude extract, DCM, EtOAc and Aq fractions were 11.13, 11.25, 11.74, and 11.28 µg mL-1, respectively. Among the sample, ferrous ion chelating was the highest in crude extract (IC50 302.90 µg mL-1), followed by EtOAc, Aq, and DCM fractions with 457.77, 547.91, and 641.82 µg mL-1, respectively. Ferric-reducing antioxidant power showed optical density at about 0.5. The samples tested exhibited low hemolytic activity under 10% up to a concentration of 50 μg mL-1. No antimicrobial activity was observed against any of the tested bacterial strains. For the cytotoxic activity, LC50 of DCM, crude extract, EtOAc, and Aq were 52.10, 83.06, 86.34, and 117.45 μg mL-1, showing high toxicity.

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.

Determination of the triterpene glycosides in sea cucumbers by liquid chromatography with evaporative light scattering and mass spectrometry detection

Holothurian triterpene glycosides possess various kinds of biological activities, including antifungal, cytotoxic, hemolytic, cytostatic, and immunomodulatory effects. In this study, a rapid extraction method of triterpene glycosides from sea cucumbers using a small column of C18 solid phase was first developed. Furthermore, a novel high-performance liquid chromatography method coupled with evaporative light scattering detection and electrospray ionization mass spectrometry was established for the determination of each triterpene glycosides from different sea cucumbers. Simultaneous separation of all kind of triterpene glycoside were achieved on a C18 column. A gradient of aqueous acetonitrile was applied, and the method was validated. The liquid chromatography method was applied to the online mass detection to identify the triterpene glycosides in the purified extraction of eight kinds of pulverized sea cucumber from the market of Qingdao, China. The negative mode of [M-H](-)/[M-Na](-) exclusively shown signals corresponding to the triterpene glycosides previously reported and the MS(2) product ions of those ions indicate the specific structure of each triterpene glycoside.

Bioactive compounds from Holothuria atra of Indian ocean

The sea cucumber (Holothuria atra) extracts have been evaluated for the presence of bioactive compounds and various biological activities. The methanol extracts showed anti proliferative activities against the Hela and MCF-7 cell lines. Similarly the inhibitory effects of Herpes simplex virus 1 and 2 cells were detected using the plaque reduction assay. The extracts of H. atra were purified using the silica gel column chromatography. The active fractions collected were observed for antimicrobial activity. The GC-MS analysis showed the availability of 59 compounds. The active bioactive compounds found in the H. atra were analyzed and their structure was identified using the ¹HNMR and ¹³C NMR experiments.

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.

Cytotoxic and apoptosis-inducing activity of triterpene glycosides from Holothuria scabra and Cucumaria frondosa against HepG2 cells

The cytotoxic effects of thirteen triterpene glycosides from Holothuria scabra Jaeger and Cucumaria frondosa Gunnerus (Holothuroidea) against four human cell lines were detected and their cytotoxicity-structure relationships were established. The apoptosis-inducing activity of a more potent glycoside echinoside A (1) in HepG2 cells was further investigated by determining its effect on the morphology, mitochondrial transmembrane potential (Δψ_m) and mRNA expression levels of the apoptosis-related genes. The results showed that the number of glycosyl residues in sugar chains and the side chain of aglycone could affect their cytotoxicity towards tumor cells and selective cytotoxicity. 1 significantly inhibited cell viability and induced apoptosis in HepG2 cells. 1 also markedly decreased the Δψ_m and Bcl-2/Bax mRNA express ratio, and up-regulated the mRNA expression levels of Caspase-3, Caspase-8 and Caspase-9 in HepG2 cells. Therefore, 1 induced apoptosis in HepG2 cells through both intrinsic and extrinsic pathway. These findings could potentially promote the usage of these glycosides as leading compounds for developing new antitumor drugs.

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.

Pseudocnoside A, a new cytotoxic and antiproliferative triterpene glycoside from the sea cucumber Pseudocnus dubiosus leoninus

A new triterpene glycoside, pseudocnoside A (1), was isolated from the sea cucumber Pseudocnus dubiosus leoninus. The structure of the new compound was established on the basis of extensive NMR spectroscopic analysis ((1)H and (13)C NMR, (1)H,(1)H-COSY, HMBC, HSQC, TOCSY and NOESY), HR-ESI-MS data and chemical transformations. In addition, the cytotoxicity and antiproliferative activities of 1 and structurally related triterpene glycosides isolated from the sea cucumbers Psolus patagonicus and Hemioedema spectabilis were evaluated against cancer cell lines A-549 and HeLa.

Screening of marine extracts for schistosomicidal activity in vitro. Isolation of the triterpene glycosides echinosides A and B with potential activity from the Sea Cucumbers Actinopyga echinites and Holothuria polii

CONTEXT

Praziquantel (PZQ) is the drug available for the treatment of schistosomiasis. The reported reduced cure rates, the failure of treatment after PZQ administration in patients and the existence of resistant parasite strains, reinforce the need to rapidly discover new effective molecules against Schistosoma parasite.

OBJECTIVE

To screen the methanol extracts of 79 marine organisms for their schistosomicidal activities against Schistosoma mansoni adult worms in vitro and perform bio-assay directed chromatography for the most active extracts to isolate the active compounds.

MATERIALS AND METHODS

Screening of the marine organisms and bio-assay directed chromatography of the most active extracts together with identification of the active isolates using 1D and 2D NMR analysis, were investigated.

RESULTS

RESULTS indicated that the isolates echinosides A and B from the sea cucumbers Actinopyga echinites Jaeger and Holothuria polii Delle Chiaie (Holothuriidae) were highly active. Their LC(50) values were equal to 0.19 μg/ml and 0.27 μg/ml, respectively. Detailed (1)HNMR data for echinosides A and B are reported here for the first time.

DISCUSSION AND CONCLUSION

These findings demonstrate that the isolated echinosides possess potential in vitro schistosomicidal activity against S. mansoni adult worms. Therefore, echinosides are promising as lead compounds for the development of new schistosomicidal agents.

In vitro and in vivo anti-tumour activities of echinoside A and ds-echinoside A from Pearsonothuria graeffei

BACKGROUND

Echinoside A (EA) and ds-echinoside A (DSEA) are triterpene glycosides isolated from the sea cucumber Pearsonothuria graeffei. DSEA, the desulfurisation product of EA, has the following structure: β-D-xylopyranosyl-holost-8(9),11(12)-diene-3β,17α-diol. In the present study, we examined the anti-tumour activities-in particular, the structure-activity relationships-of EA and DSEA in vitro and in vivo.

RESULTS

Both EA and DSEA exhibited an inhibitory effect on cell proliferation, along with apoptosis-inducing activity, in HepG2 cells. Moreover, they significantly arrested the cell cycle in the G₀/G₁ phase. A reverse transcriptase-polymerase chain reaction assay revealed that EA and DSEA significantly increased the expression of the cell-cycle-related genes, namely, p16, p21 and c-myc, and decreased that of cyclin D₁. Western blotting analysis demonstrated that they down-regulated the expression of Bcl-2, and enhanced mitochondria cytochrome c release, caspase-3 activation, and poly(adenosine diphosphate ribose) polymerase, cleavage. Nuclear factor kappa B (NF-κB) expression was significantly decreased by DSEA, but was unaffected by EA. EA and DSEA (2.5 mg kg⁻¹) treatment of mice bearing H22 hepatocarcinoma tumours reduced the tumour weight by 49.8% and 55.0%, respectively.

CONCLUSION

EA and DSEA exhibit marked anti-cancer activity in HepG2 cells, by blocking cell-cycle progression and inducing apoptosis through the mitochondrial pathway. DSEA-induced apoptosis was more potent than EA-induced apoptosis. Furthermore, the two triterpene glycosides derived from P. graeffei may induce apoptosis of HepG2 cells in an NF-κB-dependent or NF-κB-independent manner, depending on their structure.

Patagonicosides B and C, two antifungal sulfated triterpene glycosides from the sea cucumber Psolus patagonicus

Two new triterpene glycosides, patagonicosides B and C (2 and 3, resp.), together with the known patagonicoside A (1), have been isolated from the EtOH extract of the sea cucumber Psolus patagonicus. The structures of the new compounds were established on the basis of extensive NMR spectroscopic analysis ((1)H- and (13)C-NMR, (1)H,(1)H-COSY, HMBC, HSQC, TOCSY, and NOESY), HR-ESI-MS data, and chemical transformations. Compounds 1-3 and their desulfated analogs showed antifungal activities against the phytopathogenic fungus Cladosporium cladosporoides in a dose-dependent fashion.

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.

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.

Ds-echinoside A, a new triterpene glycoside derived from sea cucumber, exhibits antimetastatic activity via the inhibition of NF-κB-dependent MMP-9 and VEGF expressions

Ds-echinoside A (DSEA), a non-sulfated triterpene glycoside, was isolated from the sea cucumber Pearsonothuria graeffei. In vitro and in vivo investigations were conducted on the effects of DSEA on tumor cell adhesion, migration, invasion, and angiogenesis. In this study, we found that DSEA inhibited the proliferation of human hepatocellular liver carcinoma cells Hep G2, with a half-maximal inhibitory concentration (IC₅₀) of 2.65 μmol/L, and suppressed Hep G2 cell adhesion, migration, and invasion in a dose-dependent manner. DSEA also reduced tube formation of human endothelial cells ECV-304 on matrigel in vitro and attenuated neovascularization in the chick embryo chorioallantoic membrane (CAM) assay in vivo. Immunocytochemical analysis revealed that DSEA significantly decreased the expression of matrix metalloproteinase-9 (MMP-9), which plays an important role in the degradation of basement membrane in tumor metastasis and angiogenesis. DSEA also increased the protein expression level of tissue inhibitor of metalloproteinase-1 (TIMP-1), an important regulator of MMP-9 activation. From the results of Western blotting, the expressions of nuclear factor-kappa B (NF-κB) and vascular endothelial growth factor (VEGF) were found to be remarkably reduced by DSEA. These findings suggest that DSEA exhibits a significant anti-metastatic activity through the specific inhibition of NF-κB-dependent MMP-9 and VEGF expressions.

Differential effects of sulfated triterpene glycosides, holothurin A1, and 24-dehydroechinoside A, on antimetastasic activity via regulation of the MMP-9 signal pathway

Two sulfated triterpene glycosides, holothurin A(1) (HA(1)) and 24-dehydroechinoside A (DHEA), isolated from the sea cucumber Pearsonothuria graeffei, are of the holostane type with 18(20)-lactone and identical carbohydrate chains. DHEA has a side chain 23 (24)-double bond, while HA(1) has a hydroxyl group at C-21. In this study, we compared the effects of DHEA and HA(1) on metastasis in vitro and in vivo. The results show that HA(1) and DHEA treatment significantly suppressed adhesion of human hepatocellular liver carcinoma cells (HepG2) to both matrigel and human endothelial cells (ECV-304) and inhibited HepG2 cell migration and invasion in a dose-dependant manner. HA(1) and DHEA reduced tube formation of ECV-304 cells on the matrigel in vitro and attenuated neovascularization in the chick embryo using the chorioallantoic membrane (CAM) assay in vivo. Immunocytochemistry analyses revealed that both HA(1) and DHEA significantly decreased the expression of the matrix metallo-proteinase-9 (MMP-9) and increased the expression level of tissue inhibitor of metalloproteinase-1 (TIMP-1), an important regulator of MMP-9 activation. Western blot analyses demonstrated that HA(1) and DHEA remarkably abolished the expression of vascular endothelial growth factor (VEGF). The expression of nuclear factor-kappa B (NF-κB) was significantly decreased by HA(1), while DHEA treatment had no effect on the down regulation of NF-κB expression. These data suggest that both DHEA and HA(1) exert significant antimetastatic activities by inhibiting MMP-9 and VEGF expression. DHEA-induced antimetastasis was more potent than HA(1). In addition, only HA(1) treatment downregulated the expression level of NF-κB, suggesting that the antimetastatic activity of triterpene glycosides derived from P. graeffei can be either NF-κB-dependent or -independent, depending on their structure.

Triterpene glycosides from Antarctic sea cucumbers. 1. Structure of liouvillosides A1, A2, A3, B1, and B2 from the sea cucumber Staurocucumis liouvillei: new procedure for separation of highly polar glycoside fractions and taxonomic revision

Five new triterpene glycosides, liouvillosides A1 (1), A2 (2), A3 (3), B1 (4), and B2 (5), have been isolated from the Antarctic sea cucumber Staurocucumis liouviellei along with the known liouvilloside A(6), isolated earlier from the same species, and hemoiedemosides A (7) and B (8), isolated earlier from the Patagonian sea cucumber Hemioedema spectabilis. The isolation was carried out using a new chromatographic procedure including application of ion-pair reversed-phase chromatography followed by chiral chromatography on a cyclodextrin ChiraDex column. The structures of the new glycosides were elucidated using extensive NMR spectroscopy (1H and 13C NMR spectrometry, DEPT, 1H-(1)H COSY, HMBC, HMQC, and NOESY), ESI-FTMS, and CID MS/MS, and chemical transformations. Glycosides 1-3 are disulfated tetraosides and glycosides 4 and 5 are trisulfated tetraosides. Glycosides 2 and 3 contain 3-O-methylquinovose, found for the first time as a natural monosaccharide in sea cucumber glycosides. On the basis of analyses of glycoside structures a taxonomic revision is proposed.

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

Two new triterpene glycosides, hillasides A (1) and B (2), were isolated from the sea cucumber H. hilla Lesson, together with one known glycoside holothuria B (3). Their structures were deduced by extensive spectral analysis and chemical evidences. The presence of conjugated double bonds [22E,24-diene] in the aglycone of 1 is a rare structural feature among sea cucumber glycosides. The two glycosides showed significant cytotoxicity against eight human tumour cell lines (A-549, MCF-7, IA9, CAKI-1, PC-3, KB, KB-VIN and HCT-8) with IC(50) in the range of 0.1-3.8 microg/ml.

Cytotoxic triterpene glycosides from the sea cucumber Pseudocolochirus violaceus

A new triterpene glycoside (1) along with the known intercedenside B (2) was isolated from the sea cucumber Pseudocolochirus violaceus. Glycoside 1 was elucidated as 3-O-{6-O-sodiumsulfate-3-O-methyl-beta-D-glucopyranosyl-(1-->3)-beta-D-xylopyranosyl-(1-->4)-[beta-D-xylopyranosyl(1-->2)]-beta-D-quinovopyranosyl-(1-->2)-4-O-sodiumsulfate-beta-D-xylopyranosyl}-16beta-acetoxy-holosta-7, 24-diene-3beta-ol on the basis of extensive spectral studies and chemical evidence. Both the glycosides exhibited significant cytotoxicity against cancer cell lines MKN-45 and HCT-116.

A New Cytotoxic Lanostane-Type Triterpene Glycoside from the Sea CucumberHolothuria impatiens

A new lanostane-type triterpene glycoside, impatienside A (1), was isolated from the sea cucumber Holothuria impatiens, together with a structurally related, known compound, bivittoside D (2). Their structures were elucidated by in-depth spectroscopic and mass-spectrometric methods, including (1)H-, (13)C-, and 2D-NMR, ESI-MS, and HR-ESI-MS experiments, as well as by chemical evidence. Compounds 1 and 2 possess the same hexasaccharide moieties, but differ slightly in their holostane-type triterpene aglycone. The two glycosides were found to exhibit in vitro cytotoxicities similar to or better than those of the potent anticancer drug etoposide (V-16) against seven different human tumor cells, with IC50 values of 0.37-2.75 microg/ml.

Echinoderms: their culture and bioactive compounds

Of the five extant classes of echinoderms, it is the sea urchins (Echinoidea) and the sea cucumbers (Holothuroidea) that are both commercially fished and heavily overexploited. In sea urchins, it is the gonad of both males and females, normally referred to as'roe', that is a sought-after food. In the sea cucumber, the principal product is the boiled and dried body-wall or 'bêche-de-mer' for which there is an increasing demand. Many sea urchin and sea cucumber fisheries still have no management system or restrictions in place, and for those that do, the prognosis for catches to continue even at a reduced level is poor. Cultivation of these species increasingly becomes a necessity, both for stock enhancement programs and as a means to meet market demand. Sea urchin culture has been practised on a large scale in Japan for many decades, and effective methods for the culture and reseeding of species in these waters have been long established. Juvenile urchins are produced in their millions in state-sponsored hatcheries, for release to managed areas of seafloor. Outside of Japan, sea urchin cultivation is still a fairly recent practice, less than 10 years old, and largely still at a research level, although a range of species are now being produced in a variety of different culture systems. It is essential that the culture systems are adapted to be species-specific and meet with local environmental constraints. Sea cucumber cultivation originated in Japan in the 1930s and is now well established there and in China. Methods for mass cultivation of the tropical Holothuria scabra are now well established and practised in India, Australia, Indonesia, the Maldives and the Solomon Islands, with the focus of the research effort for both temperate and tropical species being centred on the production of juveniles in hatcheries for the restoration and enhancement of wild stocks. Like many other marine organisms, echinoderms have been, and continue to be, examined as a source of biologically active compounds with biomedical applications. Sea cucumber has been valued in Chinese medicine for hundreds of years as a cure for a wide variety of ailments. Some more recently isolated compounds, mainly from sea cucumbers and starfish, and including those with antitumour, antiviral, anticoagulant and antimicrobial activity are summarised below. When wild stocks decline, the demand created in the market place raises to the price of the product and, consequently, culturing is more likely to become viable economically. As this review shows, there have been dramatic advances in the culture methods of sea urchins and sea cucumbers in the last 10-15 years, to the extent that one can conclude that currently the major obstacles to successful cultivation are indeed economic rather than biological. Hence the future of the echinoculture industry is closely linked to that of the fisheries, whose fate will ultimately determine the market forces that will shape this growing industry.