Two new holostan-type triterpene glycosides from the sea cucumber Bohadschia marmorata JAEGER

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).

Distribution of Saponins in the Sea Cucumber Holothuria lessoni; the Body Wall Versus the Viscera, and Their Biological Activities

Sea cucumbers are an important ingredient of traditional folk medicine in many Asian countries, which are well-known for their medicinal, nutraceutical, and food values due to producing an impressive range of distinctive natural bioactive compounds. Triterpene glycosides are the most abundant and prime secondary metabolites reported in this species. They possess numerous biological activities ranging from anti-tumour, wound healing, hypolipidemia, pain relieving, the improvement of nonalcoholic fatty livers, anti-hyperuricemia, the induction of bone marrow hematopoiesis, anti-hypertension, and cosmetics and anti-ageing properties. This study was designed to purify and elucidate the structure of saponin contents of the body wall of sea cucumber Holothurialessoni and to compare the distribution of saponins of the body wall with that of the viscera. The body wall was extracted with 70% ethanol, and purified by a liquid-liquid partition chromatography, followed by isobutanol extraction. A high-performance centrifugal partition chromatography (HPCPC) was conducted on the saponin-enriched mixture to obtain saponins with a high purity. The resultant purified saponins were analyzed using MALDI-MS/MS and ESI-MS/MS. The integrated and hyphenated MS and HPCPC analyses revealed the presence of 89 saponin congeners, including 35 new and 54 known saponins, in the body wall in which the majority of glycosides are of the holostane type. As a result, and in conjunction with existing literature, the structure of four novel acetylated saponins, namely lessoniosides H, I, J, and K were characterized. The identified triterpene glycosides showed potent antifungal activities against tested fungi, but had no antibacterial effects on the bacterium Staphylococcus aureus. The presence of a wide range of saponins with potential applications is promising for cosmeceutical, medicinal, and pharmaceutical products to improve human health.

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.

Triterpene Glycosides of Sea Cucumbers (Holothuroidea, Echinodermata) as Taxonomic Markers

Triterpene glycosides are characteristic metabolites of sea cucumbers (Holothurioidea, Echinodermata). The majority of the glycosides belong to the holostane type {lanostane derivatives with an 18(20)-lactone}. Carbohydrate chains of these glycosides contain xylose, glucose, quinovose, 3- O-methylglucose, and, rarely, 3- O-methylxylose, 3- O-methylglucuronic acid, 3- O-methylquinovose, and 6- O-acetyl-glucose. The glycosides are specific for genera, groups of genera and even for species. The advantages and problems in the use of triterpene glycosides as taxonomic markers in the systematics of sea cucumbers are discussed.

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.

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.

New bioactive sulfated alkenes from the sea cucumber Apostichopus japonicus

Two new alkene sulfates, (5Z)-dec-5-en-1-yl sulfate (4) and (3E)-dec-3-en-1-yl sulfate (5), together with three known sulfated alkanes, 2,6-dimethylheptyl sulfate (1), octyl sulfate (2), and decyl sulfate (3), were isolated from the sea cucumber Apostichopus japonicus. The structures of the new compounds 4 and 5 were elucidated by spectroscopic analysis, including ¹H-, ¹³C-, and 2D-NMR, ESI-MS, and HR-ESI-MS. Compounds 2 and 3 were isolated from natural sources for the first time. In preliminary bioassays in vitro, compounds 4 and 5 showed antibacterial, antifungal, and cytotoxic activities.

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.