Anticancer activity of sea cucumber triterpene glycosides

Stichoposide C and Rhizochalin as Potential Aquaglyceroporin Modulators

Aquaporins (AQPs) are a family of integral membrane proteins that selectively transport water and glycerol across the cell membrane. Because AQPs are involved in a wide range of physiological functions and pathophysiological conditions, AQP-based therapeutics may have the broad potential for clinical utility, including for disorders of water and energy balance. However, AQP modulators have not yet been developed as suitable candidates for clinical applications. In this study, to identify potential modulators of AQPs, we screened 31 natural products by measuring the water and glycerol permeability of mouse erythrocyte membranes using a stopped-flow light scattering method. None of the tested natural compounds substantially affected the osmotic water permeability. However, several compounds considerably affected the glycerol permeability. Stichoposide C increased the glycerol permeability of mouse erythrocyte membranes, whereas rhizochalin decreased it at nanomolar concentrations. Immunohistochemistry revealed that AQP7 was the main aquaglyceroporin in mouse erythrocyte membranes. We further verified the effects of stichoposide C and rhizochalin on aquaglyceroporins using human AQP3-expressing keratinocyte cells. Stichoposide C, but not stichoposide D, increased AQP3-mediated transepithelial glycerol transport, whereas the peracetyl aglycon of rhizochalin was the most potent inhibitor of glycerol transport among the tested rhizochalin derivatives. Collectively, stichoposide C and the peracetyl aglycon of rhizochalin might function as modulators of AQP3 and AQP7, and suggests the possibility of these natural products as potential drug candidates for aquaglyceroporin modulators.

New Rare Triterpene Glycosides from Pacific Sun Star, Solaster pacificus, and Their Anticancer Activity

Six previously unknown triterpene glycosides, pacificusosides L-Q (1-6), and two previously known triterpene glycosides, cucumariosides B1 (7) and A5 (8), were isolated from an alcoholic extract of Pacific sun star, Solaster pacificus. The structures of 1-6 were determined using 1D and 2D NMR, ESIMS, and chemical modifications. Compound 1 is a rare type of triterpene glycoside with non-holostane aglycon, having a linear trisaccharide carbohydrate chain. Pacificusosides M-P (2-5) have new structures containing a Δ8(9)-3,16,18-trihydroxy tetracyclic triterpene moiety. This tetracyclic fragment in sea star or sea cucumber triterpene glycosides was described for the first time. All the compounds under study exhibit low or moderate cytotoxic activity against colorectal carcinoma HCT 116 cells, and breast cancer MDA-MB-231 cells were assessed by MTS assay. Compound 2 effectively suppresses the colony formation of cancer cells at a non-toxic concentration, using the soft-agar assay. A scratch assay has shown a significant anti-invasive potential of compound 2 against HCT 116 cells, but not against MDA-MB-231 cells.

Anticancer Activity of the Marine Triterpene Glycoside Cucumarioside A2-2 in Human Prostate Cancer Cells

Despite recent advances in the treatment of metastatic castration-resistant prostate cancer (CRPC), treatment is inevitably hampered by the development of drug resistance. Thus, new drugs are urgently needed. We investigated the efficacy, toxicity, and mechanism of action of the marine triterpene glycoside cucumarioside A2-2 (CA2-2) using an in vitro CRPC model. CA2-2 induced a G2/M-phase cell cycle arrest in human prostate cancer PC-3 cells and caspase-dependent apoptosis executed via an intrinsic pathway. Additionally, the drug inhibited the formation and growth of CRPC cell colonies at low micromolar concentrations. A global proteome analysis performed using the 2D-PAGE technique, followed by MALDI-MS and bioinformatical evaluation, revealed alterations in the proteins involved in cellular processes such as metastatic potential, invasion, and apoptosis. Among others, the regulation of keratin 81, CrkII, IL-1β, and cathepsin B could be identified by our proteomics approach. The effects were validated on the protein level by a 2D Western blotting analysis. Our results demonstrate the promising anticancer activity of CA2-2 in a prostate cancer model and provide insights on the underlying mode of action.

Bioprospecting for Rhizobacteria with the Ability to Enhance Drought Tolerance in Lessertia frutescens

Lessertia frutescens is a multipurpose medicinal plant indigenous to South Africa that is used for the management of cancer, stomach ulcers, wounds, etc. The use and demand for the raw materials from this plant have been increasing steadily over the years, putting strain on the dwindling wild populations. Although cultivation may provide relief to the strained supply, the persistent drought climate poses a threat to the plant's growth and productivity. This study explored three plant-growth-promoting rhizobacteria isolates, TUTLFNC33, TUTLFNC37 and TUTLFWC74, obtained from the root nodules of Lessertia frutescens as potential bioinoculants that can improve yield, biological activities and the production of secondary metabolites in the host plant. Isolate TUTLFNC37 was identified as the most promising isolate for inoculation of Lessertia frutescens under drought conditions as it induced drought tolerance through enhanced root proliferation, osmolyte proline accumulation and stomatal closure. Superior biomass yield, phenolics, triterpenes and antioxidant activity were evident in the extracts of Lessertia frutescens inoculated with TUTLFNC37 and under different levels of drought. Furthermore, the metabolomics of the plant extracts demonstrated the ability of the isolate to withstand drastic changes in the composition of unique metabolites, sutherlandiosides A-D and sutherlandins A-D. Molecular families which were never reported in the plant (peptides and glycerolipids) were detected and annotated in the molecular networks. Although drought had deleterious effects on Lessertia frutescens, isolate TUTLFNC37 alleviated the impact of the stress. Isolate TUTLFNC37 is therefore the most promising, environmentally friendly alternative to harmful chemicals such as nitrate-based fertilizers. The isolate should be studied to establish its field performance, cross infectivity with other medicinal plants and competition with inherent soil microbes.

Polysaccharides from marine biological resources and their anticancer activity on breast cancer

In recent decades, natural products from marine organisms have been widely studied for the treatment of various breast cancers. Among them, polysaccharides have been favored by researchers because of their good effects and safety. In this review, polysaccharides from marine algae including macroalgae and microalgae, chitosan, microorganisms such as marine bacteria and fungi, and starfish are addressed. Their anticancer activities on different breast cancers and action mechanisms are discussed in detail. In general, polysaccharides from marine organisms are potential sources of low side-effect and high efficiency anticancer drugs for development. However, further research on animals and clinical research are needed.

Effect of Marine-Derived Saccharides on Human Skin Fibroblasts and Dermal Papilla Cells

The skin is the largest organ of the human body, composed of a diverse range of cell types, non-cellular components, and an extracellular matrix. With aging, molecules that are part of the extracellular matrix undergo qualitative and quantitative changes and the effects, such as a loss of skin firmness or wrinkles, can be visible. The changes caused by the aging process do not only affect the surface of the skin, but also extend to skin appendages such as hair follicles. In the present study, the ability of marine-derived saccharides, L-fucose and chondroitin sulphate disaccharide, to support skin and hair health and minimize the effects of intrinsic and extrinsic aging was investigated. The potential of the tested samples to prevent adverse changes in the skin and hair through stimulation of natural processes, cellular proliferation, and production of extracellular matrix components collagen, elastin, or glycosaminoglycans was investigated. The tested compounds, L-fucose and chondroitin sulphate disaccharide, supported skin and hair health, especially in terms of anti-aging effects. The obtained results indicate that both ingredients support and promote the proliferation of dermal fibroblasts and dermal papilla cells, provide cells with a supply of sulphated disaccharide GAG building blocks, increase ECM molecule production (collagen and elastin) by HDFa, and support the growth phase of the hair cycle (anagen).

A Bibliometric and In Silico-Based Analysis of Anti-Lung Cancer Compounds from Sea Cucumber

Lung cancer is one of the most lethal malignancies in the world. However, current curative approaches for treating this type of cancer have some weaknesses. Therefore, scientists are attempting to discover new anti-lung cancer agents. Sea cucumber is a marine-derived source for discovering biologically active compounds with anti-lung cancer properties. To explore the anti-lung cancer properties of sea cucumber, we analyzed surveys using VOSviewer software and identified the most frequently used keywords. We then searched the Google Scholar database for compounds with anti-lung cancer properties within that keyword family. Finally, we used AutoDock 4 to identify the compounds with the highest affinity for apoptotic receptors in lung cancer cells. The results showed that triterpene glucosides were the most frequently identified compounds in studies examining the anti-cancer properties of sea cucumbers. Intercedenside C, Scabraside A, and Scabraside B were the three triterpene glycosides with the highest affinity for apoptotic receptors in lung cancer cells. To the best of our knowledge, this is the first time that anti-lung cancer properties of sea cucumber-derived compounds have been examined in in silico conditions. Ultimately, these three components displayed anti-lung cancer properties in in silico conditions and may be used for the manufacture of anti-lung cancer agents in the near future.

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.

Recent Trends in the Development of Novel Metal-Based Antineoplastic Drugs

Since the accidental discovery of the anticancer properties of cisplatin more than half a century ago, significant efforts by the broad scientific community have been and are currently being invested into the search for metal complexes with antitumor activity. Coordination compounds of transition metals such as platinum (Pt), ruthenium (Ru) and gold (Au) have proven their effectiveness as diagnostic and/or antiproliferative agents. In recent years, experimental work on the potential applications of elements including lanthanum (La) and the post-transition metal gallium (Ga) in the field of oncology has been gaining traction. The authors of the present review article aim to help the reader "catch up" with some of the latest developments in the vast subject of coordination compounds in oncology. Herewith is offered a review of the published scientific literature on anticancer coordination compounds of Pt, Ru, Au, Ga and La that has been released over the past three years with the hope readers find the following article informative and helpful.

The Potential of Rhizobacteria to Mitigate Abiotic Stress in Lessertia frutescens

Lessertia frutescens is a multipurpose medicinal plant indigenous to South Africa. The curative ability of the medicinal plant is attributed to its rich phytochemical composition, including amino acids, triterpenoids, and flavonoids. A literature review of some of the phytochemical compounds, particularly amino acids, in L. frutescens shows a steady decrease in concentration over the years. The reduction of the phytochemical compounds and diminishing biological activities may be attributed to drought and salt stress, which South Africa has been grappling with over the years. Canavanine, a phytochemical which is associated with the anticancer activity of L. frutescens, reduced slightly when the plant was subjected to salt stress. Like other legumes, L. frutescens forms a symbiotic relationship with plant-growth-promoting rhizobacteria, which facilitate plant growth and development. Studies employing commercial plant-growth-promoting rhizobacteria to enhance growth and biological activities in L. frutescens have been successfully carried out. Furthermore, alleviation of drought and salt stress in medicinal plants through inoculation with plant growth-promoting-rhizobacteria is well documented and effective. Therefore, this review seeks to highlight the potential of plant-growth-promoting rhizobacteria to alleviate the effect of salt and drought in Lessertia frutescens.

Comparison of metabolite profiles and cytotoxicity of the black sea cucumber (Holothuria atra) dried with different drying techniques

Holothuria atra is a species of sea cucumber that could be a source of cytotoxic compounds. The present work aimed to determine the effect of different drying techniques on the profile of metabolites and cytotoxicity of sea cucumber extracts. Sea cucumbers were dried in the sun for 3 d, and then oven-dried at a temperature of 40, 50, and 60°C for 24 h. Fresh sea cucumbers without drying served as a control. The dried and fresh sea cucumbers were extracted by maceration for 12 h using ethanol. The metabolite profiling was performed using Fourier-transform infrared spectroscopy (FTIR) and high-performance liquid chromatography (HPLC) analyses, whereas the cytotoxicity was assayed by MTT method using the human breast ductal carcinoma cells (T47D). Analyses of FTIR and HPLC showed that the bioactive compounds of the ethanol extract were relatively stable during drying. This was in line with its cytotoxicity against T47D cells, which did not show significant differences between treatments. Based on these results, it was concluded that drying by sun or oven did not damage the bioactive compounds in the ethanolic extract of sea cucumber.

Application of MS-Based Metabolomic Approaches in Analysis of Starfish and Sea Cucumber Bioactive Compounds

Today, marine natural products are considered one of the main sources of compounds for drug development. Starfish and sea cucumbers are potential sources of natural products of pharmaceutical interest. Among their metabolites, polar steroids, triterpene glycosides, and polar lipids have attracted a great deal of attention; however, studying these compounds by conventional methods is challenging. The application of modern MS-based approaches can help to obtain valuable information about such compounds. This review provides an up-to-date overview of MS-based applications for starfish and sea cucumber bioactive compounds analysis. While describing most characteristic features of MS-based approaches in the context of starfish and sea cucumber metabolites, including sample preparation and MS analysis steps, the present paper mainly focuses on the application of MS-based metabolic profiling of polar steroid compounds, triterpene glycosides, and lipids. The application of MS in metabolomics studies is also outlined.

Phyto-factories of anti-cancer compounds: a tissue culture perspective

Background

Cancer is one of the most critical but ubiquitous causes of death grappled from past decades. Widely used chemotherapy with cytotoxic activity blocks/ kills the cancer cell. The compounds targeted for anticancerous activity are either derived synthetically or naturally (through plants or microbial origin). Current day, versatile role of plants in medicinal field has been attributed to the secondary metabolites it produces, known for their anticancer activity. Therefore, discovery, identification and commercial production of such novel anticancer drugs is escalated and are centerpiece for pharmaceuticals.

Main body

A biotechnological approach, principally tissue culture, leads the candidacy to be an alternative method for production of anticancer compounds. A wide range of bioactive agents like alkaloids, steroids, phenolics, saponins, flavonoids, and terpenoids are in huge demand commercially. Plant tissue culture applications are constructively more advantageous over conventional methods in terms of their continuous, controlled, aseptic production, large scale and de novo synthesis opportunity. Various bioreactors are used for mass cultivation of bioactive compound at commercial level. For example: stirred tank reactors are used for production of shikonin from Lithospermum erythrorhizon, vincristine from Catharanthus roseus, podophyllotoxin from Podophyllum etc. Strategies like callus culture, suspension culture and hairy root culture are opted for mass cultivation of these bioactives.

Conclusions

This review summarizes plant tissue culture as a promising strategy proven to be a colossal breakthrough in reliable and continuous production of existing and novel anticancer compounds and help in combating the increasing future demands.

Antifouling coating based on biopolymers (PCL/ PLA) and bioactive extract from the sea cucumber Stichopus herrmanni

An important challenge to decrease the toxic effects of the common biocides in marine environments and to achieve suitable ecofriendly natural antifouling coatings is to find effective natural antifoulants and efficient biodegradable coatings. In this study, antifouling activities of nine bioactive extracts (non-polar to polar) from different organs of the sea cucumber Stichopus herrmanni were tested against five bacterial strains, barnacle and brine shrimp larvae. The ethyl acetate extract of the body wall showed the highest in-vitro antifouling activity including high antibacterial and anti-barnacle activities and low toxicity against the brine shrimp as non-target organism. Based on these results, 10 phr of the ethyl acetate extract from S.herrmanni was added to different coatings consisting of polycaprolactone (PCL)/polylactic acid (PLA) blends containing various compositions of PLA (0, 10, and 20 wt.%). Polyvinyl chloride panels were coated with the prepared antifouling coatings and immersed in seawater for three months. Panel coated with PCL 80% /PLA 20% containing 10 phr of the antifoulant (panel-5), showed the highest resistance against fouling settlement with fouling coverage of 41.66% (P < 0.05). In addition, the lowest fouling weight was measured in panel-5 as well (81.00 ± 9.85 g) (P < 0.05). These findings indicate the antibacterial and antifouling potential of semi-polar bioactive extracts from the S. herrmanni body wall as natural antifoulants, as well as the enhanced antifouling performance of PCL/the natural antifoulant coatings by adding PLA.

Stichoposide C Exerts Anticancer Effects on Ovarian Cancer by Inducing Autophagy via Inhibiting AKT/mTOR Pathway

PURPOSE

Stichoposide C (STC) is a triterpene glycoside isolated from Thelenota ananas, which is previously demonstrated to wide spectrum of anticancer effects against various tumor cells. However, the antitumor effects and underlying molecular mechanisms in ovarian cancer (OC) cells are not fully understood. Here, we examined if and through which mechanisms STC exerts anticancer effects on OC.

METHODS

CCK-8 and colony formation assays were used to detect cell viability and proliferation. Flow cytometry was used to detect apoptosis and cell cycle arrest. Protein expression and phosphorylation were measured by Western blotting analysis. Confocal fluorescence microscopy was used to observe the autophagy flux. Autophagosome formation was observed via transmission electron microscopy. Antitumor effect of STC was investigated in patient-derived organoids (PDOs) and A2780 subcutaneous xenograft tumors.

RESULTS

STC was found that not only exerted antiproliferation activity and apoptosis but also induced autophagy. Mechanistically, STC induced autophagy via inhibited the AKT/mTOR signaling pathway in ovarian cancer cells. In addition, STC and an autophagy inhibitor 3-methyladenine (3-MA) combination treatment showed significant synergetic effects on inhibiting proliferation and promoting apoptosis in vitro. Consistent with cell experiments, STC also inhibited the growth of two OC PDOs. Finally, STC markedly reduced the growth of A2780 subcutaneous xenograft tumors without organ toxicity and activated autophagy in vivo.

CONCLUSION

Stichoposide C exerts in vitro and in vivo anticancer effects on ovarian cancer by inducing autophagy via inhibiting AKT/mTOR pathway. The findings warrant further prove for STC as a potential therapeutic agent for ovarian cancer.

Antiproliferative and proapoptotic activities of Sea Cucumber H. Leucospilota extract on breast carcinoma cell line (SK-BR-3)

BACKGROUND

Sea cucumber is a natural resource rich in many important pharmacological compounds. this study aimed to investigate the effect of H. leucospilota extract on the induction of cell death and and Proapoptotic Activities.

METHODS AND RESULTS

H. leucospilota was collected, the methanolic extract was prepared and in vitro cytotoxicity of H. leucospilota extract in the range of 12.5, 25, 50, 100, and 200 μg/mL concentrations for 48 hours on SK-BR-3 and MCR5 cells was determined. Analysis of apoptosis and cell cycle stages were performed using flow cytometry. the expressions of several apoptotic-related proteins in SK-BR-3 cells were evaluated using Western blot analysis. ROS formation and caspase activity were determined. GC-MS (involving a multistep temperature gradient and trimethylsilyl derivatives) and phytochemical analysis were used for identification of bioactive compounds. Methanolic extract inhibited the proliferation of the SK-BR-3 cell line in a dose- and time-dependent manner. As it was observed, exposure of the H. leucospilota extract triggered the apoptosis of the SK-BR-3 cells, induced DNA fragmentation, and arrested the cells in G2/M phase. treatment of the methanolic extract induced the downregulation of antiapoptotic Bcl-2 protein as well as the upregulation of Bax, caspase-3, caspase-7 proteins in SK-BR-3 cells. Methanolic extract-elicited apoptosis was accompanied with the elevated level of ROS. The GC-MS and phytochemical analysis revealed 30 compounds and the extract contained alkaloids, flavonoids, steroids, terpenoids, phenols, and saponins.

CONCLUSIONS

The antiproliferative and proapoptotic activities of the tested extract suggested the pharmacologic potential of H. leucospilota. Correspondingly, further characterizations of the identified compounds are in progress.

Sea Cucumber Intestinal Peptide Induces the Apoptosis of MCF-7 Cells by Inhibiting PI3K/AKT Pathway

Sea cucumbers are one of many marine echinoderm animals that contain valuable nutrients and medicinal compounds. The bioactive substances in sea cucumbers make them have promising biological and pharmacological properties, including antioxidant, anti-bacterial, and anti-tumor effects. In this study, sea cucumber intestinal peptide (SCIP) is a small molecular oligopeptide (<1,000 Da) extracted from sea cucumber intestines hydrolyzed by alkaline protease. The analysis of amino acid composition showed that hydrophobic amino acids and branched-chain amino acids were rich in SCIP. Nowadays, although increasing studies have revealed the biological functions of the sea cucumber active substances, there are few studies on the function of SCIP. Furthermore, due to the anti-cancer activity being an essential characteristic of sea cucumber active substances, we also investigated the anti-cancer potential and the underlying mechanism of SCIP in vivo and in vitro. The results indicate that SCIP inhibits the growth of MCF-7 tumor cells in zebrafish and increases the apoptosis of human breast cancer MCF-7 cells. Further mechanism studies confirm that SCIP promotes the expression of apoptosis-related proteins and thus promotes the breast cancer cells (MCF-7) apoptosis via inhibition of PI3K/AKT signal transduction pathway.

Sea cucumber peptides inhibit the malignancy of NSCLC by regulating miR-378a-5p targeted TUSC2

Lung cancer is a common cancer with high mortality worldwide, and non-small cell lung cancer (NSCLC) accounts for the majority. The clinical treatment effect of NSCLC is not ideal. The aim of this study was to investigate the inhibitory effect of sea cucumber peptide (SCP) on NSCLC and its mechanism. The results showed that SCP could effectively inhibit the proliferation, migration and invasion of A549 cells. In addition, SCP can also inhibit the formation of pleural effusion and tumor growth in lung cancer mice, reduce liver and kidney injury, increase the levels of IL-2 and IL-12, decrease the levels of IL-6 and TNF-α, and prolong the survival time of mice. The microRNA sequencing and immunohistochemistry of mouse tumors showed that the tumor suppressor gene TUSC2 targeted by miR-378a-5p was involved in the inhibition of tumor growth by SCP. This study provides an experimental basis for the further development of SCP as an anti-tumor nutritional supplement, and provides a new idea for exploring the molecular mechanism of food derived active peptides in anti-tumor applications.

Roles of Therapeutic Bioactive Compounds in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is due to poor prognosis and lack of availability of effective treatment. Novel therapeutic strategies will be the fine tuning of intracellular ROS signaling to effectively deprive cells of ROS-induced tumor-promoting events. This review discusses the generation of ROS, the major signaling their modulation in therapeutics. We explore some of the major pathways involved in HCC, which include the VEGF, MAPK/ERK, mTOR, FGF, and Ser/Thr kinase pathways. In this review, we study cornerstone on natural bioactive compounds with their effect on hepatocarcinomas. Furthermore, we focus on oxidative stress and FDA-approved signaling pathway inhibitors, along with chemotherapy and radiotherapy enhancers which with early evidence of success. While more in vivo testing is required to confirm the findings presented here, our findings will aid future nonclinical, preclinical, and clinical studies with these compounds, as well as inspire medicinal chemistry scientists to conduct appropriate research on this promising natural compound and their derivatives.

Comprehensive review on signaling pathways of dietary saponins in cancer cells suppression

Nutrigenomics utilizes high-throughput genomic technologies to reveal changes in gene and protein levels. Excitingly, ever-growing body of scientific findings has provided sufficient evidence about the interplay between diet and genes. Cutting-edge research and advancements in genomics, epigenetics and metabolomics have deepened our understanding on the role of dietary factors in the inhibition of carcinogenesis and metastasis. Dietary saponins, a type of triterpene glycosides, are generally found in Platycodon grandifloras, Dioscorea oppositifolia, asparagus, legumes, and sea cucumber. Wealth of information has started to shed light on pleiotropic mechanistic roles of dietary saponins in cancer prevention and inhibition. In this review, we have attempted to summarize the in vitro research of dietary saponins in the last two decades by searching common databases such as Google Scholar, PubMed, Scopus, and Web of Science. The results showed that dietary saponins exerted anti-cancer activities via regulation of apoptosis, autophagy, arrest cell cycle, anti-proliferation, anti-metastasis, and anti-angiogenesis, by regulation of several critical signaling pathways, including MAPK, PI3K/Akt/mTOR, NF-κB, and VEGF/VEGFR. However, there is no data about the dosage of dietary saponins for practical anti-cancer effects in human bodies. Extensive clinical studies are needed to confirm the effectiveness of dietary saponins for further commercial and medical applications.

Progress in the Studies of Triterpene Glycosides From Sea Cucumbers (Holothuroidea, Echinodermata) Between 2017 and 2021

Structural diversity of triterpene glycosides produced by sea cucumbers or holothurians (Holothuroidea, Echinodermata) is extremely high, although all of them are either lanostane derivatives or, rarely, products of their molecular rearrangements. The majority of them are holostane derivatives possessing an 18(20)-lanostane lactone as aglycone. They contain carbohydrate chains consisting of one to six monosaccharide units including sulfated ones. The glycosides demonstrate interesting biological activities, mainly caused by membranolytic action, namely cytotoxic, ichthyotoxic, antifungal, and hemolytic properties, as well as a series of additional effects at sub-toxic doses, including immunomodulatory, and cancer preventive. This review summarizes the literature data concerning structures and biological activities of all the new triterpene glycosides isolated from sea cucumbers during 2017 to 2021.

The isolation of water-soluble natural products - challenges, strategies and perspectives

Covering period: up to 2019Water-soluble natural products constitute a relevant group of secondary metabolites notably known for presenting potent biological activities. Examples are aminoglycosides, β-lactam antibiotics, saponins of both terrestrial and marine origin, and marine toxins. Although extensively investigated in the past, particularly during the golden age of antibiotics, hydrophilic fractions have been less scrutinized during the last few decades. This review addresses the possible reasons on why water-soluble metabolites are now under investigated and describes approaches and strategies for the isolation of these natural compounds. It presents examples of several classes of hydrosoluble natural products and how they have been isolated. Novel stationary phases and chromatography techniques are also reviewed, providing a perspective towards a renaissance in the investigation of water-soluble natural products.

Glycyrrhetinic acid: a promising scaffold for the discovery of anticancer agents

INTRODUCTION

Oleanane-type pentacyclic triterpenes named glycyrrhetinic acids (GAs) featuring a C-30 carboxylic acid group, are extracted from the licorice (Glycyrrhiza uralensis). Numerous biological properties of GA have been reported and have attracted researchers from all over the world in recent years due to the peculiar GA scaffold-based semisynthetic cytotoxic effects.

AREAS COVERED

This review represents the applications of semisynthetic derivatives of GA for the development of future cancer treatments. Included in the review are important structural features of the semisynthetic GAs crucial for cytotoxic effects.

EXPERT OPINION

Numerous semisynthetic GA derivatives illustrated excellent cytotoxic effects toward various cancer cells. Notably the C-₃(OH) at ring A along with C_30-CO₂H at ring E as vital structural features, make GA very appealing as a lead scaffold for medicinal chemistry, since these two groups permit the creation of further chemical diversity geared toward improved cytotoxic effects. Furthermore, numerous GA derivatives have been synthesized and indicate that compounds featuring cyanoenone moieties in ring A, or compounds having the amino group or nitrogen comprising heterocycles and hybrids thereof, illustrate more potent cytotoxicity. Furthermore, GA has a great capability to be conjugated with other anticancer molecules to synergistically enhance their combined cytotoxicity.

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.

New Triterpene Glycosides from the Far Eastern Starfish Solaster pacificus and Their Biological Activity

Three new triterpene glycosides, pacificusosides A–C (1–3), and three previously known triterpene glycosides, cucumariosides C₁ (4), C₂ (5), and A₁₀ (6), were isolated from the alcoholic extract of the Far Eastern starfish Solaster pacificus. The structures of 1–3 were elucidated by extensive NMR and ESIMS techniques and chemical transformations. Compound 1 has a novel, unique structure, containing an aldehyde group of side chains in its triterpene aglycon. This structural fragment has not previously been found in the sea cucumber triterpene glycosides or starfish steroidal glycosides. Probably, pacificusoside A (1) is a product of the metabolism of the glycoside obtained through dietary means from a sea cucumber in the starfish. Another two new triterpene glycosides (2, 3) have closely related characteristics to sea cucumber glycosides. The cytotoxicity of compounds 1–6 was tested against human embryonic kidney HEK 293 cells, colorectal carcinoma HT-29 cells, melanoma RPMI-7951 cells, and breast cancer MDA-MB-231 cells using MTS assay. Compounds 4–6 revealed the highest cytotoxic activity against the tested cell lines, while the other investigated compounds had moderate or slight cytotoxicity. The cytotoxic effects of 2–6 were reduced by cholesterol like the similar effects of the previously investigated individual triterpene glycosides. Compounds 3, 4, and 5 almost completely suppressed the colony formation of the HT-29, RPMI-7951, and MDA-MB-231 cells at a nontoxic concentration of 0.5 µM.

Pharmacokinetics of Marine-Derived Drugs

Marine organisms represent an excellent source of innovative compounds that have the potential for the development of new drugs. The pharmacokinetics of marine drugs has attracted increasing interest in recent decades due to its effective and potential contribution to the selection of rational dosage recommendations and the optimal use of the therapeutic arsenal. In general, pharmacokinetics studies how drugs change after administration via the processes of absorption, distribution, metabolism, and excretion (ADME). This review provides a summary of the pharmacokinetics studies of marine-derived active compounds, with a particular focus on their ADME. The pharmacokinetics of compounds derived from algae, crustaceans, sea cucumber, fungus, sea urchins, sponges, mollusks, tunicate, and bryozoan is discussed, and the pharmacokinetics data in human experiments are analyzed. In-depth characterization using pharmacokinetics is useful for obtaining information for understanding the molecular basis of pharmacological activity, for correct doses and treatment schemes selection, and for more effective drug application. Thus, an increase in pharmacokinetic research on marine-derived compounds is expected in the near future.

Synthesis of Sea Cucumber Saponins with Antitumor Activities

Holostane glycosides are characteristic metabolites of sea cucumbers, which possess various biological activities. Here, we report the synthesis of two representative congeners, namely, pervicoside B and C, starting from lanosterol with the longest linear sequence of both 34 steps and in 0.3% overall yields. The flexible synthetic approach has enabled us to expeditiously prepare 16 analogues for preliminary studies on the key structural features influencing their antiproliferative activities against tumor cells. A simplified disaccharide is found to be as potent as natural tetrasaccharides, which can be used as a lead for future studies.

Characterization and anti-tumor activity of saponin-rich fractions of South Korean sea cucumbers (Apostichopus japonicus)

In this study, the saponin-rich fractions of five individual (two Red and three Black) sea cucumbers (Apostichopus japonicus) in South Korea were investigated for their antiproliferative effect against HL-60, B16F10, MCF-7, and Hep3B tumor cell lines. The red sea cucumber saponin-rich fraction (SSC) from Jeju Island (JRe) decreased the growth of HL-60 with an IC50 value of 23.55 ± 3.40 μg/mL, which represented the strongest anticancer activity among the extracts. Further, SSC downregulated B-cell lymphoma extra-large (Bcl-xL), while upregulating, to different degrees, Bcl-2-associated X protein (Bax), caspase-9, caspase-3, PARP cleavage, and apoptotic bodies in cancer cells. Evidence for SSC inducing apoptosis via the mitochondria-mediated pathway was found. The contents of SSCs were determined using ultra high-performance liquid chromatography coupled with a quadrupole orbitrap mass spectrometry to comparatively evaluate the regional influence. In West Sea, the total SSC content of A. japonicus was 15.5 mg/g, representing the highest content, while A. japonicus in the South Sea yielded the lowest content at 8 mg/g. The major saponin constituent in SSC was identified as Holotoxin A1, which may the anti-tumor compound in A. japonicus.

Northern Sea Cucumber (Cucumaria frondosa): A Potential Candidate for Functional Food, Nutraceutical, and Pharmaceutical Sector

Sea cucumber (Cucumaria frondosa) is the most abundant and widely distributed species in the cold waters of North Atlantic Ocean. C. frondosa contains a wide range of bioactive compounds, mainly collagen, cerebrosides, glycosaminoglycan, chondroitin sulfate, saponins, phenols, and mucopolysaccharides, which demonstrate unique biological and pharmacological properties. In particular, the body wall of this marine invertebrate is the major edible part and contains most of the active constituents, mainly polysaccharides and collagen, which exhibit numerous biological activities, including anticancer, anti-hypertensive, anti-angiogenic, anti-inflammatory, antidiabetic, anti-coagulation, antimicrobial, antioxidation, and anti- osteoclastogenic properties. In particular, triterpene glycosides (frondoside A and other) are the most researched group of compounds due to their potential anticancer activity. This review summarizes the latest information on C. frondosa, mainly geographical distribution, landings specific to Canadian coastlines, processing, commercial products, trade market, bioactive compounds, and potential health benefits in the context of functional foods and nutraceuticals.

Two novel non-holostane type glycosides from the viscera of sea cucumber Apostichopus japonicus

Two novel glycosides, apostichoposide A₁ (1) and B₁ (2), were isolated from the viscera of Chinese sea cucumbers (Apostichopus japonicus, Selenka) collected in the Bohai sea. Both the isolated glycosides were characterized by non-holostane type aglycones having 18(16)-lactone and 7(8)-double bond. Cytotoxic activities of the two compounds were evaluated against three human cancer cell lines. Compound 1 had adequate cytotoxic activity against MGC-803 and PC-3M cell lines. Our results indicated that glycosides present in A. japonicus viscera are an important high value resource for biotechnological applications.

The Marine-Derived Triterpenoid Frondoside A Inhibits Thrombus Formation

Background: The marine-derived triterpenoid frondoside A inhibits the phosphatidylinositol-3-kinase (PI3K) pathway in cancer cells. Because this pathway is also crucially involved in platelet activation, we studied the effect of frondoside A on thrombus formation. Methods: Frondoside A effects on platelet viability, surface adhesion molecule expression, and intracellular signaling were analyzed by flow cytometry and Western blot. The effect of frondoside A was analyzed by photochemically induced thrombus formation in the mouse dorsal skinfold chamber model and by tail vein bleeding. Results: Concentrations of up to 15 µM frondoside A did not affect the viability of platelets, but reduced their surface expression of P-selectin (CD62P) and the activation of glycoprotein (GP)IIb/IIIa after agonist stimulation. Additional mechanistic analyses revealed that this was mediated by downregulation of PI3K-dependent Akt and extracellular-stimuli-responsive kinase (ERK) phosphorylation. Frondoside A significantly prolonged the complete vessel occlusion time in the mouse dorsal skinfold chamber model of photochemically induced thrombus formation and also the tail vein bleeding time when compared to vehicle-treated controls. Conclusion: Our findings demonstrated that frondoside A inhibits agonist-induced CD62P expression and activation of GPIIb/IIIa. Moreover, frondoside A suppresses thrombus formation. Therefore, this marine-derived triterpenoid may serve as a lead compound for the development of novel antithrombotic drugs.

Antimicrobial lead compounds from marine plants

Marine environment is a home to a very wide diversity of flora and fauna, which includes an array of genetically diverse coastline and under seawater plant species, animal species, microbial species, their habitats, ecosystems, and supporting ecological processes. The Earth is home to an estimated 10 million species, of which a large chunk belongs to marine environment. Marine plants are a store house of a variety of antimicrobial compounds like classes of marine flavonoids—flavones and flavonols, terpenoids, alkaloids, peptides, carbohydrates, fatty acids, polyketides, polysaccharides, phenolic compounds, and steroids. Lot of research today is directed toward marine species, which have proved to be a potent source of structurally widely diverse and yet highly bioactive secondary metabolites. Varied species of phylum Porifera, algae including diatoms, Chlorophyta, Euglenophyta, Dinoflagellata, Chrysophyta, cyanobacteria, Rhodophyta, and Phaeophyta, bacteria, fungi, and weeds have been exploited by mankind for their inherent indigenous biological antimicrobial compounds, produced under the extreme stressful underwater conditions of temperature, atmospheric pressure, light, and nutrition. The present study aims at presenting a brief review of bioactive marine compounds possessing antimicrobial potency.

Chemical synthesis of marine saponins

Covering: 1989-2017 Saponins are characteristic metabolites of starfish and sea cucumbers, and occasionally are also found in sponges, soft coral, and small fish. These steroid or triterpenoid glycosides often show remarkable biological and pharmacological activities, such as antifungal, antifouling, shark repellent, antitumor and anti-inflammatory activities. Over one thousand marine saponins have been characterized; the majority of them can be categorized into three major structural types, i.e., asterosaponins, polyhydroxysteroid glycosides, and holostane glycosides. Thus far, only 12 marine saponins have been synthesized; those representing the major types were successfully synthesized recently. The syntheses involve preparation of the aglycones from the terrestrial steroid or triterpene materials, installation of the carbohydrate units, and manipulation of the protecting groups. Herein, we provide a comprehensive review on these syntheses.

An ethyl-acetate fraction of Holothuria scabra modulates inflammation in vitro through inhibiting the production of nitric oxide and pro-inflammatory cytokines via NF-κB and JNK pathways

Sea cucumber, Holothuria scabra, is an echinoderm marine animal that has long been used as a traditional therapeutic in various diseases due to its chemical composition and protein enrichment. Many researchers have extensively studied the efficacy of sea cucumber extracts for many health benefits in recent years. Inflammation is a complex process involved in pro-/anti-inflammatory cytokine products. However, the role of the H. scabra extracts in anti-inflammation and its molecular regulations has not been apparently elucidated yet. In this study, we investigated the anti-inflammatory effect of H. scabra extracts by using lipopolysaccharide (LPS) from E. coli to induce an inflammatory response in RAW264.7 macrophage. It was found that ethyl acetate fraction of H. scabra extracts (EAHS) inhibited pro-inflammatory cytokines synthesis at both the transcriptional and translational levels, notably nitric oxide (NO), inducible nitric oxide synthase (iNOS), interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and prostaglandin E₂ (PGE₂). In addition, EAHS was able to downregulate IκB/NF-κB, and JNK expressions. These effects may be influenced by high contents of phenolic compound and triterpene glycosides in EAHS. Therefore, EAHS might have the potential to be developed as a natural anti-inflammatory agent.

Application of a Promising Bone Graft Substitute in Bone Tissue Regeneration: Characterization, Biocompatibility, and In Vivo Animal Study

The purpose of the present study was to investigate the effect of local hydroxyapatite (HA) combined with extracted sea cucumber (Stichopus hermanni) collagen as a promising bone graft substitute on bone remodeling. Fourier-transform infrared spectroscopy, X-ray diffractometry, transmission electron microscopy, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, and Sprague-Dawley rat model were used to characterize the microstructure, in vitro cytotoxicity, and in vivo bone-healing properties of the investigated biocomposite material. Analytical results found that the hydrothermal reaction-synthesized local HA had a hexagonal close-packed structure. The addition of extracted S. hermanni collagen did not influence the microstructure and functional groups of the local HA. Moreover, the MTT assay indicated that the investigated biocomposite material possessed a good in vitro biocompatibility. The in vivo animal study also revealed that the investigated biocomposite material exhibited the highest number of osteoblasts after 14 days of healing. Therefore, the results demonstrate that the local HA combined with extracted S. hermanni collagen could potentially enhance osteoblast formation in promoting bone healing and regeneration.

Bright Spots in The Darkness of Cancer: A Review of Starfishes-Derived Compounds and Their Anti-Tumor Action

The fight against cancer represents a great challenge for researchers and, for this reason, the search for new promising drugs to improve cancer treatments has become inevitable. Oceans, due to their wide diversity of marine species and environmental conditions have proven to be precious sources of potential natural drugs with active properties. As an example, in this context several studies performed on sponges, tunicates, mollusks, and soft corals have brought evidence of the interesting biological activities of the molecules derived from these species. Also, echinoderms constitute an important phylum, whose members produce a huge number of compounds with diverse biological activities. In particular, this review is the first attempt to summarize the knowledge about starfishes and their secondary metabolites that exhibited a significant anticancer effect against different human tumor cell lines. For each species of starfish, the extracted molecules, their effects, and mechanisms of action are described.

Modulation of Doxorubicin Intracellular Accumulation and Anticancer Activity by Triterpene Glycoside Cucumarioside A2-2

The effect of treatment of Ehrlich ascites carcinoma (EAC) cells with multidrug resistance by holothurian triterpene glycoside, cucumarioside A₂-2 (CA₂-2) was evaluated. Calcein-AM efflux assay and doxorubicin (DOX) uptake and retention measurement in cancer cells, as well as determination of DOX cytotoxic and anticancer effects were applied. Treatment of EAC cells with CA₂-2 (0.01–0.1 μM) blocked Calcein-AM and DOX efflux from cancer cells and increased the accumulation and cytotoxicity of DOX in EAC cells. Moreover, pre-treatment of mice with EAC by CA₂-2 (10 μg/kg/5 days, intraperitoneal injection (i.p.)), then transplantation of tumor cells into fresh animals and subsequent treatment of these mice with DOX (2 mg/kg/3 days i.p.) significantly increased average life span (ALS) of mice bearing a tumor and therefore boosted the antitumor effect of doxorubicin in vivo.

Black sea cucumber (Holothuria atra Jaeger, 1833) rescues Pseudomonas aeruginosa-infected Caenorhabditis elegans via reduction of pathogen virulence factors and enhancement of host immunity

A strategy to circumvent the problem of multidrug resistant pathogens is the discovery of anti-infectives targeting bacterial virulence or host immunity. Black sea cucumber (Holothuria atra) is a tropical sea cucumber species traditionally consumed as a remedy for many ailments. There is a paucity of knowledge on the anti-infective capacity of H. atra and the underlying mechanisms involved. The objective of this study is to utilize the Caenorhabditis elegans-P. aeruginosa infection model to elucidate the anti-infective properties of H. atra. A bioactive H. atra extract and subsequently its fraction were shown to have the capability of promoting the survival of C. elegans during a customarily lethal P. aeruginosa infection. The same entities also attenuate the production of elastase, protease, pyocyanin and biofilm in P. aeruginosa. The treatment of infected transgenic lys-7::GFP worms with this H. atra fraction restores the repressed expression of the defense enzyme lys-7, indicating an improved host immunity. QTOF-LCMS analysis revealed the presence of aspidospermatidine, an indole alkaloid, and inosine in this fraction. Collectively, our findings show that H. atra possesses anti-infective properties against P. aeruginosa infection, by inhibiting pathogen virulence and, eventually, reinstating host lys-7 expression.

Vaccine Adjuvants Derived from Marine Organisms

Vaccine adjuvants help to enhance the immunogenicity of weak antigens. The adjuvant effect of certain substances was noted long ago (the 40s of the last century), and since then a large number of adjuvants belonging to different groups of chemicals have been studied. This review presents research data on the nonspecific action of substances originated from marine organisms, their derivatives and complexes, united by the name 'adjuvants'. There are covered the mechanisms of their action, safety, as well as the practical use of adjuvants derived from marine hydrobionts in medical immunology and veterinary medicine to create modern vaccines that should be non-toxic and efficient. The present review is intended to briefly describe some important achievements in the use of marine resources to solve this important problem.

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.

Marine anticancer drugs and their relevant targets: a treasure from the ocean

Marine organisms comprising animals and plants are wealthiest sources of bioactive compounds possessing various pharmacological properties specifically: free radical scavenging, antitumor, antimicrobial, analgesic, neuroprotective and immunomodulatory. Marine drugs provide an alternative source to meet the demand of effective, safe and low-cost drugs that are rising with the continuously growing world population. Cancer is one of the leading reasons of mortality in western nations in contrast to communicable diseases of developing nations. In spite of outstanding developments in cancer therapy in past three decades, there is still an insistent necessity for innovative drugs in the area of cancer biology, especially in the unexplored area of marine anticancer compounds. However, recent technological innovations in structure revelation, synthetic creation of new compounds and biological assays have made possible the isolation and clinical assessment of innumerable unique anticancer compounds from marine environment. This review provides an insight into the anticancer research so far conducted in the area of the marine natural products/synthetic derivatives, their possible molecular targets and the current challenges in the drug development. Graphical abstract.

Antitumor Anthraquinones from an Easter Island Sea Anemone: Animal or Bacterial Origin?

The presence of two known anthraquinones, Lupinacidin A and Galvaquinone B, which have antitumor activity, has been identified in the sea anemone (Gyractis sesere) from Easter Island. So far, these anthraquinones have been characterized from terrestrial and marine Actinobacteria only. In order to identify the anthraquinones producer, we isolated Actinobacteria associated with the sea anemone and obtained representatives of seven actinobacterial genera. Studies of cultures of these bacteria by HPLC, NMR, and HRLCMS analyses showed that the producer of Lupinacidin A and Galvaquinone B indeed was one of the isolated Actinobacteria. The producer strain, SN26_14.1, was identified as a representative of the genus Verrucosispora. Genome analysis supported the biosynthetic potential to the production of these compounds by this strain. This study adds Verrucosispora as a new genus to the anthraquinone producers, in addition to well-known species of Streptomyces and Micromonospora. By a cultivation-based approach, the responsibility of symbionts of a marine invertebrate for the production of complex natural products found within the animal’s extracts could be demonstrated. This finding re-opens the debate about the producers of secondary metabolites in sea animals. Finally, it provides valuable information about the chemistry of bacteria harbored in the geographically-isolated and almost unstudied, Easter Island.