Triterpenoids of marine origin as anti-cancer agents

Pharmacological potential of micheliolide: A focus on anti-inflammatory and anticancer activities

Micheliolide (MCL) is a chief constituent of plants such as Magnolia grandiflora L., Michelia compressa (Maxim.) Sarg. and Michelia champaca L. It is known to exhibit significant anticancer activity by various scientific investigations. This review aims to emphasize the anticancer and antiinflammatory activities of MCL. In this review, we summarized the published data in peer-reviewed manuscripts published in English. Our search was based on the following scientific search engines and databases: Scopus, Google Scholar, ScienceDirect, Springer, PubMed, and SciFinder, MCL possesses a broad spectrum of medicinal properties like other sesquiterpene lactones. The anticancer activity of this compound may be attributed to the modulation of several signaling cascades (PI3K/Akt and NF-κB pathways). It also induces apoptosis by arresting the cell cycle at the G1/G0 phase, S phase, and G2/M phase in many cancer cell lines. Very little data is available on its modulatory action on other signaling cascades like MAPK, STAT3, Wnt, TGFβ, Notch, EGFR, etc. This compound can be potentiated as a novel anticancer drug after thorough investigations in vitro, in vivo, and in silico-based studies.

Antitumor Activity and Mechanism of Terpenoids in Seaweeds Based on Literature Review and Network Pharmacology

Seaweeds are a treasure trove of natural secondary metabolites. Terpenoids extracted from seaweeds are shown to possess a variety of antitumor cellular activities. However, due to the complex and diverse structures of terpenoids, their therapeutic targets and complex mechanisms of action have not been clarified. The present study summarises the research on terpenoids from seaweeds in oncological diseases over the last 20 years. Terpenoids show different degrees of inhibitory effects on different types of tumor cells, suggesting that terpenoids in seaweeds may have potential antitumor disease potential. Terpenoids with potential antitumor activity and their mechanism of action are investigated using network pharmacology. A total of 125 terpenoids and 286 targets are obtained. Proto-oncogene tyrosine-protein kinase Src(SRC), Signal transducer and activator of transcription 3 (STAT3), Mitogen-activated protein kinase (MAPK3, MAPK1), Heat shock protein HSP 90-alpha (HSP90AA1), Phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA), and RAC-alpha serine/threonine-protein kinase (AKT1) are defined as core targets. According to GO function and Kyoto encyclopedia of genes and genomes(KEGG) enrichment analysis, terpenoids may affect the Phoshatidylinositol 3'-kinase (PI3K)-Akt signaling pathway, Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor resistance, Prostate cancer, MAPK signaling pathway, and Proteoglycans in cancer. In addition, the molecular docking results show that the selected terpenoids are all able to bind strongly to the active protein. Terpenoids may slow down the progression of cancer by controlling apoptosis, proliferation, and protein and enzyme binding.

Natural Products Derived from Marine Sponges with Antitumor Potential against Lung Cancer: A Systematic Review

Non-small-cell lung cancer (NSCLC), the most commonly diagnosed cancer and the leading cause of cancer-related death worldwide, has been extensively investigated in the last decade in terms of developing new therapeutic options that increase patient survival. In this context, marine animals are a source of new, interesting bioactive molecules that have been applied to the treatment of different types of cancer. Many efforts have been made to search for new therapeutic strategies to improve the prognosis of lung cancer patients, including new bioactive compounds and cytotoxic drugs from marine sponges. Their antitumoral effect can be explained by several cellular and molecular mechanisms, such as modulation of the cell cycle or induction of apoptosis. Thus, this systematic review aims to summarize the bioactive compounds derived from marine sponges and the mechanisms by which they show antitumor effects against lung cancer, exploring their limitations and the challenges associated with their discovery. The search process was performed in three databases (PubMed, SCOPUS, and Web of Science), yielding a total of 105 articles identified in the last 10 years, and after a screening process, 33 articles were included in this systematic review. The results showed that these natural sponge-derived compounds are a valuable source of inspiration for the development of new drugs. However, more research in this field is needed for the translation of these novel compounds to the clinic.

A Mass Spectrometry Database for Sea Cucumber Triterpene Glycosides

Sea cucumber triterpene glycosides are a class of secondary metabolites that possess distinctive chemical structures and exhibit a variety of biological and pharmacological activities. The application of MS-based approaches for the study of triterpene glycosides allows rapid evaluation of the structural diversity of metabolites in complex mixtures. However, the identification of the detected triterpene glycosides can be challenging. The objective of this study is to establish the first spectral library containing the mass spectra of sea cucumber triterpene glycosides using ultraperformance liquid chromatography-quadrupole time-of-flight mass spectrometry. The library contains the electrospray ionization tandem mass spectra and retention times of 191 triterpene glycosides previously isolated from 15 sea cucumber species and one starfish at the Laboratory of the Chemistry of Marine Natural Products of the G.B. Elyakov Pacific Institute of Bioorganic Chemistry. In addition, the chromatographic behavior and some structure-related neutral losses in tandem MS are discussed. The obtained data will accelerate the accurate dereplication of known triterpene glycosides and the annotation of novel compounds, as we demonstrated by the processing of LC-MS/MS data of Eupentacta fraudatrix extract.

Marine Aspergillus: A Treasure Trove of Antimicrobial Compounds

Secondary metabolites from marine organisms are diverse in structure and function. Marine Aspergillus is an important source of bioactive natural products. We reviewed the structures and antimicrobial activities of compounds isolated from different marine Aspergillus over the past two years (January 2021-March 2023). Ninety-eight compounds derived from Aspergillus species were described. The chemical diversity and antimicrobial activities of these metabolites will provide a large number of promising lead compounds for the development of antimicrobial agents.

Bioactive Usual and Unusual Triterpenoids Derived from Natural Sources Used in Traditional Medicine

Triterpenoids are accessible in several terrestrial plants as well as marine organisms, including sponges, algae, fungi, and sea cucumbers are examples of marine creatures. So far, more than 20,000 natural triterpenoids have exhibited several varied bioactivities, including anticancer, antimalarial, anti-HIV, inhibit HIF-1 activation, antibacterial, chemopreventive, anti-inflammatory, antioxidant, cardioprotective, antiviral, neuroprotective, hepatoprotective, insecticidal, antidiabetic, cytotoxic. Several plants are used in folklore medicine to treat numerous ailments, and the preparation or uses of traditional practices have been scientifically validated. Although various structural diversity has been observed in the triterpenoids, this review presents the sources and uses of those triterpenoids that showed significant biological activities which could be accessible and promoted to familiar people in the form of traditional medicine or for industrial, or pharmaceutical applications.

Antioxidant and Anticancer Activities of Sand Sea Cucumber (Holothuria scabra) Extracts using Wet Rendering Extraction Method

Antioxidant and anticancer activities of sand sea cucumber Holothuria scabra (dried and fresh) extracts were studied. The highest extraction yield of sea cucumber H. scabra (3.9%) was obtained using dried H. scabra at 60oC. The highest antioxidant activity was found in fresh H. scabra extract at 60°C with an IC50 value of 629.89 ± 0.15 µg/mL using the ABTS method, and the highest antioxidant activity by DPPH method was found in dried H. scabra extract at 70°C with an IC50 value of 32017.18 ± 0.82 µg/mL. The best antioxidant activity based on FRAP and TBARS methods was found in fresh H. scabra extracts at 80°C, respectively. The highest total phenol and flavonoid contained in dried H. scabra extract were 317.54 ± 8.91 mg GAE/100 g sample and 247.56 ± 11.70 mg QE/100 g sample. H. scabra extracts inhibited more than 50% of the growth of the MDA-MB-231 cell line at concentrations of 25 and 50 μg/mL except for dried H. scabra extracts at 80°C. Similarly, the extracts showed the highest cytotoxic effect up to 100% at the highest concentration (100 μg/mL) except for dried H. scabra extracts at 70°C and 80°C.

Antifungal–antiproliferative norcycloartane-type triterpenes from the Red Sea green alga Tydemania expeditionis

The current work aims to isolate the bioactive secondary metabolites from the Red Sea green alga T. expeditionis. Its organic extract was partitioned and analyzed using chromatographic and spectroscopic techniques. Four triterpenoids of the cycloartane-carbon skeleton were identified as: 29-norcycloartane-3-en-23,28-diol (1), 29-norcycloartane-5,24-dien-3-ol-23-one (2), 29-norcycloartane-3,24-dien-3-ol-23-one (3), and 29-norcycloartane-5,24-dien-3-ol (4), along with hydroxylated C-18 fatty acid, 3-hydroxyoctadeca-15(Z)-enoic acid (5). The antiproliferative activity of the isolated metabolites was examined against three cancer cell lines, i.e., HeLa, HepG-2, and MCF-7. Compounds 2 and 3 demonstrated a strong antiproliferative effect against all cells with IC50 values ranging from 17.8 ± 1.71 to 23.3 ± 1.66 µM. Compounds 1 and 4 showed a moderate antiproliferative effect against all cell lines with IC50 values ranging from 44.7 ± 2.32 to 65.0 ± 3.66 µM. The antifungal activity of all compounds has been tested against several fungi. Compounds 2–4 revealed strong inhibition against A. flavus and Fusarium oxysporum. Compounds 1–4 showed moderate to weak inhibition activity against A. niger, A. fumigatus, C. albicans, and C. tropicalis. Compound 5 showed weak to non-detected activity against all cell lines and microbes. The results indicated that norcycloartanes exhibit antiproliferative and antifungal activities, especially those with α,β-unsaturated ketones in their side chain.

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.

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.

Anticancer Effects of Seaweed-Derived Bioactive Compounds

Cancer remains a major life-threatening disease worldwide. The development of anticancer drugs using natural products obtained from marine organisms has been proposed as an alternative approach. Seaweeds are the mainstay of marine ecosystems; therefore, they are highly enriched with diverse bioactive compounds. In the past decade, a vast number of natural compounds, such as polysaccharides, polyphenols, carotenoids, and terpenoids, have been isolated from seaweeds. Seaweeds have bioactive compounds that show cytotoxicity in various cancer cell lines. These compounds prevent tumor growth by inducing apoptotic cell death and arrest growth by interfering with different kinases and cell cycle pathways. This review discussed the anticancer properties of various bioactive compounds isolated from different types of seaweeds and their therapeutic potential against cancers.

Malabaricane and Isomalabaricane Triterpenoids, Including Their Glycoconjugated Forms

In this review, we discuss structural diversity, taxonomic distribution, biological activities, biogenesis, and synthesis of a rare group of terpenoids, the so-called malabaricane and isomalabaricane triterpenoids, as well as some compounds derived from them. Representatives of these groups were found in some higher and lower terrestrial plants, as well as in some fungi, and in a relatively small group of marine sponges. The skeletal systems of malabaricanes and isomalabaricanes are similar to each other, but differ principally in the stereochemistry of their tricyclic core fragments, consisting of two six-membered and one five-membered rings. Evolution of these triterpenoids provides variety of rearranged, oxidized, and glycoconjugated products. These natural compounds have attracted a lot of attention for their biosynthetic origin and biological activity, especially for their extremely high cytotoxicity against tumor cells as well as promising neuroprotective properties in nanomolar concentrations.

Cytotoxic Activity of Triterpenoids from Cheiloclinium cognatum Branches against Chronic and Acute Leukemia Cell Lines

Cheiloclinium cognatum (Miers) A.C.Sm. is an endemic species of Brazilian Cerrado that belongs to Celastraceae family. The phytochemical study of C. cognatum branches led to the identification of ten triterpenoids (TPs), 3β-acyloxyurs-12-ene (1), friedelin (2), β-friedelinol (3), glut-5-en-3β-ol (4), α-amyrin (5), β-amyrin (6), β-sitosterol (7), canophyllol (8), 29-hydroxyfriedelan-3-one (9) and friedelane-3β,29-diol (10). TPs 4, 5 and 6 are described for the first Cheiloclinium genus and TPs 8 and 9 were isolated in expressive amounts. Their cytotoxic activities were evaluated against THP-1 and K562 leukemia cell lines. TPs 3 and 5 were the most active, exhibiting lower or similar IC₅₀ against both cell lines when compared to the controls. Their mechanisms of action were investigated suggesting an intrinsic mitochondrial pathway of apoptosis evidenced by up-regulation of BAK mRNA expression. Chemometric studies indicated that their activities may be related to their molecular size and shape as well as electronic interactions of C-3 hydroxy group with molecular targets.

Squalene deters drivers of RCC disease progression beyond VHL status

Identifying drug candidates to target cellular events/signaling that evades von Hippel-Lindau tumor suppressor (VHL) gene interaction is critical for the cure of renal cell carcinoma (RCC). Recently, we characterized a triterpene-squalene derived from marine brown alga. Herein, we investigated the potential of squalene in targeting HIF-signaling and other drivers of RCC progression. Squalene inhibited cell proliferation, induced cell dealth and reverted the cells' metastatic state (migration, clonal expansion) independent of their VHL status. Near-identical inhibition of HIF-1α and HIF-2α and the regulation of downstream targets in VHL wild type and mutant cell lines demonstrated squalene efficacy beyond VHL-HIF interaction. In a rat model of chemically induced RCC, squalene displayed chemopreventive capabilities by substantial reversal of lipid peroxidation, mitochondrial redox regulation, maintaining ∆ψ_m, inflammation [Akt, nuclear factor κB (NF-κB)], angiogenesis (VEGFα), metastasis [matrix metalloproteinase 2 (MMP-2)], and survival (Bax/Bcl2, cytochrome-c, Casp3). Squalene restored glutathione, glutathione reductase, glutathione-s-transferase, catalase, and superoxide dismutase and stabilized alkaline phosphatase, alkaline transaminase, and aspartate transaminase. The correlation of thiobarbituric acid reactive substance with VEGF/NF-κB and negative association of GSH with Casp3 show that squalene employs reduction in ROS regulation. Cytokinesis-block micronuclei (CBMN) assay in VHL^wt/mut cells revealed both direct and bystander effects of squalene with increased micronucleus (MN) frequency. Clastogenicity analysis of rat bone marrow cells demonstrated an anti-clastogenic effect of squalene, with increased polychromatic erythrocytes (PCEs), decreased MNPCE,s and MN normochromatic erythrocytes. Squalene could effectively target HIF signaling that orchestrate RCC evolution. The efficacy of squalene is similar in VHL^wt and VHL^mut RCC cells, and hence, squalene could serve as a promising drug candidate for an RCC cure beyond VHL status and VHL-HIF interaction dependency. Summary: Squalene derived from marine brown algae displays strong anti-cancer (RCC) activity, functionally targeting HIF-signaling pathway, and affects various cellular process. The significance of squalene effect for RCC is highlighted by its efficiency beyond VHL status, designating itself a promising drug candidate. Graphical abstract.

Osmolytes and membrane lipids in adaptive response of thermophilic fungus Rhizomucor miehei to cold, osmotic and oxidative shocks

In contrast to mesophiles, in which levels of trehalose and phosphatidic acids (PA) increased only under heat shock (HS), in thermophiles trehalose and PA were predominant under optimal growth conditions. To study the role of trehalose protection in the adaptation of thermophiles to various stressors, the composition of osmolytes and membrane lipids in the thermophilic fungus Rhizomucor miehei was studied under cold (CS), osmotic (OS) and oxidative (OxS) shocks. CS resulted in no accumulation of glycerol in the mycelium, while the amount of trehalose decreased. The main lipid changes were the increase in the PA proportion with simultaneous decrease of sterols (St), the increase of the unsaturation degree of polar lipids and the decrease of the ergosterol proportion in total St. OS did not cause changes in the lipid composition, but led to the decrease of ergosterol proportion too. Despite the low ability of Mucorales to produce polyols, increase in the level of arabitol and glycerol was observed under OS. OxS led to the decrease of trehalose level and had no effect on the lipid composition. Thus, our results show the similarity (OS) and the difference (CS and OxS) between adaptation mechanisms of thermophiles and mesophiles.

Curcumol: From Plant Roots to Cancer Roots

Natural products, an infinite treasure of bioactive scaffolds, have provided an excellent reservoir for the discovery of drugs since millennium. These naturally occurring, biologically active and therapeutically effective chemical entities have emerged as novel paradigm for the prevention of various diseases. This review aims to give an update on the sources as well as pharmacological profile of curcumol, a pharmacologically active sesquiterpenoid, which is an imperative bioactive constituent of several plants mainly from genus Curcuma. Curcumol has potential to fight against cancer, oxidative stress, neurodegeneration, microbial infections, and inflammation. Curcumol has been documented as potent inducer of apoptosis in numerous cancer cells via targeting key signaling pathways as MAPK/ERK, PI3K/Akt and NF-κB which are generally deregulated in several cancers. The reported data reveals multitarget activity of curcumol in cancer treatment suggesting its importance as anticancer drug in future. It is speculated that curcumol may provide an excellent opportunity for the cure of cancer but further investigations on mechanism of its action and preclinical trials are still mandatory to further validate the potential of this natural cancer killer in anticancer therapies.

Algae metabolites: from in vitro growth inhibitory effects to promising anticancer activity

Covering: 1957 to 2017 Algae constitute a heterogeneous group of eukaryotic photosynthetic organisms, mainly found in the marine environment. Algae produce numerous metabolites that help them cope with the harsh conditions of the marine environment. Because of their structural diversity and uniqueness, these molecules have recently gained a lot of interest for the identification of medicinally useful agents, including those with potential anticancer activities. In the current review, which is not a catalogue-based one, we first highlight the major biological events that lead to various types of cancer, including metastatic ones, to chemoresistance, thus to any types of current anticancer treatment relating to the use of chemotherapeutics. We then review algal metabolites for which scientific literature reports anticancer activity. Lastly, we focus on algal metabolites with promising anticancer activity based on their ability to target biological characteristics of cancer cells responsible for poor treatment outcomes. Thus, we highlight compounds that have, among others, one or more of the following characteristics: selectivity in reducing the proliferation of cancer cells over normal ones, potential for killing cancer cells through non-apoptotic signaling pathways, ability to circumvent MDR-related efflux pumps, and activity in vivo in relevant pre-clinical models.

Tubeimoside-1, Triterpenoid Saponin, as a Potential Natural Cancer Killer

Nature, an expert craftsman of molecules, has generated extensive array of bioactive molecular entities. It persists as an inexhaustible resource for discovery of drugs and supplied enormous scaffold diversification for development into effectual drugs to treat multiple pathological conditions. This review provides an update on the sources, biological, and pharmacological effects of nature's gift, a triterpenoid saponin, tubeimoside-1 which is a major bioactive constituent of the bulb of Bolbostemma paniculatum. Tubeimoside-1 is known to possess various pharmacological properties such as anti-cancer, anti-HIV, and anti-inflammatory. Recently, anti-proliferative potential of tubeimoside-1 has been widely studied. The present review article seeks to cover the recent developments of tubeimoside-1′s pharmacological position in the arena of herbal drugs, providing an insight into its current status in therapeutic pursuits. This anti-cancer triterpenoid saponin fight cancer progression by induction of apoptosis, cell cycle arrest, and inhibiting metastasis by specifically targeting multiple signaling pathways those are usually deregulated in various cancers. The reported data recommend tubeimoside-1′s mutitarget activity in preference to single effect that may perform an imperative role towards developing tubeimoside-1 into potential pharmacological drug.

The Anti-Cancer Effects of Frondoside A

Frondoside A is a triterpenoid glycoside from the Atlantic Sea Cucumber, Cucumariafrondosa. Frondoside A has a broad spectrum of anti-cancer effects, including induction of cellular apoptosis, inhibition of cancer cell growth, migration, invasion, formation of metastases, and angiogenesis. In cell lines and animal models studied to date, the anti-cancer effects of the compound are seen in all solid cancers, lymphomas, and leukemias studied to date. These effects appear to be due to potent inhibition of p21-activated kinase 1 (PAK1), which is up-regulated in many cancers. In mouse models, frondoside A has synergistic effects with conventional chemotherapeutic agents, such as gemcitabine, paclitaxel, and cisplatin. Frondoside A administration is well-tolerated. No side effects have been reported and the compound has no significant effects on body weight, blood cells, or on hepatic and renal function tests after long-term administration. Frondoside A may be valuable in the treatment of malignancies, either as a single agent or in combination with other therapeutic modalities.

The Oxepane Motif in Marine Drugs

Oceans have shown to be a remarkable source of natural products. The biological properties of many of these compounds have helped to produce great advances in medicinal chemistry. Within them, marine natural products containing an oxepanyl ring are present in a great variety of algae, sponges, fungus and corals and show very important biological activities, many of them possessing remarkable cytotoxic properties against a wide range of cancer cell lines. Their rich chemical structures have attracted the attention of many researchers who have reported interesting synthetic approaches to these targets. This review covers the most prominent examples of these types of compounds, focusing the discussion on the isolation, structure determination, medicinal properties and total synthesis of these products.

Frondoside A potentiates the effects of conventional therapeutic agents in acute leukemia

Acute leukemia is the major cause of mortality in hematological malignancies. Despite improvement of survival with current chemotherapies, patients die from the disease or side-effects of treatment. Thus, new therapeutic agents are needed. Frondoside A is a triterpenoid glycoside originally isolated from the sea cucumber, Cucumaria frondosa that has potent antitumor effects in various cancers. The current study investigated the effects of frondoside A in acute leukemia cell lines alone and in combination with drugs used for this malignancy. This study is the first comparing the efficacy of frondoside A to available conventional drugs. The acute leukemia cell lines used were CCRF-CEM, HL-60 and THP-1. Cells were cultured and treated with different concentrations of vincristine sulphate, asparaginase and prednisolone alone and in combination with frondoside A. The inhibitory concentration 50 (IC₅₀) for each compound was determined for the cell lines. CCRF-CEM cells were very sensitive to frondoside A treatment while HL-60 and THP1 were less sensitive. Frondoside A markedly enhanced the anticancer effects of all of the conventional drugs. Synergistic effects were seen with most of the combinations. Frondoside A may be valuable in the treatment of acute leukemia, particularly when used in combination with current therapeutic drugs.

Mechanisms of cancer cell killing by sea cucumber-derived compounds

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

Triterpenoids

Covering: 2013. Previous review: Nat. Prod. Rep., 2015, 29, 1028-1065This review covers the isolation and structure determination of triterpenoids reported during 2013 including squalene derivatives, lanostanes, holostanes, cycloartanes, cucurbitanes, dammaranes, euphanes, tirucallanes, tetranortriterpenoids, quassinoids, lupanes, oleananes, friedelanes, ursanes, hopanes, serratanes, isomalabaricanes and saponins; 350 references are cited.

Two rare antioxidant and anti-inflammatory oleanenes from loop root Asiatic mangrove Rhizophora mucronata

Two oleanenes, olean-18(19)-en-3β-yl-(3,6-dimethyl-3E,6Z-dienoate) and (13α)-27-frido-olean-14(15)-en-(17α)-furanyl-3β-ol representing a class of rare natural pentacyclic triterpenoids were isolated from the chloroform extract of Asiatic mangrove, Rhizophora mucronata Lam. (Family: Rhizophoraceae). The furanyl oleanene exhibited significantly greater antioxidative activities (IC₅₀ 0.73-0.76 mg/mL), than prenylated oleanene (IC₅₀ 0.84-0.96 mg/mL) (P < 0.05). No significant differences in anti-5-lipoxygenase activities of these compounds with the synthetic drug ibuprofen was discernable (IC₅₀ 0.8-0.9 mg/mL), whilst furanyl oleanene demonstrated significantly greater anti-cyclooxygenase-2 (IC₅₀ 0.84 mg/mL) and anti-5-lipoxygenase activities (IC₅₀ 0.78 mg/mL) over prenylated oleanene (IC₅₀ > 0.90 mg/mL). These compounds exhibited lesser activity against cyclooxygenase-1 than cyclooxygenase-2 isoform, and therefore, their selectivity indices remained significantly greater (anti-cyclooxygenase-1_IC50/anti-cyclooxygenase-2_IC50 > 1) than the aspirin (0.02) and ibuprofen (0.44). The lipophilic and steric molecular descriptors were found to occupy a prominent role in determining the bioactivities of the compounds. These previously undescribed oleanenes might serve as potential antioxidative and anti-inflammatory lead molecules in medicinal formulations and food industries.

Anticancer Effects of the Marine Sponge Lipastrotethya sp. Extract on Wild-Type and p53 Knockout HCT116 Cells

Interest in marine bioresources is increasing in the drug development sector. In particular, marine sponges produce a wide range of unique metabolites that enable them to survive in challenging environments, which makes them attractive sources of candidate pharmaceuticals. In previous study, we investigated over 40 marine specimens collected in Micronesia and provided by the Korean Institute of Ocean Science and Technology, for their antiproliferative effects on various cancer cell lines, and Lipastrotethya sp. extract (LSSE) was found to have a marked antiproliferative effect. In the present study, we investigated the mechanism responsible for its anticancer effect on wild-type p53 (WT) or p53 knockout (KO) HCT116 cells. LSSE inhibited cell viability and induced apoptotic cell death more so in HCT116 p53 KO cells than the WT. HCT116 WT cells treated with LSSE underwent apoptosis associated with the induction of p53 and its target genes. On the other hand, in HCT116 p53 KO cells, LSSE reduced mTOR and Bcl-2 and increased Beclin-1 and LC3-II protein levels, suggesting autophagy induction. These results indicate that the mechanisms responsible for the anticancer effect of LSSE depend on p53 status.

Cloning and Functional Characterization of Cycloartenol Synthase from the Red Seaweed Laurencia dendroidea

The red seaweed Laurencia dendroidea belongs to the Rhodophyta, a phylum of eukaryotic algae that is widely distributed across the oceans and that constitute an important source of bioactive specialized metabolites. Laurencia species have been studied since 1950 and were found to contain a plethora of specialized metabolites, mainly halogenated sesquiterpenes, diterpenes and triterpenes that possess a broad spectrum of pharmacological and ecological activities. The first committed step in the biosynthesis of triterpenes is the cyclization of 2,3-oxidosqualene, an enzymatic reaction carried out by oxidosqualene cyclases (OSCs), giving rise to a broad range of different compounds, such as the sterol precursors cycloartenol and lanosterol, or triterpene precursors such as cucurbitadienol and β-amyrin. Here, we cloned and characterized the first OSC from a red seaweed. The OSC gene was identified through mining of a L. dendroidea transcriptome dataset and subsequently cloned and heterologously expressed in yeast for functional characterization, which indicated that the corresponding enzyme cyclizes 2,3-oxidosqualene to the sterol precursor cycloartenol. Accordingly, the gene was named L. dendroidea cycloartenol synthase (LdCAS). A phylogenetic analysis using OSCs genes from plants, fungi and algae revealed that LdCAS grouped together with OSCs from other red algae, suggesting that cycloartenol could be the common product of the OSC in red seaweeds. Furthermore, profiling of L. dendroidea revealed cholesterol as the major sterol accumulating in this species, implicating red seaweeds contain a ‘hybrid’ sterol synthesis pathway in which the phytosterol precursor cycloartenol is converted into the major animal sterol cholesterol.

The Cytotoxicity of Dacarbazine Potentiated by Sea Cucumber Saponin in Resistant B16F10 Melanoma Cells through Apoptosis Induction

BACKGROUND

Malignant melanoma is a highly aggressive malignant melanocytic neoplasm which resists against the most conventional therapies. Sea cucumber as one of marine organisms contains bioactive compounds such as polysaccharide, terpenoid and other metabolites which have anti-cancer, anti-tumor, anti-inflammatory and antioxidant properties. The present study was designed to investigate the anticancer potential of saponin extracted from sea cucumber Holothuria leucospilata alone and in combination with dacarbazine on B16F10 melanoma cell line.

METHODS

The B16F10 cell line was treated with different concentrations of saponin (0, 4, 8, 12, 16, 20 μg/ml), dacarbazine (0, 1200, 1400, 1600, 18000, 1200, 1400, 1600, 2000 μg/ml) and co-administration of saponin-dacarbazine (1200 da+8 sp, 1200 da+4 sp) for 24 and 48 hr and the cytotoxic effect was examined by MTT, DAPI, acridine orange/propodium iodide, flow cytometry and caspase colorimetric assay.

RESULTS

The results exhibited that sea cucumber saponin, dacarbazine, and co-administration of saponin-dacarbazine inhibited the proliferation of melanoma cells in a dose and time dependent manner with IC50 values of 10, 1400 and 4+1200 μg/ml, respectively. Morphological observation of DAPI and acridine orange/propodium iodide staining documented typical characteristics of apoptotic cell death. Flow cytometry assay indicated accumulation of IC50 treated cells in sub-G1 peak. Additionally, saponin extracted induced intrinsic apoptosis via up-regulation of caspase-3 and caspase-9.

CONCLUSION

These results revealed that the saponin extracted from sea cucumber as a natural anti-cancer compound may be a new treatment modality for metastatic melanoma and the application of sea cucumber saponin in combination with dacarbazine demonstrated the strongest anti-cancer activity as compared with the drug alone.

Effect of Holothuria leucospilota extracted saponin on maturation of mice oocyte and granulosa cells

Sea cucumbers saponins are triterpenoid glycosides which exert beneficial biomedical effects. This study was performed to assess the effect of saponin extracted from sea cucumber Holothuria leucospilota (H. leucospilota) on maturation of mice oocytes and granulosa cells. The germinal vesicles oocytes were collected from 6-8 weeks old Naval Medical Research Institute (NMRI) mice ovaries, randomly divided into untreated and four experimental groups and cultured In vitro. Maturation medium was supplemented with 0, 1, 2, 4 and 8 μg/ml saponin for 12 days. The rates of maturation were recorded through morphological observation by measurement of follicle diameter during treatment. After 4 days, the effects of saponin on granulosa cells were investigated by reactive oxygen species (ROS) measurement, super oxide dismutase (SOD) activity, caspase assay and tumor necrosis factor-alpha (TNF-α) expression. The oocyte maturation rate was significantly higher in treated groups (1 μg/ml). The ROS and SOD assays demonstrated the antioxidant potential of saponin. The caspase assay exhibited that optimum concentrations of saponin (1, 2 μg/ml) reduced caspase activity in granulosa cells. Flow cytometry showed that optimum concentration of saponin promoted oocyte maturation via down regulation of TNF-α as follicular degenerative factor in nursing cells. These results proposed that maturation rate were obtained after the incorporation of 1 μg/ml sea cucumber saponin. Moreover, the extracted saponin at concentrations of 1, 2 μg/ml enhanced follicle growth which is accompanied by attenuating ROS formation, elevating SOD activity and reducing TNF-α expression in granulosa cells. But, further examinations are required to understand precise mechanisms of saponin action on oocyte and granulosa cells.

Marine natural products

This review covers the literature published in 2013 for marine natural products (MNPs), with 982 citations (644 for the period January to December 2013) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1163 for 2013), together with the relevant biological activities, source organisms and country of origin. Reviews, biosynthetic studies, first syntheses, and syntheses that lead to the revision of structures or stereochemistries, have been included.

Mangrove dolabrane-type of diterpenes tagalsins suppresses tumor growth via ROS-mediated apoptosis and ATM/ATR-Chk1/Chk2-regulated cell cycle arrest

Natural compounds are an important source for drug development. With an increasing cancer rate worldwide there is an urgent quest for new anti‐cancer drugs. In this study, we show that a group of dolabrane‐type of diterpenes, collectively named tagalsins, isolated from the Chinese mangrove genus Ceriops has potent cytotoxicity on a panel of hematologic cancer cells. Investigation of the molecular mechanisms by which tagalsins kill malignant cells revealed that it induces a ROS‐mediated damage of DNA. This event leads to apoptosis induction and blockage of cell cycle progression at S‐G2 phase via activation of the ATM/ATR—Chk1/Chk2 check point pathway. We further show that tagalsins suppress growth of human T‐cell leukemia xenografts in vivo. Tagalsins show only minor toxicity on healthy cells and are well tolerated by mice. Our study shows a therapeutic potential of tagalsins for the treatment of hematologic malignancies and a new source of anticancer drugs.

What's new?

Mangroves of genus Ceriops, widespread and highly utilized in China, are of growing interest in anticancer drug development due to their production of potentially cytotoxic diterpenoids and triterpenoids. Here, a group dolabrane‐type diterpenes known as tagalsins isolated from the species C. tagal are shown to possess potent killing effects on cancer cells of hematologic origin. Cell death was associated with the production of reactive oxygen species and DNA damage. In vivo, tagalsins significantly delayed the development of human T‐cell leukemia in a murine xenograft model.

Alternative and efficient extraction methods for marine-derived compounds

Marine ecosystems cover more than 70% of the globe’s surface. These habitats are occupied by a great diversity of marine organisms that produce highly structural diverse metabolites as a defense mechanism. In the last decades, these metabolites have been extracted and isolated in order to test them in different bioassays and assess their potential to fight human diseases. Since traditional extraction techniques are both solvent- and time-consuming, this review emphasizes alternative extraction techniques, such as supercritical fluid extraction, pressurized solvent extraction, microwave-assisted extraction, ultrasound-assisted extraction, pulsed electric field-assisted extraction, enzyme-assisted extraction, and extraction with switchable solvents and ionic liquids, applied in the search for marine compounds. Only studies published in the 21st century are considered.

Systems pharmacology-based drug discovery for marine resources: an example using sea cucumber (Holothurians)

ETHNOPHARMACOLOGICAL RELEVANCE

Sea cucumber, a kind of marine animal, have long been utilized as tonic and traditional remedies in the Middle East and Asia because of its effectiveness against hypertension, asthma, rheumatism, cuts and burns, impotence, and constipation. In this study, an overall study performed on sea cucumber was used as an example to show drug discovery from marine resource by using systems pharmacology model. The value of marine natural resources has been extensively considered because these resources can be potentially used to treat and prevent human diseases. However, the discovery of drugs from oceans is difficult, because of complex environments in terms of composition and active mechanisms. Thus, a comprehensive systems approach which could discover active constituents and their targets from marine resource, understand the biological basis for their pharmacological properties is necessary.

MATERIALS AND METHODS

In this study, a feasible pharmacological model based on systems pharmacology was established to investigate marine medicine by incorporating active compound screening, target identification, and network and pathway analysis.

RESULTS

As a result, 106 candidate components of sea cucumber and 26 potential targets were identified. Furthermore, the functions of sea cucumber in health improvement and disease treatment were elucidated in a holistic way based on the established compound-target and target-disease networks, and incorporated pathways.

CONCLUSIONS

This study established a novel strategy that could be used to explore specific active mechanisms and discover new drugs from marine sources.

Antitumor and antimicrobial potential of bromoditerpenes isolated from the red alga, Sphaerococcus coronopifolius

Cancer and infectious diseases continue to be a major public health problem, and new drugs are necessary. As marine organisms are well known to provide a wide range of original compounds, the aim of this study was to investigate the bioactivity of the main constituents of the cosmopolitan red alga, Sphaerococcus coronopifolius. The structure of several bromoditerpenes was determined by extensive spectroscopic analysis and comparison with literature data. Five molecules were isolated and characterized which include a new brominated diterpene belonging to the rare dactylomelane family and named sphaerodactylomelol (1), along with four already known sphaerane bromoditerpenes (2-5). Antitumor activity was assessed by cytotoxicity and anti-proliferative assays on an in vitro model of human hepatocellular carcinoma (HepG-2 cells). Antimicrobial activity was evaluated against four pathogenic microorganisms: Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Candida albicans. Compound 4 exhibited the highest antimicrobial activity against S. aureus (IC50 6.35 µM) and compound 5 the highest anti-proliferative activity on HepG-2 cells (IC50 42.9 µM). The new diterpene, sphaerodactylomelol (1), induced inhibition of cell proliferation (IC50 280 µM) and cytotoxicity (IC50 720 µM) on HepG-2 cells and showed antimicrobial activity against S. aureus (IC50 96.3 µM).

Hemolytic and cytotoxic properties of saponin purified from Holothuria leucospilota sea cucumber

BACKGROUND

Holothuroids (sea cucumbers) are members of the phylum echinodermata, which produce saponins. Saponins exhibit a wide spectrum of pharmacological and biological activities. In this study, we isolated the crude saponins from the body wall of the dominant Iranian species of sea cucumber, Holothuria leucospilota (H. leucospilota). The purpose of this study was to confirm the presence of saponins in the Persian Gulf H. leucospilota and study the hemolytic and cytotoxic activities of these compounds.

METHODS

The body wall of sea cucumber was dried and powdered and the crude saponins were isolated using various solvents. The crude saponins were further purified by column chromatography using HP-20 resin. The foam test, Thin Layer Chromatography (TLC), hemolytic assay, and Fourier Transform Infrared Spectroscopy (FTIR) confirmed the presence of saponins. Cytotoxicity was analyzed using a 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay on A549 cells, a human lung cancer cell line.

RESULTS

The foam test, hemolytic assay, and TLC supported the presence of saponin compounds in the 80% ethanol fraction of H. leucospilota. The infrared (IR) spectrum of the extract showed hydroxyl (-OH), alkyl (C-H), ether (C-O) and ester (-C=O) absorption characteristic of teriterpenoid saponins. The C-O-C absorption indicated glycoside linkages to the sapogenins. The crude saponin extracted from sea cucumber was cytotoxic to A549 cells.

CONCLUSION

The 80% ethanol fraction of saponin isolated from H. leucospilota exhibited hemolytic activity and offers promise as an anti-cancer candidate.

Advances in Preventive Therapy for Estrogen-Receptor-Negative Breast Cancer

Preventing breast cancer is an effective strategy for reducing breast cancer deaths. The purpose of chemoprevention (also termed preventive therapy) is to reduce cancer incidence by use of natural, synthetic, or biological agents. The efficacy of tamoxifen, raloxifene, and exemestane as preventive therapy against estrogen-receptor (ER)-positive breast cancer is well established for women at increased risk for breast cancer. However, because breast cancer is a heterogeneous disease, distinct preventive approaches may be required for effective prevention of each subtype. Current research is, therefore, focused on identifying alternative mechanisms by which biologically active compounds can reduce the risk of all breast cancer subtypes including ER-negative breast cancer. Promising agents are currently being developed for prevention of HER2-positive and triple-negative breast cancer (TNBC) and include inhibitors of the ErbB family receptors, COX-2 inhibitors, metformin, retinoids, statins, poly(ADP-ribose) polymerase inhibitors, and natural compounds. This review focuses on recent progress in research to develop more effective preventive agents, in particular for prevention of ER-negative breast cancer.

Multifunctional pentacyclic triterpenoids as adjuvants in cancer chemotherapy: a review

The protective adjuvants in chemotherapy.