Rare Ophiuroid-Type Steroid 3β,21-, 3β,22-, and 3α,22-Disulfates from the Slime Sea Star Pteraster marsippus and Their Colony-Inhibiting Effects against Human Breast Cancer Cells

Two new steroid 3β,21-disulfates (1, 2) and two new steroid 3β,22- and 3α,22-disulfates (3, 4), along with the previously known monoamine alkaloid tryptamine (5) were found in the ethanolic extract of the Far Eastern slime sea star Pteraster marsippus. Their structures were determined on the basis of detailed analysis of one-dimensional and two-dimensional NMR, HRESIMS, and HRESIMS/MS data. Compounds 1 and 2 have a Δ22-21-sulfoxy-24-norcholestane side chain. Compounds 3 and 4 contain a Δ24(28)-22-sulfoxy-24-methylcholestane side chain, which was first discovered in the polar steroids of starfish and brittle stars. The influence of substances 1-4 on cell viability, colony formation, and growth of human breast cancer T-47D, MCF-7, and MDA-MB-231 cells was investigated. It was shown that compounds 1 and 2 possess significant colony-inhibiting activity against T-47D cells, while compounds 3 and 4 were more effective against MDA-MB-231 cells.

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.

Cell-cycle arrest and mitochondria-dependent apoptosis induction in T-47D cells by the capsular polysaccharide from the marine bacterium Kangiella japonica KMM 3897

In this study, we reported the in vitro mechanisms of antiproliferative activity of capsular polysaccharide derived from marine Gram-negative bacteria Kangiella japonica KMM 3897 in human breast сarcinoma T-47D cells. Flow cytometric and Western blot analysis revealed that capsular polysaccharide effectively suppressed T-47D cell proliferation by inducing G0/G1 phase arrest and mitochondrial-dependent apoptosis. Moreover, polysaccharide influenced the ERK1/2 and p38 signaling pathways. The results of this study would enrich our understanding of the molecular mechanism of the anti-cancer activity of sulfated polysaccharides from marine Gram-negative bacteria.

Anthraquinone Derivatives and Other Aromatic Compounds from Marine Fungus Asteromyces cruciatus KMM 4696 and Their Effects against Staphylococcus aureus

New anthraquinone derivatives acruciquinones A-C (1-3), together with ten known metabolites, were isolated from the obligate marine fungus Asteromyces cruciatus KMM 4696. Acruciquinone C is the first member of anthraquinone derivatives with a 6/6/5 backbone. The structures of isolated compounds were established based on NMR and MS data. The absolute stereoconfigurations of new acruciquinones A-C were determined using ECD and quantum chemical calculations (TDDFT approach). A plausible biosynthetic pathway of the novel acruciquinone C was proposed. Compounds 1-4 and 6-13 showed a significant antimicrobial effects against Staphylococcus aureus growth, and acruciquinone A (1), dendryol B (4), coniothyrinone B (7), and ω-hydroxypachybasin (9) reduced the activity of a key staphylococcal enzyme, sortase A. Moreover, the compounds, excluding 4, inhibited urease activity. We studied the effects of anthraquinones 1, 4, 7, and 9 and coniothyrinone D (6) in an in vitro model of skin infection when HaCaT keratinocytes were cocultivated with S. aureus. Anthraquinones significantly reduce the negative impact of S. aureus on the viability, migration, and proliferation of infected HaCaT keratinocytes, and acruciquinone A (1) revealed the most pronounced effect.

Phytoceramides from the Marine Sponge Monanchora clathrata: Structural Analysis and Cytoprotective Effects

In our research on sphingolipids from marine invertebrates, a mixture of phytoceramides was isolated from the sponge Monanchora clathrata (Western Australia). Total ceramide, ceramide molecular species (obtained by RP-HPLC, high-performance liquid chromatography on reversed-phase column) and their sphingoid/fatty acid components were analyzed by NMR (nuclear magnetic resonance) spectroscopy and mass spectrometry. Sixteen new (1b, 3a, 3c, 3d, 3f, 3g, 5c, 5d, 5f, 5g, 6b-g) and twelve known (2b, 2e, 2f, 3b, 3e, 4a-c, 4e, 4f, 5b, 5e) compounds were shown to contain phytosphingosine-type backbones i-t17:0 (1), n-t17:0 (2), i-t18:0 (3), n-t18:0 (4), i-t19:0 (5), or ai-t19:0 (6), N-acylated with saturated (2R)-2-hydroxy C21 (a), C22 (b), C23 (c), i-C23 (d), C24 (e), C25 (f), or C26 (g) acids. The used combination of the instrumental and chemical methods permitted the more detailed investigation of the sponge ceramides than previously reported. It was found that the cytotoxic effect of crambescidin 359 (alkaloid from M. clathrata) and cisplatin decreased after pre-incubation of MDA-MB-231 and HL-60 cells with the investigated phytoceramides. In an in vitro paraquat model of Parkinson's disease, the phytoceramides decreased the neurodegenerative effect and ROS (reactive oxygen species) formation induced by paraquat in neuroblastoma cells. In general, the preliminary treatment (for 24 or 48 h) of the cells with the phytoceramides of M. clathrata was necessary for their cytoprotective functions, otherwise the additive damaging effect of these sphingolipids and cytotoxic compounds (crambescidin 359, cisplatin or paraquat) was observed.

Biological Activity and Probable Mechanisms of Action of Derivatives of Tryptanthrin and Mostotrin Alkaloids

The alkaloid tryptanthrin and its water-soluble derivative mostotrin exhibit high antimicrobial and antitumor activity. To develop more active and less toxic preparations, syntheses and testing of the biological activities of a number of new and/or little-studied analogs were performed. Some of them have been shown to have higher cytotoxicity against tumor and microbial cells than tryptanthrin and mostotrin. Thus, 8-fluorotryptanthrin effectively inhibits the proliferation of various tumor cell lines, namely: K-562/4, HCT-116 and HCT-116p53ko at lower concentrations than tryptanthrin, and 2,8-difluorostotrin exhibits a stronger antimicrobial effect against pathogenic bacteria S. aureus ATCC 29213 than mostotrin. It has been established that the antiproliferative properties of 8-fluorotryptanthrin and 8-fluoromostotrin are associated with their ability in nanomolar concentrations to inhibit the cell cycle of tumor cells at the stage of transition from the G₁ phase to the S phase. The data obtained indicate the prospects for further in-depth studies of their antitumor properties.

New Ceramides and Cerebrosides from the Deep-Sea Far Eastern Starfish Ceramaster patagonicus

Three new ceramides (1−3) and three new cerebrosides (4, 8, and 9), along with three previously known cerebrosides (ophidiocerebrosides C (5), D (6), and CE-3-2 (7)), were isolated from a deep-sea starfish species, the orange cookie starfish Ceramaster patagonicus. The structures of 1−4, 8, and 9 were determined by the NMR and ESIMS techniques and also through chemical transformations. Ceramides 1−3 contain iso-C21 or C23 Δ9-phytosphingosine as a long-chain base and have C16 or C17 (2R)-2-hydroxy-fatty acids of the normal type. Cerebroside 4 contains C22 Δ9-sphingosine anteiso-type as a long-chain base and (2R)-2-hydroxyheptadecanoic acid of the normal type, while compounds 8 and 9 contain saturated C-17 phytosphingosine anteiso-type as a long-chain base and differ from each other in the length of the polymethylene chain of (2R)-2-hydroxy-fatty acids of the normal type: C23 in 8 and C24 in 9. All the new cerebrosides (4, 8, and 9) have β-D-glucopyranose as a monosaccharide residue. The composition of neutral sphingolipids from C. patagonicus was described for the first time. The investigated compounds 1−3, 5−7, and 9 exhibit slight to moderate cytotoxic activity against human cancer cells (HT-29, SK-MEL-28, and MDA-MB-231) and normal embryonic kidney cells HEK293. Compounds 2, 5, and 6 at a concentration of 20 µM inhibit colony formation of MDA-MB-231 cells by 68%, 54%, and 68%, respectively. The colony-inhibiting activity of compounds 2, 5, and 6 is comparable to the effect of doxorubicin, which reduces the number of colonies by 70% at the same concentration.

Structure and in vitro antiproliferative activity of the acidic capsular polysaccharide from the deep-sea bacterium Psychrobacter submarinus KMM 225T

Psychrobacter submarinus KMM 225^T is a Gram-negative bacterium isolated from a sea-water sample collected at a depth of 300 m in the Northwest Pacific Ocean. Here we report the structure of the capsular polysaccharide from P. submarinus KMM 225^T and its effect on the viability and colony formation of cancer cells. The glycopolymer was purified by ultracentrifugation and chromatography methods, and the structure was elucidated using NMR spectroscopy and composition analyses. The following structure of the acidic capsular polysaccharide, containing 2-acetamido-2,4,6-trideoxy-4-[(S)-3-hydroxybutyramido]-d-glucose [d-QuipNAc4N(S-Hb)] and 4,6-O-[(S)-1-carboxyethylidene]-2-acetamido-2-deoxy-d-glucose [d-GlcpNAc4,6(S-Pyr)] was established: The capsular polysaccharide slightly reduced the viability but effectively suppressed the colony formation of different types of cancer cells, of which the most pronounced inhibition was shown for the human chronic myelogenous leukemia K-562 cells.

Melonoside B and Melonosins A and B, Lipids Containing Multifunctionalized ω-Hydroxy Fatty Acid Amides from the Far Eastern Marine Sponge Melonanchora kobjakovae

Melonoside B (1) and melonosins B (2) and A (3), new lipids based on polyoxygenated fatty acid amides, and known melonoside A (4) were isolated from two different collections of the marine sponge Melonanchora kobjakovae. The structures of these compounds, including their absolute configurations, were established using detailed analysis of 1D and 2D NMR, ECD, and mass spectra as well as chemical transformations. Melonosins 2 and 3 inhibit AP-1- and NF-kB-dependent transcriptional activities in JB6 Cl41 cells at noncytotoxic concentrations, demonstrating potential cancer preventive activity.

Furostane Series Asterosaponins and Other Unusual Steroid Oligoglycosides from the Tropical Starfish Pentaceraster regulus

Seven new asterosaponins, pentaregulosides A-G (1-7), including two furostane-type steroid oligoglycosides (2, 3), along with four previously known compounds (8-11) were isolated from the ethanolic extract of the starfish Pentaceraster regulus, collected off the coast of Vietnam. The structures of 1-7 were elucidated by extensive NMR and ESIMS techniques as well as chemical transformations. The aglycons of compounds 1 and 3 have not previously been observed in starfish steroid oligoglycosides, while the aglycons of compounds 2 and 4-6 are very rare for this structural group. Compound 1 exhibited cytotoxic activity with an IC₅₀ value of 6.4 ± 0.3 μM against RAW 264.7 murine macrophages. In contrast, nontoxic asterosaponins 3, 4, and 5 showed a potential immunomodulatory action at a concentration of 5 μM, reducing by 40%, 28%, and 55%, respectively, reactive oxygen species formation in the RAW 264.7 cells, co-stimulated with the pro-inflammatory endotoxic lipopolysaccharide from E. coli.

In vitroAnticancer Activities of Some Triterpene Glycosides from Holothurians of Cucumariidae, Stichopodidae, Psolidae, Holothuriidae and Synaptidae families

Triterpene glycosides isolated from holothurians are natural products known to possess cytotoxic properties against cancer cells. However, their anticancer prophylactic activity has not been studied sufficiently. The anticancer prophylactic, cytotoxic, and pro-apoptotic properties of 18 triterpene glycosides, as well as their effects on the transcriptional activities of activator protein-1 (AP-1) and nuclear factor-κB (NF-κB), were examined using methods that included EGF-induced JB6 Cl41 P+ cell transforation in soft agar, flow cytometry, MTS assessment of cell viability, and a luciferase activity assay. The compounds inhibited EGF-induced neoplastic JB6 Cl41 P+ cell transforation in soft agar and caused apoptosis and necrosis of human HL-60 and THP-1 leukemia cells. AP-1 and NF-κB were involved in the cellular response to the treatment by the compounds. Conclusion: glycosides isolated from holothurians of Cucumariidae, Stichopodidae, Psolidae, Holothuriidae and Synaptidae families have potential for development as new antitumor agents and as instruments to study AP-1 and NF-κB.

In vitro Anticancer Activities of Some Triterpene Glycosides from Holothurians of Cucumariidae, Stichopodidae, Psolidae, Holothuriidae and Synaptidae families

Triterpene glycosides isolated from holothurians are natural products known to possess cytotoxic properties against cancer cells. However, their anticancer prophylactic activity has not been studied sufficiently. The anticancer prophylactic; cytotoxic, and pro-apoptotic properties of 18 triterpene glycosides, as well as their effects on the transcriptional activities of activator protein-I (AP-1) and nuclear factor-KB (NF-KB), were examined using methods that included EGF-induced JB6 C141 P' cell transformation in soft agar, flow cytometry, MTS assessment of cell viability, and a luciferase activity assay. The compounds inhibited EGF-induced neoplastic JB6 C141 P' cell transformation in soft agar and caused apoptosis and necrosis of human HL-60 and THP-I leukemia cells. AP- and NF-KB were involved in the cellular response to the treatment by the compounds. Conclusion: glycosides isolated from holothurians of Cucumariidae, Stichopodidae, Psolidae, Holothuriidae and Synaptidae families have potential for development as new antitumor agents and as instruments to study AP-I and NF-kB.

Monanchocidins B-E: polycyclic guanidine alkaloids with potent antileukemic activities from the sponge Monanchora pulchra

New unusual polycyclic guanidine alkaloids monanchocidins B-E (2-5) along with monanchocidin A (1), which we recently described, were isolated from the Far-Eastern marine sponge Monanchora pulchra. Their structures were established using spectroscopic data and chemical transformations. Compounds 1-5 show potent cytotoxic activities against HL-60 human leukemia cells with IC50 values of 540, 200, 110, 830, and 650 nM, respectively.

Cancer-preventive activities of secondary metabolites from leaves of the bilberry Vaccinium smallii A. Gray

Ten secondary metabolites including flavonoids (1-8), caffeic (9) and chlorogenic (10) acids were structurally identified from the extract of Sakhalin bilberry Vaccinium smallii leaves and studied in vitro as potential cancer-preventive agents. The results showed that compounds 1-10 inhibited EGF-induced neoplastic transformation of mouse JB6 Cl 41 P+ cells in soft agar with an inhibition concentration (INCC50) of 20-80 µm. Moreover, all these natural products were non-toxic against JB6 Cl 41 P+ cells up to a concentration of 200 µm.

Monanchocidin: a new apoptosis-inducing polycyclic guanidine alkaloid from the marine sponge Monanchora pulchra

Monanchocidin (1), a guanidine alkaloid with an unprecedented skeleton system derived from a polyketide precursor, (ω-3)-hydroxy fatty acid, and containing a 2-aminoethyl- and 3-aminopropyl-substituted morpholine hemiketal ring, has been isolated from the sponge Monanhora pulchra. The structure of 1 was assigned on the basis of detailed analysis of 1D and 2D NMR spectra, mass spectrometry, and results of chemical transformations. Compound 1 shows pro-apoptotic and cytoxic activities.

The anticancer activity of 3- and 10-bromofascaplysins is mediated by caspase-8, -9, -3-dependent apoptosis

3- and 10-Bromofascaplysins was previously found to possess cytotoxic activity. In this study, we investigated their cancer preventive and proapoptotic properties. These effects were tested on mouse skin epidermal JB6 P(+) Cl41 cell line, its stable transfectants, and human tumor HL-60, THP-1, SNU-C4, SK-MEL-28, DLD-1, MDA-MB-231, and HeLa cells using a variety of assessments, including a cell viability (MTS) assay, flow cytometry, anchorage-independent soft agar assay, luciferase assay, mitochondrial permeability assay, and Western blotting. 3- and 10-Bromofascaplysins were effective at submicromolar concentrations as the anticancer agents, which exerted their action, at least in part, through the induction of caspase-8, -9, -3-dependent apoptosis.