Anti-proliferative activity of meroditerpenoids isolated from the brown alga Stypopodium flabelliforme against several cancer cell lines

The sea constitutes one of the most promising sources of novel compounds with potential application in human therapeutics. In particular, algae have proved to be an interesting source of new bioactive compounds. In this work, six meroditerpenoids (epitaondiol, epitaondiol diacetate, epitaondiol monoacetate, stypotriol triacetate, 14-ketostypodiol diacetate and stypodiol) isolated from the brown alga Stypopodium flabelliforme were tested for their cell proliferation inhibitory activity in five cell lines. Cell lines tested included human colon adenocarcinoma (Caco-2), human neuroblastoma (SH-SY5Y), rat basophilic leukemia (RBL-2H3), murine macrophages (RAW.267) and Chinese hamster fibroblasts (V79). Antimicrobial activity of the compounds was also evaluated against Staphylococcus aureus, Salmonella typhimurium, Proteus mirabilis, Bacillus cereus, Enterococcus faecalis and Micrococcus luteus. Overall, the compounds showed good activity against all cell lines, with SH-SY5Y and RAW.267 being the most susceptible. Antimicrobial capacity was observed for epitaondiol monoacetate, stypotriol triacetate and stypodiol, with the first being the most active. The results suggest that these molecules deserve further studies in order to evaluate their potential as therapeutic agents.     

Sphingosines Derived from Marine Sponge as Potential Multi-Target Drug Related to Disorders in Cancer Development

Haliclona tubifera, marine sponge species abundant in Brazilian coastline, presents only a few papers published in the literature. Recently, we have reported the isolation of two modified C18 sphingoid bases: (2R,3R,6R,7Z)-2-aminooctadec-7-ene-1,3,6-triol and and (2R,3R,6R)-2-aminooctadec-1,3,6-triol. In order to continue our research, in this work aimed at the biological investigation of fractions that led to the isolation of these compounds. We evaluated the cytotoxic effect of marine sponge H. tubifera fractions in glioma (U87) and neuroblastoma (SH-SY5Y) human cell lines. In addition, considering the link between cancer, imbalance of reactive oxygen species and coagulation disorders, we also investigated the in vitro effects on blood coagulation and their redox properties. We showed that the ethyl acetate (EtOAc) fraction, rich in sphingoid bases, had important cytotoxic effects in both cancer cell lines with an IC₅₀ < 15 μg/mL and also can inhibit the production of peroxyl radicals. Interestingly, this fraction increased the recalcification time of human blood, showing anticoagulant properties. The present study indicates the sphingosines fraction as a promising source of chemical prototypes, especially multifunctional drugs in cancer therapy.     

Antifungal activity evaluation of the constituents of Haliclona baeri and Haliclona cymaeformis, collected from the Gulf of Thailand

A new compound maleimide-5-oxime was isolated, together with 3,4-dihydroxybenzoic acid, tetillapyrone, from the ethyl acetate extract of the marine sponge Haliclona baeri while tetillapyrone, nortetillapyrone, p-hydroxybenzaldehyde and phenylacetic acid were isolated from the ethyl acetate extract of Haliclona cymaeformis, collected from the Gulf of Thailand. The structures of tetillapyrone and nortetillapyrone were re-examined using HMBC correlations. Maleimide-5-oxime, tetillapyrone and nortetillapyrone were found to be inactive against three human tumor cell lines (the estrogen-dependent ER(+) MCF-7, the estrogen-independent ER(−) MDA-MB-231 and NCI-H460. Maleimide-5-oxime, p-hydroxybenzaldehyde, phenylacetic acid, tetillapyrone and nortetillapyrone were evaluated for their growth inhibitory effect against seven yeasts and eight filamentous fungi. Only nortetillapyrone showed antifungal activity, with a preponderance on the dermatophytic filamentous fungi.     

A new diketopiperazine, cyclo-(4-S-hydroxy-R-proline-R-isoleucine), from an Australian specimen of the sponge Stelletta sp

While investigating the cytotoxic activity of the methanol extract of an Australian marine sponge Stelletta sp. (Demospongiae), a new diketopiperazine, cyclo-(4-S-hydroxy-R-proline-R-isoleucine) (1), was isolated together with the known bengamides; A (2), F (3), N (4), Y (5), and bengazoles; Z (6), C(4) (7) and C(6) (8). The isolation and structure elucidation of the diketopiperazine (1), together with the activity of 1-8 against a panel of human and mammalian cell lines are discussed.     

In Vitro Antitumor Activity of Stellettin B,a Triterpene from Marine Sponge Jaspis stellifera,on Human Glioblastoma Cancer SF295 Cells

Stellettin B was isolated from marine sponge Jaspis stellifera. In vitro antitumor activities were investigated on 39 human cancer cell lines. Stellettin B exhibited highly potent inhibition against the growth of a human glioblastoma cell line SF295, with a GI50 of 0.01 μM. In contrast, stellettin B showed very weak inhibitory activity on normal cell lines including HMEC, RPTEC, NHBE and PrEC, with GI50s higher than 10 μM, suggesting its relatively selective cytotoxicity against human cancer cells compared to normal human cell lines. We then focused on the antitumor activity of this compound on SF295 cells. Flow cytometric analysis indicated that stellettin B induced apoptosis in SF295 cells in a concentration-dependent manner. Further study indicated that stellettin B increased the production of ROS, the activity of caspase 3/7, as well as the cleavage of PARP, each of which is known to be involved in apoptosis. To investigate the molecular mechanism for cell proliferation inhibition and apoptosis induction, effect on the phosphorylation of several signal proteins of PI3K/Akt and RAS/MAPK pathways was examined. Stellettin B inhibited the phosphorylation of Akt potently, with no activity on p-ERK and p-p38, suggesting that inhibition of PI3K/Akt pathway might be involved in the antiproliferative and apoptosis-inducing effect. However, homogenous time-resolved fluorescence (HTRF) assay indicated that stellettin B did not inhibit PI3K activity, suggesting that the direct target might be signal protein upstream of Akt pathway other than PI3K.     

Anticancer activity evaluation of kuanoniamines A and C isolated from the marine sponge Oceanapia sagittaria, collected from the Gulf of Thailand

The pyridoacridine alkaloids kuanoniamines A and C were isolated together with 24 α-methylcholestanol, p-hydroxybenzaldehyde, p-hydroxybenzoic acid, phenylacetic acid and 3-formylindole from the ethyl acetate extract of the marine sponge Oceanapia sagittaria (Sollas), collected from the Gulf of Thailand. Kuanoniamines A and C were evaluated for their effect on the growth of five human tumour and a non-tumour cell lines, as well as on the proliferation of human lymphocytes. Kuanoniamine A was found to be a potent growth inhibitor of all the tumour and a non-tumour cell lines while kuanoniamine C was less potent but showed high selectivity toward the estrogen dependent (ER+) breast cancer cell line. Kuanoniamine A has shown to be a more potent inhibitor of DNA synthesis than kuanoniamine C. Kuanoniamine A was also found to cause an extensive reduction of the MCF-7 cells in G2/M phase as well as an increase in the apoptotic cells.     

Pachydictyols B and C: New Diterpenes from Dictyota dichotoma Hudson

Two new diterpenoids, pachydictyol B (1a/1b) and C (2), were isolated from the dichloromethane extract of the marine brown alga, Dictyota dichotoma, collected from the Red Sea coast of Egypt, along with the known metabolites, pachydictyol A (3a), dictyol E (4), cis-africanan-1α-ol (5a), fucosterol (6), tetrahydrothiophen-1,1-dioxide and poly-β-hydroxybutyric acid. GC-MS analysis of the nonpolar fractions also indicated the presence of β-bourbonene and nonanal, along with three hydrocarbons and five fatty acids or their simple derivatives, respectively. GC-MS analysis of the unsaponifiable algal petroleum ether extract revealed the presence of a further eight compounds, among them 2,2,6,7-tetramethyl-10-oxatricyclo[4.3.0.1(1,7)]decan-5-one (7), N-(4-bromo-n-butyl)-piperidin-2-one (8) and tert-hexadecanethiol. Structures 1–6 were assigned by 1D and 2D NMR, mass spectra (EI, CI, HREI and HRESI) and by comparison with data from related structures. The crude algal extract was potently active against the breast carcinoma tumor cell line, MCF7 (IC₅₀ = 0.6 µg mL⁻¹); pachydictyol B (1a) and dictyol E (4) showed weak antimicrobial properties, and the other compounds were inactive. Pachydictyols B (1a) and C (2) demonstrated a weak and unselective cytotoxicity against twelve human tumor cell lines with a mean IC₅₀ of >30.0 µM.     

New Dimeric Members of the Phomoxanthone Family: Phomolactonexanthones A,B and Deacetylphomoxanthone C Isolated from the Fungus Phomopsis sp.

Three new phomoxanthone compounds, phomolactonexanthones A (1), B (2) and deacetylphomoxanthone C (3), along with five known phomoxanthones, including dicerandrol A (4), dicerandrol B (5), dicerandrol (6), deacetylphomoxanthone B (7) and penexanthone A (8), were isolated in the metabolites of the fungus Phomopsis sp. HNY29-2B, which was isolated from the mangrove plants. The structures of compounds 1–3 were established on the basis of spectroscopic analysis. All compounds were evaluated against four human cancer cell lines including human breast MDA-MB-435, human colon HCT-116, human lung Calu-3 and human liver Huh7 by MTT assay. The compounds 4, 5, 7 and 8 showed cyctotoxic activities against tested cancer cell lines (IC₅₀ < 10 μM).     

Briacavatolides D�CF, New Briaranes from the Taiwanese Octocoral Briareum excavatum

In the continued search for novel bioactive substances from the Taiwanese octocoral Briareum excavatum collected at Orchid Island, three new briarane-type diterpenoids, briacavatolides D–F (1–3) were isolated from the acetone extract. The structures of these compounds were elucidated by extensive NMR spectroscopic analysis and physical data. The anti-HCMV (human cytomegalovirus) activity of 1–3 and their cytotoxicity against selected cancer cell lines were evaluated.     

Cytotoxic and Anti-Inflammatory Eunicellin-Based Diterpenoids from the Soft Coral Cladiella krempfi

Five new eunicellin-based diterpenoids, krempfielins E–I (1–5) and seven known compounds (6–12) were isolated from the organic extract of a Taiwanese soft coral Cladiella krempfi. The structures of the new metabolites were elucidated on the basis of extensive spectroscopic analysis. Metabolites 5, 6, 10 and 12 were shown to exhibit cytotoxicity against a limited panel of cancer cell lines. Furthermore, compounds 6 and 10 could potently inhibit the accumulation of the pro-inflammatory iNOS protein, and 6 and 12 could significantly reduce the expression of COX-2 protein in LPS-stimulated RAW264.7 macrophage cells.     

Molecular Mechanisms by Which a Fucus vesiculosus Extract Mediates Cell Cycle Inhibition and Cell Death in Pancreatic Cancer Cells

Pancreatic cancer is one of the most aggressive cancer entities, with an extremely poor 5-year survival rate. Therefore, novel therapeutic agents with specific modes of action are urgently needed. Marine organisms represent a promising source to identify new pharmacologically active substances. Secondary metabolites derived from marine algae are of particular interest. The present work describes cellular and molecular mechanisms induced by an HPLC-fractionated, hydrophilic extract derived from the Baltic brown seaweed Fucus vesiculosus (Fv1). Treatment with Fv1 resulted in a strong inhibition of viability in various pancreatic cancer cell lines. This extract inhibited the cell cycle of proliferating cells due to the up-regulation of cell cycle inhibitors, shown on the mRNA (microarray data) and protein level. As a result, cells were dying in a caspase-independent manner. Experiments with non-dividing cells showed that proliferation is a prerequisite for the effectiveness of Fv1. Importantly, Fv1 showed low cytotoxic activity against non-malignant resting T cells and terminally differentiated cells like erythrocytes. Interestingly, accelerated killing effects were observed in combination with inhibitors of autophagy. Our in vitro data suggest that Fv1 may represent a promising new agent that deserves further development towards clinical application.     

Evidence of Anti-Proliferative Activities in Blue Mussel (Mytilus edulis) By-Products

Shellfish waste components contain significant levels of high quality protein and are therefore a potential source for biofunctional high-value peptides. The feasibility of applying a pilot scale enzymatic hydrolysis process to whole Mytilus edulis and, by fractionation, recover hydrolysates presenting a biological activity of interest, was evaluated. Fractions were tested on four immortalized cancerous cell lines: A549, BT549, HCT15 and PC3. The 50 kDa fraction, enriched in peptides, presented anti-proliferative activity with all cell lines and results suggest a bioactive molecule synergy within the fraction. At a protein concentration of 44 µg/mL, the 50 kDa fraction induced a mortality of 90% for PC3, 89% for A549, 85% for HCT15 and of 81% for BT549 cell lines. At the low protein concentration of only 11 µg/mL the 50 kDa fraction still entails a cell mortality of 76% for A549 and 87% for PC3 cell lines. The 50 kDa fraction contains 56% of proteins, 3% of lipids and 6% of minerals on a dry weight basis and the lowest levels detected of taurine and methionine and highest levels of threonine, proline and glycine amino acids. The enzymatic hydrolysis process suggests that Mytilus edulis by-products should be viewed as high-valued products with strong potential as anti-proliferative agent and promising active ingredients in functional foods.     

Neuroprotective Effect of Cyclo-(L-Pro-L-Phe) Isolated from the Jellyfish-Derived Fungus Aspergillus flavus

Peroxisome proliferator-activated receptor (PPAR) expression has been implicated in pathological states such as cancer, inflammation, diabetes, and neurodegeneration. We isolated natural PPAR agonists—eight 2,5-diketopiperazines—from the jellyfish-derived fungus Aspergillus flavus. Cyclo-(L-Pro-L-Phe) was the most potent PPAR-γ activator among the eight 2,5-DKPs identified. Cyclo-(L-Pro-L-Phe) activated PPAR-γ in Ac2F rat liver cells and SH-SY5Y human neuroblastoma cells. The neuroprotective effect of this partial PPAR-γ agonist was examined using the 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, lactate dehydrogenase release, and the Hoechst 33342 staining assay in SH-SY5Y cells. Our findings revealed that cyclo-(L-Pro-L-Phe) reduced hydrogen peroxide-induced apoptosis as well as the generation of reactive oxygen species. Rhodamine 123 staining and western blotting revealed that cyclo-(L-Pro-L-Phe) prevented the loss of mitochondrial membrane potential and inhibited the activation of mitochondria-related apoptotic proteins, such as caspase 3 and poly (ADP-ribose) polymerase. Moreover, cyclo-(L-Pro-L-Phe) inhibited the activation and translocation of nuclear factor-kappa B. Thus, the partial PPAR-γ agonist cyclo-(L-Pro-L-Phe) demonstrated potential neuroprotective activity against oxidative stress-induced neurodegeneration in SH-SY5Y cells.     

Three New and Eleven Known Unusual C25 Steroids: Activated Production of Silent Metabolites in a Marine-Derived Fungus by Chemical Mutagenesis Strategy using Diethyl Sulphate

Three new (1–3) and 11 known (4–14) C25 steroids with an unusual bicyclo[4.4.1]A/B ring system were isolated by tracing newly produced metabolites in the EtOAc extract of an antitumor mutant AD-1-2 obtained by the diethyl sulphate (DES) mutagenesis of a marine-derived Penicillium purpurogenum G59. HPLC-PDAD-UV and HPLC-ESI-MS analyses indicated that the G59 strain did not produce these metabolites and the production of 1–14 in the mutant AD-1-2 extract was caused by the activation of silent metabolites in the original G59 strain by DES mutagenesis. The structures of the new compounds, named antineocyclocitrinols A (1) and B (2) and 23-O-methylantineocyclocitrinol (3), including their absolute configurations were determined by various spectroscopic methods, especially the NMR and Mo₂-induced CD analyses. Compounds 1–3 provide the first examples of the C25 bicyclo[4.4.1]A/B ring steroids with the Z-configuration of 20,22-double bond. All of 1–14 weakly inhibited several human cancer cell lines to varying extents. These results provided additional examples for the successful application of the chemical mutagenesis strategy using DES to discover new compounds by activating silent metabolites in fungal isolates and supported also the effectiveness and usefulness of this new strategy.     

New cytotoxic cembranolides from the soft coral Lobophytum michaelae

Six new cembranolides, michaolides L–Q (1–6), and a known cembranolide, lobomichaolide (7) were isolated from the CH₂Cl₂ extract of the soft coral Lobophytum michaelae. Their structures were established by extensive spectral analysis. The anti-HCMV (human cytomegalovirus) activity of 1–7 and their cytotoxicity against selected cell lines were evaluated.     

Structure-Activity Relationship Study of the Neuritogenic Potential of the Glycan of Starfish Ganglioside LLG-3

LLG-3 is a ganglioside isolated from the starfish Linchia laevigata. To clarify the structure-activity relationship of the glycan of LLG-3 toward rat pheochromocytoma PC12 cells in the presence of nerve growth factor, a series of mono- to tetrasaccharide glycan derivatives were chemically synthesized and evaluated in vitro. The methyl group at C8 of the terminal sialic acid residue was crucial for neuritogenic activity, and the terminal trisaccharide moiety was the minimum active motif. Furthermore, the trisaccharide also stimulated neuritogenesis in human neuroblastoma SH-SY5Y cells via mitogen-activated protein kinase (MAPK) signaling. Phosphorylation of extracellular signal-regulated kinase (ERK) 1/2 was rapidly induced by adding 1 or 10 nM of the trisaccharide. The ratio of phosphorylated ERK to ERK reached a maximum 5 min after stimulation, and then decreased gradually. However, the trisaccharide did not induce significant Akt phosphorylation. These effects were abolished by pretreatment with the MAPK inhibitor U0126, which inhibits enzymes MEK1 and MEK2. In addition, U0126 inhibited the phosphorylation of ERK 1/2 in response to the trisaccharide dose-dependently. Therefore, we concluded that the trisaccharide promotes neurite extension in SH-SY5Y cells via MAPK/ERK signaling, not Akt signaling.     

Four New Sulfated Polar Steroids from the Far Eastern Starfish Leptasterias ochotensis: Structures and Activities

Three new sulfated steroid monoglycosides, leptaochotensosides A–C (1–3), and a new sulfated polyhydroxylated steroid (4) were isolated from the alcoholic extract of the Far Eastern starfish Leptasterias ochotensis. The structures of compounds 1–4 were established by extensive nuclear magnetic resonance (NMR) and electrospray ionization mass spectrometry (ESIMS) analyses and chemical transformations. Although the isolated compounds did not show any apparent cytotoxicity against melanoma RPMI-7951 and breast cancer T-47D cell lines, leptaochotensoside A (1) demonstrated inhibition of T-47D cell colony formation in a soft agar clonogenic assay at nontoxic doses. In addition, this compound decreased the epidermal growth factor (EGF)-induced colony formation of mouse epidermal JB6 Cl41 cells. The cancer preventive action of 1 is realized through regulation of mitogen-activated protein kinase (MAPK) signaling pathway.     

Isolation and Assessment of the in Vitro Anti-Tumor Activity of Smenothiazole A and B,Chlorinated Thiazole-Containing Peptide/Polyketides from the Caribbean Sponge,Smenospongia aurea

The study of the secondary metabolites contained in the organic extract of Caribbean sponge Smenospongia aurea led to the isolation of smenothiazole A (3) and B (4), hybrid peptide/polyketide compounds. Assays performed using four solid tumor cell lines showed that smenothiazoles exert a potent cytotoxic activity at nanomolar levels, with selectivity over ovarian cancer cells and a pro-apoptotic mechanism.     

Woodylides A-C, new cytotoxic linear polyketides from the South China Sea sponge Plakortis simplex

Three new polyketides, woodylides A–C (1–3), were isolated from the ethanol extract of the South China Sea sponge Plakortis simplex. The structures were elucidated by spectroscopic data (IR, 1D and 2D NMR, and HRESIMS). The absolute configurations at C-3 of 1 and 3 were determined by the modified Mosher’s method. Antifungal, cytotoxic, and PTP1B inhibitory activities of these polyketides were evaluated. Compounds 1 and 3 showed antifungal activity against fungi Cryptococcus neoformans with IC₅₀ values of 3.67 and 10.85 µg/mL, respectively. In the cytotoxicity test, compound 1 exhibited a moderate effect against the HeLa cell line with an IC₅₀ value of 11.2 µg/mL, and compound 3 showed cytotoxic activity against the HCT-116 human colon tumor cell line and PTP1B inhibitory activity with IC₅₀ values of 9.4 and 4.7 µg/mL, respectively.