Evaluation of cancer-preventive activity and structure-activity relationships of 3-demethylubiquinone Q2, isolated from the ascidian Aplidium glabrum, and its synthetic analogs

Isolation and Characterization of One New Natural Compound with Other Potential Bioactive Secondary Metabolites from Glycosmis cyanocarpa (Blume) Spreng. (Family: Rutaceae)

Glycosmis cyanocarpa (Blume) Spreng is a plant in the Rutaceae family and a species in the Glycosmis genus that has received little attention. Therefore, this research aimed to report the chemical and biological analysis of Glycosmis cyanocarpa (Blume) Spreng. The chemical analysis involved the isolation and characterization of secondary metabolites through an extensive chromatographic study, and the structures of these metabolites were elucidated on the basis of a detailed analysis of NMR and HRESIMS spectroscopic data and by comparison with those of related compounds reported in the literature. Different partitions of the crude ethyl acetate (EtOAc) extract were evaluated for antioxidant, cytotoxic, and thrombolytic potentials. In chemical analysis, one new phenyl acetate derivative, namely 3,7,11,15-tetramethylhexadec-2-en-1-yl 2-phenylacetate (1), along with four known compounds N-methyl-3-(methylthio)-N-(2-phenylacetyl) acrylamide (2), penangin (3), β-Caryophyllene oxide (4), and acyclic diterpene-phytol (5) were isolated for the first time from the stem and leaf of the plant. The ethyl acetate fraction showed significant free radical scavenging activity with an IC₅₀ value of 11.536 µg/mL compared to standard ascorbic acid (4.816 µg/mL). In the thrombolytic assay, the dichloromethane fraction showed the maximum thrombolytic activity of 16.42% but was still insignificant compared to the standard streptokinase (65.98%). Finally, in a brine shrimp lethality bioassay, the LC₅₀ values of dichloromethane, ethyl acetate, and aqueous fractions were found to be 0.687 µg/mL, 0.805 µg/mL, and 0.982 µg/mL which are significant compared to the standard vincristine sulfate of 0.272 µg/mL.

Antitumor Potential of Immunomodulatory Natural Products

Cancer is one of the leading causes of death globally. Anticancer drugs aim to block tumor growth by killing cancerous cells in order to prevent tumor progression and metastasis. Efficient anticancer drugs should also minimize general toxicity towards organs and healthy cells. Tumor growth can also be successfully restrained by targeting and modulating immune response. Cancer immunotherapy is assuming a growing relevance in the fight against cancer and has recently aroused much interest for its wider safety and the capability to complement conventional chemotherapeutic approaches. Natural products are a traditional source of molecules with relevant potential in the pharmacological field. The huge structural diversity of metabolites with low molecular weight (small molecules) from terrestrial and marine organisms has provided lead compounds for the discovery of many modern anticancer drugs. Many natural products combine chemo-protective and immunomodulant activity, thus offering the potential to be used alone or in association with conventional cancer therapy. In this review, we report the natural products known to possess antitumor properties by interaction with immune system, as well as discuss the possible immunomodulatory mechanisms of these molecules.

Marine Natural Products from Tunicates and Their Associated Microbes

Marine tunicates are identified as a potential source of marine natural products (MNPs), demonstrating a wide range of biological properties, like antimicrobial and anticancer activities. The symbiotic relationship between tunicates and specific microbial groups has revealed the acquisition of microbial compounds by tunicates for defensive purpose. For instance, yellow pigmented compounds, "tambjamines", produced by the tunicate, Sigillina signifera (Sluiter, 1909), primarily originated from their bacterial symbionts, which are involved in their chemical defense function, indicating the ecological role of symbiotic microbial association with tunicates. This review has garnered comprehensive literature on MNPs produced by tunicates and their symbiotic microbionts. Various sections covered in this review include tunicates' ecological functions, biological activities, such as antimicrobial, antitumor, and anticancer activities, metabolic origins, utilization of invasive tunicates, and research gaps. Apart from the literature content, 20 different chemical databases were explored to identify tunicates-derived MNPs. In addition, the management and exploitation of tunicate resources in the global oceans are detailed for their ecological and biotechnological implications.

The Ascidian-Derived Metabolites with Antimicrobial Properties

Among the sub-phylum of Tunicate, ascidians represent the most abundant class of marine invertebrates, with 3000 species by heterogeneous habitat, that is, from shallow water to deep sea, already reported. The chemistry of these sessile filter-feeding organisms is an attractive reservoir of varied and peculiar bioactive compounds. Most secondary metabolites isolated from ascidians stand out for their potential as putative therapeutic agents in the treatment of several illnesses like microbial infections. In this review, we present and discuss the antibacterial activity shown by the main groups of ascidian-derived products, such as sulfur-containing compounds, meroterpenes, alkaloids, peptides, furanones, and their derivatives. Moreover, the direct evidence of a symbiotic association between marine ascidians and microorganisms shed light on the real producers of many extremely potent marine natural compounds. Hence, we also report the antibacterial potential, joined to antifungal and antiviral activity, of metabolites isolated from ascidian-associate microorganisms by culture-dependent methods.

In Vitro Antiproliferative Evaluation of Synthetic Meroterpenes Inspired by Marine Natural Products

Several marine natural linear prenylquinones/hydroquinones have been identified as anticancer and antimutagenic agents. Structure-activity relationship studies on natural compounds and their synthetic analogs demonstrated that these effects depend on the length of the prenyl side chain and on the type and position of the substituent groups in the quinone moiety. Aiming to broaden the knowledge of the underlying mechanism of the antiproliferative effect of these prenylated compounds, herein we report the synthesis of two quinones 4 and 5 and of their corresponding dioxothiazine fused quinones 6 and 7 inspired to the marine natural product aplidinone A (1), a geranylquinone featuring the 1,1-dioxo-1,4-thiazine ring isolated from the ascidian Aplidium conicum. The potential effects on viability and proliferation in three different human cancer cell lines, breast adenocarcinoma (MCF-7), pancreas adenocarcinoma (Bx-PC3) and bone osteosarcoma (MG-63), were investigated. The methoxylated geranylquinone 5 exerted the highest antiproliferative effect exhibiting a comparable toxicity in all three cell lines analyzed. Interestingly, a deeper investigation has highlighted a cytostatic effect of quinone 5 referable to a G0/G1 cell-cycle arrest in BxPC-3 cells after 24 h treatment.

Synthesis and Antiproliferative Activity of New Cyclodiprenyl Phenols against Select Cancer Cell Lines

Six new cyclodiprenyl phenols were synthesized by direct coupling of perillyl alcohol and the appropriate phenol. Their structures were established by IR, HRMS and mainly NMR. Three human cancer cell lines-breast (MCF-7), prostate (PC-3) and colon (HT-29)-were used in antiproliferative assays, with daunorubicin and dunnione as positive controls. Results described in the article suggest that dihydroxylated compounds 2⁻4 and monohydroxylated compound 5 display selectivity against cancer cell lines, cytotoxicity, apoptosis induction, and mitochondrial membrane impairment capacity. Compound 2 was identified as the most effective of the series by displaying against all cancer cell lines a cytotoxicity close to dunnione antineoplastic agent, suggesting that the cyclodiprenyl phenols from perillyl alcohol deserve more extensive investigation of their potential medicinal applications.

In Vitro Antifungal Activity of New and Known Geranylated Phenols against Phytophthora cinnamomi Rands

A series of new and known geranylated phenol/methoxyphenol derivatives has been tested in vitro as inhibitor agents of mycelial growth of Phytophthora cinnamomi. The activity of tested compounds is correlated with the nature, number, and position of the substituent group on the aromatic ring. Results indicate that the most active geranylated derivatives are those having two hydroxyl groups (or one –OH and one –OCH₃) attached to the aromatic ring. Interestingly, these derivatives are as active as Metalaxil^®, a commonly used commercial fungicide. Thus, our results suggest that some of these compounds might be of agricultural interest due to their potential use as fungicides against P. cinnamomi. The effect of structure on fungicide activity is discussed in terms of electronic distribution on both the aromatic ring and side geranyl chain. All tested compounds have been synthesized by direct coupling of geraniol and the respective phenol. Interestingly, new digeranylated derivatives were obtained by increasing the reaction time.

Natural Products Diversity of Marine Ascidians (Tunicates; Ascidiacea) and Successful Drugs in Clinical Development

This present study reviewed the chemical diversity of marine ascidians and their pharmacological applications, challenges and recent developments in marine drug discovery reported during 1994-2014, highlighting the structural activity of compounds produced by these specimens. Till date only 5% of living ascidian species were studied from <3000 species, this study represented from family didemnidae (32%), polyclinidae (22%), styelidae and polycitoridae (11-12%) exhibiting the highest number of promising MNPs. Close to 580 compound structures are here discussed in terms of their occurrence, structural type and reported biological activity. Anti-cancer drugs are the main area of interest in the screening of MNPs from ascidians (64%), followed by anti-malarial (6%) and remaining others. FDA approved ascidian compounds mechanism of action along with other compounds status of clinical trials (phase 1 to phase 3) are discussed here in. This review highlights recent developments in the area of natural products chemistry and biotechnological approaches are emphasized.

Guanidine Alkaloids from the Marine Sponge Monanchora pulchra Show Cytotoxic Properties and Prevent EGF-Induced Neoplastic Transformation in Vitro

Guanidine alkaloids from sponges Monanchora spp. represent diverse bioactive compounds, however, the mechanisms underlying bioactivity are very poorly understood. Here, we report results of studies on cytotoxic action, the ability to inhibit EGF-induced neoplastic transformation, and the effects on MAPK/AP-1 signaling of eight rare guanidine alkaloids, recently isolated from the marine sponge Monanchora pulchra, namely: monanchocidin A (1), monanchocidin B (2), monanchomycalin C (3), ptilomycalin A (4), monanchomycalin B (5), normonanchocidin D (6), urupocidin A (7), and pulchranin A (8). All of the compounds induced cell cycle arrest (apart from 8) and programmed death of cancer cells. Ptilomycalin A-like compounds 1–6 activated JNK1/2 and ERK1/2, following AP-1 activation and caused p53-independent programmed cell death. Compound 7 induced p53-independent cell death without activation of AP-1 or caspase-3/7, and the observed JNK1/2 activation did not contribute to the cytotoxic effect of the compound. Alkaloid 8 induced JNK1/2 (but not ERK1/2) activation leading to p53-independent cell death and strong suppression of AP-1 activity. Alkaloids 1–4, 7, and 8 were able to inhibit the EGF-induced neoplastic transformation of JB6 P⁺ Cl41 cells. Our results suggest that investigated guanidine marine alkaloids hold potential to eliminate human cancer cells and prevent cancer cell formation and spreading.

Synthesis of New Hydrated Geranylphenols and in Vitro Antifungal Activity against Botrytis cinerea

Geranylated hydroquinones and other geranylated compounds isolated from Aplydium species have shown interesting biological activities. This fact has prompted a number of studies where geranylated phenol derivatives have been synthesized in order to assay their bioactivities. In this work, we report the synthesis of a series of new hydrated geranylphenols using two different synthetic approaches and their inhibitory effects on the mycelial growth of Botrytis cinerea. Five new hydrated geranylphenols were obtained by direct coupling reaction between geraniol and phenol in dioxane/water and using BF₃·Et₂O as the catalyst or by the reaction of a geranylated phenol with BF₃·Et₂O. Two new geranylated quinones were also obtained. The synthesis and structural elucidation of all new compounds is presented. All hydrated geranylphenols efficiently inhibit the mycelial growth of B. cinerea. Their activity is higher than that observed for non-hydrated compounds. These results indicate that structural modification on the geranyl chain brings about an enhancement of the inhibition effect of geranylated phenol derivatives.

Antiproliferative effect and apoptotic activity of linear geranylphenol derivatives from phloroglucinol and orcinol

Sixteen synthetic linear derivatives geranylphenols, were obtained from phloroglucinol and orcinol, and cytotoxic activity was evaluated in vitro against cancer cell lines (HT-29, PC-3, MDA-MB231, DU-145) and one non-tumor cell line, human dermal fibroblast (HDF). IC50 values were determined at concentrations of 0-100 μM of each compound for 72 h. Compounds 12, 13, 17, 21, 22 and 25, showed cytotoxic activity. To elucidate whether these compounds reduce cell viability by inducing apoptosis, cell lines MCF-7, PC-3 and DHF were treated with each active compound 12, 13, 17, 21, 22 and 25 and were examined after Hoechst 33342 staining. The compounds 12, 13 and 17 induced apoptosis in various cancer cell lines, as shown by nuclear condensation and/or fragmentation. In addition, it was found that compounds 12 and 13, induced changes in mitochondrial membrane permeability in those cancer cell lines. Such induction was associated with the depletion of mitochondrial membrane potential. These activities led to the cleavage of caspases inducing the cell death process.

Synthesis and in Vitro Antifungal Activity against Botrytis cinerea of Geranylated Phenols and Their Phenyl Acetate Derivatives

The inhibitory effects on the mycelial growth of plant pathogen Botritys cinerea have been evaluated for a series of geranylphenols substituted with one, two and three methoxy groups in the aromatic ring. The results show that the antifungal activity depends on the structure of the geranylphenols, increasing from 40% to 90% by increasing the number of methoxy groups. On the other hand, the acetylation of the –OH group induces a change of activity that depends on the number of methoxy groups. The biological activity of digeranyl derivatives is lower than that exhibited by the respective monogeranyl compound. All tested geranylphenols have been synthesized by direct coupling of geraniol and the respective phenol. The effect of solvent on yields and product distribution is discussed. For monomethoxyphenols the reaction gives better yields when acetonitrile is used as a solvent and AgNO₃ is used as a secondary catalyst. However, for di- and trimethoxyphenols the reaction proceeds only in dioxane.

Aaptamines from the marine sponge Aaptos sp. display anticancer activities in human cancer cell lines and modulate AP-1-, NF-κB-, and p53-dependent transcriptional activity in mouse JB6 Cl41 cells

Aaptamine (8,9-dimethoxy-1H-benzo[de][1,6]naphthyridine) is a marine natural compound possessing antioxidative, antimicrobial, antifungal, and antiretroviral activity. Earlier, we have found that aaptamine and its derivatives demonstrate equal anticancer effects against the human germ cell cancer cell lines NT2 and NT2-R and cause some changes in the proteome of these cells. In order to explore further the mechanism of action of aaptamine and its derivatives, we studied the effects of aaptamine (1), demethyl(oxy)aaptamine (2), and isoaaptamine (3) on human cancer cell lines and on AP-1-, NF-κB-, and p53-dependent transcriptional activity in murine JB6 Cl41 cells. We showed that compounds 1–3 demonstrate anticancer activity in THP-1, HeLa, SNU-C4, SK-MEL-28, and MDA-MB-231 human cancer cell lines. Additionally, all compounds were found to prevent EGF-induced neoplastic transformation of murine JB6 Cl41 cells. Nuclear factors AP-1, NF-κB, and p53 are involved in the cellular response to high and nontoxic concentrations of aaptamine alkaloids 1–3. Furthermore, inhibition of EGF-induced JB6 cell transformation, which is exerted by the compounds 1–3 at low nontoxic concentrations of 0.7–2.1 μM, cannot be explained by activation of AP-1 and NF-κB.

Quinone and hydroquinone metabolites from the ascidians of the genus Aplidium

Ascidians of the genus Aplidium are recognized as an important source of chemical diversity and bioactive natural products. Among the compounds produced by this genus are non-nitrogenous metabolites, mainly prenylated quinones and hydroquinones. This review discusses the isolation, structural elucidation, and biological activities of quinones, hydroquinones, rossinones, longithorones, longithorols, floresolides, scabellones, conicaquinones, aplidinones, thiaplidiaquinones, and conithiaquinones. A compilation of the ¹³C-NMR spectral data of these compounds is also presented.

Synthesis of linear Geranylphenols and their effect on mycelial growth of plant pathogen Botrytis cinerea

Natural geranyl compounds are known to exhibit important biological activities. In this work a series of geranylphenols were synthesized to evaluate their effect on the mycelial growth of Botrytis cinerea. Geranyl derivatives were synthesized by direct geranylation reactions between the corresponding phenol derivatives and geraniol, using BF₃^.OEt₂ as catalyst and AgNO₃ as secondary catalyst. Previously reported molecules [geranylhydroquinone (2), geranylhydroquinone diacetate (6) and geranylphloroglucinol (9)], and new substances [(E)-4-(3,7-dimethylocta-2,6-dienyl)benzene-1,2,3-triol (geranyl-pyrogallol, 7), (E)-4-(3,7-dimethylocta-2,6-dienyl)benzene-1,2,3-triyl triacetate (8), (E)-2-(3,7-dimethylocta-2,6-dienyl)benzene-1,3,5-triyl triacetate geranylphloroglucinol triacetate (10), 2,4-bis((E)-3,7-dimethylocta-2,6-dienyl)benzene-1,3,5-triyl triacetate (11), 2,6-bis((E)-3,7-dimethylocta-2,6-dienyl)-3,5-dihydroxyphenyl acetate (12)], were obtained. All compounds were characterized by IR, HRMS and NMR spectroscopic data. The inhibitory effect of the synthesized compounds on the mycelial growth of Botrytis cinerea was tested in vitro. Excepting compound 11, all substances constrained the mycelial growth of Botrytis cinerea. The antifungal activity depends on the chemical structure of geranylphenol derivatives. Compounds 2 and 9 were the more effective substances showing inhibition degrees higher than those obtained with the commercial fungicide Captan, even at lower concentrations. Monosubstitution on the aromatic nucleus by a geranyl chain seems to be more effective for the inhibition of mycelial growth than a double substitution. These results suggest that the new derivatives of geranylphenols have the ability to block the mycelial development of the plant pathogen B. cinerea and that this capacity depends strongly on the structural features and lipophilicity of the compounds.

Meroterpenes from marine invertebrates: structures, occurrence, and ecological implications

Meroterpenes are widely distributed among marine organisms; they are particularly abundant within brown algae, but other important sources include microorganisms and invertebrates. In the present review the structures and bioactivities of meroterpenes from marine invertebrates, mainly sponges and tunicates, are summarized. More than 300 molecules, often complex and with unique skeletons originating from intra- and inter-molecular cyclizations, and/or rearrangements, are illustrated. The reported syntheses are mentioned. The issue of a potential microbial link to their biosynthesis is also shortly outlined.

The Extracts of Some Marine Invertebrates and Algae Collected off the Coast Waters of Vietnam Induce the Inhibitory Effects on the Activator Protein-1 Transcriptional Activity in JB6 Cl41 Cells

It has previously been shown that inhibition of the transcriptional activity of the oncogenic nuclear factor AP-1 can result in cancer prevention. Marine invertebrates and alga are a rich source of natural compounds that possess various biological activities. The inhibitory effects of the extracts of Vietnamese marine organisms in relation to the AP-1 transcriptional activity were examined by the luciferase method using JB6 Cl41 cells stably expressing a luciferase reporter gene controlled by AP-1 DNA binding sequence. As was found, 71 species of marine sponges out of 148 species studied contain inhibitors of the AP-1 transcriptional activity. Therefore, marine organisms as a source of biologically active compounds have a great potential for isolation of the new cancer preventive compounds that inhibit the oncogenic AP-1 nuclear factor.

Biomimetic synthesis of the apoptosis-inducing thiazinoquinone thiaplidiaquinone A

A concise total synthesis of the apoptosis-inducing, marine metabolite thiaplidiaquinone A is described. The key ring forming steps are both based on biosynthetic considerations and involve the construction of the central benzo[c]chromene quinone unit by an extremely facile oxa-6π-electrocyclic ring closure reaction of an ortho-quinone intermediate, derived by tautomerization of a bis-benzoquinone, readily accessed from two simple phenolic precursors. This is followed by the installation of the 1,4-thiazine-dioxide ring by reaction of the benzo[c]chromene quinone with hypotaurine.

Phomentrioloxin: A phytotoxic pentasubstituted geranylcyclohexentriol produced by Phomopsis sp., a potential mycoherbicide for Carthamus lanatus Biocontrol

A new phytotoxic geranylcyclohexenetriol, named phomentrioloxin, was isolated from the liquid culture of Phomopsis sp., a fungal pathogen proposed for the biological control of Carthamus lanatus, a widespread and troublesome thistle weed belonging to the Asteraceae family causing severe crop and pastures losses in Australia. The structure of phomentrioloxin was established by spectroscopic, X-ray, and chemical methods as (1S,2S,3S,4S)-3-methoxy-6-(7-methyl-3-methylene-oct-6-en-1-ynyl)cyclohex-5-ene-1,2,4-triol. At a concentration of 6.85 mM, the toxin causes the appearance of necrotic spots when applied to leaves of both host and nonhost plants. It also causes growth and chlorophyll content reduction of fronds of Lemna minor and inhibition of tomato rootlet elongation. Finally, in preliminary bioassays, phomentrioloxin did not show any antibacterial, fungicidal, or zootoxic activities.

Cacospongionolide and scalaradial, two marine sesterterpenoids as potent apoptosis-inducing factors in human carcinoma cell lines

Apoptosis, a form of programmed cell death, is a critical defence mechanism against the formation and progression of cancer and acts by eliminating potentially deleterious cells without causing such adverse effects, as inflammatory response and ensuing scar formation. Therefore, targeting apoptotic pathways becomes an intriguing strategy for the development of chemotherapeutic agents. In last decades, marine natural products, such as sesterterpenoids, have played an important role in the discovery and development of new drugs. Interestingly, many of these compounds have a strong potential as anticancer drugs by inhibiting cell proliferation and/or inducing cell death. In the present study, we investigated the effects of scalaradial and cacospongionolide, two sesterterpenoids from Cacospongia scalaris and Fasciospongia cavernosa marine sponges, on the apoptotic signalling pathway in three different human tumoral cells. Results were obtained by using DNA fragmentation, comet and viability assays, quantification of the mitochondrial transmembrane potential and Western blot. The T47D (human breast carcinoma), A431 (human epidermoid carcinoma), HeLa (human cervix carcinoma) and HCT116 (human colon carcinoma) cells were incubated for 24 h with scalaradial or cacospongionolide. Treatment of T47D cells with scalaradial or cacospongionolide for 24 h brought about a significant increase in DNA migration as well as fragmentation. Moreover, incubation of HCT116 and HeLa cells with scalaradial or cacospongionolide for 24 h caused an increased expression of pro-apoptotic proteins. Furthermore, scalaradial or cacospongionolide, added to HCT116 and HeLa cells overnight, induced a significant and concentration-dependent loss of mitochondrial transmembrane potential, an early apoptosis signalling event. These effects paralleled with those achieved with p50 and p65, NF-κB subunits, nuclear level. In conclusion, scalaradial and cacospongionolide, by determining human cancer cell apoptosis, may represent new promising compounds to inhibit cancer cell proliferation.

Diving for drugs: tunicate anticancer compounds

The marine biosphere boasts tremendous biodiversity replete with structurally unique, active and selective secondary metabolites. Bioprospecting for antitumor compounds has been rewarding, and tunicates have been especially successful in yielding prospective cancer therapies. These compounds are now subjected to clinical trials in Europe and the USA. With the ongoing search for potent and specific anticancer drugs, in this article we discuss the unique perspectives, compounds and opportunities afforded by this rich source of potential pharmaceuticals. We discuss marine-derived antitumor drugs, their structures, and their various types and levels of antitumor activities in bench and bedside efforts.

Synthesis and DPPH radical scavenging activity of prenylated phenol derivatives

The synthesis of twenty six prenylated phenols derivatives is reported. These compounds were obtained under mild conditions via Electrophilic Aromatic Substitution (EAS) coupling reactions between phenol derivatives containing electron-donor subtituents and 3-methyl-2-buten-1-ol using BF₃·OEt₂. Dialkylations were also produced with this method. The formation of a chroman ring by intramolecular cyclization between a sp² carbon from the prenyl group with the hydroxyl substituent in the ortho position occurred with some phenols. All the synthesized compounds were evaluated as antioxidants according to a DPPH radical scavenging activity assay. IC₅₀ values of five synthesized compounds indicated they were as good antioxidants as Trolox™.

Anti-inflammatory and antimalarial meroterpenoids from the New Zealand ascidian Aplidium scabellum

Bioassay-directed fractionation of an extract of the New Zealand ascidian Aplidium scabellum has afforded the anti-inflammatory secondary metabolite 2-geranyl-6-methoxy-1,4-hydroquinone-4-sulfate (1) and a family of pseudodimeric meroterpenoids scabellones A (2)-D (5). The benzo[c]chromene-7,10-dione scaffold contained within scabellones A-D is particularly rare among natural products. The structures were elucidated by interpretation of NMR data. Scabellone B was also identified as a moderately potent, nontoxic inhibitor of Plasmodium falciparum.

The anticancer effects of actinoporin RTX-A from the sea anemone Heteractis crispa (=Radianthus macrodactylus)

Four isoforms of actinoporins were isolated in 2002-2004 from the tropical sea anemone Heteractis crispa (=Radianthus macrodactylus). Their potent hemolytic activities and effects on Ehrlich ascites carcinoma bearing mice were also studied. In this study, the individual actinoporin (RTX-A) demonstrated potential cancer-preventive activity at extremely low and non-cytotoxic concentrations. The substance suppressed the malignant transformation of mouse JB6 P(+) Cl41 cells stimulated by epidermal growth factor (EGF) in soft agar with the inhibition of number of the colonies C(50) (INCC(50))=0.034 nM. Actinoporin RTX-A also was shown to inhibit the phenotype expression of HeLa human cancer cells with an INCC(50)=0.03 nM. The cytotoxic effect of RTX-A against JB6 P(+) Cl41 cells and HeLa, THP-1, MDA-MB-231, and SNU-C4 human tumor cell lines was high (IC(50)=0.57, 2.26, 1.11, 30.0 and 4.66 nM), but significantly less than their capacity to suppress tumor cell colony formation or phenotype expression. RTX-A also induced apoptosis and inhibited basal AP-1, NF-kappaB, and p53-dependent transcriptional activity in JB6 Cl41 cells. These results confirmed that actinoporin RTX-A from H. crispa, at least partially, might exhibit cancer-preventive and anticancer cytotoxic properties through the induction of p53-independent apoptosis and inhibition of the oncogenic AP-1 and NF-kappaB nuclear factors activity.

Aaptamine Alkaloids from the Vietnamese Sponge Aaptos sp

A series of aaptamines, including one new alkaloid (1), were isolated from the marine sponge Aaptos sp. collected in Vietnamese waters. The structure of 1 was elucidated using NMR and HRESIMS, as well as by chemical transformation of 1 to the previously known aaptamine and established as 3-N-morpholinyl-9-demethyl(oxy)aaptamine. The isolated compounds showed a potential cancer preventive activity.

The inhibition of TNF-alpha-induced NF-kappaB activation by marine natural products

The deregulated activation of NF-kappaB is associated with cancer development and inflammatory diseases. With an aim to find new NF-kappaB inhibitors, we purified and characterized compounds from extracts of the Fijian sponge Rhabdastrella globostellata, the crinoid Comanthus parvicirrus, the soft corals Sarcophyton sp. nov. and Sinularia sp., and the gorgonian Subergorgia sp. after an initial screening of 266 extracts from different marine origins. Results obtained show that selected purified compounds had a cytotoxic effect on the human leukaemia cell line K562, inhibited both TNF-alpha-induced NF-kappaB-DNA binding as well as TNF-alpha-induced IkappaBalpha degradation and nuclear translocation of p50/p65. Furthermore, we observed the inhibition of NF-kappaB activation induced by an overexpression of IKKbeta. Interestingly, natural products inhibited IKKbeta kinase as well as the 26S proteasome proteolytic activity.

Proapoptotic and Anticarcinogenic Activities of Leviusculoside G from the Starfish Henricia leviuscula and Probable Molecular Mechanism

Proapoptotic and anticarcinogenic properties of leviusculoside G (LSG) isolated from the starfish Henricia leviuscula and a probable mechanism of these effects were investigated in human leukemia HL-60, THP-1, and mouse skin JB6 Cl41 cells, using a variety of assessments, including a cell viability (MTS) assay, flow cytometry, anchorage-independent soft agar assay, luciferase assay, and western-blotting. Application of LSG at nontoxic doses induced apoptosis in cancer cells and decreased cell transformation. This compound exerted its actions, at least in part, through the induction of p53-dependent apoptosis and inhibition of AP-1, NF-κB, and ERKs activities.

Constituents of the sea cucumber Cucumaria okhotensis. Structures of okhotosides B1-B3 and cytotoxic activities of some glycosides from this species

Three new triterpene oligoglycosides, okhotosides B 1 ( 1), B 2 ( 2), and B 3 ( 3), have been isolated from the sea cucumber Cucumaria okhotensis along with the known compounds frondoside A ( 4), frondoside A 1, cucumarioside A 2-5, and koreoside A. The structures of 1- 3 were elucidated on the basis of their spectroscopic data (2D NMR and MS). Compounds 1- 3 were moderately toxic against HeLa tumor cells. Frondoside A ( 4) showed more potent cytotoxicity against THP-1 and HeLa tumor cell lines (with IC 50 values of 4.5 and 2.1 microg/mL, respectively) and decreased both the AP-1-dependent trascriptional activities induced by UVB, EGF, or TPA in JB6-LucAP-1 cells and the EGF-induced NF-kappaB-dependent transcriptional activity in JB6-LucNF-kB cells at doses of about 1 microg/mL. At the same doses, it increased the p53-dependent transcriptional activity in nonactivated JB6-Lucp53 cells and inhibited the colony formation of JB6 P (+) Cl 41 cells activated with EGF (INCC 50 = 0.8 microg/mL).

Inhibitory effects of caffeine analogues on neoplastic transformation: structure-activity relationship

Some xanthine analogues, including 1,3,7-trimethylxanthine (caffeine) and 1,3-dimethylxanthine (theophylline), have been shown to exert anticancer activities in both cell culture and animal models. The present study focused on the relationship of structure and activity of 50 different caffeine analogues in preventing epidermal growth factor (EGF)-induced malignant transformation of mouse epidermal JB6 promotion-sensitive (P+) Cl41 (JB6 P+) cells. Results indicated that the inhibition of cell transformation by the 1,3,7-trialkylxanthines depends on the number of carbons at the alkyl groups R1 and R3, but not R7. Notably, 1-ethyl-3-hexylxanthine (xanthine 70) was the most effective compound for inhibiting EGF-induced neoplastic transformation among the 50 xanthine analogues tested. The 50% inhibition of cell transformation (ICT(50)) value for xanthine 70 was 48- or 75-fold less than the ICT(50) value of caffeine or theophylline, respectively. Further study revealed that xanthine 70 (5-40 muM) dose dependently inhibited EGF-induced transactivation of activator protein 1 (AP-1), whereas theophylline or caffeine (up to 500 muM) had no effect on AP-1 activity. In addition, xanthine 70 (10 muM) inhibited 12-O-tetradecanoylphorbol-13-acetate- or H-Ras-induced neoplastic transformation in JB6 P+ cells by 78.2 or 62.0%, respectively. Collectively, these results indicated that the number of carbons at R1 and R3 is important for the antitumor-promoting activity of the trialkylxanthines and xanthine 70 might be a promising anticancer agent.

Marine natural products

This review covers the literature published in 2006 for marine natural products, with 758 citations (534 for the period January to December 2006) referring to compounds isolated from marine microorganisms and phytoplankton, green algae, brown algae, red algae, sponges, cnidaria, bryozoans, molluscs, tunicates and echinoderms. The emphasis is on new compounds (779 for 2006), together with their relevant biological activities, source organisms and country of origin. Biosynthetic studies, first syntheses, and syntheses that lead to the revision of structures or stereochemistries, have been included.