Marine pharmacology in 2000: antitumor and cytotoxic compounds

Didemnins as marine-derived anticancer agents: mechanistic insights and clinical potential

Didemnins, a class of cyclic depsipeptides derived from marine organisms exhibit notable anticancer properties. Among them, Didemnin B has been extensively researched for its strong antitumor activity and progression to clinical trials. Nonetheless, its clinical application has been impeded by challenges like poor bioavailability and dose-limiting toxicity. This review aims to provide a comprehensive analysis of the anticancer mechanisms of Didemnins, particularly Didemnin B, by examining studies that investigate their anticancer properties, mechanisms of action, pharmacokinetics, and clinical outcomes, while exploring their potential as therapeutic agents in cancer treatment. A comprehensive review of the literature was conducted using scientific databases, including PubMed, Google Scholar and ScienceDirect. Didemnin B has been shown to exert its anticancer effects primarily through the inhibition of protein synthesis, induction of apoptosis, and disruption of cell-cycle progression. Despite promising preclinical results, clinical trials have revealed substantial toxicity, particularly neuromuscular and hepatic, which significantly constrains its therapeutic potential. Recent progress in developing semisynthetic derivatives, including Dehydrodidemnin B (Plitidepsin, Aplidin), have led to improved efficacy and reduced toxicity. Didemnins, especially Didemnin B, hold promise as anticancer agents. However, future research should focus on optimizing delivery methods, reducing toxicity, and exploring combination therapies to enhance their therapeutic potential in oncology.

Immunomodulatory peptides-A promising source for novel functional food production and drug discovery

Immunomodulatory peptides are a complex class of bioactive peptides that encompasses substances with different mechanisms of action. Immunomodulatory peptides could also be used in vaccines as adjuvants which would be extremely desirable, especially in response to pandemics. Thus, immunomodulatory peptides in food of plant origin could be regarded both as valuable suplements of novel functional food preparation and/or as precursors or possible active ingredients for drugs design for treatment variety of conditions arising from impaired function of immune system. Given variety of mechanisms, different tests are required to assess effects of immunomodulatory peptides. Some of those effects show good correlation with in vivo results but others, less so. Certain plant peptides, such as defensins, show both immunomodulatory and antimicrobial effect, which makes them interesting candidates for preparation of functional food and feed, as well as templates for design of synthetic peptides.

The Antiproliferative and Apoptosis-Inducing Effects of the Red Macroalgae Gelidium latifolium Extract against Melanoma Cells

The red macroalga Gelidium latifolium is widely distributed in the coastal areas of Indonesia. However, current knowledge on its potential biological activities is still limited. In this study, we investigated the potential bioactive compounds in Gelidium latifolium ethanol extract (GLE), and its cytotoxic effects against the murine B16-F10 melanoma cell line. GLE shows high total phenolic content (107.06 ± 17.42 mg GAE/g) and total flavonoid content (151.77 ± 3.45 mg QE/g), which potentially contribute to its potential antioxidant activity (DPPH = 650.42 ± 2.01 µg/mL; ABTS = 557.01 ± 1.94 µg/mL). ESI-HR-TOF-MS analysis revealed large absorption in the [M-H]^- of 327.2339 m/z, corresponding to the monoisotopic molecular mass of brassicolene. The presence of this compound potentially contributes to GLE's cytotoxic activity (IC₅₀ = 84.29 ± 1.93 µg/mL). Furthermore, GLE significantly increased the number of apoptotic cells (66.83 ± 3.06%) compared to controls (18.83 ± 3.76%). Apoptosis was also confirmed by changes in the expression levels of apoptosis-related genes (i.e., p53, Bax, Bak, and Bcl2). Downregulated expression of Bcl2 indicates an intrinsic apoptotic pathway. Current results suggest that components of Gelidium latifolium should be further investigated as possible sources of novel antitumor drugs.

Recent updates on the bioactive compounds of the marine-derived genus Aspergillus

The genus Aspergillus is widely distributed in terrestrial and marine environments. In the marine environment, several Aspergillus species have proved their potential to produce a plethora of secondary metabolites including polyketides, sterols, fatty acids, peptides, alkaloids, terpenoids and miscellaneous compounds, displaying a variety of pharmacological activities such as antimicrobial, cytotoxicity, anti-inflammatory and antioxidant activity. From the beginning of 2015 until December 2020, about 361 secondary metabolites were identified from different marine Aspergillus species. In our review, we highlight secondary metabolites from various marine-derived Aspergillus species reported between January 2015 and December 2020 along with their biological potential and structural aspects whenever applicable.

Preliminary screening of the aqueous extracts of twenty-three different seaweed species in Sri Lanka with in-vitro and in-vivo assays

Background

Seaweeds are an important source of bioactive compounds which are applied in various aspects of medicinal investigations. The present study was conducted to investigate cytoxicity (in-vitro and in-vivo) and wound healing activity of different seaweed species in Sri Lanka.

Methods

Twenty-three seaweed samples, belonging to Phaeophyta (Brown), Chlorophyta (Green) and Rhodophyta (Red) were used for the experiments. Samples were collected from the inter-tidal and the sub-tidal habitats around Sri Lankan coast (Southern, Northern and North-western). Aqueous seaweed extracts were tested for cytotoxic and wound healing activity; in-vitro and in-vivo. To determine toxicity of aqueous seaweed extracts, brine shrimp lethality assay and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) colorimetric assay on mouse fibroblasts (L929) cell line were performed. Cell migration induction of seaweed extracts was assessed by scratch wound healing assay using L929 cell line. Based on the our previous experiments S.ilicifolium (SW23) was selected for the in vivo study to confirm our hypothesis. Albino mice (BALB/c) were divided into three groups (12 in each) and a circular area (44.07 ± 02.51 mm²) of full skin was excised to create a wound in mice group II and III. Group III received aqueous extract of Sargasum illicifolium (400 mg/kg BW/day for 12 days, orally), Group II received distilled water for 12 days whereas Group I was used as the control group and it was tested without forming wounds and without providing any treatment. Further, the expression level of Tumor Necrosis Factor (TNF-α) and Transforming Growth Factor-β (TGF-β) via RT-PCR were measured every three days until the end of the experiment.

Results

Phytochemical tests showed positive results to flavonoids in all the selected green seaweeds and alkaloids were observed in red seaweeds. In the toxicity assay, red seaweed, Acanthophora spicifera (SW17) was found to be highly effective on nauplii of brine shrimp (LC₅₀ = 0.072 μg/μl). LC₅₀ value of green seaweed species, Caulerpa racemosa (SW02 and SW08) and Caulerpa sertularioides (SW10) was not found within the tested concentration series. The highest cytotoxic effect on L929 cell line was exhibited by aqueous extracts of red seaweed; Jania adhaereus with 50.70 ± 7.304% cell viability compared with control group. The highest cell migration activity was observed in L929 cell line group treated with extracts of green seaweed namely; Halimeda opuntin (SW07) and extracts of brown seaweed namely; Stoechospermum polypodioides (SW11). Extracts of S. illicifolium (SW23) exhibited a significantly enhanced wound healing activity in mice group III within three days (P < 0.05) with an open wound area of 17.35 ± 1.94 mm² compared with control group (26.29 ± 2.42 mm²). TGF-β gene expression peaked on 6^th day of post-wound and subsequently decreased on 9^th day of post-wound in mice group III. TNF-α expression was suppressed in mice group III whereas it was elevated in group II. TGF-β expression is enhanced in the treatment group compared to the control group.

Conclusions

Aqueous extracts of selected seaweeds are a significant source of potential compounds with wound healing properties, which might be helpful in the healing of various wounds. This also infers that many species of brown and red seaweeds have the potential of wound healing, specifically, Sargasum illicifolium and Jania adhaereus could be a potential candidate for in-vivo studies related to wound healing and cancer therapy in the near future.

Current understanding and biotechnological application of the bacterial diterpene synthase CotB2

CotB2 catalyzes the first committed step in cyclooctatin biosynthesis of the soil bacterium Streptomyces melanosporofaciens. To date, CotB2 represents the best studied bacterial diterpene synthase. Its reaction mechanism has been addressed by isoptope labeling, targeted mutagenesis and theoretical computations in the gas phase, as well as full enzyme molecular dynamic simulations. By X-ray crystallography different snapshots of CotB2 from the open, inactive, to the closed, active conformation have been obtained in great detail, allowing us to draw detailed conclusions regarding the catalytic mechanism at the molecular level. Moreover, numerous alternative geranylgeranyl diphosphate cyclization products obtained by CotB2 mutagenesis have exciting applications for the sustainable production of high value bioactive substances.

Acetylenic Aquatic Anticancer Agents and Related Compounds

Although acetylenes are common as components of terrestrial plants, it is only within the last 30 years that biologically active polyacetylenes having unusual structural features have been reported from aquatic organisms: cyanobacteria, algae, fungi, invertebrates, and other sources. Naturally occurring aquatic acetylenes are of particular interest since many of them display important biological activities and possess antitumor, antibacterial, antimicrobial, antifouling, antifungal, pesticidal, phototoxic, HIV inhibitory, and immuno-suppressive properties. There is no doubt that they are of great interest, especially for the medicinal and/or pharmaceutical industries. This review presents structures and describes cytotoxic and anticancer activities of more than 230 acetylenic metabolites isolated from aquatic organisms. With the computer program PASS some additional biological activities are also predicted, which point toward possible new applications of these compounds. This review emphasizes the role of aquatic acetylenic compounds as an important source of leads for drug discovery.

Meta-Analysis for Correlating Structure of Bioactive Peptides in Foods of Animal Origin with Regard to Effect and Stability

Amino acid (AA) sequences of 807 bioactive peptides from foods of animal origin were examined in order to correlate peptide structure with activity (antihypertensive, antioxidative, immunomodulatory, antimicrobial, hypolipidemic, antithrombotic, and opioid) and stability in vivo. Food sources, such as milk, meat, eggs, and marine products, show different frequencies of bioactive peptides exhibiting specific effects. There is a correlation of peptide structure and effect, depending on type and position of AA. Opioid peptides contain a high percentage of aromatic AA residues, while antimicrobial peptides show an excess of positively charged AAs. AA residue position is significant, with those in the first and penultimate positions having the biggest effects on peptide activity. Peptides that have activity in vivo contain a high percentage (67%) of proline residues, but the positions of proline in the sequence depend on the length of the peptide. We also discuss the influence of processing on activity of these peptides, as well as methods for predicting release from the source protein and activity of peptides.

Extraction and Characterization of Chick PEA (Cicer arietinum) Extract with Immunostimulant Activity in BALB/C MICE

Traditional plant medicines are used for a range of cancer conditions. The chickpea is highly proteinaceous and consumed as a staple in many parts of the world. An evaluation of chemoprotective and immunomodulatory activities of Cicer arietinum (CE) in cisplatin-induced immunosuppressed mice was here performed. Cisplatin was given at 100mg/kg, intraperitoneally, and after induction of immunosuppression mice were treated with Cicer arietinum (0.5 mg/dose/animal/IP) for a period of 10-day. The influence of the extract on lymphoid organ weight, bone marrow cellularity, alpha esterase activity and on enzyme levels such as (SGOT,SGPT, Urea, Creatinine was assessed to identify any chemoprotective influence. Administration of CE to cisplatin-treated mice alleviated the drastic reduction in bone marrow cellularity and α- esterase positive cells seen with cisplatin. Thus myelosuppression was reversed or inhibited. Cisplatin bids to DNA and causes damage resulting in chromosome breaks, micronucleus formation and cell death. CE is comprised of numerous middle-chain aliphatic alcohols, aldehydes and ketones, in addition to compounds like 7-hydroxy-1-methoxy-6-methylanthraquinone, cyclohexadecane (CAS) and 6-(amino methyl)-2-naphthol. These latter are thought to contribute to the characteristic aroma of C. arietimnum. In conclusion, administration of CE in cisplatin-treated mice, boosted bone marrow cellularity and increased α- esterase positive cells, thus reversing myelosupproession.

Discovery and characterization of Isofistularin-3, a marine brominated alkaloid, as a new DNA demethylating agent inducing cell cycle arrest and sensitization to TRAIL in cancer cells

We characterized the brominated alkaloid Isofistularin-3 (Iso-3), from the marine sponge Aplysina aerophoba, as a new DNA methyltransferase (DNMT)1 inhibitor. Docking analysis confirmed our in vitro DNMT inhibition data and revealed binding of Iso-3 within the DNA binding site of DNMT1. Subsequent increased expression of tumor suppressor gene aryl hydrocarbon receptor (AHR) could be correlated to decreased methylation of CpG sites within the essential Sp1 regulatory region of its promoter. Iso-3 induced growth arrest of cancer cells in G0/G1 concomitant with increased p21 and p27 expression and reduced cyclin E1, PCNA and c-myc levels. Reduced proliferation was accompanied by morphological changes typical of autophagy revealed by fluorescent and transmission electron microscopy and validated by LC3I-II conversion. Furthermore, Iso-3 strongly synergized with tumor-necrosis-factor related apoptosis inducing ligand (TRAIL) in RAJI [combination index (CI) = 0.22] and U-937 cells (CI = 0.21) and increased TRAIL-induced apoptosis via a mechanism involving reduction of survivin expression but not of Bcl-2 family proteins nor X-linked inhibitor of apoptosis protein (XIAP). Iso-3 treatment decreased FLIP_L expression and triggered activation of endoplasmatic reticulum (ER) stress with increased GRP78 expression, eventually inducing TRAIL receptor death receptor (DR)5 surface expression. Importantly, as a potential candidate for further anticancer drug development, Iso-3 reduced the viability, colony and in vivo tumor forming potential without affecting the viability of PBMCs from healthy donors or zebrafish development.

Imminent Angiotensin-converting Enzyme Inhibitor from Microbial Source for Cancer Therapy

Background

Drugs targeting Angiotensin I-converting enzyme (ACE) have been used broadly in cancer chemotherapy. The recent past coupled with our results demonstrates the effective use of ACE inhibitors (ACEi) as anticancer agents, and they are potentially relevant in deriving new inhibitors.

Methods

Bacterial strains were isolated from cow milk collected in Coimbatore, Tamil Nadu, India and plated on nutrient agar medium. The identity of the strain was ascertained by 16s rRNA gene sequencing method and was submitted to the NCBI GenBank nucleotide database. Various substrates were screened for ACEi production by the fermentation with the isolated strain. ACEi was purified by sequential steps of ethanol precipitation, ion exchange column chromatography and gel filtration column chromatography. The apparent molecular mass was determined by SDS-PAGE. The anticancer property was analyzed by studying the cytotoxicity effects of ACEi using Breast cancer MCF-7 cell lines.

Results

The isolate coded as BUCTL09 was selected and identified as Micrococcus luteus. Among the seven substrates, only beef extract fermented broth showed an inhibition of 79% and was reported as the best substrate. The peptide was purified and molecular mass was determined. The IC50 value of peptide was found to be 59.5 μg/ml. The purified peptide has demonstrated to induce apoptosis of cancer cell.

Conclusions

The results of this study revealed that Peptide has been determined as an active compound that inhibited the activity of ACE. These properties indicate the possibilities of the use of purified protein as a potent anticancer agent.

In vitro cytotoxicity and antimicrobial activity of Talaromyces flavus SP5 inhabited in the marine sediment of Southern Coast of India

Marine sediment samples were collected from the coastal areas of Southern India, particularly in Kanyakumari District. Twenty-eight different fungal strains were isolated. The screening of fungi from marine sediment was done to isolate a potent fungus that can produce bioactive compounds for biomedical applications. Only three strains viz Trichoderma gamsii SP4, Talaromyces flavus SP5 and Aspergillus oryzae SP6 were screened for further studies. The intracellular bioactive compounds were extracted using solvent extraction method. The crude extracts were tested for its anti-microbial and anti-cancer properties and analytically characterized using Gas Chromatography Mass Spectrometry (GC-MS). All the three extracts were active, but the extract from T. flavus SP5 was found to be more active against various human pathogens, viz., Pseudomonas aeruginosa ATCC 27853 (17.8 ± 0.1), Escherichia coli ATCC 52922 (18.3 ± 0.3), and Candida tropicalis ATCC 750 (17.7 ± 0.4). It also exhibited cytotoxic activity against HEp2 carcinoma cell line with the LC₅₀ value of 25.7 μg·L^-1. The GC-MS data revealed the presence of effective bioactive compounds. These results revealed that the extract from isolated fungus T. flavus SP5 acted as a potent antimicrobial, antifungal, and anticancer agent, providing basic information on the potency of marine fungi towards biomedical applications; further investigation may lead to the development of novel anticancer drugs.

The Effects of Purified Artemia Extract Proteins on Proliferation, Differentiation and Apoptosis of Human Leukemic HL-60 Cells

There has been an increment in the number of studies focused on marine bioactive materials. Many peptides and other biomaterials with anticancer potential have been extracted from various marine animals. Artemia extracts have found uses in sun-light protection cosmetics and anti-aging products. However, contents of biochemical compounds in Artemia spp. and molecular mechanisms of have not been clearly studied in leukemic cells in vitro. In this work, we isolated and purified proteins of Artemia Urmiana. Six clear fractions (A-F) observed on DEAE-cellulose chromatography were assayed for effects on cell growth, differentiation and apoptosis using the human leukemic HL-60 cell line. Cell proliferation analysis by MTT and BrdU assays indicated that did not affect cells, growth. Cells treated with crude extract and fractions A, B and C, but not E and F (up to 100 µg/mL), exhibited increase of cell growth in a dose dependent manner. Stimulatory effects of fraction D were observed at concentrations of 10 µg/ml and above. In nitro blue tetrazolium (NBT) reduction assays, treatment with 100 µg/mL of fraction E or F for 96 hr increased the fraction of differentiated cells up to 14.8 ± 3.56% and 16.5 ± 2.08% respectively. Combination of those fractions with retinoic acid had significant synergistic effects on the differentiation of cells (56.8 ± 3.7% and 67.4 ± 4.2%, p≤0.01). Annexin-V FITC staining for apoptosis and flow cytometric assays indicated induction of apoptosis by fractions E and F up to 23.8 and 31.8% of cells.

Blue-Print Autophagy: Potential for Cancer Treatment

The marine environment represents a very rich source of biologically active compounds with pharmacological applications. This is due to its chemical richness, which is claiming considerable attention from the health science communities. In this review we give a general overview on the marine natural products involved in stimulation and inhibition of autophagy (a type of programmed cell death) linked to pharmacological and pathological conditions. Autophagy represents a complex multistep cellular process, wherein a double membrane vesicle (the autophagosome) captures organelles and proteins and delivers them to the lysosome. This natural and destructive mechanism allows the cells to degrade and recycle its cellular components, such as amino acids, monosaccharides, and lipids. Autophagy is an important mechanism used by cells to clear pathogenic organism and deal with stresses. Therefore, it has also been implicated in several diseases, predominantly in cancer. In fact, pharmacological stimulation or inhibition of autophagy have been proposed as approaches to develop new therapeutic treatments of cancers. In conclusion, this blue-print autophagy (so defined because it is induced and/or inhibited by marine natural products) represents a new strategy for the future of biomedicine and of biotechnology in cancer treatment.

A microalga, Euglena tuba induces apoptosis and suppresses metastasis in human lung and breast carcinoma cells through ROS-mediated regulation of MAPKs

Background

Euglena tuba, a microalga, is known for its excellent antioxidant and iron-chelation activities; however its anticancer efficacies have not been reported yet. This study investigates the antitumor and antimetastatic activities of 70 % methanolic extract of Euglena tuba (ETME) against human lung (A549) and breast cancer (MCF-7) cells in vitro. Moreover, we had examined ETME’s role in inducing intracellular ROS with the regulation of antioxidants and MAPK pathway.

Methods

Anticancer activity of ETME was thoroughly studied using flow cytometry, confocal microscopy and western blotting; along with various biochemical assays for analysing ROS-induced regulation of antioxidant enzymes. Inhibition of invasion and migration of malignant cells by ETME were investigated by wound healing and zymographic studies. DNA–Protein interaction with ETME was also studied.

Results

ETME inhibited the growth of both A549 (IC₅₀ 92.14 µg/ml) and MCF-7 cells (IC₅₀ 50.27 µg/ml) by inducing apoptosis, while remained non-toxic against nomral WI-38 cells (IC₅₀ 911.43 µg/ml). ETME treatment resulted in increasing Bax/Bcl-2 ratio, BID truncation and activation of caspase cascade. This ultimately leads to PARP degradation and apoptosis through the intrinsic and extrinsic pathway in both A549 and MCF-7 cells. Wound healing and gelatin zymography studies revealed that ETME significantly inhibited the invasion and migration of both A549 and MCF-7 cells dose-dependently through the downregulation of MMP-9. Further investigations showed that ETME selectively induces intracellular ROS, regulated the levels of intracellular antioxidants and suppresses the activation of ERK1/2, JNK, P38 mitogen-activated protein kinase pathways in both type of malignant cells. Further DNA and protein binding studies revealed that ETME strongly interact with DNA as well as protein attributing the possibilities of presence of components which are targeting the macromolecules in cancer cells. Moreover, when the identified compounds from ETME were examined for their cytotoxicities individually, it was found that they lost their specificities towards cancer cells and also attacked normal cells.

Conclusions

Our study suggests that ETME retards the growth of both lung and breast cancer cells, in vitro, through multivariate mechanisms, proving its candidature for the development of better and safer drugs against these cancers.

Extract from Arca granosa L. Inhibits Proliferation of Human Tumour Cell Lines with Kidney and Lung Origin

Marine organisms are being considered increasingly as sources of anti-tumour agents. The extract from Arca granosa L. has been shown to decrease the growth of tumours and this study was undertaken to determine its ability and mechanism of inhibition. The extract inhibited the proliferation of six human tumour cell lines from different origins with varying sensitivity. The cell lines Ketr-3, A549 and NCI-H460 with kidney or lung origins were more sensitive to the extract than those of the HepG-2, MCF-7 and MGC-803 cells from other origins. In the three sensitive cell lines (Ketr-3, A549 and NCI-H460) the extract was shown to block different phases of the cell cycle progression and inhibit DNA synthesis in a concentration-dependent manner. It was concluded that the extract from A. granosa is potentially a novel anti-tumour agent, especially on kidney and lung tumour cell lines.

Alterations in the antibacterial potential of Synechococcus spp. PCC7942 under the influence of UV-B radiations on skin pathogens

Marine organisms are seen as a source of novel drugs and the discovery of new pharmaceutical is increasingly in demand. Cyanobacteria are regarded as a potential target for this as antibacterial, antiviral, antifungal, algicide and cytotoxic activities have been reported in these organisms. They have been identified as a new and rich source of bioactive compounds belonging to diversified groups. Radiation in the UV-B range interferes with various metabolic reactions by generating free radicals and active oxygen species. These deleterious compounds are inactivated by antioxidants. Among them are the carotenoids and phycocyanin which protect against photodynamic action in different ways. Stress plays an important role in the production of bioactive metabolites from organisms. Synechococcus spp. PCC7942 was studied for antibacterial activity against various pathogenic bacteria resistant to a number of available antibiotics after being exposed to UV-B radiation. The antibacterial activity of Synechococcus spp. PCC7942 was studied on five potent skin pathogens. The highest antibacterial activity was seen the methanol extracts of 24 h UV-B exposed cultures of Synechococcus spp. PCC7942. It can be concluded that there was moderate antibacterial activity. Results showed stress, solvent and dose-dependent activity. This antibacterial activity might be due to the enhanced synthesis of carotenoids and phycocyanin under UV-B stress. The purpose of the present study was to relate the inhibitory effects of the cyanobacterial compounds specifically on skin pathogens with exposure to UV-B radiation as UV protecting compounds are already reported in these organisms.

Statistical research on the bioactivity of new marine natural products discovered during the 28 years from 1985 to 2012

Every year, hundreds of new compounds are discovered from the metabolites of marine organisms. Finding new and useful compounds is one of the crucial drivers for this field of research. Here we describe the statistics of bioactive compounds discovered from marine organisms from 1985 to 2012. This work is based on our database, which contains information on more than 15,000 chemical substances including 4196 bioactive marine natural products. We performed a comprehensive statistical analysis to understand the characteristics of the novel bioactive compounds and detail temporal trends, chemical structures, species distribution, and research progress. We hope this meta-analysis will provide useful information for research into the bioactivity of marine natural products and drug development.

Bioactive compounds from Holothuria atra of Indian ocean

The sea cucumber (Holothuria atra) extracts have been evaluated for the presence of bioactive compounds and various biological activities. The methanol extracts showed anti proliferative activities against the Hela and MCF-7 cell lines. Similarly the inhibitory effects of Herpes simplex virus 1 and 2 cells were detected using the plaque reduction assay. The extracts of H. atra were purified using the silica gel column chromatography. The active fractions collected were observed for antimicrobial activity. The GC-MS analysis showed the availability of 59 compounds. The active bioactive compounds found in the H. atra were analyzed and their structure was identified using the ¹HNMR and ¹³C NMR experiments.

Apoptosis inducing lead compounds isolated from marine organisms of potential relevance in cancer treatment

Apoptosis is a critical defense mechanism against the formation and progression of cancer and exhibits distinct morphological and biochemical traits. Targeting apoptotic pathways becomes an intriguing strategy for the development of chemotherapeutic agents particularly if the process is selective to cancer cells. Marine natural products have become important sources in the discovery of antitumour drugs, especially when recent technological and methodological advances have increased the scope of investigations of marine organisms. A high number of individual compounds from diverse organisms have induced apoptosis in several tumour cell lines via a number of mechanisms. Here, we review the effects of selected marine natural products and their synthetic derivatives on apoptosis signalling pathways in association with their pharmacological properties. Providing an outlook into the future, we also examine the factors that contribute to new discoveries and the difficulties associated with translating marine-derived compounds into clinical trials.

Microorganisms living on macroalgae: diversity, interactions, and biotechnological applications

Marine microorganisms play key roles in every marine ecological process, hence the growing interest in studying their populations and functions. Microbial communities on algae remain underexplored, however, despite their huge biodiversity and the fact that they differ markedly from those living freely in seawater. The study of this microbiota and of its relationships with algal hosts should provide crucial information for ecological investigations on algae and aquatic ecosystems. Furthermore, because these microorganisms interact with algae in multiple, complex ways, they constitute an interesting source of novel bioactive compounds with biotechnological potential, such as dehalogenases, antimicrobials, and alga-specific polysaccharidases (e.g., agarases, carrageenases, and alginate lyases). Here, to demonstrate the huge potential of alga-associated organisms and their metabolites in developing future biotechnological applications, we first describe the immense diversity and density of these microbial biofilms. We further describe their complex interactions with algae, leading to the production of specific bioactive compounds and hydrolytic enzymes of biotechnological interest. We end with a glance at their potential use in medical and industrial applications.

Anticancer and antitumor potential of fucoidan and fucoxanthin, two main metabolites isolated from brown algae

Seaweed is one of the largest producers of biomass in marine environment and is a rich arsenal of active metabolites and functional ingredients with valuable beneficial health effects. Being a staple part of Asian cuisine, investigations on the crude extracts of Phaeophyceae or brown algae revealed marked antitumor activity, eliciting a variety of research to determine the active ingredients involved in this potential. The sulfated polysaccharide of fucoidan and carotenoid of fucoxanthin were found to be the most important active metabolites of brown algae as potential chemotherapeutic or chemopreventive agents. This review strives to provide detailed account of all current knowledge on the anticancer and antitumor activity of fucoidan and fucoxanthin as the two major metabolites isolated from brown algae.

Cytotoxic and cytolytic cnidarian venoms. A review on health implications and possible therapeutic applications

The toxicity of Cnidaria is a subject of concern for its influence on human activities and public health. During the last decades, the mechanisms of cell injury caused by cnidarian venoms have been studied utilizing extracts from several Cnidaria that have been tested in order to evaluate some fundamental parameters, such as the activity on cell survival, functioning and metabolism, and to improve the knowledge about the mechanisms of action of these compounds. In agreement with the modern tendency aimed to avoid the utilization of living animals in the experiments and to substitute them with in vitro systems, established cell lines or primary cultures have been employed to test cnidarian extracts or derivatives. Several cnidarian venoms have been found to have cytotoxic properties and have been also shown to cause hemolytic effects. Some studied substances have been shown to affect tumour cells and microorganisms, so making cnidarian extracts particularly interesting for their possible therapeutic employment. The review aims to emphasize the up-to-date knowledge about this subject taking in consideration the importance of such venoms in human pathology, the health implications and the possible therapeutic application of these natural compounds.

Antiproliferative activity of methanolic extracts from two green algae, Enteromorpha intestinalis and Rizoclonium riparium on HeLa cells

Background

Natural compounds can be alternative sources for finding new lead anti-cancer molecules. Marine algae have been a traditional source for bioactive compounds. Enteromorpha intestinalis and Rhizoclonium riparium are two well distributed saline/brackish water algae from Sundarbans. There’s no previous report of these two for their anti-proliferative activities.

Methods

Cytotoxicity of the algal methanolic extracts (AMEs) on HeLa cells were assayed by 3-(4, 5-dimethylthiazol-2-yl)-2, 5- diphenyltetrazolium bromide (MTT) reduction assay. Morphological examinations were done by Haematoxylin, Hoechst 33258 and Acridine orange staining. DNA fragmentation was checked. Gene expressions of Cysteine aspartate protease (Caspase) 3, Tumor protein (TP) 53, Bcl-2 associated protein X (Bax) were studied by Reverse transcription- polymerase chain reaction (RT-PCR) keeping Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) as internal control. Protein expressions were studied for Caspase 3, phospho-p53, Bax, Microtubule associated proteins-1/ light chain B (MAP1/LC3B) by western blot.

Results

The AMEs were found to be cytotoxic with Inhibitory concentration 50 (IC50) values 309.048 ± 3.083 μg/ml and 506.081 ± 3.714 μg/ml for E. intestinalis and R. riparium extracts respectively. Treated cells became round with blebbings with condensed nuclei. Acidic lysosomal vacuoles formation occurred in treated cells. Expression of apoptotic genes in both mRNA and protein level was lowered. Expression of LC3B-II suggested occurrence of autophagy in treated cells.

Conclusions

These two algae can be potent candidates for isolating new lead anticancer molecules. So they need further characterization at both molecular and structural levels.

Marine-derived Aspergillus species as a source of bioactive secondary metabolites

This report reviews biologically active secondary metabolites from marine-derived members of the fungal genus Aspergillus. Pharmacological activities and biological roles of the secondary metabolites from marine-derived Aspergillus spp. were addressed in respect of pharmaceutical potential.

Hurgadacin: a new steroid from Sinularia polydactyla

Hurgadacin (1), a 24,25-bishomo-26-methylenecholesterol was isolated from the soft coral Sinularia polydactyla, collected from the Red Sea, near Hurghada at the Egyptian coast. The new steroid 1 was isolated together with the closely related polyhydroxy steroids 24-methylenecholestane-3β,5α,6β-triol (2) and 24-methylenecholestane-1α,3β,5α,6β,11α-pentol (3), in addition to the sesquiterpene lactiflorenol (4) and the trinorcarotenolide acetate peridinin (5), The structures of the isolated compounds were confirmed by intensive studies of their 1D and 2D NMR spectra and mass data. The antimicrobial and cytotoxic activities of the soft coral extract and the corresponding constituents were evaluated against diverse pathogenic microorganisms and brine shrimps, respectively.

Potential for green microalgae to produce hydrogen, pharmaceuticals and other high value products in a combined process

Green microalgae for several decades have been produced for commercial exploitation, with applications ranging from health food for human consumption, aquaculture and animal feed, to coloring agents, cosmetics and others. Several products from green algae which are used today consist of secondary metabolites that can be extracted from the algal biomass. The best known examples are the carotenoids astaxanthin and β-carotene, which are used as coloring agents and for health-promoting purposes. Many species of green algae are able to produce valuable metabolites for different uses; examples are antioxidants, several different carotenoids, polyunsaturated fatty acids, vitamins, anticancer and antiviral drugs. In many cases, these substances are secondary metabolites that are produced when the algae are exposed to stress conditions linked to nutrient deprivation, light intensity, temperature, salinity and pH. In other cases, the metabolites have been detected in algae grown under optimal conditions, and little is known about optimization of the production of each product, or the effects of stress conditions on their production. Some green algae have shown the ability to produce significant amounts of hydrogen gas during sulfur deprivation, a process which is currently studied extensively worldwide. At the moment, the majority of research in this field has focused on the model organism, Chlamydomonas reinhardtii, but other species of green algae also have this ability. Currently there is little information available regarding the possibility for producing hydrogen and other valuable metabolites in the same process. This study aims to explore which stress conditions are known to induce the production of different valuable products in comparison to stress reactions leading to hydrogen production. Wild type species of green microalgae with known ability to produce high amounts of certain valuable metabolites are listed and linked to species with ability to produce hydrogen during general anaerobic conditions, and during sulfur deprivation. Species used today for commercial purposes are also described. This information is analyzed in order to form a basis for selection of wild type species for a future multi-step process, where hydrogen production from solar energy is combined with the production of valuable metabolites and other commercial uses of the algal biomass.

Biosynthesis of Athmu, a α,γ-hydroxy-β-amino acid of pahayokolides A-B

Pahayokolides A-B are cyanobacteria derived non-ribosomal peptides which exhibit cytotoxicity against a number of cancer cell lines. The biosynthetic origin of the 3-amino-2,5,7,8-tetrahydroxy-10-methylundecanoic acid (Athmu) moiety has been investigated using stable isotope incorporation experiments. While α-ketoisocaproic acid (α-KIC), α-hydroxyisocaproic acid (α-HIC) and leucine all serve as precursors to Athmu, the feeding of [1-(13)C] α-KIC results in more than threefold greater (13)C enrichment than the other precursors. This result suggests that α-KIC is the immediate precursor which is selected and activated by the adenylation domain of the loading NRPS module and subsequently reduced in a fashion similar to that of the recently identified pathways for cryptophycins A-B, cereulide and valinomycin.

Bioactive peptides and depsipeptides with anticancer potential: sources from marine animals

Biologically active compounds with different modes of action, such as, antiproliferative, antioxidant, antimicrotubule, have been isolated from marine sources, specifically algae and cyanobacteria. Recently research has been focused on peptides from marine animal sources, since they have been found as secondary metabolites from sponges, ascidians, tunicates, and mollusks. The structural characteristics of these peptides include various unusual amino acid residues which may be responsible for their bioactivity. Moreover, protein hydrolysates formed by the enzymatic digestion of aquatic and marine by-products are an important source of bioactive peptides. Purified peptides from these sources have been shown to have antioxidant activity and cytotoxic effect on several human cancer cell lines such as HeLa, AGS, and DLD-1. These characteristics imply that the use of peptides from marine sources has potential for the prevention and treatment of cancer, and that they might also be useful as molecular models in anticancer drug research. This review focuses on the latest studies and critical research in this field, and evidences the immense potential of marine animals as bioactive peptide sources.

Exploring marine cyanobacteria for lead compounds of pharmaceutical importance

The Ocean, which is called the "mother of origin of life," is also the source of structurally unique natural products that are mainly accumulated in living organisms. Cyanobacteria are photosynthetic prokaryotes used as food by humans. They are excellent source of vitamins and proteins vital for life. Several of these compounds show pharmacological activities and are helpful for the invention and discovery of bioactive compounds, primarily for deadly diseases like cancer, acquired immunodeficiency syndrome (AIDS), arthritis, and so forth, while other compounds have been developed as analgesics or to treat inflammation, and so forth. They produce a large variety of bioactive compounds, including substances with anticancer and antiviral activity, UV protectants, specific inhibitors of enzymes, and potent hepatotoxins and neurotoxins. Many cyanobacteria produce compounds with potent biological activities. This paper aims to showcase the structural diversity of marine cyanobacterial secondary metabolites with a comprehensive coverage of alkaloids and other applications of cyanobacteria.

Didemnins, tamandarins and related natural products

Since the discovery and isolation of the didemnin family of marine depsipeptides in 1981, the synthesis and biological activity of its congeners have been of great interest to the scientific community. The didemnins have demonstrated antitumor, antiviral, and immunosuppressive activity at low nano- and femtomolar levels. Of the congeners, didemnin B was the first marine natural product to reach phase II clinical trials in the United States, stimulating many analogue syntheses to date. About two decades later, tamandarins A and B were isolated, and were found to possess very similar structure and biological activity to that of the didemnin B. These compounds have shown impressive biological activity and some progress has been made in establishing structure-activity relationships. However, their molecular mechanism of action still remains unclear. This review highlights the long-standing study of didemnins and its critical application towards the understanding of the molecular mechanism of action of tamandarins and their potential use as therapeutic agents.

Bioactive substances with anti-neoplastic efficacy from marine invertebrates: Porifera and Coelenterata

An ever increasing demand for new lead compounds in the pharmaceutical industry has led scientists to search for natural bioactive products. Based on this extensive research, marine invertebrates now represent a rich source of novel substances with significant anti-neoplastic activities. As the current approach of synthesizing new and chemically modifying old drugs seems to have slowed down, and the identification of new anticancer drugs is not too promising, a new approach is clearly needed. The objective of this review is to present up-to-date data on these newer compounds. Based on the data summarized in this short review, it is clear that marine invertebrates represent an extremely important source of compounds with potential anti-cancer effects. Considering that we tested only a tiny number of Porifera and Coelenterata, the best is yet to come.

Bioactive substances with anti-neoplastic efficacy from marine invertebrates: Bryozoa, Mollusca, Echinodermata and Urochordata

The marine environment provides a rich source of natural products with potential therapeutic application. This has resulted in an increased rate of pharmaceutical agents being discovered in marine animals, particularly invertebrates. Our objective is to summarize the most promising compounds which have the best potential and may lead to use in clinical practice, show their biological activities and highlight the compounds currently being tested in clinical trials. In this paper, we focused on Bryozoa, Mollusca, Echinodermata and Urochordata.

Natural products from ethnodirected studies: revisiting the ethnobiology of the zombie poison

Wade Davis's study of Haitian “zombification” in the 1980s was a landmark in ethnobiological research. His research was an attempt to trace the origins of reports of “undead” Haitians, focusing on the preparation of the zombification poison. Starting with this influential ethnopharmacological research, this study examines advances in the pharmacology of natural products, focusing especially on those of animal-derived products. Ethnopharmacological, pharmacological, and chemical aspects are considered. We also update information on the animal species that reportedly constitute the zombie poison. Several components of the zombie powder are not unique to Haiti and are used as remedies in traditional medicine worldwide. This paper emphasizes the medicinal potential of products from zootherapy. These biological products are promising sources for the development of new drugs.

Dieckol from Ecklonia cava Regulates Invasion of Human Fibrosarcoma Cells and Modulates MMP-2 and MMP-9 Expression via NF-κB Pathway

The matrix metalloproteinase (MMP) family is involved in the breakdown of extracellular matrix in normal physiological processes, as well as in the disease processes such as arthritis and cancer metastasis. In the present study, dieckol was obtained with high yield from marine brown alga Ecklonia cava (EC), and its effect was assessed on the expression of MMP-2 and -9 and morphological changes in human fibrosarcoma cell line (HT1080). Dieckol inhibited the expression of MMP-2 and -9 in a dose-dependent manner and also suppressed the cell invasion and the cytomorphology in 3D culture system on HT1080 cells. Moreover, dieckol may influence nuclear factor kappa B (NF-κB) pathway without obvious influence on activator protein-1 (AP-1) pathway and tissue inhibitor of metalloproteinases (TIMPs). In conclusion, dieckol could significantly suppress MMP-2 and -9 expression and alter cytomorphology of HT1080 cell line via NF-κB pathway.

ANTIMICROBIAL AND ANTIHYPERLIPIDEMIC ACTIVITIES OF ISOLATED QUERCETIN FROM ANABAENA AEQUALIS(1)

This study aimed to isolate quercetin (for the first time) from Anabaena aequalis Borge, which inhabits soil surface of Wadi El-Alaqui Protectorate located in Aswan city, Egypt. The isolated compound showed significant antibacterial activity against the gram-positive bacteria Sarcina maxima and Micrococcus kristinae, the gram-negative bacterium Klebsiella pneumoniae, as well as against the filamentous fungus Aspergillus flavus. The isolated compound was identified as quercetin using the structure elucidation based on UV, electrospray ionization mass spectrometry (ESIMS), (1) H and (13) C NMR, proton-proton correlation spectroscopy ((1) H-(1) H COSY), distortionless enhancement by polarization transfer (DEPT), heteronuclear single quantum coherence (HSQC), and heteronuclear multiple bond correlations spectrum (HMBC). Medium lethal dose (LD50 ) of the isolated compound and its side effects against hyperlipidemia induced by ethanol intake in albino rats were carried out. No deaths were reported in rats within 72 h, which suggests that the isolated compound plays a beneficial role as an antihyperlipidemic agent in the treatment of alcohol-induced hepatic tissue damage, which can be described as one of the therapeutic values.

Marine pharmacology in 2007-8: Marine compounds with antibacterial, anticoagulant, antifungal, anti-inflammatory, antimalarial, antiprotozoal, antituberculosis, and antiviral activities; affecting the immune and nervous system, and other miscellaneous mechanisms of action

The peer-reviewed marine pharmacology literature in 2007-8 is covered in this review, which follows a similar format to the previous 1998-2006 reviews of this series. The preclinical pharmacology of structurally characterized marine compounds isolated from marine animals, algae, fungi and bacteria is discussed in a comprehensive manner. Antibacterial, anticoagulant, antifungal, antimalarial, antiprotozoal, antituberculosis and antiviral activities were reported for 74 marine natural products. Additionally, 59 marine compounds were reported to affect the cardiovascular, immune and nervous systems as well as to possess anti-inflammatory effects. Finally, 65 marine metabolites were shown to bind to a variety of receptors and miscellaneous molecular targets, and thus upon further completion of mechanism of action studies, will contribute to several pharmacological classes. Marine pharmacology research during 2007-8 remained a global enterprise, with researchers from 26 countries, and the United States, contributing to the preclinical pharmacology of 197 marine compounds which are part of the preclinical marine pharmaceuticals pipeline. Sustained preclinical research with marine natural products demonstrating novel pharmacological activities, will probably result in the expansion of the current marine pharmaceutical clinical pipeline, which currently consists of 13 marine natural products, analogs or derivatives targeting a limited number of disease categories.

Pharmacological Developments Obtained from Marine Natural Products and Current Pipeline Perspective

Marine organisms represent a new extensive source for bioactive molecules. They have the potential to provide new therapeutic alternatives to treat human diseases. In this paper, we describe and discuss a variety of isolated and semisynthetic molecules obtained from marine sources. These compounds are in phase II, phase III and at the commercialization stage of new drug development. A description of the mechanism of action, dosage used and side effects are also reported. The positive results obtained from these studies have triggered the development of new studies to evaluate the prospects for utilization of marine organisms.

New peptides isolated from Lyngbya species: a review

Cyanobacteria of the genus Lyngbya have proven to be prodigious producers of secondary metabolites. Many of these compounds are bioactive and show potential for therapeutic use. This review covers peptides and hybrid polyketide-non-ribosomal peptides isolated from Lyngbya species. The structures and bioactivities of 50 Lyngbya peptides which were reported since 2007 are presented.

Cell-based assay coupled with chromatographic fractioning: a strategy for marine toxins detection in natural samples

Cell-based assays (CBA) have been proposed for the evaluation of toxicity caused by marine toxins in natural samples (fish, shellfish and microalgae). However, their application has been hindered due to the interferences present in biological matrices that may cause cellular response and interfere in toxicity evaluation. This work reviews in an extensive introduction the use of CBA for toxicity evaluation of marine toxins. Afterwards, the coupling of chromatographic fractioning with neuroblastoma Neuro-2a CBA is presented to enhance the applicability of CBA for complex matrices. Examples of application are provided for mussel samples (Mytilus galloprovincialis) and microalgae (Gambierdiscus sp.), and the results demonstrated the great potential of the combined strategy for reliable toxicological evaluation without ethical concern. Fractioning of an equivalent of 72 mg eq mL(-1) of mussel sample allowed the identification of non-toxic and toxic fractions whereas only 2.5mg eq mL(-1) of non-purified mussel sample was responsible for 20% of cell mortality. Furthermore, the application of CBA allowed selectively distinguishing between ciguatoxin-like and other unspecific toxicity in Gambierdiscus sp. extract.