A Survey of Marine Natural Compounds and Their Derivatives with Anti-cancer Activity Reported in 2012

A Marine Natural Product, Harzianopyridone, as an Anti-ZIKV Agent by Targeting RNA-Dependent RNA Polymerase

The Zika virus (ZIKV) is a mosquito-borne virus that already poses a danger to worldwide human health. Patients infected with ZIKV generally have mild symptoms like a low-grade fever and joint pain. However, severe symptoms can also occur, such as Guillain-Barré syndrome, neuropathy, and myelitis. Pregnant women infected with ZIKV may also cause microcephaly in newborns. To date, we still lack conventional antiviral drugs to treat ZIKV infections. Marine natural products have novel structures and diverse biological activities. They have been discovered to have antibacterial, antiviral, anticancer, and other therapeutic effects. Therefore, marine products are important resources for compounds for innovative medicines. In this study, we identified a marine natural product, harzianopyridone (HAR), that could inhibit ZIKV replication with EC50 values from 0.46 to 2.63 µM while not showing obvious cytotoxicity in multiple cellular models (CC50 > 45 µM). Further, it also reduced the expression of viral proteins and protected cells from viral infection. More importantly, we found that HAR directly bound to the ZIKV RNA-dependent RNA polymerase (RdRp) and suppressed its polymerase activity. Collectively, our findings provide HAR as an option for the development of anti-ZIKV drugs.

Synergistic Cytotoxicity of Extracts of Chaga Mushroom and Microalgae against Mammalian Cancer Cells In Vitro

Chaga mushroom (Inonotus obliquus) contains bioactive metabolites and has been used to treat various ailments, including cancer. Similarly, marine microalgae are considered a sustainable food supplement with anticancer and antioxidant properties. This study investigated the cytotoxicity of different extracts prepared from I. obliquus and microalgae using cultured human and canine cancer cell lines (MCF-7, HepG2, HOS, D-17, and DH-82). MTS cell viability assay was used to study the cytotoxicity of I. obliquus and microalgae extracts, and a synergy matrix effect was used to study the combined effect of the extracts. Isobologram analysis and the highest single agent synergy model were applied to study and validate the synergy between the extracts from I. obliquus and microalgae. Ethanol-based extraction and supercritical water extract significantly inhibited the growth of various mammalian cancer cells compared to aqueous extracts. Osteosarcoma cells were more susceptible to the supercritical extracts of I. obliquus and chlorophyll-free and sugar-free ethanol extracts of microalgae. A combination of ethanol-based I. obliquus extract and chlorophyll-free microalgae extract resulted in a synergistic interaction with various tested cancer cells. This study provides experimental evidence supporting the potential therapeutic application of I. obliquus and microalgae extracts with a synergistic effect to inhibit the growth of various mammalian cancer cells. Additional in vivo studies are required to fully explore possible therapeutic applications of these unique mixtures to be used in treating cancers.

A new cembranoid from the Red Sea soft coral Sarcophyton acutum

The Red Sea soft coral Sarcophyton acutum ethyl acetate extract has afforded one new cembranoid; sarcacutumolid A (1), along with six known metabolites have been isolated from S. acutum for the first time (2-7). Chemical structures were elucidated by employing several spectroscopic analyses. The cytotoxic potential of the isolated compounds was assessed against four human cancer cell lines; hepatocellular (HepG2), cervical (HeLa), breast (MCF-7) and colorectal cancer (Colo-205). Sarcacutumolid A (1) and gorgosterol (7) inhibited colorectal cancer cell proliferation in a concentration-dependent manner with IC50 values of 35.5 and 44.0 μM, respectively.

Sea Conch Peptides Hydrolysate Alleviates DSS-Induced Colitis in Mice through Immune Modulation and Gut Microbiota Restoration

Inflammatory bowel disease (IBD) is a persistent, lifelong inflammation of the digestive system. Dextran sulfate sodium is commonly used to induce colitis in experimental animal models, which causes epithelial damage, intestinal inflammation, mucin depletion, and dysbiosis of the gut microbiota. Various prebiotics, polysaccharides, and polypeptides are used for IBD treatment. In this study, we used a murine model utilizing BALB/c mice, with 10 mice per group, to investigate the treatment effect of sea conch peptide hydrolysate (CPH) on DSS-induced colitis mice. Colitis was induced through the administration of 2.5% DSS in drinking water over a seven-days period. Furthermore, on the eighth day of the experiment, sea conch peptide hydrolysate (CPH) at low (100 mg/kg), medium (200 mg/kg), and high (400 mg/kg) doses, which were continued for 14 days, were assessed for medicinal purposes in DSS-induced colitis mice. Our results showed that CPH treatment significantly alleviated the severity and symptoms of colitis. The epithelial integrity and histological damage were improved. Intestinal inflammation and inflammatory cell infiltration were improved. Furthermore, the expression of pro-inflammatory cytokines was reduced, and intestinal barrier integrity was restored by elevating the tight junction proteins. Moreover, 16s RNA sequencing revealed dysbiosis of the gut microbiota was observed upon DSS treatment, which was reinstated after CPH treatment. An increased level of Firmicutes and Lactobacillus was observed in the treatment groups. Finally, our results suggest that CPH would be recommended as a functional food source and also have the potential to be used as a medicinal product for different gastrointestinal disorders.

Promising Antiparasitic Natural and Synthetic Products from Marine Invertebrates and Microorganisms

Parasitic diseases still threaten human health. At present, a number of parasites have developed drug resistance, and it is urgent to find new and effective antiparasitic drugs. As a rich source of biological compounds, marine natural products have been increasingly screened as candidates for developing new antiparasitic drugs. The literature related to the study of the antigenic animal activity of marine natural compounds from invertebrates and microorganisms was selected to summarize the research progress of marine compounds and the structure-activity relationship of these compounds in the past five years and to explore the possible sources of potential antiparasitic drugs for parasite treatment.

Crosstalk between biological and chemical diversity with cytotoxic and cytostatic effects of Aphanothece halophytica in vitro

Different solvent extracts from Aphanothece halophytica (A. halophytica) were evaluated for their cytotoxic effects against four human cancer cell lines. The samples demonstrated different percentages of cyanobacteria species populations. The samples containing 100% A. halophytica and 90% A. halophytica showed a significant cytotoxic effect in human breast cancer cells MDA231. The cytostatic effect was demonstrated in MDA231 and human glioblastoma T98G cells regardless of the treatment, resulting in a significant cell cycle arrest in the S phase. The chemical profiles of the extracts were proven to be diverse in qualitative and quantitative compositions. This variability was dependent on the A. halophytica´s abundance in each extract. The 100% A. halophytica extract induced cytotoxic and cytostatic effects in breast cancer cells, and those could be associated with the predominance of fatty acids, hydrocarbons and phthalates, indicating that A. halophytica is an interesting source of novel compound with anticancer effect.

Antitumor immunity and therapeutic properties of marine seaweeds-derived extracts in the treatment of cancer

Marine seaweeds are important sources of drugs with several pharmacological characteristics. The present study aims to evaluate the antitumor and antitumor immunological potentials of the extracts from the brown alga Padina pavonica and the red alga Jania rubens, inhibiting the Egyptian marine coasts. Hep-G2 cell lines were used for assessment of the antitumor efficacy of Padina pavonica and Jania rubens extracts in vitro, while Ehrlich ascites carcinoma (EAC) cells were applied to gain more antitumor immunity and antitumor insights of P. pavonica and J. rubens extracts in vivo. In vitro antitumor potentials of P. pavonica and J. rubens extracts were analyzed against human liver cancer Hep-G2 cells by MTT and trypan blue exclusion assays. In vivo antitumor immunological potentials of P. pavonica and J. rubens extracts at low, high, and prophylactic doses were analyzed by blood counting and flow cytometry in mice challenged with Ehrlich ascites carcinoma (EAC) cells. In vitro results revealed that P. pavonica and J. rubens extracts caused significant decreases in the number and viability of Hep-G2 cells in a dose-dependent manner as compared to untreated Hep-G2 cells or Cisplatin®-treated Hep-G2 cells. In vivo findings showed that P. pavonica and J. rubens extracts at low, high, and prophylactic doses significantly reduced the number and viability of EAC tumor cells accompanied by increases in EAC apoptosis compared to naïve EAC mouse. Additionally, P. pavonica and J. rubens extracts at low and prophylactic doses remarkably increased both the total WBC count and the relative numbers of lymphocytes and decreased the relative numbers of neutrophils and monocytes. Flow cytometric analysis showed that P. pavonica and J. rubens extracts at the treatment and the prophylactic doses resulted in a significant increase in the phenotypic expressions of CD4+ T, CD8+ T, and CD335 cells compared to naïve EAC mouse. Overall, both extracts P. pavonica and J. rubens possess potential antitumor and antitumor immunological effects with less toxicity, opening new approaches for further studies of the chemical and biological mechanisms behind these effects.

Evaluation of in vitro cytotoxic activity of different solvent extracts of Clerodendrum thomsoniae Balf.f and its active fractions on different cancer cell lines

Background

Clerodendrumis a genus of about 500 species belongs to the family Lamiaceae. Many species of this genus have been proved for the treatment of various diseases. This study was aimed to evaluate the cytotoxic effect of different solvents and their most active fractions ofClerodendrum thomsoniaeBalf.f. in different human cancer cell lines. Aerial parts of the plant were subjected to Soxhlet extraction. Phytochemical analysis was done by using standard tests. In vitro anti-cancer activity on MCF-7, Hep-G2, A549, HT-29, MOLT-4, Hela, and Vero cell lines were evaluated by MTT assay.

Results

Phytochemical analysis confirmed the presence of most of the phytoconstituents in ethyl acetate extracts and the same extracts were found to be more cytotoxic activity to cancer cell lines MCF-7,Hep-G2,A549,HT–29, MOLT-4, and Hela with IC50values 29.43 ± 1.44 μg/ml, 43.22 ± 1.02 μg/ml, 56.93 ± 1.41 μg/ml, 60.68 ± 1.05 μg/ml, 69.83 ± 1.33 μg/ml, and 40.02 ± 1.14 μg/ml respectively, while it had no cytotoxic effect on normal Vero cells IC50= 367.5 ± 1.03 μg/ml. Ethyl acetate extracts were selected for the fractionation and MCF-7 cell line was used repeat MTT assay and found that fraction F5 was the most active fraction with IC5017.33 ± 0.54 μg/ml.

Conclusion

These findings have proved thatClerodendrum thomsoniaeBalf.f. have significant cytotoxicity especially for breast cancer cell lines. Further studies are required for the isolation of constituents and to explore the mechanism of action.

Cyanobacteria derived compounds: Emerging drugs for cancer management

The wide diversity of cyanobacterial species and their role in a variety of biological activities have been reported in the previous few years. Cyanobacteria, especially from marine sources, constitutes a major source of biologically active metabolites that have gained great attention especially due to their anticancer potential. Numerous chemically diverse metabolites from various cyanobacterial species have been recognized to inhibit the growth and progression of tumor cells through the induction of apoptosis in many different types of cancers. These metabolites activate the apoptosis in the cancer cells by different molecular mechanisms, however, the dysregulation of the mitochondrial pathway, death receptors signaling pathways, and the activation of several caspases are the crucial mechanisms that got considerable interest. The array of metabolites and the range of mechanisms involved may also help to overcome the resistance acquired by the different tumor types against the ongoing therapeutic agents. Therefore, the primary or secondary metabolites from the cyanobacteria as well as their synthetic derivates could be used to develop novel anticancer drugs alone or in combination with other chemotherapeutic agents. In this study, we have discussed the role of cyanobacterial metabolites in the induction of cytotoxicity and the potential to inhibit the growth of cancer cells through the induction of apoptosis, cell signaling alteration, oxidative damage, and mitochondrial dysfunctions. Moreover, the various metabolites produced by cyanobacteria have been summarized with their anticancer mechanisms. Furthermore, the ongoing trials and future developments for the therapeutic implications of these compounds in cancer therapy have been discussed.

Secondary Metabolites from Marine Sources with Potential Use as Leads for Anticancer Applications

The development of novel anticancer agents is essential to finding new ways to treat this disease, one of the deadliest diseases. Some marine organisms have proved to be important producers of chemically active compounds with valuable bioactive properties, including anticancer. Thus, the ocean has proved to be a huge source of bioactive compounds, making the discovery and study of these compounds a growing area. In the last few years, several compounds of marine origin, which include algae, corals, and sea urchins, have been isolated, studied, and demonstrated to possess anticancer properties. These compounds, mainly from securamines and sterols families, have been tested for cytotoxic/antiproliferative activity in different cell lines. Bioactive compounds isolated from marine organisms in the past 5 years that have shown anticancer activity, emphasizing the ones that showed the highest cytotoxic activity, such as securamines H and I, cholest-3β,5α,6β-triol, (E)-24-methylcholest-22-ene-3β,5α,6β-triol, 24-methylenecholesta-3β,5α,6β-triol, and 24-methylcholesta-3β,5α,6β-triol, will be discussed in this review. These studies reveal the possibility of new compounds of marine origin being used as new therapeutic agents or as a source of inspiration to develop new therapeutic agents.

Marine Natural Products: A Potential Source of Anti-hepatocellular Carcinoma Drugs

Hepatocellular carcinoma (HCC) has high associated morbidity and mortality rates. Although chemical medication represents a primary HCC treatment strategy, low response rates and therapeutic resistance serve to reduce its efficacy. Hence, identifying novel effective drugs is urgently needed, and many researchers have sought to identify new anti-cancer drugs from marine organisms. The marine population is considered a "blue drug bank" of unique anti-cancer compounds with diverse groups of chemical structures. Here, we discuss marine-derived compounds, including PM060184 and bryostatin-1, with demonstrated anti-cancer activity in vitro or in vivo. Based on the marine source (sponges, algae, coral, bacteria, and fungi), we introduce pharmacological parameters, compound-induced cytotoxicity, effects on apoptosis and metastasis, and potential molecular mechanisms. Cumulatively, this review provides insights into anti-HCC research conducted to date in the field of marine natural products and marine-derived compounds, as well as the potential pharmacological mechanisms of these compounds and their status in drug development.

Induction of Apoptosis by Acanthaster planci sp., and Diadema setosum sp., Fractions in Human Cervical Cancer Cell Line, HeLa

Cancer is an uncontrolled multiplication of cells. The desire efficacy and severe toxicity of current anticancer drugs urge exploring and investigating a better alternative to existing chemotherapeutics. Natural products of marine origin are excellent sources of potential new drugs of enhanced biological activities.

OBJECTIVES

Thus, the cytotoxic effects along with investigating the mode of cell death exerted by fractions, AP-9, AP-THR, DS-8 and DS-9 fraction of Acanthaster planci, Diadema setosum sp., on the human cervical cancer cell line, HeLa.

METHODS

The cytotoxicity of fractions has determined by using an MTS assay. The early and late apoptosis was studied by using the High content Screening (HCS) instrument.

RESULTS

The four fractions produced effective cytotoxicity effects with IC50 values at 72hr of less than 20 μg/ml in the order of AP-9 > DS-9 > APTHR-9 > DS-8. The fraction s exhibited cytotoxicity via mediating apoptotic mode of cell death. The early apoptosis by exposure of phosphatidylserine to the outer leaflet of the plasma membrane and late apoptosis due to the presence of green stain (DNA fragmentation) in treated cells.

CONCLUSION

The potent bioactive compounds might be responsible for inducing apoptosis in cancer cells and, thus, the potential to be a successful candidate for exploring upcoming chemotherapeutic drugs.

Phytochemical analysis of Holothuria leucospilota, a sea cucumber from Persian Gulf

Sea cucumbers are widely consumed in traditional medicine and food. These animals have a considerable secondary metabolite and also several potential biological activities. This study investigated the phytochemical and cytotoxic evaluation of Holothuria leucospilota (H. leucospilota), a sea cucumber from Persian Gulf. The saponin composition of H. leucospilota was studied by different partitioning and chromatography methods such as thin layer chromatography (TLC), medium pressure liquid chromatography (MPLC) and high performance LC (HPLC). The marine sea cucumber Holostane-type triterpenoids (1-3) were characterized by physical and spectroscopic examination (1 and 2 dimensional neuclear magnetic resonance and mass experiments) with data analysis. The structure of compounds 1-3 identified as echinoside A, holothurine A, and 24-dehydroechinoside A, showed moderate cytotoxic activity with IC50 values of 1.9 ± 0.07, 6.8 ± 0.23, and 2.57 ± 0.18 μg/mL against HeLa and 10.4 ± 0.32, 8.9 ± 0.24, and 4.4 ± 0.13 on HUVEC cell line, respectively. In conclusion, the holostane-type triterpenoids showed moderate cytotoxic activity against HeLa cell line and have a prosperous future to be introduced as a lead structure.

Marine Natural Products: A Source of Novel Anticancer Drugs

Cancer remains one of the most lethal diseases worldwide. There is an urgent need for new drugs with novel modes of action and thus considerable research has been conducted for new anticancer drugs from natural sources, especially plants, microbes and marine organisms. Marine populations represent reservoirs of novel bioactive metabolites with diverse groups of chemical structures. This review highlights the impact of marine organisms, with particular emphasis on marine plants, algae, bacteria, actinomycetes, fungi, sponges and soft corals. Anti-cancer effects of marine natural products in in vitro and in vivo studies were first introduced; their activity in the prevention of tumor formation and the related compound-induced apoptosis and cytotoxicities were tackled. The possible molecular mechanisms behind the biological effects are also presented. The review highlights the diversity of marine organisms, novel chemical structures, and chemical property space. Finally, therapeutic strategies and the present use of marine-derived components, its future direction and limitations are discussed.

Marine Natural Products: A Source of Novel Anticancer Drugs

Cancer remains one of the most lethal diseases worldwide. There is an urgent need for new drugs with novel modes of action and thus considerable research has been conducted for new anticancer drugs from natural sources, especially plants, microbes and marine organisms. Marine populations represent reservoirs of novel bioactive metabolites with diverse groups of chemical structures. This review highlights the impact of marine organisms, with particular emphasis on marine plants, algae, bacteria, actinomycetes, fungi, sponges and soft corals. Anti-cancer effects of marine natural products in in vitro and in vivo studies were first introduced; their activity in the prevention of tumor formation and the related compound-induced apoptosis and cytotoxicities were tackled. The possible molecular mechanisms behind the biological effects are also presented. The review highlights the diversity of marine organisms, novel chemical structures, and chemical property space. Finally, therapeutic strategies and the present use of marine-derived components, its future direction and limitations are discussed.

Sandensolide Induces Oxidative Stress-Mediated Apoptosis in Oral Cancer Cells and in Zebrafish Xenograft Model

Presently, natural sources and herbs are being sought for the treatment of human oral squamous cell carcinoma (OSCC) in order to alleviate the side effects of chemotherapy. This study investigates the effect of sandensolide, a cembrane isolated from Sinularia flexibilis, to inhibit human OSCC cell growth with the aim of developing a new drug for the treatment of oral cancer. In vitro cultured human OSCC models (Ca9.22, SCC9 and HSC-3 cell lines) and oral normal cells (HGF-1), as well as a zebrafish xenograft model, were used to test the cytotoxicity of sandensolide (MTT assay), as well as to perform cell cycle analysis and Western blotting. Both the in vitro bioassay and the zebrafish xenograft model demonstrated the anti-oral cancer effect of sandensolide. Moreover, sandensolide was able to significantly suppress colony formation and induce apoptosis, as well as cell cycle arrest, in OSCC by regulating multiple key proteins. Induction of reactive oxygen species (ROS) was observed in sandensolide-treated oral cancer cells. However, these apoptotic changes were rescued by NAC pretreatment. These findings contribute to the knowledge of the model of action of sandensolide, which may induce oxidative stress-mediated cell death pathways as a potential agent in oral cancer therapeutics.

Selective Cytotoxicity of α-Santonin from the Persian Gulf Sponge Dysidea Avara on Pediatric ALL B-lymphocytes via Mitochondrial Targeting

Background: Acute lymphoblastic leukemia (ALL) is one of the most dominant malignancies among children, characterized by production of immature and dysfunctional blasts which are resistant to cytotoxic chemotherapeutic agents. Therefore, research protocols are currently focusing on discovery of novel anti-cancer agents to enhance survival rates and decrease unwanted side effects. Approximately two-thirds of the planet is covered by oceans with a massive range of marine organisms of interest to scientists in pharmaceutical fields. Methods: Among marine resources, sponges are known to have beneficial effects in the treatment of numerous malignancies. One fraction of crude extracts containing α-Santonin was made from the Persian Gulf marine sponge, Dysidea avara, and investigated for anticancer effects. Results: Treatment of ALL B-lymphocytes with the Dysidea avara extract caused augmentation in ROS generation, decline in mitochondrial membrane potential, mitochondrial swelling, release of cytochrome c from mitochondria and activation of caspase-3 only in mitochondria isolated from B-ALL lymphocytes. Conclusion: In brief, our results suggest that Dysidea avara extracts may selectively induce apoptosis in malignant pediatric lymphocytes.

From Marine Origin to Therapeutics: The Antitumor Potential of Marine Algae-Derived Compounds

Marine environment has demonstrated to be an interesting source of compounds with uncommon and unique chemical features on which the molecular modeling and chemical synthesis of new drugs can be based with greater efficacy and specificity for the therapeutics. Cancer is a growing public health threat, and despite the advances in biomedical research and technology, there is an urgent need for the development of new anticancer drugs. In this field, it is estimated that more than 60% of commercially available anticancer drugs are natural biomimetic inspired. Among the marine organisms, algae have revealed to be one of the major sources of new compounds of marine origin, including those exhibiting antitumor and cytotoxic potential. These compounds demonstrated ability to mediate specific inhibitory activities on a number of key cellular processes, including apoptosis pathways, angiogenesis, migration and invasion, in both in vitro and in vivo models, revealing their potential to be used as anticancer drugs. This review will focus on the bioactive molecules from algae with antitumor potential, from their origin to their potential uses, with special emphasis to the alga Sphaerococcus coronopifolius as a producer of cytotoxic compounds.

The In Vitro Anti-Tumor Activity of Phycocyanin against Non-Small Cell Lung Cancer Cells

Phycocyanin, a type of functional food colorant, is shown to have a potent anti-cancer property. Non-small cell lung cancer (NSCLC) is one of the most aggressive form of cancers with few effective therapeutic options. Previous studies have demonstrated that phycocyanin exerts a growth inhibitory effect on NSCLC A549 cells. However, its biological function and underlying regulatory mechanism on other cells still remain unknown. Here, we investigated the in vitro function of phycocyanin on three typical NSCLC cell lines, NCI-H1299, NCI-H460, and LTEP-A2, for the first time. The results showed that phycocyanin could significantly induce apoptosis, cell cycle arrest, as well as suppress cell migration, proliferation, and the colony formation ability of NSCLC cells through regulating multiple key genes. Strikingly, phycocyanin was discovered to affect the cell phenotype through regulating the NF-κB signaling of NSCLC cells. Our findings demonstrated the anti-neoplastic function of phycocyanin and provided valuable information for the regulation of phycocyanin in NSCLC cells.

Radiosensitization by Marine Sponge Agelas sp. Extracts in Hepatocellular Carcinoma Cells with Autophagy Induction

Although radiation therapy is an effective treatment modality in many cancers, there is an urgent need to develop therapeutic drugs capable of overcoming radioresistance or minimizing normal tissue toxicity. A wide variety of marine-derived bioactive compounds have been screened for anti-cancer drug discovery, but little is known regarding radiation therapy applications. In this study, six different extracts of marine sponges collected from the Micronesian sea were screened for anti-cancer and radiosensitizing activity. Two extracts derived from Agelas sponges collected off the coast of Kosrae and Chuuk, the Federated States of Micronesia significantly decreased clonogenic survival of hepatocellular carcinoma (HCC) cells after exposure to ionizing radiation (IR). The Agelas extracts augmented IR-induced apoptosis and accumulation of reactive oxygen species (ROS). Endoplasmic reticulum (ER) stress was increased via unfolded protein response stimulation, which induced autophagy. N-acetylcysteine, a ROS scavenger, diminished ER stress and autophagy induction effects. This result indicated that Agelas extracts may sensitize HCC cells to IR via ROS overproduction in vitro. Our findings suggest that the Agelas sp. may have potential utility in radiosensitizer development.

Pseudoalteromonas haloplanktis TAC125 produces 4-hydroxybenzoic acid that induces pyroptosis in human A459 lung adenocarcinoma cells

In order to exploit the rich reservoir of marine cold-adapted bacteria as a source of bioactive metabolites, ethyl acetate crude extracts of thirteen polar marine bacteria were tested for their antiproliferative activity on A549 lung epithelial cancer cells. The crude extract from Pseudoalteromonas haloplanktis TAC125 was the most active in inhibiting cell proliferation. Extensive bioassay-guided purification and mass spectrometric characterization allowed the identification of 4-hydroxybenzoic acid (4-HBA) as the molecule responsible for this bioactivity. We further demonstrate that 4-HBA inhibits A549 cancer cell proliferation with an IC₅₀ value ≤ 1 μg ml^-1, and that the effect is specific, since the other two HBA isomers (i.e. 2-HBA and 3-HBA) were unable to inhibit cell proliferation. The effect of 4-HBA is also selective since treatment of normal lung epithelial cells (WI-38) with 4-HBA did not affect cell viability. Finally, we show that 4-HBA is able to activate, at the gene and protein levels, a specific cell death signaling pathway named pyroptosis. Accordingly, the treatment of A549 cells with 4-HBA induces the transcription of (amongst others) caspase-1, IL1β, and IL18 encoding genes. Studies needed for the elucidation of mode of action of 4-HBA will be instrumental in depicting novel details of pyroptosis.

Bio-Catalytic Structural Transformation of Anti-cancer Steroid, Drostanolone Enanthate with Cephalosporium aphidicola and Fusarium lini, and Cytotoxic Potential Evaluation of Its Metabolites against Certain Cancer Cell Lines

In search of selective and effective anti-cancer agents, eight metabolites of anti-cancer steroid, drostanolone enanthate (1), were synthesized via microbial biotransformation. Enzymes such as reductase, oxidase, dehydrogenase, and hydrolase from Cephalosporium aphidicola, and Fusarium lini were likely involved in the biotransformation of 1 into new metabolites at pH 7.0 and 26°C, yielding five new metabolites, 2α-methyl-3α,14α,17β-trihydroxy-5α-androstane (2), 2α-methyl-7α-hydroxy-5α-androstan-3,17-dione (3), 2-methylandrosta-11α-hydroxy-1, 4-diene-3,17-dione (6), 2-methylandrosta-14α-hydroxy-1,4-diene-3,17-dione (7), and 2-methyl-5α-androsta-7α-hydroxy-1-ene-3,17-dione (8), along with three known metabolites, 2α-methyl-3α,17β-dihydroxy-5α-androstane (4), 2-methylandrosta-1, 4-diene-3,17-dione (5), and 2α-methyl-5α-androsta-17β-hydroxy-3-one (9), on the basis of NMR, and HREI-MS data, and single-crystal X-ray diffraction techniques. Interestingly, C. aphidicola and F. lini were able to catalyze hydroxylation only at alpha positions of 1. Compounds 1–9 showed a varying degree of cytotoxicity against HeLa (human cervical carcinoma), PC3 (human prostate carcinoma), H460 (human lung cancer), and HCT116 (human colon cancer) cancer cell lines. Interestingly, metabolites 4 (IC₅₀ = 49.5 ± 2.2 μM), 5 (IC₅₀ = 39.8 ± 1.5 μM), 6 (IC₅₀ = 40.7 ± 0.9 μM), 7 (IC₅₀ = 43.9 ± 2.4 μM), 8 (IC₅₀ = 19.6 ± 1.4 μM), and 9 (IC₅₀ = 25.1 ± 1.6 μM) were found to be more active against HeLa cancer cell line than the substrate 1 (IC₅₀ = 54.7 ± 1.6 μM). Similarly, metabolites 2 (IC₅₀ = 84.6 ± 6.4 μM), 3 (IC₅₀ = 68.1 ± 1.2 μM), 4 (IC₅₀ = 60.4 ± 0.9 μM), 5 (IC₅₀ = 84.0 ± 3.1 μM), 6 (IC₅₀ = 58.4 ± 1.6 μM), 7 (IC₅₀ = 59.1 ± 2.6 μM), 8 (IC₅₀ = 51.8 ± 3.4 μM), and 9 (IC₅₀ = 57.8 ± 3.2 μM) were identified as more active against PC-3 cancer cell line than the substrate 1 (IC₅₀ = 96.2 ± 3.0 μM). Metabolite 9 (IC₅₀ = 2.8 ± 0.2 μM) also showed potent anticancer activity against HCT116 cancer cell line than the substrate 1 (IC₅₀ = 3.1 ± 3.2 μM). In addition, compounds 1–7 showed no cytotoxicity against 3T3 normal cell line, while compounds 8 (IC₅₀ = 74.6 ± 3.7 μM), and 9 (IC₅₀ = 62.1 ± 1.2 μM) were found to be weakly cytotoxic.

Synthesis and Structural Modification of Marine Natural Products

In the last decades, marine natural products (MNPs), have attracted extensive interest from both chemists and pharmacologists due to their chemical and bioactive diversities. This special issue, collecting total synthesis and structural modification of six different type of bioactive MNPs, is expected to inspire and attract more research effects invested into MNP research.

Bioactivities of ethanol extract from the Antarctic freshwater microalga, Chloromonas sp. Int J Med Sci 2017;14. [PMID: 28638272 PMCID: PMC5479125 DOI: 10.7150/ijms.18702]

Cancer is the principal cause of human death and occurs through highly complex processes that involve the multiple coordinated mechanisms of tumorigenesis. A number of studies have indicated that the microalgae extracts showed anticancer activity in a variety of human cancer cells and can provide a new insight in the development of novel anti-cancer therapy. Here, in order to investigate molecular mechanisms of anticancer activity in the Antarctic freshwater microalga, Chloromonas sp., we prepared ethanol extract of Chloromonas sp. (ETCH) and performed several in vitro assays using human normal keratinocyte (HaCaT) and different types of cancer cells including cervical, melanoma, and breast cancer cells (HeLa, A375 and Hs578T, respectively). We revealed that ETCH had the antioxidant capacity, and caused significant cell growth inhibition and apoptosis of cancer cells in a dose-dependent manner, whereas it showed no anti-proliferation to normal cells. In addition, ETCH had a significant inhibitory effect on cell invasion without the cytotoxic effect. Furthermore, ETCH-induced apoptosis was mediated by increase in pro-apoptotic proteins including cleaved caspase-3 and p53, and by decrease in anti-apoptotic protein, Bcl-2 in ETCH-treated cancer cells. Taken together, this work firstly explored the antioxidant and anticancer activities of an Antarctic freshwater microalga, and ETCH could be a potential therapeutic candidate in the treatment of human cancer.

Partially Purified Extracts of Sea Anemone Anemonia viridis Affect the Growth and Viability of Selected Tumour Cell Lines

In the last few years, marine species have been investigated for the presence of natural products with anticancer activity. Using reversed phase chromatography, low molecular weight proteins were fractionated from the sea anemone Anemonia viridis. Four different fractions were evaluated for their cytotoxic activity by means of erythrocyte haemolysis test, MTS, and LDH assays. Finally, the antiproliferative activities of three of these fractions were studied on PC3, PLC/PRF/5, and A375 human cancer cell lines. Our analysis revealed that the four fractions showed different protein contents and diverse patterns of activity towards human PBMC and cancer cell lines. Interestingly, fractions III and IV exerted cytotoxic effects on human cells. Conversely, fractions I and II displayed very low toxic effects associated with antiproliferative activities on cancer cell lines.

5-Episinuleptolide Decreases the Expression of the Extracellular Matrix in Early Biofilm Formation of Multi-Drug Resistant Acinetobacter baumannii

Nosocomial infections and increasing multi-drug resistance caused by Acinetobacter baumannii have been recognized as emerging problems worldwide. Moreover, A. baumannii is able to colonize various abiotic materials and medical devices, making it difficult to eradicate and leading to ventilator-associated pneumonia, and bacteremia. Development of novel molecules that inhibit bacterial biofilm formation may be an alternative prophylactic option for the treatment of biofilm-associated A. baumannii infections. Marine environments, which are unlike their terrestrial counterparts, harbor an abundant biodiversity of marine organisms that produce novel bioactive natural products with pharmaceutical potential. In this study, we identified 5-episinuleptolide, which was isolated from Sinularia leptoclados, as an inhibitor of biofilm formation in ATCC 19606 and three multi-drug resistant A. baumannii strains. In addition, the anti-biofilm activities of 5-episinuleptolide were observed for Gram-negative bacteria but not for Gram-positive bacteria, indicating that the inhibition mechanism of 5-episinuleptolide is effective against only Gram-negative bacteria. The mechanism of biofilm inhibition was demonstrated to correlate to decreased gene expression from the pgaABCD locus, which encodes the extracellular polysaccharide poly-β-(1,6)-N-acetylglucosamine (PNAG). Scanning electron microscopy (SEM) indicated that extracellular matrix of the biofilm was dramatically decreased by treatment with 5-episinuleptolide. Our study showed potentially synergistic activity of combination therapy with 5-episinuleptolide and levofloxacin against biofilm formation and biofilm cells. These data indicate that inhibition of biofilm formation via 5-episinuleptolide may represent another prophylactic option for solving the persistent problem of biofilm-associated A. baumannii infections.

Non-canonical programmed cell death mechanisms triggered by natural compounds

Natural compounds are the fundament of pharmacological treatments and more than 50% of all anticancer drugs are of natural origins or at least derived from scaffolds present in Nature. Over the last 25 years, molecular mechanisms triggered by natural anticancer compounds were investigated. Emerging research showed that molecules of natural origins are useful for both preventive and therapeutic purposes by targeting essential hallmarks and enabling characteristics described by Hanahan and Weinberg. Moreover, natural compounds were able to change the differentiation status of selected cell types. One of the earliest response of cells treated by pharmacologically active compounds is the change of its morphology leading to ultra-structural perturbations: changes in membrane composition, cytoskeleton integrity, alterations of the endoplasmic reticulum, mitochondria and of the nucleus lead to formation of morphological alterations that are a characteristic of both compound and cancer type preceding cell death. Apoptosis and autophagy were traditionally considered as the most prominent cell death or cell death-related mechanisms. By now multiple other cell death modalities were described and most likely involved in response to chemotherapeutic treatment. It can be hypothesized that especially necrosis-related phenotypes triggered by various treatments or evolving from apoptotic or autophagic mechanisms, provide a more efficient therapeutic outcome depending on cancer type and genetic phenotype of the patient. In fact, the recent discovery of multiple regulated forms of necrosis and the initial elucidation of the corresponding cell signaling pathways appear nowadays as important tools to clarify the immunogenic potential of non-canonical forms of cell death induction.

Marine Invertebrate Metabolites with Anticancer Activities: Solutions to the "Supply Problem"

Marine invertebrates provide a rich source of metabolites with anticancer activities and several marine-derived agents have been approved for the treatment of cancer. However, the limited supply of promising anticancer metabolites from their natural sources is a major hurdle to their preclinical and clinical development. Thus, the lack of a sustainable large-scale supply has been an important challenge facing chemists and biologists involved in marine-based drug discovery. In the current review we describe the main strategies aimed to overcome the supply problem. These include: marine invertebrate aquaculture, invertebrate and symbiont cell culture, culture-independent strategies, total chemical synthesis, semi-synthesis, and a number of hybrid strategies. We provide examples illustrating the application of these strategies for the supply of marine invertebrate-derived anticancer agents. Finally, we encourage the scientific community to develop scalable methods to obtain selected metabolites, which in the authors' opinion should be pursued due to their most promising anticancer activities.

Biosurfactants Produced by Marine Microorganisms with Therapeutic Applications

Marine microorganisms possess unique metabolic and physiological features and are an important source of new biomolecules, such as biosurfactants. Some of these surface-active compounds synthesized by marine microorganisms exhibit antimicrobial, anti-adhesive and anti-biofilm activity against a broad spectrum of human pathogens (including multi-drug resistant pathogens), and could be used instead of existing drugs to treat infections caused by them. In other cases, these biosurfactants show anti-cancer activity, which could be envisaged as an alternative to conventional therapies. However, marine biosurfactants have not been widely explored, mainly due to the difficulties associated with the isolation and growth of their producing microorganisms. Culture-independent techniques (metagenomics) constitute a promising approach to study the genetic resources of otherwise inaccessible marine microorganisms without the requirement of culturing them, and can contribute to the discovery of novel biosurfactants with significant biological activities. This paper reviews the most relevant biosurfactants produced by marine microorganisms with potential therapeutic applications and discusses future perspectives and opportunities to discover novel molecules from marine environments.

Cyanobacterial Metabolite Calothrixins: Recent Advances in Synthesis and Biological Evaluation

The marine environment is host to unparalleled biological and chemical diversity, making it an attractive resource for the discovery of new therapeutics for a plethora of diseases. Compounds that are extracted from cyanobacteria are of special interest due to their unique structural scaffolds and capacity to produce potent pharmaceutical and biotechnological traits. Calothrixins A and B are two cyanobacterial metabolites with a structural assembly of quinoline, quinone, and indole pharmacophores. This review surveys recent advances in the synthesis and evaluation of the biological activities of calothrixins. Due to the low isolation yields from the marine source and the promise this scaffold holds for anticancer and antimicrobial drugs, organic and medicinal chemists around the world have embarked on developing efficient synthetic routes to produce calothrixins. Since the first review appeared in 2009, 11 novel syntheses of calothrixins have been published in the efforts to develop methods that contain fewer steps and higher-yielding reactions. Calothrixins have shown their potential as topoisomerase I poisons for their cytotoxicity in cancer. They have also been observed to target various aspects of RNA synthesis in bacteria. Further investigation into the exact mechanism for their bioactivity is still required for many of its analogs.

Coffee provides a natural multitarget pharmacopeia against the hallmarks of cancer

Coffee is the second most popular beverage in the world after water with a consumption of approximately two billion cups per day. Due to its low cost and ease of preparation, it is consumed in almost all countries and by all social classes of the population through different modes of preparation. Despites its simple appearance, a cup of coffee is in fact a complex mixture that contains hundreds of molecules, the composition and concentration of which vary widely and depend on factors including the origin of the coffee tree or its metabolism. Although an excessive consumption of coffee can be harmful, many molecules that are present in this black decoction exert anticancer properties. This review aims to describe the different primary coffee-containing substances that exert chemopreventive and bioactive activities against the different hallmarks and enabling characteristics of cancer, thus explaining the anticancer health benefit of black coffee.

Synthesis, Characterization and Biological Evaluation of Some Quinoxaline Derivatives: A Promising and Potent New Class of Antitumor and Antimicrobial Agents

In continuation of our endeavor towards the development of potent and effective anticancer and antimicrobial agents; the present work deals with the synthesis of some novel tetrazolo[1,5-a]quinoxalines, N-pyrazoloquinoxalines, the corresponding Schiff bases, 1,2,4-triazinoquinoxalines and 1,2,4-triazoloquinoxalines. These compounds were synthesized via the reaction of the key intermediate hydrazinoquinoxalines with various reagents and evaluated for anticancer and antimicrobial activity. The results indicated that tetrazolo[1,5-a]quinoxaline derivatives showed the best result, with the highest inhibitory effects towards the three tested tumor cell lines, which were higher than that of the reference doxorubicin and these compounds were non-cytotoxic to normal cells (IC₅₀ values > 100 μg/mL). Also, most of synthesized compounds exhibited the highest degrees of inhibition against the tested strains of Gram positive and negative bacteria, so tetrazolo[1,5-a]quinoxaline derivatives show dual activity as anticancer and antimicrobial agents.