A journey under the sea: the quest for marine anti-cancer alkaloids

Mechanisms of Antitumor Invasion and Metastasis of the Marine Fungal Derivative Epi-Aszonalenin A in HT1080 Cells

Epi-aszonalenin A (EAA) is an alkaloid that is isolated and purified from the secondary metabolites of coral symbiotic fungi and has been shown to have good atherosclerotic intervention activity and anti-angiogenic activity in our previous studies. In the present study, antiangiogenic activity was used as a basis of an intensive study of its mechanism of action against tumor metastasis and invasion. Invasive metastatic pairs are a hallmark of malignancy, and the dissemination of tumor cells is the most dangerous process in the development of tumors. The results of cell wound healing and the Transwell chamber assay showed that EAA interfered well with PMA-induced migration and invasion of HT1080 cells. Western blot and the ELISA assay showed that EAA decreased MMPs and vascular endothelial growth factor (VEGF) activity and inhibited the expression of N-cadherin and hypoxia-inducible factor-1α (HIF-1α) by regulating the phosphorylation of downstream mitogen-activated protein kinase (MAPK), PI3K/AKT, and NF-κB pathways. Simultaneous molecular docking results revealed that the mimic coupling between the EAA and MMP-2/-9 molecules formed a stable interaction. The results of this study provide a research basis for the inhibition of tumor metastasis by EAA, and together with previous studies, confirm the potential pharmacology and drug potential for this class of compound for application in angiogenesis-related diseases and further improve the availability of coral symbiotic fungi.

Peimine-induced apoptosis and inhibition of migration by regulating reactive oxygen species-mediated MAPK/STAT3/NF-κB and Wnt/β-catenin signaling pathways in gastric cancer MKN-45 cells

Peimine (PM), a natural product extracted from Fritillaria, has anti-inflammatory, drug resistance reversal, and other pharmacological effects. The purpose of this study was to investigate the antitumor effects and the molecular mechanisms of PM using gastric cancer MKN-45 cells. Cell counting kit-8 assays were used to evaluate the viability of gastric cancer cells after treatment with PM. The results showed that PM significantly reduced the activity of gastric cancer cells, and the effect was most obvious in MKN-45 cells. Annexin V-FITC/propidium iodide staining and flow cytometry were used to assess apoptosis of MKN-45 cells after PM treatment. Our results showed that PM-induced apoptosis of MKN-45 cells. Flow cytometry was also used to determine the mitochondrial membrane potential and reactive oxygen species (ROS) levels, and to assess PM-induced cell-cycle arrest. Additionally, Western blot was used to analyze the expression of signaling pathway proteins and the relationship between apoptosis and ROS accumulation. Our findings showed that PM destroyed the mitochondria by diminishing the mitochondrial membrane potential. In addition, PM regulated the mitogen-activated protein kinase (MAPK), signal transducer and activator of transcription 3, and nuclear factor kappa-B signaling pathways by promoting the accumulation of ROS in MKN-45 cells. PM also caused cell-cycle arrest in the G2/M phase by increasing ROS accumulation. Furthermore, PM inhibited cell migration by regulating the Wnt/β-catenin pathway. In conclusion, PM plays an anticancer role through endogenous apoptosis pathways and by inhibiting cell migration, and it has the potential to be a useful treatment for gastric cancers.

Marine Migrastatics: A Comprehensive 2022 Update

Metastasis is responsible for the bad prognosis in cancer patients. Advances in research on metastasis prevention focus attention on the molecular mechanisms underlying cancer cell motility and invasion to improve therapies for long-term survival in cancer patients. The so-called “migrastatics” could help block cancer cell invasion and lead to the rapid development of antimetastatic therapies, improving conventional cancer therapies. In the relentless search for migrastatics, the marine environment represents an important source of natural compounds due to its enormous biodiversity. Thus, this review is a selection of scientific research that has pointed out in a broad spectrum of in vitro and in vivo models the anti-cancer power of marine-derived products against cancer cell migration and invasion over the past five years. Overall, this review might provide a useful up-to-date guide about marine-derived compounds with potential interest for pharmaceutical and scientific research on antimetastatic drug endpoints.

Marine Natural Products from Tunicates and Their Associated Microbes

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

Fused-azepinones: Emerging scaffolds of medicinal importance

Hymenialdisine an alkaloid of oroidin class has drawn the attention of researchers owing to its unique structural features and interesting biological properties. Hymenialdisine exhibited promising inhibitory activity against a number of therapeutically important kinases viz., CDKs, GSK-3β etc., and showed anti-cancer, anti-inflammatory, anti-HIV, neuroprotective, anti-fouling, anti-plasmodium properties. Hymenialdisine and other structurally related oroidin alkaloids such as dibromo-hymenialdisine, stevensine, hymenin, axinohydantoin, spongicidines A-D, latonduines and callyspongisines contain pyrrolo[2,3-c] azepin-8-one core in common. Keeping in view of the interesting structural and therapeutic features of HMD, several structural modifications were carried around the fused-azepinone core which resulted in a number of diverse structural motifs like indolo-azepinones, paullones, aza-paullones, darpones and 5,7-dihydro-6H-benzo[b]pyrimido[4,5-d] azepin-6-one. In this review, an attempt is made to collate and review the structures of diverse hymenialdisine and related fused-azepinones of synthetic/natural origin and their biological properties.

Targeting cell cycle by β-carboline alkaloids in vitro: Novel therapeutic prospects for the treatment of cancer

Cell cycle dysregulation is the mainstay of aberrant cell proliferation, which leads to tumor progression. Mutations in tumor cells initiate various dysregulated pathways and spontaneous over-proliferation with genomic/chromosomal instability. Despite advances in cancer therapy, it has remained a medicinal challenge to treat. Besides, the complexity of pathophysiological pathways behind cancer raises the need for novel multi-target agents, possessing fewer side effects. Alkaloid-based therapies have been explored so far to target cell division in cancer, including vinca alkaloids. As a class of hopeful β-carboline derivatives, growing evidence has indicated their auspicious roles in combating cancer by inhibiting topoisomerase (TOPO), kinesin Eg5, telomerase, cyclin-dependent kinase (CDK), IκB kinase (IKK), and polo-like kinase-1 (PLK1) in the transition phases of cell cycle. In this review, in vitro potential of β-carboline has been revealed through targeting cell division cycle at different phases. In conclusion, β-carboline alkaloids could be introduced as novel candidates in cancer therapy.

Bioactive Metabolites from Marine Ascidians: Future Treatment for Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a developmental disorder that influences communication and behavior. Numerous researches propose that genes can act together with manipulations from the environment to affect development in ways that lead to ASD. The broad range of issues facing people with ASD means that there is no single proper drug and treatment for ASD. Numerous shortcomings associated with the present conventional therapeutic strategies have forced researchers to venture into alternative natural sources for effective compounds. The marine environment has emerged as an alternate search environment due to its versatile conditions where organisms employ various biodefense mechanisms for their survival. Ascidians are an excellent source for unique bioactive compounds with nutritive and therapeutic content and it still holds credit for being an underused source from marine animals. Bioactive compounds isolated from ascidians have various commendable biomedical applications due to their unique chemical structures. The present chapter will focus on the potential of bioactive compounds derived from ascidians for the treatment of the neurologic disorder-ASD.

Algae metabolites: from in vitro growth inhibitory effects to promising anticancer activity

Covering: 1957 to 2017 Algae constitute a heterogeneous group of eukaryotic photosynthetic organisms, mainly found in the marine environment. Algae produce numerous metabolites that help them cope with the harsh conditions of the marine environment. Because of their structural diversity and uniqueness, these molecules have recently gained a lot of interest for the identification of medicinally useful agents, including those with potential anticancer activities. In the current review, which is not a catalogue-based one, we first highlight the major biological events that lead to various types of cancer, including metastatic ones, to chemoresistance, thus to any types of current anticancer treatment relating to the use of chemotherapeutics. We then review algal metabolites for which scientific literature reports anticancer activity. Lastly, we focus on algal metabolites with promising anticancer activity based on their ability to target biological characteristics of cancer cells responsible for poor treatment outcomes. Thus, we highlight compounds that have, among others, one or more of the following characteristics: selectivity in reducing the proliferation of cancer cells over normal ones, potential for killing cancer cells through non-apoptotic signaling pathways, ability to circumvent MDR-related efflux pumps, and activity in vivo in relevant pre-clinical models.

Fragment-Based Structural Optimization of a Natural Product Itampolin A as a p38α Inhibitor for Lung Cancer

Marine animals and plants provide abundant secondary metabolites with antitumor activity. Itampolin A is a brominated natural tyrosine secondary metabolite that is isolated from the sponge Iotrochota purpurea. Recently, we have achieved the first total synthesis of this brominated tyrosine secondary metabolite, which was found to be a potent p38α inhibitor exhibiting anticancer effects. A fragment-based drug design (FBDD) was carried out to optimize itampolin A. Forty-five brominated tyrosine derivatives were synthesized with interesting biological activities. Then, a QSAR study was carried out to explore the structural determinants responsible for the activity of brominated tyrosine skeleton p38α inhibitors. The lead compound was optimized by a FBDD method, then three series of brominated tyrosine derivatives were synthesized and evaluated for their inhibitory activities against p38α and tumor cells. Compound 6o (IC₅₀ = 0.66 μM) exhibited significant antitumor activity against non-small cell lung A549 cells (A549). This also demonstrated the feasibility of the FBDD method of structural optimization.

Anti-proliferative and anti-inflammatory activities of the sea cucumber Holothuria polii aqueous extract

Objective:

Sea cucumbers are considered among the most important functional foods. Following bioassay guided fractionation, we assessed the anti-proliferative and anti-inflammatory activities of Holothuria polii (H. polii) extracts.

Methods:

Sea cucumber ethanolic extract and the partially purified aqueous fractions were assessed for their anti-proliferative activities. These latter bioactivities were evaluated in the highly invasive MDA-MB-231 human breast cancer cells in two-dimensional and three-dimensional cultures using trypan blue exclusion assay. The tumor-suppressive effects of sea cucumber ethanolic extract and aqueous fractions were assayed by measuring the trans-well invasion of MDA-MB-231 cells and the expression of some epithelial mesenchymal transition markers using quantitative reverse-transcription polymerase chain reaction and western blot analysis. The anti-inflammatory activity of the aqueous fraction was tested by measuring the secreted levels of interleukin-6, nitric oxide, and matrix metalloproteinase 9 in endotoxin-induced mammary epithelial SCp2 cells and interleukin-1β in phorbol-12-myristate-13-acetate-activated human monocytic THP-1 cells.

Results:

Sea cucumber ethanolic extract and the aqueous fraction significantly decreased the proliferation of MDA-MB-231 cells by more than 50% at similar and noncytotoxic concentrations and caused an arrest in the S-phase of the cell cycle of treated cells. In contrast, petroleum ether, chloroform, ethyl acetate, and n-butanol organic fractions did not show any significant activity. Furthermore, sea cucumber ethanolic extract and aqueous fraction reduced the proliferation of MDA-MB-231 cells in three-dimensional cultures by more than 60% at noncytotoxic concentrations. In addition, treatment with these concentrations resulted in the loss of stellate outgrowths in favor of spherical aggregates and a 30% decrease in invasive properties. Both sea cucumber ethanolic extract and aqueous decreased the transcription of vimentin and the protein expression levels of vimentin and N-cadherin in three-dimensional cultures. The aqueous fraction decreased the levels of inflammatory markers interleukin-6, nitric oxide, and matrix metalloproteinase 9 in the mouse mammary SCp2 cells, and the level of interleukin-1β produced by phorbol-12-myristate-13-acetate-activated THP-1 human monocytic cells.

Conclusion:

The data reveal for the first time promising anti-proliferative and anti-inflammatory activities in H. polii water extract in two-dimensional and three-dimensional culture models.

Spatial Distribution of Collections Yielding Marine Natural Products

The societal benefits of coral reef ecosystems include shoreline protection, habitat provision for reef fish, tourism, and recreation. Rarely considered in valuation of reefs is the considerable contribution of marine natural products (MNPs) to both human health and the economy. To better understand the relation of MNP discovery with the characteristics and condition of coral reef ecosystems, we initiated a study to track the collection location and taxonomic identity of organisms that have provided pharmacological products. We reviewed collection information and associated data from 298 pharmacological products originating from marine biota during the past 47 years. The products were developed from 232 different marine species representing 15 phyla, and the 1296 collections of these specimens occurred across 69 countries and seven continents. Our evaluation of the collection data was hampered by sundry observational and reporting issues, including imprecise location descriptions and omission of collection dates. Nonetheless, the study provides an important synopsis and appraisal of years of study and exploration by the marine natural product community. Understanding and quantifying the benefits of MNP discovery will depend upon improved reporting of collections, including accurate taxonomic identification, collection dates, and locations.

Hydroamination of alkenyl N-arylhydrazones mediated by t-BuOK for the synthesis of nitrogen heterocycles

The t-BuOK-mediated reactions of γ,δ-alkenyl hydrazones enabled intramolecular hydroamination with the outer nitrogen, affording tetrahydropyridazine derivatives.

Single step incorporation of isatin to enaminone: a recyclable catalyst towards assembly of diverse four ring fused pyrrolo[2,3,4-kl]acridin-1-ones

Single step synthesis of four ring fused pyrrolo[2,3,4-kl]acridin-1-ones using recoverable sulfonated carbonaceous material as heterogeneous catalyst.

Selective Toxicity of Persian Gulf Sea Cucumber (Holothuria parva) and Sponge (Haliclona oculata) Methanolic Extracts on Liver Mitochondria Isolated from an Animal Model of Hepatocellular Carcinoma

BACKGROUND

Natural products isolated from marine environments are well known for their pharmacodynamic potential in diverse disease treatments, such as for cancer or inflammatory conditions. Sea cucumbers are marine animals of the phylum Echinoderm and the class Holothuroidea, with leathery skin and gelatinous bodies. Sponges are important components of Persian Gulf animal communities, and the marine sponges of the genus Haliclona have been known to display broad-spectrum biological activity. Many studies have shown that sea cucumbers and sponges contain antioxidants and anti-cancer compounds.

OBJECTIVES

This study was designed to determine the selective toxicity of Persian Gulf sea cucumber (Holothuria parva) and sponge (Haliclona oculata) methanolic extracts on liver mitochondria isolated from an animal model of hepatocellular carcinoma, as part of a national project that hopes to identify novel potential anticancer candidates among Iranian Persian Gulf flora and fauna.

MATERIALS AND METHODS

To induce hepatocarcinogenesis, rats were given diethylnitrosamine (DEN) injections (200 mg/kg i.p. by a single dose), and then the cancer was promoted with 2-acetylaminofluorene (2-AAF) (0.02 w/w) for two weeks. Histopathological evaluations were performed, and levels of liver injury markers and a specific liver cancer marker (alpha-fetoprotein), were determined for confirmation of hepatocellular carcinoma induction. Finally, mitochondria were isolated from cancerous and non-cancerous hepatocytes.

RESULTS

Our results showed that H. parva methanolic extracts (250, 500, and 1000 µg/mL) and H. oculata methanolic extracts (200, 400, and 800 µg/mL) increased reactive oxygen species (ROS) formation, mitochondrial membrane potential (MMP), mitochondrial swelling, and cytochrome c release in the mitochondria obtained from cancerous hepatocytes, but not in mitochondria obtained from non-cancerous liver hepatocytes. These extracts also induced caspase-3 activation, which is known as a final mediator of apoptosis, in the hepatocytes obtained only from cancerous, not non-cancerous, rat livers.

CONCLUSIONS

Our results suggest that H. parva and H. oculata may be promising therapeutic candidates for the treatment of HCC, following further confirmatory in vivo experiments and clinical trials.

Marine Drugs Regulating Apoptosis Induced by Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand (TRAIL)

Marine biomass diversity is a tremendous source of potential anticancer compounds. Several natural marine products have been described to restore tumor cell sensitivity to TNF-related apoptosis inducing ligand (TRAIL)-induced cell death. TRAIL is involved during tumor immune surveillance. Its selectivity for cancer cells has attracted much attention in oncology. This review aims at discussing the main mechanisms by which TRAIL signaling is regulated and presenting how marine bioactive compounds have been found, so far, to overcome TRAIL resistance in tumor cells.

anti-Selective aminofluorination of alkenes with amidines mediated by hypervalent iodine(iii) reagents

anti-Selective aminofluorination of alkenes with amidines was enabled by hypervalent iodine(iii) reagents, affording 4-fluoroalkyl-2-imidazolines. Further reductive ring-opening of the 2-imidazoline moiety could deliver highly functionalized 3-fluoropropane-1,2-diamine derivatives.

Potential of four marine-derived fungi extracts as anti-proliferative and cell death-inducing agents in seven human cancer cell lines

OBJECTIVE

To evaluate the in vitro anticancer activity of crude ethyl acetate extracts of the culture of four marine-derived fungi Aspergillus similanensis KUFA 0013 (E1), Neosartorya paulistensis KUFC 7897 (E2), Neosartorya siamensis KUFA 0017 (E4) and Talaromyces trachyspermus KUFC 0021 (E3) on a panel of seven human cancer cell lines.

METHODS

Effects on cell proliferation, induction of DNA damage and cell death were assessed by MTT and clonogenic assays, comet assay and nuclear condensation assay, respectively.

RESULTS

The proliferation of HepG2, HCT116 and A375 cells decreased after incubation with the extracts E2 and E4. The anti-proliferative effect was confirmed by morphologic alterations and by clonogenic assay. Both extracts also induced cell death in HepG2 and HCT116 cells. Doxorubicin was used as a positive control and showed in vitro anticancer activity.

CONCLUSIONS

This study demonstrated, for the first time, that extracts of Neosartorya paulistensis and Neosartorya siamensis have selective anti-proliferative and cell death activities in HepG2, HCT16 and A375 cells. The bioactivity of these extracts suggests a potential for biotechnological applications and substantiates that both should be further considered for the elucidation of the molecular targets and signal transduction pathways involved.

Bromoalkaloids protect primary cortical neurons from induced oxidative stress

Bromoalkaloids are secondary metabolites with a demonstrated high activity in several therapeutic areas. In this research, we probe the neuroprotective and antioxidant activities of hymenialdisine and hymenin. Both structures were tested in an oxidative stress cellular model, consisting of cortical neurons that are incubated with the oxidative stress inducer hydrogen peroxide and the tested compound. Several oxidation biomarkers were analyzed, and the results of the oxidative stress induced neurons in the presence and absence of bromoalkaloids were compared. Both compounds demonstrated significant neuroprotective ability under stress conditions at low nanomolar concentrations, with hymenialdisine highlighted for demonstrating a more complete protection. Also, the activity of hymenialdisine and hymenin was studied in the nuclear factor erythroid 2-related factor 2 (Nrf2)-antioxidant response element (ARE) pathway, and, for the first time, these halogenated metabolites are described as Nrf2 inducers, reinforcing the antioxidant capacity observed and therefore opening a new path of investigation. These results, added to the previously described effect of this compound family in negatively modulating several kinases and proinflammatory cytokines, position hymenialdisine and hymenin as good candidates for the development of new drugs for neurodegenerative diseases.

Activity of alkaloids on peptic ulcer: what's new?

Peptic ulcer is a common disease characterized by lesions that affect the mucosa of the esophagus, stomach and/or duodenum, and may extend into the muscular layer of the mucosa. Natural products have played an important role in the process of development and discovery of new drugs, due to their wide structural diversity and present, mostly specific and selective biological activities. Among natural products the alkaloids, biologically active secondary metabolites, that can be found in plants, animals or microorganisms stand out. The alkaloids are compounds consisting of a basic nitrogen atom that may or may not be part of a heterocyclic ring. This review will describe 15 alkaloids with antiulcer activity in animal models and in vitro studies.

Evaluation of antitumor and antioxidant activity of Sargassum tenerrimum against Ehrlich ascites carcinoma in mice

CONTEXT

In the last half century, discovering, developing and introducing of clinical agents from marine sources have seen great successes, with examples including the anti-cancer compound trabectedin. However, with increasing need for new anticancer drugs, further exploration for novel compounds from marine organism sources is strongly justified.

OBJECTIVE

The major aim of this study was to evaluate the antitumor and antioxidant potential of Sargassum tenerrimum J.Agardh (Sargassaceae) on Ehrlich ascites carcinoma (EAC) in Swiss albino mice.

MATERIALS AND METHODS

An ethanol extract of S. tenerrimum (EEST) from whole algae was used to evaluate cytotoxicity followed by in vivo assessment of toxicity, using biochemical parameters including hepatic and non-hepatic enzymes. Antioxidant properties were examined in animals bearing EAC treated with daily oral administration of 100-300 mg/kg extract suspension.

RESULTS

Antitumor effects of EEST in EAC bearing mice was observed with LD50 1815 mg/kg. Parameters like body weight, tumor volume, packed cell volume, tumor cell count, mean survival time and increase in life span in animals in the EAC bearing animals treated with EEST 300 mg/kg was comparable with control group. Significant differences were also seen with changes in total protein content, hepatic enzymes contents, MDA level, and free radical scavenging enzymes in untreated vs. EEST treated group animals.

CONCLUSIONS

Evaluation of antioxidant enzymes and hepatic enzymes in the EAC animal model treated with EEST exhibited similar effects as the positive control drug 5-flurouracil. S. tenerrimum extracts contain effective antioxidants with significant antitumor activity.

Shikonin shortens the circadian period: possible involvement of Top2 inhibition

The naphthoquinone pigment, shikonin, is a natural product derived from Lithospermum erythrorhizon and an active component of a Chinese traditional herbal therapeutic. We identified shikonin as a candidate for shortening the circadian period using real-time reporter gene assays based on NIH3T3-derived stable reporter cells. Period length that became shortened in cells incubated with shikonin or etoposide reverted to that of control cells after continued incubation without these compounds. These findings indicated that shikonin and etoposide shorten the circadian period reversibly and through similar mechanisms. Topoisomerase II (Top2)-specific decatenation assays confirmed that shikonin, liker etoposide, is a Top2 inhibitor. Shikonin was incorporated into the nucleus and Top2 was located in the Bmal1 promoter, suggesting the relationship between Bmal1 transcription and Top2 inhibition. Top2a siRNA also shortened period length, suggesting that Top2 is involved in this process. Promoter assays showed that Top2a siRNA, etoposide and shikonin reduce Bmal1 promoter activity. These findings indicated that Top2 is involved in Bmal1 transcription and influences the circadian period, and that shikonin is a novel contributor to the control of period length in mammalian cells.

Marine natural products

This review covers the literature published in 2011 for marine natural products, with 870 citations (558 for the period January to December 2011) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1152 for 2011), together with the relevant biological activities, source organisms and country of origin. Biosynthetic studies, first syntheses, and syntheses that lead to the revision of structures or stereochemistries, have been included.