Augmenting anti-cancer natural products with a small molecule adjuvant

Ecology of freshwater harmful euglenophytes: A review

A diverse array of aquatic ecosystems are inhabited by the euglenophytes, a group of autotrophic and eukaryotic organisms. In inland waterbodies, the red bloom is caused by a rapid development or accumulation of euglenophytes. Recent studies have designated euglenophytes as bioindicator of organic pollution. The ecology of euglenophytes is influenced by the changes in the intensity of sunlight, temperature, nutrient cycles, and seasons. Most of the species of euglenophytes grow prolifically with the increase of water temperature. Nitrogen and phosphorus are often thought to be the main nutrients that influence the cellular growth of toxic euglenophytes. A high concentration of nutrients is required for the euglenophytes to grow and to form bloom. Heavy bloom of euglenophytes in the summer season is the characteristic of eutrophic ponds. Inland waterbodies in many countries suffer from euglenophyte blooms, which shade submerged vegetation, deplete the dissolved oxygen and disrupt the aquatic food webs. Dense bloom of euglenophytes clog the gills of fishes, cause breathing difficulties and in extreme cases results mortality. Red blooms of the deadly toxin producing Euglena sanguinea negatively affect the water quality resulting massive mortality of fishes. Consequently, aquaculture systems and fisheries are facing a serious threat from the predicted outbreak of toxic red blooms of euglenophytes worldwide. To ensure sustainability in the fisheries and aquaculture industry, it is essential to analyze the ecology of euglenophytes. Again, interesting research on euglenophycin, a Euglena-derived natural product, has shown that it can be utilized as a potential anti-cancer drug. This paper comes up with a thorough review of the latest research in this area, revealing new insights and solutions that can help mitigate the negative impact of the freshwater harmful euglenophytes. By implementing considerable management strategies, the health of the valuable aquatic ecosystems and the future of the aquaculture and fisheries can also be secured.

Protective Effect of Methanolic Extract of Euglena tuba Against Dalton Lymphoma Induced Oxidative Stress in BALB/c Mice

The identification and pharmacological validation of plant-based lead compounds for the cure of different diseases including cancer have always been globally strived. In addition to possessing numerous medicinal properties, many of the phytochemicals display antioxidant potential activities. Reactive oxygen species (ROS) causeoxidative stress leading to several severe diseases such as cancer. The antioxidants are substances that fight against ROS to protect the cells from their damaging effects. In the present study, the effects of methanol extract of Euglena tuba(ETME) have been evaluated for its antioxidant and antitumor potential against Dalton's lymphoma (DL) introduced in BALB/cmice. After 24 h of intraperitoneal inoculation of DL cells in mice, ETME (300 mg kg-1 body weight) was administered intraperitoneally upto18 alternative days. On the 18th day, the mice were sacrificed; the blood and tissues (liver and brain) were collected to determine the tumor growth parameters including morphological, behavioural, haematological profile, and antioxidant indices. The results indicated that ETME exhibited significant antioxidative and antitumor properties when compared with the data from DL bearing mice. The results from the present study indicated that ETME contained remarkable antitumor efficacy, which was mediated through amelioration of oxidative stress. The data suggested that ETME could be used as a potential natural anticancer agent.

Anabaenopeptins: What We Know So Far

Cyanobacteria are microorganisms with photosynthetic mechanisms capable of colonizing several distinct environments worldwide. They can produce a vast spectrum of bioactive compounds with different properties, resulting in an improved adaptative capacity. Their richness in secondary metabolites is related to their unique and diverse metabolic apparatus, such as Non-Ribosomal Peptide Synthetases (NRPSs). One important class of peptides produced by the non-ribosomal pathway is anabaenopeptins. These cyclic hexapeptides demonstrated inhibitory activity towards phosphatases and proteases, which could be related to their toxicity and adaptiveness against zooplankters and crustaceans. Thus, this review aims to identify key features related to anabaenopeptins, including the diversity of their structure, occurrence, the biosynthetic steps for their production, ecological roles, and biotechnological applications.

Cyanobacterial bioactive metabolites-A review of their chemistry and biology

Cyanobacterial blooms occur when algal densities exceed baseline population concentrations. Cyanobacteria can produce a large number of secondary metabolites. Odorous metabolites affect the smell and flavor of aquatic animals, whereas bioactive metabolites cause a range of lethal and sub-lethal effects in plants, invertebrates, and vertebrates, including humans. Herein, the bioactivity, chemistry, origin, and biosynthesis of these cyanobacterial secondary metabolites were reviewed. With recent revision of cyanobacterial taxonomy by Anagnostidis and Komárek as part of the Süβwasserflora von Mitteleuropa volumes 19(1-3), names of many cyanobacteria that produce bioactive compounds have changed, thereby confusing readers. The original and new nomenclature are included in this review to clarify the origins of cyanobacterial bioactive compounds. Due to structural similarity, the 157 known bioactive classes produced by cyanobacteria have been condensed to 55 classes. This review will provide a basis for more formal procedures to adopt a logical naming system. This review is needed for efficient management of water resources to understand, identify, and manage cyanobacterial harmful algal bloom impacts.

Cyanobacterial bioactive metabolites-A review of their chemistry and biology

Cyanobacterial blooms occur when algal densities exceed baseline population concentrations. Cyanobacteria can produce a large number of secondary metabolites. Odorous metabolites affect the smell and flavor of aquatic animals, whereas bioactive metabolites cause a range of lethal and sub-lethal effects in plants, invertebrates, and vertebrates, including humans. Herein, the bioactivity, chemistry, origin, and biosynthesis of these cyanobacterial secondary metabolites were reviewed. With recent revision of cyanobacterial taxonomy by Anagnostidis and Komárek as part of the Süβwasserflora von Mitteleuropa volumes 19(1-3), names of many cyanobacteria that produce bioactive compounds have changed, thereby confusing readers. The original and new nomenclature are included in this review to clarify the origins of cyanobacterial bioactive compounds. Due to structural similarity, the 157 known bioactive classes produced by cyanobacteria have been condensed to 55 classes. This review will provide a basis for more formal procedures to adopt a logical naming system. This review is needed for efficient management of water resources to understand, identify, and manage cyanobacterial harmful algal bloom impacts.

Cyanobufalins: Cardioactive Toxins from Cyanobacterial Blooms

Cyanobufalins A-C (1-3), a new series of cardiotoxic steroids, have been discovered from cyanobacterial blooms in Buckeye Lake and Grand Lake St. Marys in Ohio. Compounds 1-3 contain distinctive structural features, including geminal methyl groups at C-4, a 7,8 double bond, and a C-16 chlorine substituent that distinguish them from plant- or animal-derived congeners. Despite these structural differences, the compounds are qualitatively identical to bufalin in their cytotoxic profiles versus cell lines in tissue culture and cardiac activity, as demonstrated in an impedance-based cellular assay conducted with IPSC-derived cardiomyocytes. Cyanobufalins are nonselectively toxic to human cells in the single-digit nanomolar range and show stimulation of contractility in cardiomyocytes at sub-nanomolar concentrations. The estimated combined concentration of 1-3 in the environment is in the same nanomolar range, and consequently more precise quantitative analyses are recommended along with more detailed cardiotoxicity studies. This is the first time that cardioactive steroid toxins have been found associated with microorganisms in an aquatic environment. Several factors point to a microbial biosynthetic origin for the cyanobufalins.

Microcystins Containing Doubly Homologated Tyrosine Residues from a Microcystis aeruginosa Bloom: Structures and Cytotoxicity

Four new microcystin congeners are described including the first three examples of microcystins containing the rare doubly homologated tyrosine residue 2-amino-5-(4-hydroxyphenyl)pentanoic acid (Ahppa) (1-4). Large-scale harvesting and biomass processing allowed the isolation of substantial quantities of these compounds, thus enabling complete structure determination by NMR as well as cytotoxicity evaluation against selected cancer cell lines. The new Ahppa-toxins all incorporate Ahppa residues at the 2-position, and one of these also has a second Ahppa at position 4. The two most lipophilic Ahppa-containing microcystins showed 10-fold greater cytotoxic potency against human tumor cell lines (A549 and HCT-116) compared to microcystin-LR (5). The presence of an Ahppa residue in microcystin congeners is difficult to ascertain by MS methods alone, due to the lack of characteristic fragment ions derived from the doubly homologated side chain. Owing to their unexpected cytotoxic potency, the potential impact of the compounds on human health should be further evaluated.

Evaluation of ethyl N-(2-phenethyl) carbamate analogues as biofilm inhibitors of methicillin resistant Staphylococcus aureus

A small molecule library consisting of 45 compounds was synthesized based on the bacterial metabolite ethyl N-(2-phenethyl) carbamate. Screening of the compounds revealed a potent analogue capabale of inhibiting several strains of Methicillin Resistant S. aureus biofilms with low to moderate micromolar IC50 values.

Therapeutic effects of the euglenoid ichthyotoxin, euglenophycin, in colon cancer

Colorectal cancer (CRC) remains one of the most commonly diagnosed cancers and the 3^rd leading cause of cancer-related mortality. The emergence of drug resistance poses a major challenge in CRC care or treatment. This can be addressed by determining cancer mechanisms, discovery of druggable targets, and development of new drugs. In search for novel agents, aquatic microorganisms offer a vastly untapped pharmacological source that can be developed for cancer therapeutics. In this study, we characterized the anti-colorectal cancer potential of euglenophycin, a microalgal toxin from Euglena sanguinea. The toxin (49.1-114.6 μM) demonstrated cytotoxic, anti-proliferative, anti-clonogenic, and anti-migration effects against HCT116, HT29, and SW620 CRC cells. We identified G1 cell cycle arrest and cell type - dependent modulation of autophagy as mechanisms of growth inhibition. We validated euglenophycin’s anti-tumorigenic activity in vivo using CRL:Nu(NCr)Foxn1^nu athymic nude mouse CRC xenograft models. Intraperitoneal toxin administration (100 mg/kg; 5 days) decreased HCT116 and HT29 xenograft tumor volumes (n=10 each). Tumor inhibition was associated with reduced expression of autophagy negative regulator mechanistic target of rapamycin (mTOR) and decreased trend of serum pro-inflammatory cytokines. Together, these results provide compelling evidence that euglenophycin can be a promising anti-colorectal cancer agent targeting multiple cancer-promoting processes. Furthermore, this study supports expanding natural products drug discovery to freshwater niches as prospective sources of anti-cancer compounds.

Euglenophycin is produced in at least six species of euglenoid algae and six of seven strains of Euglena sanguinea

Euglena sanguinea is known to produce the alkaloid toxin euglenophycin and is known to cause fish kills and inhibit mammalian tissue and microalgal culture growth. An analysis of over 30 species of euglenoids for accumulation of euglenophycin identified six additional species producing the toxin; and six of the seven E. sanguinea strains produced the toxin. A phylogenetic assessment of these species confirmed most taxa were in the Euglenaceae, whereas synthesis capability apparently has been lost in the Phacus, Eutreptiella, and Discoplastis branches.

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.