The prodigiosins, proapoptotic drugs with anticancer properties

Copper(II) and Zinc(II) Complexes with Bacterial Prodigiosin Are Targeting Site III of Bovine Serum Albumin and Acting as DNA Minor Groove Binders

The negative environmental and social impacts of food waste accumulation can be mitigated by utilizing bio-refineries' approach where food waste is revalorized into high-value products, such as prodigiosin (PG), using microbial bioprocesses. The diverse biological activities of PG position it as a promising compound, but its high production cost and promiscuous bioactivity hinder its wide application. Metal ions can modulate the electronic properties of organic molecules, leading to novel mechanisms of action and increased target potency, while metal complex formation can improve the stability, solubility and bioavailability of the parent compound. The objectives of this study were optimizing PG production through bacterial fermentation using food waste, allowing good quantities of the pure natural product for further synthesizing and evaluating copper(II) and zinc(II) complexes with it. Their antimicrobial and anticancer activities were assessed, and their binding affinity toward biologically important molecules, bovine serum albumin (BSA) and DNA was investigated by fluorescence emission spectroscopy and molecular docking. The yield of 83.1 mg/L of pure PG was obtained when processed meat waste at 18 g/L was utilized as the sole fermentation substrate. The obtained complexes CuPG and ZnPG showed high binding affinity towards target site III of BSA, and molecular docking simulations highlighted the affinity of the compounds for DNA minor grooves.

AHL-Based Quorum Sensing Regulates the Biosynthesis of a Variety of Bioactive Molecules in Bacteria

Bacteria are social microorganisms that use communication systems known as quorum sensing (QS) to regulate diverse cellular behaviors including the production of various secreted molecules. Bacterial secondary metabolites are widely studied for their bioactivities including antibiotic, antifungal, antiparasitic, and cytotoxic compounds. Besides playing a crucial role in natural bacterial niches and intermicrobial competition by targeting neighboring organisms and conferring survival advantages to the producer, these bioactive molecules may be of prime interest to develop new antimicrobials or anticancer therapies. This review focuses on bioactive compounds produced under acyl homoserine lactone-based QS regulation by Gram-negative bacteria that are pathogenic to humans and animals, including the Burkholderia, Serratia, Pseudomonas, Chromobacterium, and Pseudoalteromonas genera. The synthesis, regulation, chemical nature, biocidal effects, and potential applications of these identified toxic molecules are presented and discussed in light of their role in microbial interactions.

Prodigiosin Inhibits Transforming Growth Factor β Signaling by Interfering Receptor Recycling and Subcellular Translocation in Epithelial Cells

Prodigiosin (PG) is a naturally occurring polypyrrole red pigment produced by numerous microorganisms including some Serratia and Streptomyces strains. PG has exhibited promising anticancer activity; however, the molecular mechanisms of action of PG on malignant cells remain ambiguous. Transforming growth factor-β (TGF-β) is a multifunctional cytokine that governs a wide array of cellular processes in development and tissue homeostasis. Malfunctions of TGF-β signaling are associated with numerous human cancers. Emerging evidence underscores the significance of internalized TGF-β receptors and their intracellular trafficking in initiating signaling cascades. In this study, we identified PG as a potent inhibitor of the TGF-β pathway. PG blocked TGF-β signaling by targeting multiple sites of this pathway, including facilitating the sequestering of TGF-β receptors in the cytoplasm by impeding the recycling of type II TGF-β receptors to the cell surface. Additionally, PG prompts a reduction in the abundance of receptors on the cell surface through the disruption of the receptor glycosylation. In human Caucasian lung carcinoma cells and human hepatocellular cancer cell line cells, nanomolar concentrations of PG substantially diminish TGF-β-triggered phosphorylation of Smad2 protein. This attenuation is further reflected in the suppression of downstream target gene expression, including those encoding fibronectin, plasminogen activator inhibitor-1, and N-cadherin. SIGNIFICANCE STATEMENT: Prodigiosin (PG) emerges from this study as a potent TGF-β pathway inhibitor, disrupting receptor trafficking and glycosylation and reducing TGF-β signaling and downstream gene expression. These findings not only shed light on PG's potential therapeutic role but also present a captivating avenue towards future anti-TGF-β strategies.

Prodigiosin/celecoxib-loaded into zein/sodium caseinate nanoparticles as a potential therapy for triple negative breast cancer

Nowadays, breast cancer is considered one of the most upsetting malignancies among females. Encapsulation of celecoxib (CXB) and prodigiosin (PDG) into zein/sodium caseinate nanoparticles (NPs) produce homogenous and spherical nanoparticles with good encapsulation efficiencies (EE %) and bioavailability. In vitro cytotoxicity study conducted on human breast cancer MDA-MB-231 cell lines revealed that there was a significant decline in the IC50 for encapsulated drugs when compared to each drug alone or their free combination. In addition, results demonstrated that there is a synergism between CXB and PDG as their combination indices were 0.62251 and 0.15493, respectively. Moreover, results of scratch wound healing assay revealed enhanced antimigratory effect of free drugs and fabricated NPs in comparison to untreated cells. Furthermore, In vitro results manifested that formulated nanoparticles exhibited induction of apoptosis associated with reduced angiogenesis, proliferation, and inflammation. In conclusion, nanoencapsulation of multiple drugs into nanoparticles might be a promising approach to develop new therapies for the managing of triple negative breast cancer.

Progress and prospects toward supramolecular bioactive ion transporters

The majority of cellular physiological processes depend on natural ion channels, which are pore-forming membrane-embedded proteins that let ions flow across the cell membranes selectively. This selective movement of ions across the membranes balances the osmolality within and outside the cell. However, mutations in the genes that encode essential membrane transport proteins or structural reorganisation of these proteins can cause life-threatening diseases like cystic fibrosis. Artificial ion transport systems have opened up a way to replace dysfunctional natural ion channels to cure such diseases through channel replacement therapy. Moreover, recent research has also demonstrated the ability of these systems to kill cancer cells, reigniting interest in the field among scientists. Our contributions to the recent progress in the design and development of artificial chloride ion transporters and their effect on biological systems have been discussed in this review. This review would provide current vistas and future directions toward the development of novel ion transporters with improved biocompatibility and desired anti-cancer properties. Additionally, it strongly emphasises stimuli-responsive ion transport systems, which are crucial for obtaining target-specificity and may speed up the application of these systems in clinical therapeutics.

Antimetastatic Properties of Prodigiosin and the BH3-Mimetic Obatoclax (GX15-070) in Melanoma

Metastasis is the primary cause of death in cancer patients. Many current chemotherapeutic agents only show cytotoxic, but not antimetastatic properties. This leads to a reduction in tumor size, but allows cancer cells to disseminate, which ultimately causes patient death. Therefore, novel anticancer compounds with both effects need to be developed. In this work, we analyze the antimetastatic properties of prodigiosin and obatoclax (GX15-070), anticancer drugs of the Prodiginines (PGs) family. We studied PGs' effects on cellular adhesion and morphology in the human primary and metastatic melanoma cell lines, SK-MEL-28 and SK-MEL-5, and in the murine melanoma cell line, B16F10A. Cell adhesion sharply decreased in the treated cells, and this was accompanied by a reduction in filopodia protrusions and a significant decrease in the number of focal-adhesion structures. Moreover, cell migration was assessed through the wound-healing assay and cell motility was severely inhibited after 24 h of treatment. To elucidate the molecular mechanisms involved, changes in metastasis-related genes were analyzed through a gene-expression array. Key genes related to cellular invasion, migration and chemoresistance were significantly down-regulated. Finally, an in vivo model of melanoma-induced lung metastasis was established and significant differences in lung tumors were observed in the obatoclax-treated mice. Altogether, these results describe, in depth, PGs' cellular antimetastatic effects and identify in vivo antimetastatic properties of Obatoclax.

Prodigiosin inhibits the proliferation of glioblastoma by regulating the KIAA1524/PP2A signaling pathway

Prodigiosin (PG), a member of a family of natural red pigments produced by a variety of bacteria, was first discovered in Serratia marcescens. PG has been reported to have an apoptosis-inducing effect in many cancers, such as lymphoma, colon cancer and nasopharyngeal carcinoma. For this study, we used three glioblastoma (GBM) cell lines (LN229, U251 and A172) to explore the effect of prodigiosin on GBM cells. A CCK8 assay was used to evaluate cell viability. We determinedthe cell cycle distribution by flow cytometry and measured proliferation by an EdU incorporation assay. The expression of different molecules was investigated by western blotting and RT-PCR. We further confirmed our results by plasmid transfection and lentiviral transduction. The LN229 xenograft model was used to study the effect of prodigiosin in vivo. We confirmed that prodigiosin played an anticancer role in several GBM cell lines through the KIAA1524/PP2A/Akt signalling pathway. Prodigiosin inhibited the protein expression of KIAA1524 by suppressing its transcription, which led to activation of PP2A. Afterward, PP2A inhibited the phosphorylation of Akt, thereby inducing increased expression of p53/p21. Furthermore, it was verified that prodigiosin inhibited the KIAA1524/PP2A/Akt axis in vivo in the LN229 xenograft model. These data improve the understanding of the anticancer effects of prodigiosin and further highlight the potential of prodigiosin for the development of anti-glioma drugs.

Prodigiosin: a promising biomolecule with many potential biomedical applications

Pigments are among the most fascinating molecules found in nature and used by human civilizations since the prehistoric ages. Although most of the bio-dyes reported in the literature were discovered around the eighties, the necessity to explore novel compounds for new biological applications has made them resurface as potential alternatives. Prodigiosin (PG) is an alkaloid red bio-dye produced by diverse microorganisms and composed of a linear tripyrrole chemical structure. PG emerges as a really interesting tool since it shows a wide spectrum of biological activities, such as antibacterial, antifungal, algicidal, anti-Chagas, anti-amoebic, antimalarial, anticancer, antiparasitic, antiviral, and/or immunosuppressive. However, PG vehiculation into different delivery systems has been proposed since possesses low bioavailability because of its high hydrophobic character (XLogP3-AA = 4.5). In the present review, the general aspects of the PG correlated with synthesis, production process, and biological activities are reported. Besides, some of the most relevant PG delivery systems described in the literature, as well as novel unexplored applications to potentiate its biological activity in biomedical applications, are proposed.

Crystal structures of PigF, an O-methyltransferase involved in the prodigiosin synthetic pathway, reveal an induced-fit substrate-recognition mechanism

Prodigiosin, a red linear tripyrrole pigment, is a typical secondary metabolite with numerous biological functions, such as anticancer, antibacterial and immunosuppressant activities, and is synthesized through a bifurcated biosynthesis pathway from 4-methoxy-2,2'-bipyrrole-5-carbaldehyde (MBC) and 2-methyl-3-n-amylpyrrole (MAP). The last step in the biosynthetic pathway of MBC is catalysed by PigF, which transfers a methyl group to 4-hydroxy-2,20-bipyrrole-5-carbaldehyde (HBC) to form the final product MBC. However, the catalytic mechanism of PigF is still elusive. In this study, crystal structures of apo PigF and S-adenosylhomocysteine (SAH)-bound PigF were determined. PigF forms a homodimer and each monomer consists of two domains: a C-terminal catalytic domain and an N-terminal dimerization domain. Apo PigF adopts an open conformation, while the structure of the complex with the product SAH adopts a closed conformation. The binding of SAH induces dramatic conformational changes of PigF, suggesting an induced-fit substrate-binding mechanism. Further structural comparison suggests that this induced-fit substrate-recognition mechanism may generally exist in O-methyltransferases. Docking and mutation studies identified three key residues (His98, His247 and Asp248) that are crucial for enzyme activity. The essential function of His247 and Asp248 and structure analysis suggests that both residues are involved in activation of the HBC substrate of PigF. The invariance of Asp248 in PigF further confirmed its essential role. The invariance and essential role of His98 in PigF suggests that it is involved in correctly positioning the substrate. This study provides new insight into the catalytic mechanism of PigF, reveals an induced-fit substrate-recognition model for PigF and broadens the understanding of O-methyltransferases.

Optimized prodigiosin production with Pseudomonas putida KT2440 using parallelized non-invasive online monitoring

The red pigment prodigiosin is of high pharmaceutical interest, due to its potential applications as an antitumor drug and antibiotic agent. As previously demonstrated, Pseudomonas putida KT2440 is a suitable host for prodigiosin production, as it exhibits high tolerance towards the antimicrobial properties of prodigiosin. So far, prodigiosin concentrations of up to 94 mg/L have been achieved in shake flask cultivations. For the characterization and optimization of the prodigiosin production process, the scattered light of P. putida and fluorescence of prodigiosin was measured. The excitation and emission wavelengths for prodigiosin measurement were analyzed by recording 2D fluorescence spectra. The strongest prodigiosin fluorescence was obtained at a wavelength combination of 535/560 nm. By reducing the temperature to 18 °C and using 16 g/L glucose, the prodigiosin concentration was more than doubled compared to the initial cultivation conditions. The obtained results demonstrate the capabilities of parallelized microscale cultivations combined with non-invasive online monitoring of fluorescence for rapid bioprocess development, using prodigiosin as a molecule of current biotechnological interest.

Promising bioactive compounds from the marine environment and their potential effects on various diseases

Background

The marine environment hosts a wide variety of species that have evolved to live in harsh and challenging conditions. Marine organisms are the focus of interest due to their capacity to produce biotechnologically useful compounds. They are promising biocatalysts for new and sustainable industrial processes because of their resistance to temperature, pH, salt, and contaminants, representing an opportunity for several biotechnological applications. Encouraged by the extensive and richness of the marine environment, marine organisms’ role in developing new therapeutic benefits is heading as an arable field.

Main body of the abstract

There is currently much interest in biologically active compounds derived from natural resources, especially compounds that can efficiently act on molecular targets, which are involved in various diseases. Studies are focused on bacteria and fungi, isolated from sediments, seawater, fish, algae, and most marine invertebrates such as sponges, mollusks, tunicates, coelenterates, and crustaceans. In addition to marine macro-organisms, such as sponges, algae, or corals, marine bacteria and fungi have been shown to produce novel secondary metabolites (SMs) with specific and intricate chemical structures that may hold the key to the production of novel drugs or leads. The marine environment is known as a rich source of chemical structures with numerous beneficial health effects. Presently, several lines of studies have provided insight into biological activities and neuroprotective effects of marine algae, including antioxidant, anti-neuroinflammatory, cholinesterase inhibitory activity, and neuronal death inhibition.

Conclusion

The application of marine-derived bioactive compounds has gained importance because of their therapeutic uses in several diseases. Marine natural products (MNPs) display various pharmaceutically significant bioactivities, including antibiotic, antiviral, neurodegenerative, anticancer, or anti-inflammatory properties. The present review focuses on the importance of critical marine bioactive compounds and their role in different diseases and highlights their possible contribution to humanity.

PLGA-CS-PEG Microparticles for Controlled Drug Delivery in the Treatment of Triple Negative Breast Cancer Cells

In this study, we explore the development of controlled PLGA-CS-PEG microspheres, which are used to encapsulate model anticancer drugs (prodigiosin (PGS) or paclitaxel (PTX)) for controlled breast cancer treatment. The PLGA microspheres are blended with hydrophilic polymers (chitosan and polyethylene glycol) in the presence of polyvinyl alcohol (PVA) that were synthesized via a water-oil-water (W/O/W) solvent evaporation technique. Chitosan (CS) and polyethylene glycol (PEG) were used as surface-modifying additives to improve the biocompatibility and reduce the adsorption of plasma proteins onto the microsphere surfaces. These PLGA-CS-PEG microspheres are loaded with varying concentrations (5 and 8 mg/mL) of PGS or PTX, respectively. Scanning electron microscopy (SEM) revealed the morphological properties while Fourier transform infrared spectroscopy (FTIR) was used to elucidate the functional groups of drug-loaded PLGA-CS-PEG microparticles. A thirty-day, in vitro, encapsulated drug (PGS or PTX) release was carried out at 37 °C, which corresponds to human body temperature, and at 41 °C and 44 °C, which correspond to hyperthermic temperatures. The thermodynamics and kinetics of in vitro drug release were also elucidated using a combination of mathematical models and the experimental results. The exponents of the Korsmeyer–Peppas model showed that the kinetics of drug release was well characterized by anomalous non-Fickian drug release. Endothermic and nonspontaneous processes are also associated with the thermodynamics of drug release. Finally, the controlled in vitro release of cancer drugs (PGS and PTX) is shown to decrease the viability of MDA-MB-231 cells. The implications of the results are discussed for the development of drug-encapsulated PLGA-CS-PEG microparticles for the controlled release of cancer drugs in treatment of triple negative breast cancer.

Natural DNA Intercalators as Promising Therapeutics for Cancer and Infectious Diseases

Cancer and infectious diseases are one of the greatest challenges of modern medicine. An unhealthy lifestyle, the improper use of drugs, or their abuse are conducive to the increase of morbidity and mortality caused by these diseases. The imperfections of drugs currently used in therapy for these diseases and the increasing problem of drug resistance have forced a search for new substances with therapeutic potential. Throughout history, plants, animals, fungi and microorganisms have been rich sources of biologically active compounds. Even today, despite the development of chemistry and the introduction of many synthetic chemotherapeutics, a substantial part of the new compounds being tested for treatment are still of natural origin. Natural compounds exhibit a great diversity of chemical structures, and thus possess diverse mechanisms of action and molecular targets. Nucleic acids seem to be a good molecular target for substances with anticancer potential in particular, but they may also be a target for antimicrobial compounds. There are many types of interactions of small-molecule ligands with DNA. This publication focuses on the intercalation process. Intercalators are compounds that usually have planar aromatic moieties and can insert themselves between adjacent base pairs in the DNA helix. These types of interactions change the structure of DNA, leading to various types of disorders in the functioning of cells and the cell cycle. This article presents the most promising intercalators of natural origin, which have aroused interest in recent years due to their therapeutic potential.

Bacteria as a treasure house of secondary metabolites with anticancer potential

Cancer stands in the frontline among leading killers worldwide and the annual mortality rate is expected to reach 16.4 million by 2040. Humans suffer from about 200 different types of cancers and many of them have a small number of approved therapeutic agents. Moreover, several types of major cancers are diagnosed at advanced stages as a result of which the existing therapies have limited efficacy against them and contribute to a dismal prognosis. Therefore, it is essential to develop novel potent anticancer agents to counteract cancer-driven lethality. Natural sources such as bacteria, plants, fungi, and marine microorganisms have been serving as an inexhaustible source of anticancer agents. Notably, over 13,000 natural compounds endowed with different pharmacological properties have been isolated from different bacterial sources. In the present article, we have discussed about the importance of natural products, with special emphasis on bacterial metabolites for cancer therapy. Subsequently, we have comprehensively discussed the various sources, mechanisms of action, toxicity issues, and off-target effects of clinically used anticancer drugs (such as actinomycin D, bleomycin, carfilzomib, doxorubicin, ixabepilone, mitomycin C, pentostatin, rapalogs, and romidepsin) that have been derived from different bacteria. Furthermore, we have also discussed some of the major secondary metabolites (antimycins, chartreusin, elsamicins, geldanamycin, monensin, plicamycin, prodigiosin, rebeccamycin, salinomycin, and salinosporamide) that are currently in the clinical trials or which have demonstrated potent anticancer activity in preclinical models. Besides, we have elaborated on the application of metagenomics in drug discovery and briefly described about anticancer agents (bryostatin 1 and ET-743) identified through the metagenomics approach.

Anticancer Potential of Compounds from the Brazilian Blue Amazon

"Blue Amazon" is used to designate the Brazilian Economic Exclusive Zone, which covers an area comparable in size to that of its green counterpart. Indeed, Brazil flaunts a coastline spanning 8000 km through tropical and temperate regions and hosting part of the organisms accredited for the country's megadiversity status. Still, biodiversity may be expressed at different scales of organization; besides species inventory, genetic characteristics of living beings and metabolic expression of their genes meet some of these other layers. These metabolites produced by terrestrial creatures traditionally and lately added to by those from marine organisms are recognized for their pharmaceutical value, since over 50% of small molecule-based medicines are related to natural products. Nonetheless, Brazil gives a modest contribution to the field of pharmacology and even less when considering marine pharmacology, which still lacks comprehensive in-depth assessments toward the bioactivity of marine compounds so far. Therefore, this review examined the last 40 years of Brazilian natural products research, focusing on molecules that evidenced anticancer potential-which represents ~ 15% of marine natural products isolated from Brazilian species. This review discusses the most promising compounds isolated from sponges, cnidarians, ascidians, and microbes in terms of their molecular targets and mechanisms of action. Wrapping up, the review delivers an outlook on the challenges that stand against developing groundbreaking natural products research in Brazil and on a means of surpassing these matters.

Bacterial pathogens: threat or treat (a review on bioactive natural products from bacterial pathogens)

Covering: up to the second quarter of 2020 Threat or treat? While pathogenic bacteria pose significant threats, they also represent a huge reservoir of potential pharmaceuticals to treat various diseases. The alarming antimicrobial resistance crisis and the dwindling clinical pipeline urgently call for the discovery and development of new antibiotics. Pathogenic bacteria have an enormous potential for natural products drug discovery, yet they remained untapped and understudied. Herein, we review the specialised metabolites isolated from entomopathogenic, phytopathogenic, and human pathogenic bacteria with antibacterial and antifungal activities, highlighting those currently in pre-clinical trials or with potential for drug development. Selected unusual biosynthetic pathways, the key roles they play (where known) in various ecological niches are described. We also provide an overview of the mode of action (molecular target), activity, and minimum inhibitory concentration (MIC) towards bacteria and fungi. The exploitation of pathogenic bacteria as a rich source of antimicrobials, combined with the recent advances in genomics and natural products research methodology, could pave the way for a new golden age of antibiotic discovery. This review should serve as a compendium to communities of medicinal chemists, organic chemists, natural product chemists, biochemists, clinical researchers, and many others interested in the subject.

Screening an Established Natural Product Library Identifies Secondary Metabolites That Potentiate Conventional Antibiotics

Health organizations worldwide have warned that we are on the cusp of a "post-antibiotic era," necessitating new approaches to combat antibiotic resistant infections. One such approach is the development of antibiotic adjuvants, which have little or no inherent antibiotic activity at their active concentrations but instead potentiate the activity of antibiotics against antibiotic-resistant bacteria. Recently, we demonstrated that meridianin D, a natural product originally reported to have activity against Staphylococcus aureus and Mycobacterium tuberculosis, possesses the ability to reverse colistin resistance in colistin resistant bacteria. As most natural product screens typically involve screening for only certain activities (anticancer, antiviral, and antimicrobial are typical), we posited that the meridianin D discovery was not unique and there are potentially many natural products that have adjuvant activity. To explore this, the National Cancer Institute (NCI) Natural Product Library Set IV was screened for adjuvant activity using four classes of antibiotics (β-lactams, aminoglycosides, macrolides, and polymyxins) against three bacterial pathogens (methicillin-resistant Staphylococcus aureus (MRSA), Acinetobacter baumannii, and Klebsiella pneumoniae). Sixteen compounds suppressed β-lactam resistance in MRSA, five of which effected a 16-fold reduction in the oxacillin minimum inhibitory concentration (MIC). Two natural products effectively suppressed aminoglycoside resistance in both of the Gram-negative species tested, and no hits were observed with macrolides. In contrast, a larger number of natural product adjuvants were identified when screening against colistin-resistant strains of A. baumannii and K. pneumoniae. Nine compounds reduced the colistin MIC to its breakpoint or lower (up to a 1024-fold reduction). Clorobiocin, novobiocin, and prodigiosin were most effective, reducing the colistin MIC in K. pneumoniae strain B9 to 2 μg/mL at concentrations as low as 0.625, 2.5, and 1.25 μM, respectively. Restored sensitivity to colistin with these compounds does not appear to coincide with known mechanisms of colistin resistance.

Quinine-Based Semisynthetic Ion Transporters with Potential Antiproliferative Activities

Synthetic ion transporters have attracted tremendous attention for their therapeutic potential against various ion-transport-related diseases, including cancer. Inspired by the structure and biological activities of natural products, we synthesized a small series of squaramide and thiourea derivatives of quinine and investigated their ion transport activities. The involvement of a quinuclidine moiety for the cooperative interactions of Cl^- and H⁺ ions with the thiourea or squaramide moiety resulted in an effectual transport of these ions across membranes. The interference of ionic equilibrium by the potent Cl^- ion carrier selectively induced cancer cell death by endorsing caspase-arbitrated apoptosis. In vivo assessment of the potent ionophore showed an efficient reduction in tumor growth with negligible immunotoxicity to other organs.

Cytotoxic Effect of Prodigiosin, Natural Red Pigment, Isolated from Serratia marcescens UFPEDA 398

Prodigiosin is a secondary metabolite, with red pigmentation, produced by Serratia marcescens. Red pigment is a natural alkaloid whose chemical structure has three pyrrole rings. Prodigiosin has been described for several biological activities, including antitumor, inducing apotosis in T and B lymphocytes. This work aimed to evaluate the cytotoxic activity of prodigiosin in NCHI-292, HEp-2, MCF-7 and HL-60 tumor cell lines. The red pigment was isolated from Serratia marcescens UFPEDA 398 biomass whose fractions were previously separated by column chromatography, purified, identified and further characterized by GC-MS and compared with the computerized library of m/z values. The pigment corresponded to prodigiosin with maximum absorption at 534 nm, molecular weight 323 and structural formula C20H25N3O. During the prodigiosin purification process a purple absorbance fraction at 272.65 nm was also observed. Significant cytotoxic effects of prodigiosin were evidenced for NCHI-292, Hep-2, MCF-7 and HL-60 tumor cell lines. The isolated purple fraction had no cytotoxic effect (IC50 11.3 µg/mL) when compared to prodigiosin (IC50 3.4 µg/mL) for the tumor cell lines studied. The MCF-7 strain was slightly more pigment resistant (IC50 5.1 µg/mL). Therefore, further studies will be needed to elucidate the antitumor mechanisms of prodigiosin action against tumor strains from flow cytometry tests. However, although these data are preliminary, it was evidenced that prodigiosin showed cytotoxic activity in tumor cell lines suggesting promising antitumor properties. In this sense, future studies on the cytotoxic and genotoxic effects of prodigiosin produced by S. marcecsens UFPEDA 398 are suggested.

Selective Cytotoxic Activity of Prodigiosin@halloysite Nanoformulation

Prodigiosin, a bioactive secondary metabolite produced by Serratia marcescens, is an effective proapoptotic agent against various cancer cell lines, with little or no toxicity toward normal cells. The hydrophobicity of prodigiosin limits its use for medical and biotechnological applications, these limitations, however, can be overcome by using nanoscale drug carriers, resulting in promising formulations for target delivery systems with great potential for anticancer therapy. Here we report on prodigiosin-loaded halloysite-based nanoformulation and its effects on viability of malignant and non-malignant cells. We have found that prodigiosin-loaded halloysite nanotubes inhibit human epithelial colorectal adenocarcinoma (Caco-2) and human colon carcinoma (HCT116) cells proliferative activity. After treatment of Caco-2 cells with prodigiosin-loaded halloysite nanotubes, we have observed a disorganization of the F-actin structure. Comparison of this effects on malignant (Caco-2, HCT116) and non-malignant (MSC, HSF) cells suggests the selective cytotoxic and genotoxic activity of prodigiosin-HNTs nanoformulation.

Genomics-Metabolomics Profiling Disclosed Marine Vibrio spartinae 3.6 as a Producer of a New Branched Side Chain Prodigiosin

A wide range of prescreening tests for antimicrobial activity of 59 bacterial isolates from sediments of Ria Formosa Lagoon (Algarve, Portugal) disclosed Vibrio spartinae 3.6 as the most active antibacterial producing strain. This bacterial strain, which has not previously been submitted for chemical profiling, was subjected to de novo whole genome sequencing, which aided in the discovery and elucidation of a prodigiosin biosynthetic gene cluster that was predicted by the bioinformatic tool KEGG BlastKoala. Comparative genomics led to the identification of a new membrane di-iron oxygenase-like enzyme, annotated as Vspart_02107, which is likely to be involved in the biosynthesis of cycloprodigiosin and analogues. The combined genomics-metabolomics profiling of the strain led to the isolation and identification of one new branched-chain prodigiosin (5) and to the detection of two new cyclic forms. Furthermore, the evaluation of the minimum inhibitory concentrations disclosed the major prodigiosin as very effective against multi-drug-resistant pathogens including Stenotrophomonas maltophilia, a clinical isolate of Listeria monocytogenes, as well as some human pathogens reported by the World Health Organization as prioritized targets.

Biologically active pigment and ShlA cytolysin of Serratia marcescens induce autophagy in a human ocular surface cell line

BACKGROUND

The cellular process of autophagy is essential for maintaining the health of ocular tissue. Dysregulation of autophagy is associated with several ocular diseases including keratoconus and macular degeneration. It is known that autophagy can be used to respond to microbial infections and that certain microbes can exploit the autophagic process to their benefit. In this study, a genetic approach was used to identify surface-associated and secreted products generated by the opportunistic pathogen Serratia marcescens involved in activation of autophagy.

METHODS

A recombinant human corneal limbal epithelial cell line expressing a LC3-GFP fusion protein was challenged with normalized secretomes from wild-type and mutant S. marcescens derivatives. LC3-GFP fluorescence patterns were used to assess the ability of wild-type and mutant bacteria to influence autophagy. Purified prodigiosin was obtained from stationary phase bacteria and used to challenge ocular cells.

RESULTS

Mutations in the global regulators eepR and gumB genes highly reduced the ability of the bacteria to activate autophagy in corneal cells. This effect was further narrowed down to the secreted cytolysin ShlA and the biologically active pigment prodigiosin. Purified prodigiosin and ShlA from Escherichia coli further supported the role of these factors in activating autophagy in human corneal cells. Additional genetic data indicate a role for flagellin and type I pili, but not the nuclease, S-layer protein, or serratamolide biosurfactant in activation of autophagy.

CONCLUSIONS

This work identifies specific bacterial components that activate autophagy and give insight into potential host-pathogen interactions or compounds that can be used to therapeutically manipulate autophagy.

A Rapid and High Throughput MIC Determination Method to Screen Uranium Resistant Microorganisms

The assessment of minimum inhibitory concentration (MIC) is a conventional technique used for the screening of microbial resistance against antibiotics, biocides, and contaminants such as heavy metals. However, as part of our ongoing work, we have observed biases associated with using traditional liquid MIC method to screen microbial heavy metal resistance, including both bacterial and fungal strains. Specifically, the addition of uranium into synthetic media causes immediate precipitation prior to the initiation of microbial growth, thus hampering the optical density measurements, and the obtained MIC values are thus flawed and inaccurate. To address this discrepancy, we report the optimization and development of a serial-dilution-based MIC method conducted on solid growth media supplemented with uranium, which is more accurate, relative to the testing of MICs performed in liquid cultures. Notably, we report on the efficacy of this method to screen not only bacteria that are resistant to uranium but also demonstrate the successful application to yeast and fungal isolates, for their ability to resist uranium, is more accurate and sensitive relative to the liquid method. We believe that this newly developed method to screen heavy metal resistance, such as uranium, is far superior to the existing liquid MIC method and propose replacing the liquid assay with the solid plate MIC reported herein.

Degradable porous drug-loaded polymer scaffolds for localized cancer drug delivery and breast cell/tissue growth

This paper presents the results of a combined experimental and analytical study of blended FDA-approved polymers [polylactic-co-glycolic acid (PLGA), polyethylene glycol (PEG) and polycaprolactone (PCL)] with the potential for sustained localized cancer drug release. Porous drug-loaded 3D degradable PLGA-PEG and PLGA-PCL scaffolds were fabricated using a multistage process that involved solvent casting and particulate leaching with lyophilization. The physicochemical properties including the mechanical, thermal and biostructural properties of the drug-loaded microporous scaffolds were characterized. The release of the encapsulated prodigiosin (PG) or paclitaxel (PTX) drug (from the drug-loaded polymer scaffolds) was also studied experimentally at human body temperature (37 °C) and hyperthermic temperatures (41 and 44 °C). These characteristic controlled and localized in vitro drug release from the properties of the microporous scaffold were analyzed using kinetics and thermodynamic models. Subsequently, normal breast cells (MCF-10A) were cultured for a 28-day period on the resulting 3D porous scaffolds in an effort to study the possible regrowth of normal breast tissue, following drug release. The effects of localized cancer drug release on breast cancer cells and normal breast cell proliferation are demonstrated for scenarios that are relevant to palliative breast tumor surgery for 16 weeks under in vivo conditions. Results from the in vitro drug release show a sustained anomalous (non-Fickian) drug release that best fits the Korsmeyer-Peppas (KP) kinetic model with a non-spontaneous thermodynamic process that leads to a massive decrease in breast cancer cell (MDA-MB-231) viability. Our findings from the animal suggest that localized drug release from drug-based 3D resorbable porous scaffolds can be used to eliminate/treat local recurred triple negative breast tumors and promote normal breast tissue regeneration after surgical resection.

Novel Prodiginine Derivatives Demonstrate Bioactivities on Plants, Nematodes, and Fungi

Bacterial metabolites represent an invaluable source of bioactive molecules which can be used as such or serve as chemical frameworks for developing new antimicrobial compounds for various applications including crop protection against pathogens. Prodiginines are tripyrrolic, red-colored compounds produced by many bacterial species. Recently, due to the use of chemical-, bio-, or mutasynthesis, a novel group of prodiginines was generated. In our study, we perform different assays to evaluate the effects of prodigiosin and five derivatives on nematodes and plant pathogenic fungi as well as on plant development. Our results showed that prodigiosin and the derivatives were active against the bacterial feeding nematode Caenorhabditis elegans in a concentration- and derivative-dependent manner while a direct effect on infective juveniles of the plant parasitic nematode Heterodera schachtii was observed for prodigiosin only. All compounds were found to be active against the plant pathogenic fungi Phoma lingam and Sclerotinia sclerotiorum. Efficacy varied depending on compound concentration and chemical structure. We observed that prodigiosin (1), the 12 ring- 9, and hexenol 10 derivatives are neutral or even positive for growth of Arabidopsis thaliana depending on the applied compound concentration, whereas other derivatives appear to be suppressive. Our infection assays revealed that the total number of developed H. schachtii individuals on A. thaliana was decreased to 50% in the presence of compounds 1 or 9. Furthermore, female nematodes and their associated syncytia were smaller in size. Prodiginines seem to indirectly inhibit H. schachtii parasitism of the plant. Further research is needed to elucidate their mode of action. Our results indicate that prodiginines are promising metabolites that have the potential to be developed into novel antinematodal and antifungal agents.

Novel Efficient Bioprocessing of Marine Chitins into Active Anticancer Prodigiosin

Marine chitins (MC) have been utilized for the production of vast array of bioactive products, including chitooligomers, chitinase, chitosanase, antioxidants, anti-NO, and antidiabetic compounds. The aim of this study is the bioprocessing of MC into a potent anticancer compound, prodigiosin (PG), via microbial fermentation. This bioactive compound was produced by Serratia marcescens TKU011 with the highest yield of 4.62 mg/mL at the optimal conditions of liquid medium with initial pH of 5.65-6.15 containing 1% α-chitin, 0.6% casein, 0.05% K₂HPO₄, and 0.1% CaSO₄. Fermentation was kept at 25 °C for 2 d. Notably, α-chitin was newly investigated as the major potential material for PG production via fermentation; the salt CaSO₄ was also found to play the key role in the enhancement of PG yield of Serratia marcescens fermentation for the first time. PG was qualified and identified based on specific UV, MALDI-TOF MS analysis. In the biological activity tests, purified PG demonstrated potent anticancer activities against A549, Hep G2, MCF-7, and WiDr with the IC₅₀ values of 0.06, 0.04, 0.04, and 0.2 µg/mL, respectively. Mytomycin C, a commercial anti-cancer compound was also tested for comparison purpose, showing weaker activity with the IC₅₀ values of 0.11, 0.1, 0.14, and 0.15 µg/mL, respectively. As such, purified PG displayed higher 2.75-fold, 1.67-fold, and 3.25-fold efficacy than Mytomycin C against MCF-7, A549, and Hep G2, respectively. The results suggest that marine chitins are valuable sources for production of prodigiosin, a potential candidate for cancer drugs.

Targeted Delivery Prodigiosin to Choriocarcinoma by Peptide-Guided Dendrigraft Poly-l-lysines Nanoparticles

The available and effective therapeutic means to treat choriocarcinoma is seriously lacking, mainly due to the toxic effects caused by chemotherapy and radiotherapy. Accordingly, we developed a method for targeting delivery of chemotherapeutical drugs only to cancer cells, not normal cells, in vivo, by using a synthetic placental chondroitin sulfate (CSA)-binding peptide (plCSA-BP) derived from malarial protein VAR2CSA. A 28 amino acids placental CSA-binding peptide (plCSA-BP) from the VAR2CSA was synthesized as a guiding peptide for tumor-targeting delivery, dendrigraft poly-L-lysines (DGL) was modified with plCSA-BP and served as a novel targeted delivery carrier. Choriocarcinoma was selected to test the effect of targeted delivery carrier, and prodigiosin isolated from Serratia marcescens subsp. lawsoniana was selected as a chemotherapeutical drug and encapsulated in the DGL modified by the plCSA-BP nanoparticles (DGL/CSA-PNPs). DGL/CSA-PNPs had a sustained slow-release feature at pH 7.4, which could specifically bind to the JEG3 cells and exhibited better anticancer activity than that of the controls. The DGL/CSA-PNPs induced the apoptosis of JEG3 cells through caspase-3 and the P53 signaling pathway. DGL/CSA-PNPs can be used as an excellent targeted delivery carrier for anticancer drugs, and the prodigiosin could be an alternative chemotherapeutical drug for choriocarcinoma.

Vinylpyrroles: solid-state structures and aggregation-induced emission properties

An aggregation-induced emission chromophore, vinylpyrrole, was prepared from a formylpyrrole derivative, Meldrum's acid, and 1,3-dimethylbarbituric acid. The optical properties of the chromophore both in the solution and solid states were investigated by UV-vis and fluorescence spectroscopy. Single crystal X-ray diffraction measurements revealed that the dimethylbarbituric acid adduct formed a J-aggregate in the solid and resulted in higher fluorescence quantum yield compared to the Meldrum's acid adduct. Emission enhancement was found to occur by the restriction of molecular rotation in the solid state.

A cyclic ester and a cyclic amide functionalized monopyrroles show aggregation-induced emission (AIE) by the restriction of intramolecular rotation (RIR) mechanism.

Heavy Pnictogenium Cations as Transmembrane Anion Transporters in Vesicles and Erythrocytes

Our work on the complexation of fluoride anions using group 15 Lewis acids has led us to investigate the use of these main group compounds as anion transporters. In this paper, we report on the anion transport properties of tetraarylstibonium and tetraarylbismuthonium cations of the general formula [Ph₃PnAr]⁺ with Pn = Sb or Bi and with Ar = phenyl, naphthyl, anthryl, or pyrenyl. Using EYPC-based large unilamellar vesicles, we show that these main group cations transport hydroxide, fluoride and chloride anions across phospholipid bilayers. A comparison of the properties of [Ph₃SbAnt]⁺ and [Ph₃BiAnt]⁺ (Ant = 9-anthryl) illustrates the favorable role played by the Lewis acidity of the central pnictogen element with respect to the anion transport. Finally, we show that [Ph₃SbAnt]⁺ accelerates the fluoride-induced hemolysis of human red blood cells, an effect that we assign to the transporter-facilitated influx of toxic fluoride anions.

Using prodigiosin against some gram-positive and gram-negative bacteria and Trypanosoma cruzi

Background

This work aimed to explore the action of natural prodigiosin on both bacterial organisms and Trypanosoma cruzi cells.

Methods

Natural prodigiosin pigment was extracted and purified from cultures of Serratia marcescens. Two media, peanut broth and peptone glycerol broth, both recommended in the literature for prodigiosin production, were compared. The prodigiosin obtained was employed to explore its antimicrobial properties against both bacteria and Trypanosoma cruzi cells.

Results

Peanut broth yielded four times more prodigiosin. The prodigiosin showed remarkable activity (minimal inhibitory concentrations in the range of 2-8 µM for bacteria and half maximal inhibitory concentration of 0.6 µM for Trypanosoma cruzi). In fact, the prodigiosin concentration required to inhibit parasite growth was as low as 0.25 mg/l versus 4.9 mg/l of benznidazole required. Furthermore, atomic force microscopy revealed marked morphological alterations in treated epimastigote forms, although no pore-formation activity was detected in protein-free environments.

Conclusions

This work demonstrates the potential usefulness of prodigiosin against some gram-positive and gram-negative bacteria and Trypanosoma cruzi although further studies must be done in order to assess its value as a candidate molecule.

Thermoregulation of Prodigiosin Biosynthesis by Serratia marcescens is Controlled at the Transcriptional Level and Requires HexS

Several biotypes of the Gram-negative bacterium Serratia marcescens produce the tri-pyrole pigment and secondary metabolite prodigiosin. The biological activities of this pigment have therapeutic potential. For over half a century it has been known that biosynthesis of prodi giosin is inhibited when bacteria are grown at elevated temperatures, yet the fundamental mechanism underlying this thermoregulation has not been characterized. In this study, chromosomal and plasmid-borne luxCDABE transcriptional reporters revealed reduced transcription of the prodigiosin biosynthetic operon at 37°C compared to 30°C indicating transcriptional control of pigment production. Moreover, induced expression of the prodigiosin biosynthetic operon at 37°C was able to produce pigmented colonies and cultures demonstrating that physiological conditions at 37°C allow prodigiosin production and indicating that post-transcriptional control is not a major contributor to the thermoregulation of prodigiosin pigmentation. Genetic experiments support the model that the HexS transcription factor is a key contributor to thermoregulation of pigmentation, whereas CRP plays a minor role, and a clear role for EepR and PigP was not observed. Together, these data indicate that thermoregulation of prodigiosin production at elevated temperatures is controlled largely, if not exclusively, at the transcriptional level.

The Natural Product Butylcycloheptyl Prodiginine Binds Pre-miR-21, Inhibits Dicer-Mediated Processing of Pre-miR-21, and Blocks Cellular Proliferation

Identification of RNA-interacting pharmacophores could provide chemical probes and, potentially, small molecules for RNA-based therapeutics. Using a high-throughput differential scanning fluorimetry assay, we identified small-molecule natural products with the capacity to bind the discrete stem-looped structure of pre-miR-21. The most potent compound identified was a prodiginine-type compound, butylcycloheptyl prodiginine (bPGN), with the ability to inhibit Dicer-mediated processing of pre-miR-21 in vitro and in cells. Time-dependent RT-qPCR, western blot, and transcriptomic analyses showed modulation of miR-21 expression and its target genes such as PDCD4 and PTEN upon treatment with bPGN, supporting on-target inhibition. Consequently, inhibition of cellular proliferation in HCT-116 colorectal cancer cells was also observed when treated with bPGN. The discovery that bPGN can bind and modulate the expression of regulatory RNAs such as miR-21 helps set the stage for further development of this class of natural product as a molecular probe or therapeutic agent against miRNA-dependent diseases.

Prodigiosin induces apoptosis and inhibits autophagy via the extracellular signal-regulated kinase pathway in K562 cells

Prodigiosin contains a tripyrrole skeleton and shows impressive anticancer potential in multiple cell lines. Numerous studies have been conducted on prodigiosin-induced apoptosis and the related mechanisms. However, few reports have considered the effects of prodigiosin on autophagy and the relationship between apoptosis and autophagy. Here, we examined whether prodigiosin affected apoptosis and autophagy through the extracellular signal-regulated (ERK) signaling pathway in K562 cells, employing cell proliferation, flow cytometry, caspase activity, and western blot analyses. Inhibition of the ERK signaling pathway with PD184352 was conducted to verify the role of this pathway on prodigiosin-mediated processes. Our findings revealed that prodigiosin inhibited the proliferation of K562 cells, increased reactive oxygen species (ROS), induced apoptosis and inhibited autophagy in K562 cells. Additionally, the ROS scavenger, N-Acetyl-L-cysteine (NAC), partially prevented prodigiosin-induced apoptosis but did not reduce prodigiosin-inhibited autophagy in K562 cells. Furthermore, prodigiosin treatment in K562 cells reduced the phosphorylation of c-Jun N-terminal kinases (JNKs) and P38, and activated ERK signaling pathway. When ERK1/2 phosphorylation was blocked by PD184352, prodigiosin-induced apoptosis and the inhibition of autophagy decreased significantly. Taken together, these results demonstrated that the ERK signaling pathway was involved in prodigiosin-induced apoptosis and prodigiosin-inhibited autophagy.

Insights into the anti-infective properties of prodiginines

Prodiginines are a large family of tripyrrole alkaloids that contain natural members produced by various bacteria and non-natural members obtained from chemical synthesis, enzymatic synthesis, and mutasynthesis. These compounds have attracted a great deal of attention due to their wide range of fascinating properties including anti-infective, anticancer, and immunosuppressive activities. In consideration of the great need for novel and effective anti-infective agents, this review is mainly focused on the current status of research on the anti-infective properties of prodiginines, highlighting their antibacterial, antifungal, antiprotozoal, anti-larval, and antiviral activities. Additionally, the multiple mechanisms by which prodiginines exert their anti-infective effects will also be discussed.

Transmembrane H+/Cl− cotransport activity of bis(amido)imidazole receptors

Bis(amide) appended imidazole having a sickle-shaped trivalent hydrogen-bonding structure reported as a transmembrane H⁺/Cl⁻ symporter.

Biological Potential and Mechanism of Prodigiosin from Serratia marcescens Subsp. lawsoniana in Human Choriocarcinoma and Prostate Cancer Cell Lines

Tripyrrole molecules have received renewed attention due to reports of numerous biological activities, including antifungal, antibacterial, antiprotozoal, antimalarial, immunosuppressive, and anticancer activities. In a screen of bacterial strains with known toxicities to termites, a red pigment-producing strain, HDZK-BYSB107, was isolated from Chamaecyparis lawsoniana, which grows in Oregon, USA. Strain HDZK-BYSB107 was identified as Serratia marcescens subsp. lawsoniana. The red pigment was identified as prodigiosin using ultraviolet absorption, LC-MS, and 1H-NMR spectroscopy. The bacterial prodigiosin had an inhibitory effect on both Gram-negative and Gram-positive bacteria. The main objective of this study was to explore the anticancer activities and mechanism of strain HDZK-BYSB107 prodigiosin by using human choriocarcinoma (JEG3) and prostate cancer cell lines (PC3) in vitro and JEG3 and PC3 tumor-bearing nude mice in vivo. In vitro anticancer activities showed that the bacterial prodigiosin induced apoptosis in JEG3 cells. In vivo anticancer activities indicated that the prodigiosin significantly inhibited the growth of JEG3 and PC3 cells, and the inhibitory activity was dose and time dependent. The anticancer efficacy of the bacterial prodigiosin on JEG3 and PC3 cells, JEG3 and PC3 tumor exhibited a correlation with the down regulation of the inhibitor of IAP family, including XIAP, cIAP-1 and cIAP-2, and the activation of caspase-9 and caspase-3 accompanied by proteolytic degradation of poly (ADP-ribose)-polymerase. The expressions of P53 and Bax/Bcl-2 in JEG3 and PC3 cells were significantly higher than in untreated groups. Our results indicated that the bacterial prodigiosin extracted from C. lawsoniana is a promising molecule due to its potential for therapeutic applications.

Production of Prodiginines Is Part of a Programmed Cell Death Process in Streptomyces coelicolor

Actinobacteria are prolific producers of antitumor antibiotics with antiproliferative activity, but why these bacteria synthetize metabolites with this bioactivity has so far remained a mystery. In this work we raised the hypothesis that under certain circumstances, production of antiproliferative agents could be part of a genetically programmed death of the producing organism. While programmed cell death (PCD) has been well documented when Streptomyces species switch from vegetative (nutrition) to aerial (reproduction) growth, lethal determinants are yet to be discovered. Using DNA-damaging prodiginines of Streptomyces coelicolor as model system, we revealed that, under certain conditions, their biosynthesis is always triggered in the dying zone of the mycelial network prior to morphological differentiation, right after an initial round of cell death. The programmed massive death round of the vegetative mycelium is absent in a prodiginine non-producer (ΔredD strain), and mutant complementation restored both prodiginine production and cell death. The redD null mutant of S. coelicolor also showed increased DNA, RNA, and proteins synthesis when most of the mycelium of the wild-type strain was dead when prodiginines accumulated. Moreover, addition of the prodiginine synthesis inhibitors also resulted in enhanced accumulation of viable filaments. Overall, our data enable us to propose a model where the time-space production of prodiginines is programmed to be triggered by the perception of dead cells, and their biosynthesis further amplifies the PCD process. As prodiginine production coincides with the moment S. coelicolor undergoes morphogenesis, the production of these lethal compounds might be used to eradicate the obsolete part of the population in order to provide nutrients for development of the survivors. Hence, next to weapons in competition between organisms or signals in inter- and intra-species communications, we propose a third role for antibiotics (in the literal meaning of the word ‘against life’) i.e., elements involved in self-toxicity in order to control cell proliferation, and/or for PCD associated with developmental processes.

Preparation of Cyclic Prodiginines by Mutasynthesis in Pseudomonas putida KT2440

Prodiginines are a group of naturally occurring pyrrole alkaloids produced by various microorganisms and known for their broad biological activities. The production of nature-inspired cyclic prodiginines was enabled by combining organic synthesis with a mutasynthesis approach based on the GRAS (generally recognized as safe) certified host strain Pseudomonas putida KT2440. The newly prepared prodiginines exerted antimicrobial effects against relevant alternative biotechnological microbial hosts whereas P. putida itself exhibited remarkable tolerance against all tested prodiginines, thus corroborating the bacterium's exceptional suitability as a mutasynthesis host for the production of these cytotoxic secondary metabolites. Moreover, the produced cyclic prodiginines proved to be autophagy modulators in human breast cancer cells. One promising cyclic prodiginine derivative stood out, being twice as potent as prodigiosin, the most prominent member of the prodiginine family, and its synthetic derivative obatoclax mesylate.

Photo-induced anticancer activity and singlet oxygen production of prodigiosenes

The photo-induced cytotoxicity of prodigiosenes is reported. One prodigiosene represents a synthetic analogue of the natural product prodigiosin, and two are conjugated to molecules that target the estrogen receptor (ER). A comparison of incubation and irradiation frameworks for the three prodigiosenes is reported, with activity against ER- and ER+ lines explored. Furthermore, the ability of the three prodigiosenes to photosensitise the production of singlet oxygen is demonstrated, shedding mechanistic light onto possible photodynamic therapeutic effects of this class of tripyrroles.

Prodigiosenes conjugated to tamoxifen and estradiol

We report the synthesis of the first click-appended prodigiosene conjugates. Four prodigiosene conjugates of estradiol functionalised at the 7α-position were prepared, as were three prodigiosene conjugates of tamoxifen. The coupling between a prodigiosene and an 11-hydroxy estradiol derivative via an ether linkage was investigated, as was the 11- and 7-functionalisation of the estradiol core. The robustness of estradiol protecting groups was severely challenged by reactions typically used to equip such frameworks for 11- and 7-functionalisation. Specifically, and important to synthesis involving estradiol, TBS, TMS and THP are not useful protecting groups for the functionalisation of this core. When the chemical features of the therapeutic agent limit the choice of protecting group (in this case, prodigiosenes bearing aryl, NH, alkenyl and ester groups), click chemistry becomes an attractive synthetic strategy. The anti-cancer activity of the seven click prodigiosene conjugates was evaluated.

Rieske non-heme iron-dependent oxygenases catalyse diverse reactions in natural product biosynthesis

The role played by Rieske non-heme iron-dependent oxygenases in natural product biosyntheses is reviewed, with particular focus on experimentally characterised examples.

An anion receptor that facilitates transmembrane proton–anion symport by deprotonating its sulfonamide N–H proton

Indole-based amide-sulfonamide derivatives were synthesized. The X-ray crystal structure and chloride binding studies in solution showed a 1 : 1 stoichiometry. The ion transport study indicated the proton–anion symport across the lipid bilayer membrane.

New Prodigiosin Derivatives Obtained by Mutasynthesis in Pseudomonas putida

The deeply red-colored natural compound prodigiosin is a representative of the prodiginine alkaloid family, which possesses bioactivities as antimicrobial, antitumor, and antimalarial agents. Various bacteria including the opportunistic human pathogen Serratia marcescens and different members of the Streptomycetaceae and Pseudoalteromonadaceae produce prodiginines. In addition, these microbes generally accumulate many structurally related alkaloids making efficient prodiginine synthesis and purification difficult and expensive. Furthermore, it is known that structurally different natural prodiginine variants display differential bioactivities. In the herein described mutasynthesis approach, 13 different derivatives of prodigiosin were obtained utilizing the GRAS (generally recognized as safe) classified strain Pseudomonas putida KT2440. Genetic engineering of the prodigiosin pathway together with incorporation of synthetic intermediates thus resulted in the formation of a so far unprecedented structural diversity of new prodiginine derivatives in P. putida. Furthermore, the formed products allow reliable conclusions regarding the substrate specificity of PigC, the final condensing enzyme in the prodigiosin biosynthesis pathway of S. marcescens. The biological activity of prodigiosin toward modulation of autophagy was preserved in prodiginine derivatives. One prodiginine derivative displayed more potent autophagy inhibitory activity than the parent compound or the synthetic clinical candidate obatoclax.