Isolation and Characterization of a Serratia rubidaea from a Shallow Water Hydrothermal Vent.

Microbial life present in the marine environment has to be able to adapt to rapidly changing and often extreme conditions. This makes these organisms a putative source of commercially interesting compounds since adaptation provides different biochemical routes from those found in their terrestrial counterparts. In this work, the goal was the identification of a marine bacterium isolated from a sample taken at a shallow water hydrothermal vent and of its red product. Genomic, lipidomic, and biochemical approaches were used simultaneously, and the bacterium was identified as Serratia rubidaea. A high-throughput screening strategy was used to assess the best physico-chemical conditions permitting both cell growth and production of the red product. The fatty acid composition of the microbial cells was studied to assess adaptation at the lipid level under stressful conditions, whilst several state-of-the-art techniques, such as DSC, FTIR, NMR, and Ultra-High Resolution Qq-Time-of-Flight mass spectrometry, were used to characterize the structure of the pigment. We hypothesize that the pigment, which could be produced by the cells up to 62 °C, is prodigiosin linked to an aliphatic compound that acts as an anchor to keep it close to the cells in the marine environment.

Recent Advances in Prodigiosin as a Bioactive Compound in Nanocomposite Applications.

Bionanocomposites based on natural bioactive entities have gained importance due to their abundance; renewable and environmentally benign nature; and outstanding properties with applied perspective. Additionally, their formulation with biological molecules with antimicrobial, antioxidant, and anticancer activities has been produced nowadays. The present review details the state of the art and the importance of this pyrrolic compound produced by microorganisms, with interest towards Serratia marcescens, including production strategies at a laboratory level and scale-up to bioreactors. Promising results of its biological activity have been reported to date, and the advances and applications in bionanocomposites are the most recent strategy to potentiate and to obtain new carriers for the transport and controlled release of prodigiosin. Prodigiosin, a bioactive secondary metabolite, produced by Serratia marcescens, is an effective proapoptotic agent against bacterial and fungal strains as well as cancer cell lines. Furthermore, this molecule presents antioxidant activity, which makes it ideal for treating wounds and promoting the general improvement of the immune system. Likewise, some of the characteristics of prodigiosin, such as hydrophobicity, limit its use for medical and biotechnological applications; however, this can be overcome by using it as a component of a bionanocomposite. This review focuses on the chemistry and the structure of the bionanocomposites currently developed using biorenewable resources. Moreover, the work illuminates recent developments in pyrrole-based bionanocomposites, with special insight to its application in the medical area.

Prodigiosin production from Serratia marcescens strain CSK and their antioxidant, antibacterial, cytotoxic effect and in silico study of caspase-3 apoptotic protein.

The present study emphasizes the production and optimization of prodigiosin (PG) pigment from Serratia marcescens strain CSK, which was isolated from Shevaroy Hills, Salem district, Tamil Nadu, India. The response surface methodology analysis was applied for the optimization process of PG production. The maximum production of PG (2950 mg/L) was obtained at pH 7.0 with the addition of tryptophan (4.0 g/L) and sucrose (3.0 g/L) with 60 h of incubation. Further, the PG was characterized using high-performance liquid chromatography, Fourier-transform infrared spectroscopy, and gas chromatography-mass spectrometry. The purified PG exhibited strong antioxidant and antibacterial activities. Also, PG's cytotoxic effects against human breast cancer (MCF-7) cells were observed through acridine orange-ethidium bromide (AO-EB) and Hoechst staining. Molecular dockingstudies revealed that PG could bind positively to the caspase-3 (breast cancer protein 1RE1) binding site with a binding energy score of 17.37 kcal/mol. Overall, the novel PG was found to be an anticancer drug for potential applications in the pharmaceutical industry.

HPLC with fluorescence detection for the bioanalysis and pharmacokinetic study of Doxorubicin and Prodigiosin loaded on eco-friendly casein nanomicelles in rat plasma.

A rapid, efficient, and sensitive liquid chromatographic assay hyphenated to fluorometric detector (HPLC-FLD) was developed and validated for the determination of doxorubicin (DXR) and prodigiosin (PDG) in rat plasma. The sample pre-treatment involves a protein precipitation with acetonitrile with satisfying extraction efficiency (98% and 85% for DXR and PDG, respectively). The chromatographic separation was accomplished using stationary phase: Agilent Zorbax Eclipse plus-C18 analytical column (250 × 4.6 mm, 5 µm) and gradient eluting mobile phase of ammonium acetate (pH = 3), acetonitrile and methanol with programmed fluorescence detection. As the proposed method has been validated, it was subsequently implemented to evaluate DXR and PDG loaded on novel eco-friendly Casein nano drug delivery system after intravenous injection in healthy rats. A comparative pharmacokinetics' study was carried out in rats for DXR in free form, DXR alone entrapped in the nanomicelle and DXR with PDG entrapped in the nano micelle. After testing the differences in pharmacokinetic parameters of the different formulations using ANOVA, the results showed insignificant differences among the tested parameters. This indicates that the presented nanomicelle delivery system has succeeded to incorporate PDG and DXR in a hydrophilic, safe, and potent formulation. This novel nanomicelle has negligible effect on the distribution and elimination of DXR.

Utilization of Cassava Wastewater for Low-Cost Production of Prodigiosin via Serratia marcescens TNU01 Fermentation and Its Novel Potent α-Glucosidase Inhibitory Effect.

The purpose of this study was to reuse cassava wastewater (CW) for scaled-up production, via the fermentation of prodigiosin (PG), and to conduct an evaluation of its bioactivities. PG was produced at the yield of high 6150 mg/L in a 14 L-bioreactor system, when the designed novel medium (7 L), containing CW and supplemented with 0.25% casein, 0.05% MgSO4, and 0.1% K2HPO4, was fermented with Serratia marcescens TNU01 at 28 °C in 8 h. The PG produced and purified in this study was assayed for some medical effects and showed moderate antioxidant, high anti-NO (anti-nitric oxide), and potential α-glucosidase inhibitory activities. Notably, PG was first reported as a novel effective α-glucosidase inhibitor with a low IC50 value of 0.0183 µg/mL. The commercial anti-diabetic drug acarbose was tested for comparison and had a lesser effect with a high IC50 value of 328.4 µg/mL, respectively. In a docking study, the cation form of PG (cation-PG) was found to bind to the enzyme α-glucosidase by interacting with two prominent amino acids, ASP568 and PHE601, at the binding site on the target enzyme, creating six linkages and showing a better binding energy score (-14.6 kcal/mol) than acarbose (-10.5 kcal/mol). The results of this work suggest that cassava wastewater can serve as a low-cost raw material for the effective production of PG, a potential antidiabetic drug candidate.

Two component system CpxR/A regulates the prodigiosin biosynthesis by negative control in Serratia marcescens FS14.

Prodigiosin is a tripyrrole red secondary metabolite synthesized by many microorganisms, including Serratia marcescens. In this study, we found that the deletion of the gene of sensor kinase CpxA dramatically decreased the prodigiosin production, while the deletion of the gene of the response regulator CpxR or both genes of CpxRA has no effect on prodigiosin production, the kinase function of CpxA is not essential for its regulation on prodigiosin production while the phosphorylation site of CpxR is required. We further demonstrated that the CpxA regulates the prodigiosin biosynthesis at the transcriptional level and the phosphatase activity of CpxA plays vital roles in the regulation of prodigiosin biosynthesis. Finally, we proposed that CpxR/A regulates the prodigiosin biosynthesis by negative control and the phosphorylation level of CpxR may determine the positive or negative control of the genes it regulated.

Prodigiosin of Serratia marcescens ZPG19 Alters the Gut Microbiota Composition of Kunming Mice.

Prodigiosin is a red pigment produced by Serratia marcescens with anticancer, antimalarial, and antibacterial effects. In this study, we extracted and identified a red pigment from a culture of S. marcescens strain ZPG19 and investigated its effect on the growth performance and intestinal microbiota of Kunming mice. High-performance liquid chromatography/mass spectrometry revealed that the pigment had a mass-to-charge ratio (m/z) of 324.2160, and thus it was identified as prodigiosin. To investigate the effect of prodigiosin on the intestinal microbiota, mice (n = 5) were administered 150 µg/kg/d prodigiosin (crude extract, 95% purity) via the drinking water for 18 days. Administration of prodigiosin did not cause toxicity in mice. High-throughput sequencing analysis revealed that prodigiosin altered the cecum microbiota abundance and diversity; the relative abundance of Desulfovibrio significantly decreased, whereas Lactobacillus reuteri significantly increased. This finding indicates that oral administration of prodigiosin has a beneficial effect on the intestinal microbiota of mice. As prodigiosin is non-toxic to mouse internal organs and improves the mouse intestinal microbiota, we suggest that it is a promising candidate drug to treat intestinal inflammation.

Prodigiosin Sensitizes Sensitive and Resistant Urothelial Carcinoma Cells to Cisplatin Treatment.

Cisplatin-based treatment is the standard of care therapy for urothelial carcinomas. However, complex cisplatin resistance mechanisms limit the success of this approach. Both apoptosis and autophagy have been shown to contribute to this resistance. Prodigiosin, a secondary metabolite from various bacteria, exerts different biological activities including the modulation of these two cellular stress response pathways. We analyzed the effect of prodigiosin on protein levels of different autophagy- and apoptosis-related proteins in cisplatin-sensitive and -resistant urothelial carcinoma cells (UCCs). Furthermore, we investigated the effect on cell viability of prodigiosin alone or in combination with cisplatin. We made use of four different pairs of cisplatin-sensitive and -resistant UCCs. We found that prodigiosin blocked autophagy in UCCs and re-sensitized cisplatin-resistant cells to apoptotic cell death. Furthermore, we found that prodigiosin is a potent anticancer agent with nanomolar IC50 values in all tested UCCs. In combination studies, we observed that prodigiosin sensitized both cisplatin-sensitive and -resistant urothelial carcinoma cell lines to cisplatin treatment with synergistic effects in most tested cell lines. These effects of prodigiosin are at least partially mediated by altering lysosomal function, since we detected reduced activities of cathepsin B and L. We propose that prodigiosin is a promising candidate for the therapy of cisplatin-resistant urothelial carcinomas, either as a single agent or in combinatory therapeutic approaches.

Solution Structure and Conformational Dynamics of a Doublet Acyl Carrier Protein from Prodigiosin Biosynthesis.

The acyl carrier protein (ACP) is an indispensable component of both fatty acid and polyketide synthases and is primarily responsible for delivering acyl intermediates to enzymatic partners. At present, increasing numbers of multidomain ACPs have been discovered with roles in molecular recognition of trans-acting enzymatic partners as well as increasing metabolic flux. Further structural information is required to provide insight into their function, yet to date, the only high-resolution structure of this class to be determined is that of the doublet ACP (two continuous ACP domains) from mupirocin synthase. Here we report the solution nuclear magnetic resonance (NMR) structure of the doublet ACP domains from PigH (PigH ACP1-ACP2), which is an enzyme that catalyzes the formation of the bipyrrolic intermediate of prodigiosin, a potent anticancer compound with a variety of biological activities. The PigH ACP1-ACP2 structure shows each ACP domain consists of three conserved helices connected by a linker that is partially restricted by interactions with the ACP1 domain. Analysis of the holo (4'-phosphopantetheine, 4'-PP) form of PigH ACP1-ACP2 by NMR revealed conformational exchange found predominantly in the ACP2 domain reflecting the inherent plasticity of this ACP. Furthermore, ensemble models obtained from SAXS data reveal two distinct conformers, bent and extended, of both apo (unmodified) and holo PigH ACP1-ACP2 mediated by the central linker. The bent conformer appears to be a result of linker-ACP1 interactions detected by NMR and might be important for intradomain communication during the biosynthesis. These results provide new insights into the behavior of the interdomain linker of multiple ACP domains that may modulate protein-protein interactions. This is likely to become an increasingly important consideration for metabolic engineering in prodigiosin and other related biosynthetic pathways.

Utilization of Crab Waste for Cost-Effective Bioproduction of Prodigiosin.

This study aimed to establish the culture process for the cost-effective production of prodigiosin (PG) from demineralized crab shell powder (de-CSP), a fishery processing byproduct created via fermentation. Among the tested PG-producing strains, Serratia marcescens TNU02 was demonstrated to be the most active strain. Various ratios of protein/de-CSP were used as the sources of C/N for PG biosynthesis. The PG yield was significantly enhanced when the casein/de-CSP ratio was controlled in the range of 3/7 to 4/6. TNU02 produced PG with a high yield (5100 mg/L) in a 15 L bioreactor system containing 4.5 L of a newly-designed liquid medium containing 1.6% C/N source (protein/de-CSP ratio of 3/7), 0.02% (NH4)2SO4, 0.1% K2HPO4, and an initial pH of 6.15, at 27 °C for 8 h in dark conditions. The red pigment was purified from the culture broth and then quantified as being PG by specific Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry (MALDI-TOF MS) and UV spectra analysis. The purified PG demonstrated moderate antioxidant and effective inhibition against four cancerous cell lines. Notably, this study was the first to report on using crab wastes for PG bioproduction with high-level productivity (5100 mg/L) in a large scale (4.5 L per pilot) in a short period of fermentation time (8 h). The salt compositions, including (NH4)2SO4 and K2HPO4, were also a novel finding for the enhancement of PG yield by S. marcescens in this report.

The different anion transport capability of prodiginine- and tambjamine-like molecules.

Prodiginines and tambjamines are anion-selective ionophores capable of facilitating the transport of anions across the plasma membrane in mammalian cells. One of the potential applications of these anionophores is the possibility of employing them as a substitutive therapy for pathologies involving anion channels, as in cystic fibrosis. We have studied the interaction of a large anion as gluconate with three prodiginine- and two tambjamine-like compounds. Apparent dissociation constants for the chloride, iodide and gluconate complexes were estimated from iodide influx experiments in mammalian cells exposed to different extracellular anion combinations. Our experiments indicate that gluconate is not transported by the prodiginines, leaving the anionophores free to transport chloride and iodide. Conversely, gluconate would be transported to some extent by the tambjamines, competing with halides for the anionophores, and consequently reducing their flux. This might be related to the different structural features of both families of compounds. These data have important implications for the selection of impermeable anions in the analysis of the anionophore mechanism.

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.

Ion Mobility Mass Spectrometry as an Efficient Tool for Identification of Streptorubin B in Streptomyces coelicolor M145.

Ion mobility spectrometry was utilized to corroborate the identity of streptorubin B (2) as the natural product produced by Streptomyces coelicolor. Natural product 2 was initially assigned as butylcycloheptylprodigiosin (3), and only relatively recently was this assignment clarified. We present additional evidence of this assignment by comparing collisional cross sections (Ω) of synthetic standards of 2, 3, and metacycloprodigiosin (4) to the cyclic prodiginine produced by S. coelicolor. Calculated theoretical Ω values demonstrate that cyclic prodiginines could be identified without standards. This work highlights ion mobility as an efficient tool for the dereplication of natural products.

Purification and Kinetic Characterization of the Essential Condensation Enzymes Involved in Prodiginine and Tambjamine Biosynthesis.

Prodiginines and tambjamines are related families of bioactive alkaloid natural products with pharmaceutical potential. Both compound families result from a convergent biosynthetic pathway ending in the condensation of a conserved bipyrrole core with a variable partner. This reaction is performed by unique condensation enzymes, and has the potential to be manipulated to produce new pyrrolic compounds. We have purified and reconstituted the in vitro activity of the condensation enzymes PigC and TamQ from Pseudoalteromonas sp., which are involved, respectively, in the prodiginine and tambjamine biosynthetic pathways. Kinetic analysis confirmed a Uni Uni Bi Uni ping-pong reaction sequence with competitive and uncompetitive substrate inhibition for PigC and TamQ respectively. The kinetic parameters of each enzyme provide insight into their differing substrate scope, and suggest that TamQ may have evolved a wide substrate tolerance that can be used for the production of novel prodiginines and tambjamines.

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.

Synthetic Anion Transporters as Endoplasmic Reticulum (ER) Stress Inducers.

Cl--ion transporters (2a-2h) were synthesized based on the binding motifs of prodigiosin. Transporter 2e clearly displays Cl--ion transportation activity across both model and live cell membranes. Furthermore, 2e can disrupt Ca2+ homeostasis and increase the intracellular concentration of Ca2+ in the DLD-1 cell. This disruption can lead to Caspase-dependent apoptosis supported by CHOP expression (a marker of ER stress) and the appearance of the cleaved forms of Caspase 3 and PARP.

Broad-spectrum antimicrobial activity of secondary metabolites produced by Serratia marcescens strains.

The genus Serratia is a predominantly unexplored source of antimicrobial secondary metabolites. The aim of the current study was thus to isolate and evaluate the antimicrobial properties of biosurfactants produced by Serratia species. Forty-nine (n = 34 pigmented; n = 15 non-pigmented) biosurfactant producing Serratia strains were isolated from environmental sources and selected isolates (n = 11 pigmented; n = 11 non-pigmented) were identified as Serratia marcescens using molecular typing. The swrW gene (serrawettin W1 synthetase) was detected in all the screened pigmented strains and one non-pigmented strain and primers were designed for the detection of the swrA gene (non-ribosomal serrawettin W2 synthetase), which was detected in nine non-pigmented strains. Crude extracts obtained from S. marcescens P1, NP1 and NP2 were chemically characterised using ultra-performance liquid chromatography coupled to electrospray ionisation mass spectrometry (UPLC-ESI-MS), which revealed that P1 produced serrawettin W1 homologues and prodigiosin, while NP1 produced serrawettin W1 homologues and glucosamine derivative A. In contrast, serrawettin W2 analogues were predominantly identified in the crude extract obtained from S. marcescens NP2. Both P1 and NP1 crude extracts displayed broad-spectrum antimicrobial activity against clinical, food and environmental pathogens, such as multidrug-resistant Pseudomonas aeruginosa, methicillin-resistant Staphylococcus aureus and Cryptococcus neoformans. In contrast, the NP2 crude extract displayed antibacterial activity against a limited range of pathogenic and opportunistic pathogens. The serrawettin W1 homologues, in combination with prodigiosin and glucosamine derivatives, produced by pigmented and non-pigmented S. marcescens strains, could thus potentially be employed as broad-spectrum therapeutic agents against multidrug-resistant bacterial and fungal pathogens.

Voltage-Switchable HCl Transport Enabled by Lipid Headgroup-Transporter Interactions.

Synthetic anion transporters that facilitate transmembrane H+ /Cl- symport (cotransport) have anti-cancer potential due to their ability to neutralize pH gradients and inhibit autophagy in cells. However, compared to the natural product prodigiosin, synthetic anion transporters have low-to-modest H+ /Cl- symport activity and their mechanism of action remains less well understood. We report a chloride-selective tetraurea macrocycle that has a record-high H+ /Cl- symport activity similar to that of prodigiosin and most importantly demonstrates unprecedented voltage-switchable transport properties that are linked to the lack of uniport activity. By studying the anion binding affinity and transport mechanisms of four other anion transporters, we show that the lack of uniport and voltage-dependent H+ /Cl- symport originate from strong binding to phospholipid headgroups that hampers the diffusion of the free transporters through the membrane, leading to an unusual H+ /Cl- symport mechanism that involves only charged species. Our work provides important mechanistic insights into different classes of anion transporters and a new approach to achieve voltage-switchability in artificial membrane transport systems.

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.