Bacterial tyrosinases and their inhibitors.

Bacterial tyrosinase is a copper-containing metalloenzyme with diverse physio-chemical properties, that have been identified in various bacterial strains, including actinobacteria and proteobacteria. Tyrosinases are responsible for the rate-limiting catalytic steps in melanin biosynthesis and enzymatic browning. The physiological role of bacterial tyrosinases in melanin biosynthesis has been harnessed for the production of coloring and dyeing agents. Additionally, bacterial tyrosinases have the capability of cross-linking activity, demonstrated material functionalization applications, and applications in food processing with varying substrate specificities and stability features. These characteristics make bacterial tyrosinases a valuable alternative to well-studied mushroom tyrosinases. The key feature of substrate specificity of bacterial tyrosinase has been exploited to engineer biosensors that have the ability to detect the minimal amount of different phenolic compounds. Today, the world is facing the challenge of multi-drugs resistance in various diseases, especially antibiotic resistance, skin cancer, enzymatic browning of fruits and vegetables, and melanogenesis. To address these challenges, medicinal scientists are developing novel chemotherapeutic agents by inhibiting bacterial tyrosinases. To serve this purpose, heterocyclic compounds are of particular interest due to their vast spectrum of biological activities and their potential as effective tyrosinase inhibitors. In this chapter, a plethora of research explores applications of bacterial tyrosinases in different fields, such as the production of dyes and pigments, catalytic applications in organic synthesis, bioremediation, food and feed applications, biosensors, wool fiber coating and the rationalized synthesis, and structure-activity relationship of bacterial tyrosinase inhibitors.

Linear and Angular Heteroannulated Pyridines Tethered 6-Hydroxy-4,7-Dimethoxybenzofuran: Synthesis and Antimicrobial Activity.

2-Chloropyridine-3-carbonitrile derivative 1 was utilized as a key precursor to build a series of linear and angular annulated pyridines linked to a 6-hydroxy-4,7-dimethoxybenzofuran moiety. Reaction of substrate 1 with various hydrazines afforded pyrazolo[3,4-b]pyridines. Treatment of substrate 1 with 1,3-N,N-binucleophiles including 3-amino-1,2,4-triazole, 5-amino-1H-tetrazole, 3-amino-6-methyl-1,2,4-triazin-5(4H)-one and 2-aminobenzimidazole produced the novel angular pyrido[3,2-e][1,2,4]triazolo[4,3-a]pyrimidine, pyrido[3,2-e][1,2,4]tetrazolo[1,5-a]pyrimidine, pyrido[3',2':5,6] pyrimido[2,1-c][1,2,4]triazine and benzo[4,5]imidazo[1,2-a]pyrido[3,2-e]pyrimidine, respectively. Reaction of substrate 1 with 1,3-C,N-binucleophiles including cyanoacetamides and 1H-benzimidazol-2-ylacetonitrile furnished 1,8-naphthyridines and benzoimidazonaphthyridine. Moreover, reacting substrate 1 with 5-aminopyrazoles gave pyrazolo[3,4-b][1,8]naphthyridines. Finally, reaction of compound 1 with 6-aminouracils as cyclic enamines yielded pyrimido[4,5-b][1,8]naphthyridines. Some of the synthesized products showed noteworthy antimicrobial efficiency against all types of microbial strains. Structures of the produced compounds were established using analytical and spectroscopic tools.

Radiolabeled Probes from Derivatives of Natural Compounds Used in Nuclear Medicine.

Natural compounds are important precursors for the synthesis of new drugs. The development of novel molecules that are useful for various diseases is the main goal of researchers, especially for the diagnosis and treatment of many diseases. Some pathologies need to be treated with radiopharmaceuticals, and, for this reason, radiopharmaceuticals that use the radiolabeling of natural derivates molecules are arousing more and more interest. Radiopharmaceuticals can be used for both diagnostic and therapeutic purposes depending on the radionuclide. ß+- and gamma-emitting radionuclides are used for diagnostic use for PET or SPECT imaging techniques, while α- and ß--emitting radionuclides are used for in metabolic radiotherapy. Based on these assumptions, the purpose of this review is to highlight the studies carried out in the last ten years, to search for potentially useful radiopharmaceuticals for nuclear medicine that use molecules of natural origin as lead structures. In this context, the main radiolabeled compounds containing natural products as scaffolds are analyzed, in particular curcumin, stilbene, chalcone, and benzofuran. Studies on structural and chemical modifications are emphasized in order to obtain a collection of potential radiopharmaceuticals that exploit the biological properties of molecules of natural origin. The radionuclides used to label these compounds are 68Ga, 44Sc, 18F, 64Cu, 99mTc, and 125I for diagnostic imaging.

Distinct Characteristic Binding Modes of Benzofuran Core Inhibitors to Diverse Genotypes of Hepatitis C Virus NS5B Polymerase: A Molecular Simulation Study.

The benzofuran core inhibitors HCV-796, BMS-929075, MK-8876, compound 2, and compound 9B exhibit good pan-genotypic activity against various genotypes of NS5B polymerase. To elucidate their mechanism of action, multiple molecular simulation methods were used to investigate the complex systems of these inhibitors binding to GT1a, 1b, 2a, and 2b NS5B polymerases. The calculation results indicated that these five inhibitors can not only interact with the residues in the palm II subdomain of NS5B polymerase, but also with the residues in the palm I subdomain or the palm I/III overlap region. Interestingly, the binding of inhibitors with longer substituents at the C5 position (BMS-929075, MK-8876, compound 2, and compound 9B) to the GT1a and 2b NS5B polymerases exhibits different binding patterns compared to the binding to the GT1b and 2a NS5B polymerases. The interactions between the para-fluorophenyl groups at the C2 positions of the inhibitors and the residues at the binding pockets, together with the interactions between the substituents at the C5 positions and the residues at the reverse ß-fold (residues 441-456), play a key role in recognition and the induction of the binding. The relevant studies could provide valuable information for further research and development of novel anti-HCV benzofuran core pan-genotypic inhibitors.

Cytotoxicity of Benzofuran-Containing Simplified Viniferin Analogues.

Within the huge class of plant secondary metabolites, resveratrol-derived stilbenoids show wide structural diversity and mediate a great number of biological responses relevant for human health, including cancer prevention and cytotoxicity. Resveratrol is known to modulate several pathways directly linked to cancer progression, as well as its analogue pterostilbene, characterized by an increased metabolic stability and significant pharmacological activities. To study the potential anticancer activity of other stilbenoids, a home-made collection of resveratrol dimers and simplified analogues was tested on melanoma A375, non-small cell lung cancer H460 and PC3 prostate cancer cell lines. The structural determinants responsible for the antiproliferative activity have been highlighted. Moreover, to investigate the DNA damage ability of the selected molecules, the expression of the γ-H2AX after compound exposure was evaluated.

Synthesis of Benzofuran Derivatives via a DMAP-Mediated Tandem Cyclization Reaction Involving ortho-Hydroxy α-Aminosulfones.

An efficient cascade cyclization strategy was developed to synthesize aminobenzofuran spiroindanone and spirobarbituric acid derivatives utilizing 2-bromo-1,3-indandione, 5-bromo-1,3-dimethylbarbituric acid, and ortho-hydroxy α-aminosulfones as substrates. Under the optimized reaction conditions, the corresponding products were obtained with high efficiency, exceeding 95% and 85% yields for the respective derivatives. This protocol demonstrates exceptional substrate versatility and robust scalability up to the Gram scale, establishing a stable platform for the synthesis of 3-aminobenzofuran derivative. The successful synthesis paves the way for further biological evaluations with potential implications in scientific research.

Developing a fluorescent probe containing benzofuranone moiety for imaging sulphite in living hypoxia pulmonary cells.

In this work, a benzofuranone-derived fluorescent probe BFSF was developed for imaging the sulphite level in living hypoxia pulmonary cells. Under the excitation of 510 nm, BFSF showed a strong fluorescence response at 570 nm when reacted with sulphite. In the solution system, the constructed hypercapnia and serious hypercapnia conditions did not affect the fluorescence response. In comparison with the recently reported probes, BFSF suggested the advantages including rapid response, steady signal reporting, high specificity and low cytotoxicity upon living lung cells. Under a normal incubation atmosphere, BFSF realized the imaging of both exogenous and endogenous sulphite in living pulmonary cells. In particular, BFSF achieved imaging the decrease of the sulphite level under severe hypoxia as well as the recovery of the sulphite level with urgent oxygen supplement. With the imaging capability for the sulphite level in living pulmonary cells under hypoxia conditions, BFSF together with the information herein was meaningful for investigating the anaesthesia-related biological indexes.

Determination of bactericidal activity against 3HC-2-Tre-labelled Mycobacterium abscessus (Mycobacteroides abscessus) by automated fluorescence microscopy.

The minimum bactericidal concentration (MBC) of antibiotics is an important parameter for the potency of a drug in eradicating a bacterium as well as an important measure of the potential of a drug candidate in research and development. We have established a fluorescence-based microscopy method for the determination of MBCs against the non-tuberculous mycobacterium Mycobacterium abscessus (Mycobacteroides abscessus) to simplify and accelerate the performance of MBC determination compared to counting colony forming units on agar. Bacteria are labelled with the trehalose-coupled dye 3HC-2-Tre and analysed in a 96-well plate. The results of the new method are consistent with MBC determination by plating on agar. The method was used to evaluate the bactericidality of the antibiotics rifabutin, moxifloxacin, amikacin, clarithromycin and bedaquiline. Bactericidal effects against M. abscessus were observed, which are consistent with literature data.

Development of a 213Bi-Labeled Pyridyl Benzofuran for Targeted α-Therapy of Amyloid-ß Aggregates.

Alzheimer disease is a neurodegenerative disorder with limited treatment options. It is characterized by the presence of several biomarkers, including amyloid-ß aggregates, which lead to oxidative stress and neuronal decay. Targeted α-therapy (TAT) has been shown to be efficacious against metastatic cancer. TAT takes advantage of tumor-localized α-particle emission to break disease-associated covalent bonds while minimizing radiation dose to healthy tissues due to the short, micrometer-level, distances traveled. We hypothesized that TAT could be used to break covalent bonds within amyloid-ß aggregates and facilitate natural plaque clearance mechanisms. Methods: We synthesized a 213Bi-chelate-linked benzofuran pyridyl derivative (BiBPy) and generated [213Bi]BiBPy, with a specific activity of 120.6 GBq/µg, dissociation constant of 11 ± 1.5 nM, and logP of 0.14 ± 0.03. Results: As the first step toward the validation of [213Bi]BiBPy as a TAT agent for the reduction of Alzheimer disease-associated amyloid-ß, we showed that brain homogenates from APP/PS1 double-transgenic male mice (6-9 mo old) incubated with [213Bi]BiBPy exhibited a marked reduction in amyloid-ß plaque concentration as measured using both enzyme-linked immunosorbent and Western blotting assays, with a half-maximal effective concentration of 3.72 kBq/pg. Conclusion: This [213Bi]BiBPy-concentration-dependent activity shows that TAT can reduce amyloid plaque concentration in vitro and supports the development of targeting systems for in vivo validations.

Synthesis of Cytotoxic Benzofurans and Ethers Derivatives of Paeonol.

Paeonol is a broadly studied natural product due to its many biological activities. Using a methodology previously employed by our research group, 11 derivatives of paeonol were synthesized (seven of them are unpublished compounds), including four ethers and seven benzofurans. Additionally, we determined the crystal structure of one of these ether derivatives (1a) and of five benzofuran derivatives (2a, 2b, 2c, 2f and 2g) by single crystal X-Ray diffraction. To continue studying the cytotoxicity of this natural product and its derivatives, all compounds were tested against two cancer cell lines, HCT116 and MCF-7. Compounds 2b, 2e, and 2g were considered active against the colorectal adenocarcinoma cells HCT116 (Growth inhibition > 60%). Compound 2e showed an IC50 of 0.2 µM and was selected for further analysis, results reinforce its anticancer potential.

Acute 2-phenyl-3-(phenylselanyl)benzofuran treatment reverses the neurobehavioral alterations induced by sleep deprivation in mice.

Sleep is a fundamental state for maintaining the organism homeostasis. Disruptions in sleep patterns predispose to the appearance of memory impairments and mental disorders, including depression. Recent pre-clinical studies have highlighted the antidepressant-like properties of the synthetic compound 2-phenyl-3-(phenylselanyl)benzofuran (SeBZF1). To further investigate the neuromodulatory effects of SeBZF1, this study aimed to assess its therapeutic efficacy in ameliorating neurobehavioral impairments induced by sleep deprivation (SD) in mice. For this purpose, a method known as multiple platforms over water was used to induce rapid eye movement (REM) SD. Two hours after acute SD (24 h), male Swiss mice received a single treatment of SeBZF1 (5 mg/kg, intragastric route) or fluoxetine (a positive control, 20 mg/kg, intraperitoneal route). Subsequently, behavioral tests were conducted to assess spontaneous motor function (open-field test), depressive-like behavior (tail suspension test), and memory deficits (Y-maze test). Brain structures were utilized to evaluate oxidative stress markers, monoamine oxidase (MAO) and acetylcholinesterase (AChE) activities. Our findings revealed that SD animals displayed depressive-like behavior and memory impairments, which were reverted by SeBZF1 and fluoxetine treatments. SeBZF1 also reverted the increase in lipoperoxidation levels and glutathione peroxidase activity in the pre-frontal cortex in mice exposed to SD. Besides, the increase in hippocampal AChE activity induced by SD was overturned by SeBZF1. Lastly, cortical MAO-B activity was reestablished by SeBZF1 in mice that underwent SD. Based on the main findings of this study, it can be inferred that the compound SeBZF1 reverses the neurobehavioral alterations induced by sleep deprivation in male Swiss mice.

Benzofuran-2-Carboxamide Derivatives as Immunomodulatory Agents Blocking the CCL20-Induced Chemotaxis and Colon Cancer Growth.

The correlation between the CCL20/CCR6 axis and autoimmune and non-autoimmune disorders is widely recognized. Inhibition of the CCL20-dependent cell migration represents therefore a promising approach for the treatment of many diseases, such as inflammatory bowel diseases and colorectal cancer. We report herein our efforts to explore the biologically relevant chemical space around the benzofuran scaffold of MR120, a modulator of the CCL20/CCR6 axis previously discovered by our group. A functional screening allowed us to identify C4 and C5-substituted derivatives as the most effective inhibitors of the CCL20-induced chemotaxis of human peripheral blood mononuclear cells (PBMC). Moreover, selected compounds (16 e and 24 b) also proved to potently inhibit the growth of different colon cancer cell lines, with cytotoxic/cytostatic and antiproliferative activity.

Antitumor aspochalasin and antiviral benzofuran derivatives from a marine-derived fungus Aspergillus sp. SCSIO41032.

Chemical investigation of the EtOAc extract of a deep-sea derived fungus Aspergillus sp. SCSIO41032 resulted in the isolation of ten known compounds, including eight aspochalasins. Their structures were elucidated by using extensive NMR spectroscopic, mass spectrometric and single crystal X-ray diffraction analysis. The detailed crystallographic data for structures 1, 2, and 4, along with the relative configurations of aspochalasin E (3) determined by its acetonide derivative were reported for the first time. The results of antitumor and antiviral activities showed that 3 displayed moderate antitumor activities against 22Rv1, PC-3, A549, and HCT-15 cell lines with IC50 values ranged from 5.9 ± 0.8 to 19.0 ± 7.7 µM, and 9 exhibited moderate antiviral activities against HSV-1/2 with EC50 values of 9.5 ± 0.5 and 5.4 ± 0.6 µM, respectively. Plate clone formation assays results indicated that 3 inhibited the 22Rv1, PC-3 cells growth in a dose-dependent manner.

Iron-Catalyzed C-H Alkylation/Ring Opening with Vinylbenzofurans Enabled by Triazoles.

We report an unprecedented iron-catalyzed C-H annulation using readily available 2-vinylbenzofurans as the reaction pattern. The redox-neutral strategy, based on cheap, non-toxic, and earth-abundant iron catalysts, exploits triazole assistance to promote a cascade C-H alkylation, benzofuran ring-opening and insertion into a Fe-N bond, to form highly functionalized isoquinolones. Detailed mechanistic studies supported by DFT calculations fully disclosed the manifold of the iron catalysis.

Undescribed Cyclohexene and Benzofuran Alkenyl Derivatives from Choerospondias axillaris, a Potential Hypoglycemic Fruit.

The fruit of Choerospondias axillaris (Anacardiaceae), known as south wild jujube in China, has been consumed widely in several regions of the world to produce fruit pastille and leathers, juice, jam, and candy. A comprehensive chemical study on the fresh fruits led to the isolation and identification of 18 compounds, including 7 new (1-7) and 11 known (8-18) comprised of 5 alkenyl (cyclohexenols and cyclohexenones) derivatives (1-5), 3 benzofuran derivatives (6-8), 6 flavonoids (9-14) and 4 lignans (15-18). Their structures were elucidated by extensive spectroscopic analysis. The known lignans 15-18 were isolated from the genus Choerospondias for the first time. Most of the isolates exhibited significant inhibitory activity on α-glucosidase with IC50 values from 2.26 ± 0.06 to 43.9 ± 0.96 µM. Molecular docking experiments strongly supported the potent α-glucosidase inhibitory activity. The results indicated that C. axillaris fruits could be an excellent source of functional foods that acquire potential hypoglycemic bioactive components.

A triphenylamine-benzofuran-derived fluorescent probe for monitoring sulfite in Chinese medicinal materials and bioimaging.

In this work, a triphenylamine-benzofuran-derived fluorescent probe TBSF was developed for monitoring the sulfite level in Chinese medicinal materials and imaging in living cells. In the testing system, under 445 nm excitation, TBSF responded to sulfite steadily with a 540 nm fluorescence reporting signal. The testing system showed advantages including high sensitivity, rapid response, and high selectivity. In particular, TBSF achieved the sulfite detection in the water decoction of Chinese medicinal materials from both addition and excessive fumigation. It also realized the intracellular imaging of both exogenous and endogenous sulfite in living HepG2 cells. The imaging in water decoction-treated cells inferred the potential for the interdisciplinary detection.

In Vitro Evaluation of the Antioxidant Capacity of 3,3-Disubstituted-3H-benzofuran-2-one Derivatives in a Cellular Model of Neurodegeneration.

Oxidative stress represents a hallmark for many degenerative pathologies of the Central Nervous System. Throughout life, the constant pressure of noxious stimuli and/or episodes of traumatic events may expose the brain to a microenvironment where the non-balanced reactive oxygen species inevitably lead to neuronal loss and cognitive decline. HO-1, a 32 kDa heat-shock protein catalyzing the degradation of heme into carbon monoxide (CO), iron and biliverdin/bilirubin is considered one of the main antioxidant defense mechanisms playing pivotal roles in neuroprotection. Restoring the redox homeostasis is the goal of many natural or synthetic antioxidant molecules pursuing beneficial effects on brain functions. Here, we investigated the antioxidant capacity of four selected benzofuran-2-one derivatives in a cellular model of neurodegeneration represented by differentiated SH-SY5Y cells exposed to catechol-induced oxidative stress. Our main results highlight how all the molecules have antioxidant properties, especially compound 9, showing great abilities in reducing intracellular ROS levels and protecting differentiated SH-SY5Y cells from catechol-induced death. This compound above all seems to boost HO-1 mRNA and perinuclear HO-1 protein isoform expression when cells are exposed to the oxidative insult. Our findings open the way to consider benzofuran-2-ones as a novel and promising adjuvant antioxidant strategy for many neurodegenerative disorders.

Iodine-Catalyzed Cascade Annulation of 4-Hydroxycoumarins with Aurones: Access to Spirocyclic Benzofuran-Furocoumarins.

An attractive approach for the preparation of spirocyclic benzofuran-furocoumarins has been developed through iodine-catalyzed cascade annulation of 4-hydroxycoumarins with aurones. The reaction involves Michael addition, iodination, and intramolecular nucleophilic substitution in a one-step process, and offers an efficient method for easy access to a series of valuable spirocyclic benzofuran-furocoumarins in good yields (up to 99%) with excellent stereoselectivity. Moreover, this unprecedented protocol provides several advantages, including readily available materials, an environmentally benign catalyst, a broad substrate scope, and a simple procedure.

The mechanism of anthracene degradation by tryptophan -2,3-dioxygenase (T23D) in Comamonas testosteroni.

It is well known that anthracene is a persistent organic pollutant. Among the four natural polycyclic aromatic hydrocarbons (PAHs) degrading strains, Comamonas testosterone (CT1) was selected as the strain with the highest degradation efficiency. In the present study, prokaryotic transcriptome analysis of CT1 revealed an increase in a gene that encodes tryptophane-2,3-dioxygenase (T23D) in the anthracene and erythromycin groups compared to CK. Compared to the wild-type CT1 strain, anthracene degradation by the CtT23D knockout mutant (CT-M1) was significantly reduced. Compared to Escherichia coli (DH5α), CtT23D transformed DH5α (EC-M1) had a higher degradation efficiency for anthracene. The recombinant protein rT23D oxidized tryptophan at pH 7.0 and 37 °C with an enzyme activity of 2.42 ± 0.06 µmol min-1·mg-1 protein. In addition, gas chromatography-mass (GC-MS) analysis of anthracene degradation by EC-M1 and the purified rT23D revealed that 2-methyl-1-benzofuran-3-carbaldehyde is an anthracene metabolite, suggesting that it is a new pathway.

Targeted isolation, identification, and antioxidant evaluation of aromatic polyketides from a plant-derived fungus Ophiobolus cirsii LZU-1509.

There are >350 species of the Ophiobolus genus, which is not yet very well-known and lacks research reports on secondary metabolites. Three new 3,4-benzofuran polyketides 1-3, a new 3,4-benzofuran polyketide racemate 4, two new pairs of polyketide enantiomers (±)-5 and (±)-7, two new acetophenone derivatives 6 and 8, and three novel 1,4-dioxane aromatic polyketides 9-11, were isolated from a fungus Ophiobolus cirsii LZU-1509 derived from an important medicinal and economic crop Anaphalis lactea. The isolation was guided by LC-MS/MS-based GNPS molecular networking analysis. The planar structures and relative configurations were mainly elucidated by NMR and HR-ESI-MS data. Their absolute configurations were determined by using X-ray diffraction analysis and via comparing computational and experimental ECD, NMR, and specific optical rotation data. 9 possesses an unreported 5/6/6/6/5 five-ring framework with a 1,4-dioxane, and 10 and 11 feature unprecedented 6/6/6/5 and 6/6/5/6 four-ring frames containing a 1,4-dioxane. The biosynthetic pathways of 9-11 were proposed. 1-11 were nontoxic in HT-1080 and HepG2 tumor cells at a concentration of 20 µM, whereas 3 and 5 exerted higher antioxidant properties in the hydrogen peroxide-stimulated model in the neuron-like PC12 cells. They could be potential antioxidant agents for neuroprotection.