Cocrystallization improves the tabletability of ligustrazine despite a reduction in plasticity

Cocrystallization is an effective method for altering the tableting performance of crystals by modifying their mechanical properties. In this study, cocrystals of ligustrazine (LIG) with malonic acid (MA) and salicylic acid (SA) were investigated to better understand how modifying crystal structure can affect tableting properties. LIG suffered from overcompression at high pressures despite its high plasticity. Both LIG-MA and LIG-SA displayed lower plasticity than LIG, which was confirmed by both an in-die Heckel and energy framework analyses. The LIG-MA cocrystal displayed slightly worse tabletability than LIG, as expected from its lower plasticity. However, LIG-SA surprisingly showed improved tabletability despite its lower plasticity. This was explained by the higher bonding strength of LIG-SA compared with LIG. This work not only provided new examples of tabletability modulation through crystal engineering but also highlighted the risk of failed tabletability predictions based on plasticity alone. Instead, more reliable tabletability predictions of different crystal forms must consider the bonding area - bonding strength interplay.

Comparative investigation into the anticancer activity of analogs of marine coelenterazine and coelenteramine

Cancer is still one of the most challenging diseases to treat, making the pursuit for novel molecules with potential anticancer activity an important research topic. Herein, we have performed a comparative investigation into the anticancer activity of analogs of marine coelenterazine and coelenteramine. The former is a well-known bioluminescent substrate, while the latter is a metabolic product of the resulting bioluminescent reaction. While both types of analogs showed anticancer activity toward lung and gastric cancer cell lines, we have obtained data that highlight relevant differences between the activity of these two types of compounds. More specifically, we observed relevant differences in structure-activity relationships between these types of compounds. Also, coelenteramine analogs showed time-dependent activity, while coelenterazine-based compounds usually present time-independent activity. Coelenterazine analogs also appear to be relatively safer toward noncancer cells than coelenteramine analogs. There was also seen a correlation between the activity of the coelenterazine-based compounds and their light-emission properties. Thus, these results further indicate the potential of the marine coelenterazine chemi-/bioluminescent system as a source of new molecules with anticancer activity, while providing more insight into their modes of action.

Discovery of 3-oxo-1,2,3,4-tetrahydropyrido[1,2-a]pyrazin derivatives as SARS-CoV-2 main protease inhibitors through virtual screening and biological evaluation

The COVID-19 caused by SARS-CoV-2 has led to a global pandemic that continues to impact societies and economies worldwide. The main protease (Mpro) plays a crucial role in SARS-CoV-2 replication and is an attractive target for anti-SARS-CoV-2 drug discovery. Herein, we report a series of 3-oxo-1,2,3,4-tetrahydropyrido[1,2-a]pyrazin derivatives as non-peptidomimetic inhibitors targeting SARS-CoV-2 Mpro through structure-based virtual screening and biological evaluation. Further similarity search and structure-activity relationship study led to the identification of compound M56-S2 with the enzymatic IC50 value of 4.0 μM. Moreover, the molecular simulation and predicted ADMET properties, indicated that non-peptidomimetic inhibitor M56-S2 might serve as a useful starting point for the further discovery of highly potent inhibitors targeting SARS-CoV-2 Mpro.

Pyrazines in food samples: Recent update on occurrence, formation, sampling, pretreatment and analysis methods

Pyrazines are a class of active aromatic substances existing in various foods. The accumulation of pyrazines has an impact on flavor and quality of food products. This review encompasses the formation mechanisms and control strategies of pyrazines via Maillard reaction (MR), including the new reactants and emerging techniques. Pyrazines characteristics are better understood through the developed sample pretreatments and detection methods. Herein, an in-depth review of pretreatments and analysis methods since 2010 is presented to explore the simple, fast, green, and effective strategies. Sample preparation methods include liquid phase extraction, solid phase extraction, supercritical fluid extraction, and microextraction methods such as liquid phase microextraction, and solid phase microextraction, etc. Detections are made by chromatographic methods, and sensors, etc. Advantages and limitations are discussed and compared for providing insights to further studies.

Exploring the interaction between myofibrillar proteins and pyrazine compounds: Based on molecular docking, molecular dynamics simulation, and multi-spectroscopy techniques

Flavor is one of the most important factors that affect consumers' preference for processed meat products. This study aimed to investigate effects of heating on interaction between myofibrillar proteins (MPs) and pyrazine compounds and understand the underlying mechanisms. A combination of multispectral, molecular docking, and molecular dynamics technologies was used to achieve study's aim. Results demonstrated that MPs underwent structural reconstruction and expansion during heating, which significantly altered surface hydrophobicity and SH content. MPs' zeta potential reduced from -7.29 to -10.47 when a short heating time. Additionally, a positive correlation was found between β-sheet content and ability of MPs to adsorb pyrazine compounds. Molecular docking analysis revealed 13 binding sites for pyrazines and MPs. Furthermore, amino acid residues and pyrazine compounds were found to interact by four different forms of forces, primarily van der Waals forces, carbon‑hydrogen bonds, alkyl groups, and π-alkyl groups. Obtained results demonstrated that adequate or optimized heat treatment could expose more binding sites, hence enhancing the binding of MPs to pyrazine compounds. This study may be used to better understand how structural changes in MPs during processing affect MPs' capacity to bind flavor substances, which can help improve flavor of processed meats to encourage their consumption.

Natural Products-Pyrazine Hybrids: A Review of Developments in Medicinal Chemistry

Pyrazine is a six-membered heterocyclic ring containing nitrogen, and many of its derivatives are biologically active compounds. References have been downloaded through Web of Science, PubMed, Science Direct, and SciFinder Scholar. The structure, biological activity, and mechanism of natural product derivatives containing pyrazine fragments reported from 2000 to September 2023 were reviewed. Publications reporting only the chemistry of pyrazine derivatives are beyond the scope of this review and have not been included. The results of research work show that pyrazine-modified natural product derivatives have a wide range of biological activities, including anti-inflammatory, anticancer, antibacterial, antiparasitic, and antioxidant activities. Many of these derivatives exhibit stronger pharmacodynamic activity and less toxicity than their parent compounds. This review has a certain reference value for the development of heterocyclic compounds, especially pyrazine natural product derivatives.

Discovery and characterization of a novel cGAS covalent inhibitor for the treatment of inflammatory bowel disease

Cyclic GMP-AMP synthase (cGAS), a cytosolic DNA sensor, acts as a nucleotidyl transferase that catalyzes ATP and GTP to form cyclic GMP-AMP (cGAMP) and plays a critical role in innate immunity. Hyperactivation of cGAS-STING signaling contributes to hyperinflammatory responses. Therefore, cGAS is considered a promising target for the treatment of inflammatory diseases. Herein, we report the discovery and identification of several novel types of cGAS inhibitors by pyrophosphatase (PPiase)-coupled activity assays. Among these inhibitors, 1-(1-phenyl-3,4-dihydro-1H-pyrrolo[1,2-a]pyrazin-2-yl)prop-2-yn-1-one (compound 3) displayed the highest potency and selectivity at the cellular level. Compound 3 exhibited better inhibitory activity and pathway selectivity than RU.521, which is a selective cGAS inhibitor with anti-inflammatory effects in vitro and in vivo. Thermostability analysis, nuclear magnetic resonance and isothermal titration calorimetry assays confirmed that compound 3 directly binds to the cGAS protein. Mass spectrometry and mutation analysis revealed that compound 3 covalently binds to Cys419 of cGAS. Notably, compound 3 demonstrated promising therapeutic efficacy in a dextran sulfate sodium (DSS)-induced mouse colitis model. These results collectively suggest that compound 3 will be useful for understanding the biological function of cGAS and has the potential to be further developed for inflammatory disease therapies.

Electrochemical reactor dictates site selectivity in N-heteroarene carboxylations

Pyridines and related N-heteroarenes are commonly found in pharmaceuticals, agrochemicals and other biologically active compounds1,2. Site-selective C-H functionalization would provide a direct way of making these medicinally active products3-5. For example, nicotinic acid derivatives could be made by C-H carboxylation, but this remains an elusive transformation6-8. Here we describe the development of an electrochemical strategy for the direct carboxylation of pyridines using CO2. The choice of the electrolysis setup gives rise to divergent site selectivity: a divided electrochemical cell leads to C5 carboxylation, whereas an undivided cell promotes C4 carboxylation. The undivided-cell reaction is proposed to operate through a paired-electrolysis mechanism9,10, in which both cathodic and anodic events play critical roles in altering the site selectivity. Specifically, anodically generated iodine preferentially reacts with a key radical anion intermediate in the C4-carboxylation pathway through hydrogen-atom transfer, thus diverting the reaction selectivity by means of the Curtin-Hammett principle11. The scope of the transformation was expanded to a wide range of N-heteroarenes, including bipyridines and terpyridines, pyrimidines, pyrazines and quinolines.

Design of Novel Imidazopyrazine Derivative against Breast Cancer via Targeted NPY1R Antagonist

INTRODUCTION

Breast cancer is the most frequent malignancy in women with more than one in ten new cancer diagnoses each year. Synthetic products are a key source for the identification of new anticancer medicines and drug leads.

OBJECTIVES

Imidazopyrazine is a highly favored skeleton for the design of new anticancer drugs. In silico designed derivatives were screened using computer aided drug design techniques and validated using MTT assay.

METHODS

A template-based methodology was used in the current work to create novel Imidazopyrazine derivatives, targeting the NPY1R protein. Molecular docking, Diffusion docking, MD simulation, MM-GBSA and meta-dynamics techniques were followed. MTT assay was performed to validate the activity of principal compound.

RESULTS

A docking score of -6.660 and MMGBSA value of -108.008 (+/-) 9.14 kcal/mol was obtained from the investigations conducted. In addition, molecular dynamics simulation was carried out for 500 ns, yielding a stable RMSD and value of 5.6 Å, thus providing insights on the stability of the protein conformation on interaction with the principal compound. Furthermore, the in vivo validation studies conducted via MTT assay showed an IC50 value of 73.45 (+/-) 0.45 μg /mL.

CONCLUSION

The research has produced encouraging findings and can be applied as a model for precise enumerations in the future. It also encourages the study of novel synthetic compounds with potential anti-cancer properties.

Folium Ginkgo extract and tetramethylpyrazine sodium chloride injection (Xingxiong injection) protects against focal cerebral ischaemia/reperfusion injury via activating the Akt/Nrf2 pathway and inhibiting NLRP3 inflammasome activation

CONTEXT

Folium Ginkgo extract and tetramethylpyrazine sodium chloride injection (Xingxiong injection) is a compound preparation commonly used for treating cerebral ischaemia/reperfusion injury in ischaemic stroke in China. However, its potential mechanisms on ischaemic stroke remain unknown.

OBJECTIVE

This study explores the potential mechanisms of Xingxiong injection in vivo or in vitro.

MATERIALS AND METHODS

Sprague-Dawley (SD) rats were randomly assigned to five groups: the sham (normal saline), the model (normal saline) and the Xingxiong injection groups (12.5, 25 or 50 mL/kg). The rats were subjected to 2 h of middle cerebral artery occlusion (MCAO) followed by reperfusion for 14 d. Xingxiong injection was administered via intraperitoneal (i.p.) injection immediately after ischaemia induction for 14 d. Afterwards, rats were sacrificed at 14 d induced by administration of Xingxiong injection.

RESULTS

Xingxiong injection significantly reduces infarct volume (23%) and neurological deficit scores (93%) compared with the MCAO/R group. Additionally, Xingxiong injection inhibits the loss in mitochondrial membrane potential (43%) and reduces caspase-3 level (44%), decreases NOX (41%), protein carbonyl (29%), 4-HNE (40%) and 8-OhdG (41%) levels, inhibits the expression of inflammatory factors, such as TNF-α (26%), IL-1β (34%), IL-6 (39%), MCP-1 (36%), CD11a (41%) and ICAM-1 (43%). Moreover, Xingxiong injection can increase p-Akt/Akt (35%) and Nrf2 (47%) protein expression and inhibit NLRP3 (42%) protein expression.

CONCLUSIONS

Xingxiong injection prevents cerebral ischaemia/reperfusion injury via activating the Akt/Nrf2 pathway and inhibiting NLRP3 inflammasome. These findings provide experimental evidence for clinical use of drugs in the treatment of ischaemic stroke.

Construction of 5-(Alkylamino)-6-aryl/alkylpyrazine-2,3-dicarbonitriles via the One-Pot Reaction of Alkyl Isocyanides with Aryl/Alkyl Carbonyl Chlorides and Diaminomaleonitrile: Fluorescence and Antimicrobial Activity Evaluation

5-(Alkylamino)-6-aryl/alkylpyrazine-2,3-dicarbonitriles were successfully synthesized in good to moderate yields by reacting alkyl isocyanides with aryl/alkyl carbonyl chlorides, followed by the addition of diaminomaleonitrile. The synthesized pyrazines were fully characterized in this investigation, and X-ray crystal structure analysis was performed on some derivatives. The antibacterial and antifungal activities of the newly synthesized pyrazine-2,3-dicarbonitriles were assessed in addition to their UV and fluorescence results. All the compounds showed similar UV-Vis spectral features with absorption peaks (λ_max) around 267, 303, and 373 nm.

Comparative Investigation of the Chemiluminescent Properties of a Dibrominated Coelenterazine Analog

Chemi- and bioluminescence are remarkable light-emitting phenomena, in which thermal energy is converted into excitation energy due to a (bio)chemical reaction. Among a wide variety of chemi-/bioluminescent systems, one of the most well-known and studied systems is that of marine imidazopyrazinones, such as Coelenterazine and Cypridina luciferin. Due to the increasing usefulness of their chemi-/bioluminescent reactions in terms of imaging and sensing applications, among others, significant effort has been made over the years by researchers to develop new derivatives with enhanced properties. Herein, we report the synthesis and chemiluminescent characterization of a novel dibrominated Coelenterazine analog. This novel compound consistently showed superior luminescence, in terms of total light output and emission lifetime, to natural imidazopyrazinones and commercially available analogs in aprotic media, while being capable of yellow light emission. Finally, this new compound showed enhanced chemiluminescence in an aqueous solution when triggered by superoxide anion, showing potential to be used as a basis for optimized probes for reactive oxygen species. In conclusion, bromination of the imidazopyrazinone scaffold appears to be a suitable strategy for obtaining Coelenterazines with enhanced properties.

Low-Molecular Pyrazine-Based DNA Binders: Physicochemical and Antimicrobial Properties

Pyrazine and its derivatives are a large group of compounds that exhibit broad biological activity, the changes of which can be easily detected by a substituent effect or a change in the functional group. The present studies combined theoretical research with the density functional theory (DFT) approach (B3LYP/6-311+G**) and experimental (potentiometric and spectrophotometric) analysis for a thorough understanding of the structure of chlorohydrazinopyrazine, its physicochemical and cytotoxic properties, and the site and nature of interaction with DNA. The obtained results indicated that 2-chloro-3-hydrazinopyrazine (2Cl3HP) displayed the highest affinity to DNA. Cytotoxicity studies revealed that the compound did not exhibit toxicity toward human dermal keratinocytes, which supported the potential application of 2Cl3HP in clinical use. The study also attempted to establish the possible equilibria occurring in the aqueous solution and, using both theoretical and experimental methods, clearly showed the hydrophilic nature of the compound. The experimental and theoretical results of the study confirmed the quality of the compound, as well as the appropriateness of the selected set of methods for similar research.

Docking, Binding Free Energy Calculations and In Vitro Characterization of Pyrazine Linked 2-Aminobenzamides as Novel Class I Histone Deacetylase (HDAC) Inhibitors

Class I histone deacetylases, HDAC1, HDAC2, and HDAC3, represent potential targets for cancer treatment. However, the development of isoform-selective drugs for these enzymes remains challenging due to their high sequence and structural similarity. In the current study, we applied a computational approach to predict the selectivity profile of developed inhibitors. Molecular docking followed by MD simulation and calculation of binding free energy was performed for a dataset of 2-aminobenzamides comprising 30 previously developed inhibitors. For each HDAC isoform, a significant correlation was found between the binding free energy values and in vitro inhibitory activities. The predictive accuracy and reliability of the best preforming models were assessed on an external test set of newly designed and synthesized inhibitors. The developed binding free-energy models are cost-effective methods and help to reduce the time required to prioritize compounds for further studies.

Ab Initio Insight into the Interaction of Metal-Decorated Fluorinated Carbon Fullerenes with Anti-COVID Drugs

We theoretically investigated the adsorption of two common anti-COVID drugs, favipiravir and chloroquine, on fluorinated C₆₀ fullerene, decorated with metal ions Cr³⁺, Fe²⁺, Fe³⁺, Ni²⁺. We focused on the effect of fluoridation on the interaction of fullerene with metal ions and drugs in an aqueous solution. We considered three model systems, C₆₀, C₆₀F₂ and C₆₀F₄₈, and represented pristine, low-fluorinated and high-fluorinated fullerenes, respectively. Adsorption energies, deformation of fullerene and drug molecules, frontier molecular orbitals and vibrational spectra were investigated in detail. We found that different drugs and different ions interacted differently with fluorinated fullerenes. Cr³⁺ and Fe²⁺ ions lead to the defluorination of low-fluorinated fullerenes. Favipiravir also leads to their defluorination with the formation of HF molecules. Therefore, fluorinated fullerenes are not suitable for the delivery of favipiravir and similar drugs molecules. In contrast, we found that fluorine enhances the adsorption of Ni²⁺ and Fe³⁺ ions on fullerene and their activity to chloroquine. Ni²⁺-decorated fluorinated fullerenes were found to be stable and suitable carriers for the loading of chloroquine. Clear shifts of infrared, ultraviolet and visible spectra can provide control over the loading of chloroquine on Ni²⁺-doped fluorinated fullerenes.

Pyrazine and Phenazine Heterocycles: Platforms for Total Synthesis and Drug Discovery

There are numerous pyrazine and phenazine compounds that demonstrate biological activities relevant to the treatment of disease. In this review, we discuss pyrazine and phenazine agents that have shown potential therapeutic value, including several clinically used agents. In addition, we cover some basic science related to pyrazine and phenazine heterocycles, which possess interesting reactivity profiles that have been on display in numerous cases of innovative total synthesis approaches, synthetic methodologies, drug discovery efforts, and medicinal chemistry programs. The majority of this review is focused on presenting instructive total synthesis and medicinal chemistry efforts of select pyrazine and phenazine compounds, and we believe these incredible heterocycles offer promise in medicine.

Natural inspired ligustrazine-based SLC-0111 analogues as novel carbonic anhydrase inhibitors

Ligustrazine is the principle bioactive alkaloid in the widely-used Chinese herb Chuan Xiong rhizome. Herein, a series of novel derivatives has been designed as human carbonic anhydrases inhibitors (hCAIs) starting from the natural product Ligustrazine inserted as a tail instead of the 4-fluorophenyl tail of SLC-0111, a front-runner selective hCA IX inhibitor currently in clinical trials as antitumor/antimetastatic agent. Other derivatives were designed via incorporation of different linkers, of amide and ester type, or incorporation of different zinc anchoring groups such as secondary sulfamoyl and carboxylic acid functionalities. The newly designed molecules were prepared following different synthetic pathways, and were assessed for their inhibitory actions against four isoforms: the widespread cytosolic (hCA I and II), and the transmembrane tumor-related (hCA IX and XII). The primary sulfonamides efficiently inhibited the target hCA IX and hCA XII in the nanomolar range (K_Is: 6.2-951.5 nM and 3.3-869.3 nM, respectively). The most selective hCA IX inhibitors 6c and 18 were assessed for their potential anticancer effects, and displayed anti-proliferative activity against MCF-7 cancer cell line with IC₅₀s of 11.9 and 36.7 μM, respectively. Molecular modelling studies unveiled the relationship between structural features and inhibitory profiles against the off-target hCA II and the target, tumor-related isoforms hCA IX and XII.

Synthetic Coelenterazine Derivatives and Their Application for Bioluminescence Imaging

Bioluminescence (BL), the emission light resulting from the enzyme-catalyzed oxidative reaction, is a powerful imaging modality for monitoring biological phenomena both in vitro and in vivo. Coelenterazine (CTZ), the known widespread luciferin found in bioluminescent organisms, develops bioluminescence imaging (BLI). Here, we describe an approach to synthesize a series of novel CTZ derivatives for diversifying the toolbox of the BL substrates. Furthermore, we exemplify some of them display excellent BL signals in vitro and in vivo, and thus should be noted as one of the ideal substrates for in vivo BLI compared with a well-known conventional substrate, DeepBlueC.

Synthesis, Molecular Docking and Biological Characterization of Pyrazine Linked 2-Aminobenzamides as New Class I Selective Histone Deacetylase (HDAC) Inhibitors with Anti-Leukemic Activity

Class I histone deacetylases (HDACs) are key regulators of cell proliferation and they are frequently dysregulated in cancer cells. We report here the synthesis of a novel series of class-I selective HDAC inhibitors (HDACi) containing a 2-aminobenzamide moiety as a zinc-binding group connected with a central (piperazin-1-yl)pyrazine or (piperazin-1-yl)pyrimidine moiety. Some of the compounds were additionally substituted with an aromatic capping group. Compounds were tested in vitro against human HDAC1, 2, 3, and 8 enzymes and compared to reference class I HDACi (Entinostat (MS-275), Mocetinostat, CI994 and RGFP-966). The most promising compounds were found to be highly selective against HDAC1, 2 and 3 over the remaining HDAC subtypes from other classes. Molecular docking studies and MD simulations were performed to rationalize the in vitro data and to deduce a complete structure activity relationship (SAR) analysis of this novel series of class-I HDACi. The most potent compounds, including 19f, which blocks HDAC1, HDAC2, and HDAC3, as well as the selective HDAC1/HDAC2 inhibitors 21a and 29b, were selected for further cellular testing against human acute myeloid leukemia (AML) and erythroleukemic cancer (HEL) cells, taking into consideration their low toxicity against human embryonic HEK293 cells. We found that 19f is superior to the clinically tested class-I HDACi Entinostat (MS-275). Thus, 19f is a new and specific HDACi with the potential to eliminate blood cancer cells of various origins.

A Derivative of Piperlongumine and Ligustrazine as a Potential Thioredoxin Reductase Inhibitor in Drug-Resistant Hepatocellular Carcinoma

The natural products piperlongumine (1) and ligustrazine (2) have been reported to exert antiproliferative effects against various types of cancer cells by up-regulating the level of reactive oxidative species (ROS). However, the moderate activities of 1 and 2 limit their application. To improve their potential antitumor activity, novel piperlongumine/ligustrazine derivatives were designed and prepared, and their potential pharmacological effects were determined in vitro and in vivo. Among the derivatives obtained, 11 exerted more prominent inhibitory activities against proliferation of drug-sensitive/-resistant cancer cells with lower IC50 values than 1. Particularly, the IC50 value of 11 against drug-resistant Bel-7402/5-FU cells was 0.9 μM, which was about 9-fold better than that of 1 (IC50 value of 8.4 μM). Mechanistic studies showed that 11 demonstrated thioredoxin reductase (TrxR) inhibitory activity, increase of ROS levels, decrease of mitochondrial transmembrane potential levels, and occurrence of DNA damage and autophagy, in a dose-dependent manner, via regulation of DNA damage protein H2AX and autophagy-associated proteins LC3, beclin-1, and p62 in drug-resistant Bel-7402/5-FU cells. Finally, compound 11 at 5 mg/kg displayed potent antitumor activity in vivo with tumor suppression of 76% (w/w). Taken together, compound 11 may represent a promising candidate drug for the chemotherapy of drug-resistant hepatocellular carcinoma and warrant more intensive study.

QSAR Studies and Structure Property/Activity Relationships Applied in Pyrazine Derivatives as Antiproliferative Agents Against the BGC823

Electronic structures, the effect of the substitution, structure physicochemical property/activity relationships and drug-likeness applied in pyrazine derivatives, have been studied at ab initio (HF, MP2) and B3LYP/DFT (density functional theory) levels. In the paper, the calculated values, i.e., NBO (natural bond orbitals) charges, bond lengths, dipole moments, electron affinities, heats of formation and quantitative structure-activity relationships (QSAR) properties are presented. For the QSAR studies, we used multiple linear regression (MLR) and artificial neural network (ANN) statistical modeling. The results show a high correlation between experimental and predicted activity values, indicating the validation and the good quality of the derived QSAR models. In addition, statistical analysis reveals that the ANN technique with (9-4-1) architecture is more significant than the MLR model. The virtual screening based on the molecular similarity method and applicability domain of QSAR allowed the discovery of novel anti-proliferative activity candidates with improved activity.

Design, synthesis and biological evaluation of substituted 3-amino-N-(thiazol-2-yl)pyrazine-2-carboxamides as inhibitors of mycobacterial methionine aminopeptidase 1

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb) is the number one cause of deaths due to a single infectious agent worldwide. The treatment of TB is lengthy and often complicated by the increasing drug resistance. New compounds with new mechanisms of action are therefore needed. We present the design, synthesis, and biological evaluation of pyrazine-based inhibitors of a prominent antimycobacterial drug target - mycobacterial methionine aminopeptidase 1 (MtMetAP1). The inhibitory activities of the presented compounds were evaluated against the MtMetAP1a isoform, and all derivatives were tested against a broad spectrum of myco(bacteria) and fungi. The cytotoxicity of the compounds was also investigated using Hep G2 cell lines. Overall, high inhibition of the isolated enzyme was observed for 3-substituted N-(thiazol-2-yl)pyrazine-2-carboxamides, particularly when the substituent was represented by 2-substituted benzamide. The extent of inhibition was strongly dependent on the used metal cofactor. The highest inhibition was seen in the presence of Ni²⁺. Several compounds also showed mediocre in vitro potency against Mtb (both Mtb H37Ra and H37Rv). Despite the structural similarities of bacterial and fungal MetAP1 to mycobacterial MtMetAP1, title compounds did not exert antibacterial nor antifungal activity. The reasons behind the higher activity of 2-substituted benzamido derivatives, as well as the correlation of enzyme inhibition with the in vitro growth inhibition activity is discussed.

Identification of (6S)-cyclopropyl-6,7-dihydropyrazolo[1,5-a]pyrazine-5(4H)-carboxamines as new HBV capsid assembly modulators

GYH2-18 is a type II HBV CAM with 6,7-dihydropyrazolo[1,5-a]pyrazine-5(4H)-carboxamine (DPPC) skeleton discovered by Roche INC. A series of GYH2-18 derivatives were designed, synthesized and evaluated for their anti-HBV activity. Two compounds 2f and 3k exhibited excellent anti-HBV activity, low cytotoxicity and accepted oral PK profiles. Chiral separation of 2f and 3k was conducted successfully, and (6S)-cyclopropyl DPPC isomers 2f-1, 2f-3, 3k-1 and 3k-3 were identified to be much more active than the corresponding (6R)-ones. The preliminary structure-activity relationship, particle gel assay and molecular modeling studies were also discussed, which provide useful indications for guiding the further rational design of new (6S)-cyclopropyl DPPC analogues.

Induced intra- and intermolecular template switching as a therapeutic mechanism against RNA viruses

Viral RNA-dependent RNA polymerases (RdRps) are a target for broad-spectrum antiviral therapeutic agents. Recently, we demonstrated that incorporation of the T-1106 triphosphate, a pyrazine-carboxamide ribonucleotide, into nascent RNA increases pausing and backtracking by the poliovirus RdRp. Here, by monitoring enterovirus A-71 RdRp dynamics during RNA synthesis using magnetic tweezers, we identify the "backtracked" state as an intermediate used by the RdRp for copy-back RNA synthesis and homologous recombination. Cell-based assays and RNA sequencing (RNA-seq) experiments further demonstrate that the pyrazine-carboxamide ribonucleotide stimulates these processes during infection. These results suggest that pyrazine-carboxamide ribonucleotides do not induce lethal mutagenesis or chain termination but function by promoting template switching and formation of defective viral genomes. We conclude that RdRp-catalyzed intra- and intermolecular template switching can be induced by pyrazine-carboxamide ribonucleotides, defining an additional mechanistic class of antiviral ribonucleotides with potential for broad-spectrum activity.

Prevalence and Management of Alkyl-Methoxypyrazines in a Changing Climate: Viticultural and Oenological Considerations

Alkyl-methoxypyrazines are an important class of odor-active molecules that contribute green, ‘unripe’ characters to wine and are considered undesirable in most wine styles. They are naturally occurring grape metabolites in many cultivars, but can also be derived from some Coccinellidae species when these ‘ladybugs’ are inadvertently introduced into the must during harvesting operations. The projected impacts of climate change are discussed, and we conclude that these include an altered alkyl-methoxypyrazine composition in grapes and wines in many wine regions. Thus, a careful consideration of how to manage them in both the vineyard and winery is important and timely. This review brings together the relevant literatures on viticultural and oenological interventions aimed at mitigating alkyl-methoxypyrazine loads, and makes recommendations on their management with an aim to maintaining wine quality under a changing and challenging climate.

Determination of the Absolute Configuration of Bioactive Indole-Containing Pyrazino[2,1-b]quinazoline-3,6-diones and Study of Their In Vitro Metabolic Profile

In recent decades, fungi-derived naturally occurring quinazolines have emerged as potential drug candidates. Nevertheless, most studies are conducted for bioactivity assays, and little is known about their absorption, distribution, metabolism, and elimination (ADME) properties. To perform metabolic studies, the synthesis of the naturally occurring quinazolinone, fiscalin B (1), and its chloro derivative, 4-((1H-indol-3-yl)methyl)-8,10-dichloro-1-isobutyl-1,2-dihydro-6H-pyrazino[2,1-b]quinazoline-3,6(4H)-dione (2), disclosed as an antibacterial agent, was performed in a gram scale using a microwave-assisted polycondensation reaction with 22% and 17% yields, respectively. The structure of the non-natural (+)-fiscalin B was established, for the first time, by X-ray crystallography as (1R,4S)-1, and the absolute configuration of the naturally occurring fiscalin B (-)-1 was confirmed by comparison of its calculated and experimental electronic circular dichroism (ECD) spectra as (1S,4R)-1. in vitro metabolic studies were monitored for this class of natural products for the first time by ultra-high-performance liquid chromatography (UHPLC) coupled with high-resolution mass spectrometry (HRMS). The metabolic characteristics of 1 and 2 in human liver microsomes indicated hydration and hydroxylation mass changes introduced to the parent drugs.

Synthesis of Novel Methyl 7-[(Hetero)arylamino]thieno[2,3-b]pyrazine-6-carboxylates and Antitumor Activity Evaluation: Effects in Human Tumor Cells Growth, Cell Cycle Analysis, Apoptosis and Toxicity in Non-Tumor Cells

Several novel methyl 7-[(hetero)arylamino]thieno[2,3-b]pyrazine-6-carboxylates were synthesized by Pd-catalyzed C–N Buchwald–Hartwig cross-coupling of either methyl 7-aminothieno[3,2-b]pyrazine-6-carboxylate with (hetero)arylhalides or 7-bromothieno[2,3-b]pyrazine-6-carboxylate with (hetero)arylamines in good-to-excellent yields (50% quantitative yield), using different reaction conditions, namely ligands and solvents, due to the different electronic character of the substrates. The antitumoral potential of these compounds was evaluated in four human tumor cell lines: gastric adenocarcinoma (AGS), colorectal adenocarcinoma (CaCo-2), breast carcinoma (MCF7), and non-small-cell lung carcinoma (NCI-H460) using the SRB assay, and it was possible to establish some structure–activity relationships. Furthermore, they did not show relevant toxicity against a non-tumor cell line culture from the African green monkey kidney (Vero). The most promising compounds (GI₅₀ ≤ 11 µM), showed some selectivity either against AGS or CaCo-2 cell lines without toxicity at their GI₅₀ values. The effects of the methoxylated compounds 2b (2-OMeC₆H₄), 2f and 2g (3,4- or 3,5-diOMeC₆H₃, respectively) on the cell cycle profile and induction of apoptosis were further studied in the AGS cell line. Nevertheless, even for the most active (GI₅₀ = 7.8 µM) and selective compound (2g) against this cell line, it was observed that a huge number of dead cells gave rise to an atypical distribution on the cell cycle profile and that these cells were not apoptotic, which points to a different mechanism of action for the AGS cell growth inhibition.

Synthesis, Structural Investigations, Molecular Docking, and Anticancer Activity of Some Novel Schiff Bases and Their Uranyl Complexes

Three novel 2-aminopyrazine Schiff bases derived from salicylaldehyde derivatives and their uranyl complexes were synthesized and characterized by elemental analysis, UV-vis, FTIR, molar conductance, and thermal gravimetric analysis (TGA). The proposed structures were optimized using density functional theory (DFT/B3LYP) and 6-311G ∗(d,p) basis sets. All uranyl complexes are soluble in DMSO and have low molar conductance, which indicates that all the complexes are nonelectrolytes. The DNA binding of those Schiff bases and their uranyl complexes was studied using UV-vis spectroscopy, and screening of their ability to bind to calf thymus DNA (CT-DNA) showed that the complexes interact with CT-DNA through an intercalation mode, for which the K_b values ranged from 1 × 10⁶ to 3.33 × 10⁵ M^-1. The anticancer activities of the Schiff base ligands and their uranyl complexes against two ovarian (Ovcar-3) and melanoma cell lines (M14) were investigated, and the results indicated that uranyl complexes exhibit better results than the Schiff base ligands. Molecular docking identified the distance, energy account, type, and position of links contributing to the interactions between these complexes and two different cancer proteins (3W2S and 2OPZ).

Plain 1 H nuclear magnetic resonance analysis streamlines the quality control of antiviral favipiravir and congeneric World Health Organization essential medicines

Favipiravir is an established antiviral that is currently being assessed as an investigational drug for the treatment of COVID-19. Favipiravir is strikingly similar to two molecules that the World Health Organization (WHO) lists as essential medicines, which also consist of a six-membered aromatic N-heterocycle bearing a carboxamide function: the anti-tuberculosis agent, pyrazinamide, and nicotinamide, also known as vitamin B₃ . We demonstrate the utility of ¹ H nuclear magnetic resonance (NMR) profiling, an emerging pharmacopoeial tool, for the highly specific identification, selective differentiation of congeners, and subsequent detection of drug falsification or adulteration of these medicines. The straightforward comparison of basic 1-D ¹ H NMR spectra, obtained with benchtop or advanced NMR instruments alike, offers a rapid identity assay and works independently of physical reference materials. This approach accelerates and advances pharmaceutical quality control measures under situations of increased drug demand and altered economy, such as during a pandemic.

Electron Density Analysis of SARS-CoV-2 RNA-Dependent RNA Polymerase Complexes

The work is devoted to the study of the complementarity of the electronic structures of the ligands and SARS-CoV-2 RNA-dependent RNA polymerase. The research methodology was based on determining of 3D maps of electron densities of complexes using an original quantum free-orbital AlteQ approach. We observed a positive relationship between the parameters of the electronic structure of the enzyme and ligands. A complementarity factor of the enzyme-ligand complexes has been proposed. The console applications of the AlteQ complementarity assessment for Windows and Linux (alteq_map_enzyme_ligand_4_win.exe and alteq_map_enzyme_ligand_4_linux) are available for free at the ChemoSophia webpage.

Headspace Solid-Phase Microextraction Analysis of Volatile Components in Peanut Oil

Peanut oil is favored by consumers due to its rich nutritional value and unique flavor. This study used headspace solid-phase microextraction (HS-SPME) combined with gas chromatography (GC) and gas chromatography–mass spectrometry (GC-MS) to examine the differences in the peanut oil aroma on the basis of variety, roasting temperatures, and pressing components. The results revealed that the optimal conditions for extracting peanut oil were achieved through the use of 50/30 μm DVB/CAR/PDMS fibers at 60 °C for 50 min. The primary compounds present in peanut oil were pyrazines. When peanuts were roasted, the temperature raised from 120 °C to 140 °C and the content of aldehydes in peanut oil increased; however, the content of aldehydes in No. 9 oil at 160 °C decreased. The components of peanut shell oil varied depending on the peanut variety. The most marked difference was observed in terms of the main compound at the two roasting temperatures. This compound was a pyrazine, and the content increased with the roasting temperature in hekei oils. When the roasting temperature was lower, No. 9 oil contained more fatty acid oxidation products such as hexanal, heptanal, and nonanal. When the roasting temperature increased, No. 9 oil contained more furfural and 5-methylfurfural. Heren oil was easier to oxidize and produced nonanal that possessed a fatty aroma.

A novel dipeptide coupled with pyrazine-oxadiazole derivative as a potential antitubercular agent: Synthesis, radioiodination and bioevaluation

Tuberculosis (TB) is a disease caused by Mycobacterium and usually attack the lung. Synthesis of new dipeptide derivatives attached to antitubercular active heterocyclic rings like pyrazine and 1,3,4-oxadiazole called ethyl 2-(2-(5-((pyrazin-2-ylamino) methyl)-1,3,4-oxadiazol-2-ylthio) acetamido) acetamido)-3-(4-hydroxyphenyl) propanoate (EPOGTP) and iodinated EPOGTP are reported. The compounds have been characterized by mass, FT-IR and ¹H NMR spectroscopy. Their in vitro investigation against Mycobacterium tuberculosis cell line indicated good IC₅₀value of 210 μg/ml for EPOGTP and 86 μg/ml for iodo-EPOGTP. For study the biodisriution, the direct radioiodination of EPOGTP with iodine-131 using mild oxidizing agent, N-Bromosuccinimide (NBS), was performed and optimized for obtaining the maximum radiochemical purity (97.3 ± 0.47%). Then, the in vivo biodistribution in healthy mice showed good accumulation of radioiodinated EPOGTP in lung of about 41.83 ± 0.23% (the percentage of injected dose per gram of organ) at 15 min post-injection. As a conclusion, the synthetized dipeptide and its iodinated derivative could be further evaluated as a potential antitubercular agents.

Synthesis of New Triazolopyrazine Antimalarial Compounds

A radical approach to late-stage functionalization using photoredox and Diversinate^™ chemistry on the Open Source Malaria (OSM) triazolopyrazine scaffold (Series 4) resulted in the synthesis of 12 new analogues, which were characterized by NMR, UV, and MS data analysis. The structures of four triazolopyrazines were confirmed by X-ray crystal structure analysis. Several minor and unexpected side products were generated during these studies, including two resulting from a possible disproportionation reaction. All compounds were tested for their ability to inhibit the growth of the malaria parasite Plasmodium falciparum (3D7 and Dd2 strains) and for cytotoxicity against a human embryonic kidney (HEK293) cell line. Moderate antimalarial activity was observed for some of the compounds, with IC₅₀ values ranging from 0.3 to >20 µM; none of the compounds displayed any toxicity against HEK293 at 80 µM.

IRE1α Is a Therapeutic Target for Cystic Fibrosis Airway Inflammation

New anti-inflammatory treatments are needed for CF airway disease. Studies have implicated the endoplasmic reticulum stress transducer inositol requiring enzyme 1α (IRE1α) in CF airway inflammation. The activation of IRE1α promotes activation of its cytoplasmic kinase and RNase, resulting in mRNA splicing of X-box binding protein-1 (XBP-1s), a transcription factor required for cytokine production. We tested whether IRE1α kinase and RNase inhibition decreases cytokine production induced by the exposure of primary cultures of homozygous F508del CF human bronchial epithelia (HBE) to supernatant of mucopurulent material (SMM) from CF airways. We evaluated whether IRE1α expression is increased in freshly isolated and native CF HBE, and couples with increased XBP-1s levels. A FRET assay confirmed binding of the IRE1α kinase and RNase inhibitor, KIRA6, to the IRE1α kinase. F508del HBE cultures were exposed to SMM with or without KIRA6, and we evaluated the mRNA levels of XBP-1s, IL-6, and IL-8, and the secretion of IL-6 and IL-8. IRE1α mRNA levels were up-regulated in freshly isolated CF vs. normal HBE and coupled to increased XBP-1s mRNA levels. SMM increased XBP-1s, IL-6, and IL-8 mRNA levels and up-regulated IL-6 and IL-8 secretion, and KIRA6 blunted these responses in a dose-dependent manner. Moreover, a triple combination of CFTR modulators currently used in the clinic had no effect on SMM-increased XBP-1s levels coupled with increased cytokine production in presence or absence of KIRA6. These findings indicate that IRE1α mediates cytokine production in CF airways. Small molecule IRE1α kinase inhibitors that allosterically reduce RNase-dependent XBP-1s may represent a new therapeutic strategy for CF airway inflammation.

Evaluation of NanoLuc substrates for bioluminescence imaging of transferred cells in mice

NanoLuc luciferase recently gained popularity due to its small size and superior bioluminescence performance. For in vivo imaging applications, NanoLuc has been limited by its substrate furimazine, which has low solubility and bioavailability. Herein, we compared the performances of recently reported NanoLuc luciferase substrates for in vivo imaging in mice. Two substrates with improved aqueous solubility, hydrofurimazine and fluorofurimazine, were evaluated along with three stabilized O-acetylated furimazine analogues, the hikarazines. All 5 analogues, when tested in vitro, displayed greater signal intensity and reaction duration, in comparison to the standard NanoLuc substrate, furimazine. The two best-performing analogues from the in vitro study were selected for further in vivo testing. The NanoLuc/fluorofurimazine pair demonstrated the highest bioluminescence intensity, post intravenous administration. It was found to be around 9-fold brighter compared to the NanoLuc/furimazine and 11-fold more intense than the NanoLuc/hikarazine-003 pair, with an average of 3-fold higher light emission when the substrate was injected intraperitoneally, in a subcutaneous model. Excitingly, despite the fact that NanoLuc/fluorofurimazine emits mostly blue light, we prove that cells trapped in mice lungs vasculature could be visualised via the NanoLuc/fluorofurimazine pair and compare the results to the AkaLuc/AkaLumine system. Therefore, among the tested analogues, fluorofurimazine enables higher substrate loading and improved optical imaging sensitivity in small animals, upgrading the use of NanoLuc derived bioluminescent systems for deep tissue imaging.

Structure of the SARS-CoV-2 RNA-dependent RNA polymerase in the presence of favipiravir-RTP

The RNA polymerase inhibitor favipiravir is currently in clinical trials as a treatment for infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), despite limited information about the molecular basis for its activity. Here we report the structure of favipiravir ribonucleoside triphosphate (favipiravir-RTP) in complex with the SARS-CoV-2 RNA-dependent RNA polymerase (RdRp) bound to a template:primer RNA duplex, determined by electron cryomicroscopy (cryoEM) to a resolution of 2.5 Å. The structure shows clear evidence for the inhibitor at the catalytic site of the enzyme, and resolves the conformation of key side chains and ions surrounding the binding pocket. Polymerase activity assays indicate that the inhibitor is weakly incorporated into the RNA primer strand, and suppresses RNA replication in the presence of natural nucleotides. The structure reveals an unusual, nonproductive binding mode of favipiravir-RTP at the catalytic site of SARS-CoV-2 RdRp, which explains its low rate of incorporation into the RNA primer strand. Together, these findings inform current and future efforts to develop polymerase inhibitors for SARS coronaviruses.

DFT calculations towards the geometry optimization, electronic structure, infrared spectroscopy and UV-vis analyses of Favipiravir adsorption on the first-row transition metals doped fullerenes; a new strategy for COVID-19 therapy

With the global epidemic of the COVID-19 virus, extensive and rapid research on drug therapy is underway around the world. In this regard, one of the most widely studied drugs is Favipiravir. Our aim in this paper is to conduct comprehensive research based on the Density Functional Theory (DFT) on the potential of metallofullerenes as suitable drug carriers. The surface interaction of Favipiravir with organometallic compound resulted by doping of the five transition metals of the first row of the periodic table (Ti, Cr, Cr, Fe, Ni, and Zn) was examined in depth to select the most suitable metallofullerenes. First, the adsorption geometries of Favipiravir drug onto each metallofullerene were deeply investigated. It was found that Cr-, Fe-, and Ni-doped fullerenes provide the excellent adsorbent property with adsorption energies of -148.2, -149.6, and -146.6 kJ/mol, respectively. The Infrared spectroscopy (IR) study was conducted to survey the stretching vibration of bonds involving in the systems, specialty the CO in the drug, CM in the metallofullerene, and MO in the metallofullerene-drug complex. Finally, the UV-vis analysis showed that the absorption spectra for the studied systems may be attributed to the transition from π-π* and/or n-π*.

Tetraphenylpyrazine-Based Luminescent Metal-Organic Framework for Chemical Sensing of Carcinoids Biomarkers

A new non-interpenetrated three-dimensional (3D) pillared-layered TPP-based LMOF [Zn₃(TPyTPP)_0.5(BDC)₃]·8DMF (denoted as Zn-MOF 1) was successfully prepared (TPyTPP = tetrakis(4-(pyridin-4-yl)phenyl)pyrazine and H₂BDC = 1,4-benzenedicarboxylic acid). Zn-MOF 1 was characterized by single-crystal X-ray diffraction, PXRD, IR, N₂ adsorption, thermogravimetric analysis, and luminescent spectrum. Impressively, luminescent sensing studies reveal that activated Zn-MOF 1 not only displays excellent luminescence-quenching efficiency with the values of high K_sv and low LODs toward 5-hydroxytryptamine (5-HT) and 5-hydroxyindole-3-acetic acid (5-HIAA), respectively, but also possesses outstanding sensing characteristics in terms of fast response, high sensitivity, and specific selectivity. Zn-MOF 1 performs as efficient sensing of carcinoid biomarkers to provide a fresh detection platform for the diagnosis of carcinoids. In addition, the sensing mechanism was also explored on the basis of ultraviolet-visible (UV-vis) absorption, DFT calculations, and structural analysis.

Focal adhesion kinase (FAK) inhibitor-defactinib suppresses the malignant progression of human esophageal squamous cell carcinoma (ESCC) cells via effective blockade of PI3K/AKT axis and downstream molecular network

The clinical therapeutic efficacy toward esophageal squamous cell carcinoma (ESCC) is undesirable, due to the lack of targeted agents. Focal adhesion kinase (FAK), a nonreceptor tyrosine kinase involved in multiple fields of tumorigenesis, recently has been indicated as a promising therapeutic target in ESCC treatment. Here, we revealed that defactinib, a specific FAK inhibitor, effectively suppressed the malignancy of ESCC cells. Mechanistically, defactinib dose and time-dependently induced the dissociation of phosphoinositide-3-kinase (PI3K) from FAK, resultantly led to blockade of protein kinase B (AKT) signaling, and the expression of several oncogenes, such as SOX2, MYC, EGFR, MET, MDM2, or TGFBR2, identified by microarray and real-time polymerase chain reaction assay. Specifically, this FAK inhibition-mediated suppression of PI3K/AKT signaling and downstream ESCC specific biomarkers was maintained to 24 h in in vitro experiments to guarantee the treatment durability and efficacy. Importantly, defactinib suppressed tumor growth, metastatic ability, and increased overall survival of xenografted animals without producing significantly systematic toxicity. Our data suggest that FAK inhibition provides an excellent targeted therapy toward ESCC by effectively inhibiting PI3K/AKT pathway and downstream molecular network.

Highly Bright NIR-BRET System for Imaging Molecular Events in Live Cells

The present protocol demonstrates a novel mammalian cell imaging platform exerting a bioluminescence resonance energy transfer (BRET) system. This platform achieves a ~300 nm blue-to-near infrared shift of the emission (NIR-BRET) with the development of a unique coelenterazine (CTZ) derivative named BBlue2.3 and a fusion reporter protein probe named iRFP-RLuc8.6-535SG. The best NIR-BRET shift was achieved by tuning the blue emission peak of BBlue2.3 to a Soret band of the iRFP. In mammalian cells, BBlue2.3 emits light that is ~50-fold brighter than DeepBlueC in cell imaging when combined with RLuc8.6-535SG. This NIR-BRET platform is sufficiently brighter to be used for imaging live mammalian cells at single-cell level, and also for imaging metastases in deep tissues in live mice without generating considerable autoluminescence. This unique optical platform provides the brightest NIR-BLI template that can be used for imaging a diverse group of cellular events in living subjects.

Targeting the RdRp of Emerging RNA Viruses: The Structure-Based Drug Design Challenge

The RNA-dependent RNA polymerase (RdRp) is an essential enzyme for the viral replication process, catalyzing the viral RNA synthesis using a metal ion-dependent mechanism. In recent years, RdRp has emerged as an optimal target for the development of antiviral drugs, as demonstrated by recent approvals of sofosbuvir and remdesivir against Hepatitis C virus (HCV) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), respectively. In this work, we overview the main sequence and structural features of the RdRp of emerging RNA viruses such as Coronaviruses, Flaviviruses, and HCV, as well as inhibition strategies implemented so far. While analyzing the structural information available on the RdRp of emerging RNA viruses, we provide examples of success stories such as for HCV and SARS-CoV-2. In contrast, Flaviviruses' story has raised attention about how the lack of structural details on catalytically-competent or ligand-bound RdRp strongly hampers the application of structure-based drug design, either in repurposing and conventional approaches.

Interactions Between Remdesivir, Ribavirin, Favipiravir, Galidesivir, Hydroxychloroquine and Chloroquine with Fragment Molecular of the COVID-19 Main Protease with Inhibitor N3 Complex (PDB ID:6LU7) Using Molecular Docking

We started a study on the molecular docking of six potential pharmacologically active inhibitors compounds that can be used clinically against the COVID-19 virus, in this case, remdesivir, ribavirin, favipiravir, galidesivir, hydroxychloroquine and chloroquine interacting with the main COVID-19 protease in complex with a COVID-19 N3 protease inhibitor. The highest values of affinity energy found in order from highest to lowest were chloroquine (CHL), hydroxychloroquine (HYC), favipiravir (FAV), galidesivir (GAL), remdesivir (REM) and ribavirin (RIB). The possible formation of hydrogen bonds, associations through London forces and permanent electric dipole were analyzed. The values of affinity energy obtained for the hydroxychloroquine ligands was -9.9 kcal/mol and for the chloroquine of -10.8 kcal/mol which indicate that the coupling contributes to an effective improvement of the affinity energies with the protease. Indicating that, the position chosen to make the substitutions may be a pharmacophoric group, and cause changes in the protease.

Accelerated Green Process of 2,5-Dimethylpyrazine Production from Glucose by Genetically Modified Escherichia coli

2,5-Dimethylpyrazine (2,5-DMP) is an indispensable additive for flavoring in the food industry and an important substrate for producing hypoglycemic and antilipolytic drugs. However, 2,5-DMP is produced by chemical synthesis in industry. Herein, a "green" strategy to produce 2,5-DMP has been reported for the first time. To do this, we rewrote the de novo 2,5-DMP biosynthesis pathway and substrate transmembrane transport in an l-threonine high-yielding strain to promote highly efficient 2,5-DMP production from glucose by submerged fermentation. The final strain T6-47-7 could produce 1.43 ± 0.07 g/L of 2,5-DMP with a carbon yield of 6.78% and productivity of 0.715 g/(L·d) in shake-flask fermentation using a phase-wise manner of hypoxia-inducible expression. The design-based strategy for constructing the 2,5-DMP high-yielding strain reported here could serve as a general concept for breeding high-yielding strains that produce some other type of alkylpyrazine.

[12]aneN3-Based Gemini-Type Amphiphiles with Two-Photon Absorption Properties for Enhanced Nonviral Gene Delivery and Bioimaging

Although a plethora of nonviral gene vectors have been developed for potential gene therapy, imageable gemini surfactants with stimuli-responsiveness and high transfection efficiency are still scarce for gene delivery. Herein, three gemini amphiphiles (DEDPP-4/8/12) consisting of an aggregation-induced emission (AIE) central fluorophore: 5,6-diphenylpyrazine-2,3-diester (DEDPP), decorated with triazole-[12]aneN₃ as the hydrophilic moiety and alkyl chains of various lengths as the hydrophobic moiety, were designed and synthesized for trackable gene delivery via optical imaging. All three amphiphiles exhibited ultralow critical micelle concentrations (CMCs) (up to 3.40 × 10^-6 M), prominent two-photon absorption properties, and solvatochromic fluorescence. Gel electrophoresis assays demonstrated that the migration of plasmid DNA was completely retarded after condensation with these gemini amphiphiles at low concentrations (up to 10 μM). In addition, the ester bond in these amphiphiles may facilitate vector degradation and DNA release, in response to esterase and the acidic environment inside cells. Upon self-assembly with DOPE to form liposomes, DEDPP-8/DOPE achieved the best transfection efficiency in four cell lines, and the transfection efficiency of DEDPP-8/DOPE in HeLa cell lines was 23.5-fold higher than that of Lipo2000, which is unusually high for small organic molecule-based nonviral vectors. Furthermore, excellent transfection efficiency of DEDPP-8/DOPE was obtained in the presence of serum, and the red fluorescence protein (RFP) gene was successfully transfected in zebrafish embryos. Both one- and two-photon fluorescence imaging clearly demonstrated the delivery process of plasmid DNA. This study demonstrated that gemini-type amphiphiles composed of a two-photon fluorophore core conjugated with triazole-[12]aneN₃ via an ester bond afforded an unprecedentedly high transfection efficiency with excellent biocompatibility, which may provide new insights for the design and development of multifunctional nonviral gene vectors for imageable gene delivery.

Seeing (and Using) the Light: Recent Developments in Bioluminescence Technology

Bioluminescence has long been used to image biological processes in vivo. This technology features luciferase enzymes and luciferin small molecules that produce visible light. Bioluminescent photons can be detected in tissues and live organisms, enabling sensitive and noninvasive readouts on physiological function. Traditional applications have focused on tracking cells and gene expression patterns, but new probes are pushing the frontiers of what can be visualized. The past few years have also seen the merger of bioluminescence with optogenetic platforms. Luciferase-luciferin reactions can drive light-activatable proteins, ultimately triggering signal transduction and other downstream events. This review highlights these and other recent advances in bioluminescence technology, with an emphasis on tool development. We showcase how new luciferins and engineered luciferases are expanding the scope of optical imaging. We also highlight how bioluminescent systems are being leveraged not just for sensing-but also controlling-biological processes.

Bioluminescent Properties of Semi-Synthetic Obelin and Aequorin Activated by Coelenterazine Analogues with Modifications of C-2, C-6, and C-8 Substituents

Ca2+-regulated photoproteins responsible for bioluminescence of a variety of marine organisms are single-chain globular proteins within the inner cavity of which the oxygenated coelenterazine, 2-hydroperoxycoelenterazine, is tightly bound. Alongside with native coelenterazine, photoproteins can also use its synthetic analogues as substrates to produce flash-type bioluminescence. However, information on the effect of modifications of various groups of coelenterazine and amino acid environment of the protein active site on the bioluminescent properties of the corresponding semi-synthetic photoproteins is fragmentary and often controversial. In this paper, we investigated the specific bioluminescence activity, light emission spectra, stopped-flow kinetics and sensitivity to calcium of the semi-synthetic aequorins and obelins activated by novel coelenterazine analogues and the recently reported coelenterazine derivatives. Several semi-synthetic photoproteins activated by the studied coelenterazine analogues displayed sufficient bioluminescence activities accompanied by various changes in the spectral and kinetic properties as well as in calcium sensitivity. The poor activity of certain semi-synthetic photoproteins might be attributed to instability of some coelenterazine analogues in solution and low efficiency of 2-hydroperoxy adduct formation. In most cases, semi-synthetic obelins and aequorins displayed different properties upon being activated by the same coelenterazine analogue. The results indicated that the OH-group at the C-6 phenyl ring of coelenterazine is important for the photoprotein bioluminescence and that the hydrogen-bond network around the substituent in position 6 of the imidazopyrazinone core could be the reason of different bioluminescence activities of aequorin and obelin with certain coelenterazine analogues.

Photosensitive and pH-dependent activity of pyrazine-functionalized carbazole derivative as promising antifungal and imaging agent

Carbazole skeleton plays a significant role as a structural scaffold of many pharmacologically active compounds. Pyrazine-functionalized carbazole derivative was constructed by coupling 2-amino-5-bromo-3-methylaminepyrazine (ABMAP) into 3 and 6 positions of the carbazole ring. Multi-experimental methods were used, e.g., potentiometric, spectroscopic (ATR, UV, XRD powder,1H and13C NMR), electrochemical (cyclic voltammetry), and optical techniques, to receive the complete structural analysis, physicochemical (pKa, logP) and biological profile of a new carbazole derivative with acronym 3,6-PIRAMICAR. The interaction ability of the compound studied with potential cellular targets like Calf Thymus DNA (CT-DNA), or Bovine Serum Albumin (BSA) were also taken into account. Experiments showed the existence of strong binding, but no DNA or BSA cleavage was observed. The comparative analyzes of compounds anti-Candida action clearly show pH-dependent antifungal activity of 3,6-PIRAMICAR, which was strongly stimulated in the acidic media. Surprisingly, the titled compound turn out to be much more effective (14 times by MIC50; 8 times by MIC; c.a. 4 times by MFC) against Candida krusei than fluconazole at pH 4.

6-Amino[1,2,5]oxadiazolo[3,4-b]pyrazin-5-ol Derivatives as Efficacious Mitochondrial Uncouplers in STAM Mouse Model of Nonalcoholic Steatohepatitis

Small molecule mitochondrial uncouplers have recently garnered great interest for their potential in treating nonalcoholic steatohepatitis (NASH). In this study, we report the structure-activity relationship profiling of a 6-amino[1,2,5]oxadiazolo[3,4-b]pyrazin-5-ol core, which utilizes the hydroxy moiety as the proton transporter across the mitochondrial inner membrane. We demonstrate that a wide array of substituents is tolerated with this novel scaffold that increased cellular metabolic rates in vitro using changes in oxygen consumption rate as a readout. In particular, compound SHS4121705 (12i) displayed an EC50 of 4.3 μM in L6 myoblast cells and excellent oral bioavailability and liver exposure in mice. In the STAM mouse model of NASH, administration of 12i at 25 mg kg-1 day-1 lowered liver triglyceride levels and improved liver markers such as alanine aminotransferase, NAFLD activity score, and fibrosis. Importantly, no changes in body temperature or food intake were observed. As potential treatment of NASH, mitochondrial uncouplers show promise for future development.

Novel Coronavirus Polymerase and Nucleotidyl-Transferase Structures: Potential to Target New Outbreaks

The pandemic outbreak of a new coronavirus (CoV), SARS-CoV-2, has captured the world's attention, demonstrating that CoVs represent a continuous global threat. As this is a highly contagious virus, it is imperative to understand RNA-dependent-RNA-polymerase (RdRp), the key component in virus replication. Although the SARS-CoV-2 genome shares 80% sequence identity with severe acute respiratory syndrome SARS-CoV, their RdRps and nucleotidyl-transferases (NiRAN) share 98.1% and 93.2% identity, respectively. Sequence alignment of six coronaviruses demonstrated higher identity among their RdRps (60.9%-98.1%) and lower identity among their Spike proteins (27%-77%). Thus, a 3D structural model of RdRp, NiRAN, non-structural protein 7 (nsp7), and nsp8 of SARS-CoV-2 was generated by modeling starting from the SARS counterpart structures. Furthermore, we demonstrate the binding poses of three viral RdRp inhibitors (Galidesivir, Favipiravir, and Penciclovir), which were recently reported to have clinical significance for SARS-CoV-2. The network of interactions established by these drug molecules affirms their efficacy to inhibit viral RNA replication and provides an insight into their structure-based rational optimization for SARS-CoV-2 inhibition.