The role of microenvironments on computed vibrationally-resolved emission spectra: The case of oxazines.

Oxazine dyes act as reporters of their near environment by the response of their fluorescence spectra. At the same time, their fluorescence spectra exhibit a pronounced vibrational progression. In this work, we computationally investigate the impact of near-environment models consisting of aggregated water as well as betaine molecules on the vibrational profile of fluorescence spectra of different oxazine derivatives. For aggregated betaine and a water molecule located above the plane of the dyes, we observe a distinct modification of the vibrational profile, which is more pronounced than the effect of a continuum description of a solvent environment. Our analysis shows that this effect cannot be explained by a pure change in the electronic structure, but that also vibrational degrees of freedom of the environment can be decisive for the vibrational profile and should, hence, not generally be neglected.

POxload: Machine Learning Estimates Drug Loadings of Polymeric Micelles.

Block copolymers, composed of poly(2-oxazoline)s and poly(2-oxazine)s, can serve as drug delivery systems; they form micelles that carry poorly water-soluble drugs. Many recent studies have investigated the effects of structural changes of the polymer and the hydrophobic cargo on drug loading. In this work, we combine these data to establish an extended formulation database. Different molecular properties and fingerprints are tested for their applicability to serve as formulation-specific mixture descriptors. A variety of classification and regression models are built for different descriptor subsets and thresholds of loading efficiency and loading capacity, with the best models achieving overall good statistics for both cross- and external validation (balanced accuracies of 0.8). Subsequently, important features are dissected for interpretation, and the DrugBank is screened for potential therapeutic use cases where these polymers could be used to develop novel formulations of hydrophobic drugs. The most promising models are provided as an open-source software tool for other researchers to test the applicability of these delivery systems for potential new drug candidates.

Design, Green Synthesis and in silico Studies of New Substituted Naphtho[1,2-e][1,3]Oxazines as Potential Acetylcholinesterase Inhibitors.

Alzheimer's disease (AD) is a prevalent neurodegenerative condition characterized by progressive cognitive decline and memory impairment resulting from the degeneration and death of brain neurons. Acetylcholinesterase (AChE) inhibitors as the primary pharmacotherapy for numerous neurodegenerative conditions, leveraging their capacity to modulate acetylcholine levels crucial for cognitive function. Recently, oxazines  have brought worthy synthetic interest due to their extensive biological activities including, anti-tubercular, anti-convulsant, and anti-cancer activities. In this study, a series of novel naphtho[1,2-e][1,3]oxazine derivatives has been designed  and synthesized with potential of acetylcholinesterase (AChE) inhibition. The target products have been prepared by a one-pot and three-component condensation reaction of 2-naphthol, aromatic aldehydes, and arylmethanimine in the presence of 3-methyl-1-sulfonic acid imidazolium chloride ([Msim]Cl) as an effective and recyclable catalyst under microwave irradiation solvent-free condition. The molecular docking studies has also been performed to investigate the synthetic compounds in the the AChE active site gorge. The results showed that all these derivatives interact with the enzymes with high affinity in binding pocket. The MM-GBSA studies were performed for all synthesized derivatives and among them, compound 3-(4-Chlorophenyl)-1-phenyl-2,3-dihydro-1H-naphtho[1,2-e][1,3]oxazine 5f, showed the lowest the binding free energy (-48.04 kcal mol-1). In general, oxazine derivatives could be proposed as the strong AChE inhibitors.

Synthesis and Inhibitor Effect Novel Alkoxymethyl Derivatives of Dihetero Cycloalkanes on Carbonic Anhydrase and Acetylcholinesterase.

1,3-Diheterocycloalkanes derivatives are important starting materials in fine organic synthesis. These compounds can be widely used in various fields such as industry, medicine, biotechnology and chemical technology. The paper is focused on synthesis and study of alkoxymethyl derivatives of diheterocycloalkanes (M1-M15) and inhibition effect on carbonic anhydrase and acetylcholinesterase. The structures of compounds were confirmed by 1H and 13C NMR spectroscopy. Also, in this study alkoxymethyl derivatives of diheterocycloalkanes were assessed for their influence on various metabolic enzymes, including acetylcholinesterase (AChE) and human carbonic anhydrase isoenzymes (hCA I and hCA II). The results demonstrated that all these compounds exhibited potent inhibitory effects on all the target enzymes, surpassing the standard inhibitors, as evidenced by their IC50 and Ki values. The Ki values for the compounds concerning AChE, hCA I, and hCA II enzymes were in the ranges of 1.02±0.17-8.38±1.02, 15.30±3.15-58.14±5.17 and 24.05±3.70-312.94±27.24 nM, respectively.

Unravel the Tangle: Atomistic Insight into Ultrahigh Curcumin-Loaded Polymer Micelles.

Amphiphilic ABA-triblock copolymers, comprised of poly(2-oxazoline) and poly(2-oxazine), can solubilize poorly water-soluble molecules in a structure-dependent manner forming micelles with exceptionally high drug loading. All-atom molecular dynamics simulations are conducted on previously experimentally characterized, curcumin-loaded micelles to dissect the structure-property relationships. Polymer-drug interactions for different levels of drug loading and variation in polymer structures of both the inner hydrophobic core and outer hydrophilic shell are investigated. In silico, the system with the highest experimental loading capacity shows the highest number of drug molecules encapsulated by the core. Furthermore, in systems with lower loading capacity outer A blocks show a greater extent of entanglement with the inner B blocks. Hydrogen bond analyses corroborate previous hypotheses: poly(2-butyl-2-oxazoline) B blocks, found experimentally to have reduced loading capacity for curcumin compared to poly(2-propyl-2-oxazine), establish fewer but longer-lasting hydrogen bonds. This possibly results from different sidechain conformations around the hydrophobic cargo, which is investigated by unsupervised machine learning to cluster monomers in smaller model systems mimicking different micelle compartments. Exchanging poly(2-methyl-2-oxazoline) with poly(2-ethyl-2-oxazoline) leads to increased drug interactions and reduced corona hydration; this suggests an impairment of micelle solubility or colloidal stability. These observations can help driving forward a more rational a priori nanoformulation design.

Antifouling Properties of Poly(2-Oxazoline)s and Poly(2-Oxazine)s: Direct Comparison of Polymer-Coated Surfaces with the Same Coating Parameters.

This study presents a systematic comparison of the antifouling properties of water-soluble poly(2-oxazoline) (PAOx) and poly(2-oxazine) (PAOzi) brushes grafted to gold surfaces. PAOx and PAOzi are emerging polymer classes in biomedical sciences and are being considered superior alternatives to widely used polyethylene glycol (PEG). Four different polymers, poly(2-methyl-2-oxazoline) (PMeOx), poly(2-ethyl-2-oxazoline) (PEtOx), poly(2-methyl-2-oxazine) (PMeOzi), and poly(2-ethyl-2-oxazine) (PEtOzi), each of them in three different chain lengths, are synthesized and characterized for their antifouling properties. Results show that all polymer-modified surfaces display better antifouling properties than bare gold surfaces as well as analogous PEG coatings. The antifouling properties increase in the following order: PEtOx < PMeOx ≈ PMeOzi < PEtOzi. The study suggests that the resistance to protein fouling derives from both surface hydrophilicity and the molecular structural flexibility of the polymer brushes. PEtOzi brushes with moderate hydrophilicity show the best antifouling performance, possibly due to their highest chain flexibility. Overall, the research contributes to the understanding of antifouling properties in PAOx and PAOzi polymers, with potential applications in various biomaterials.

Design, synthesis of benzimidazole tethered 3,4-dihydro-2H-benzo[e] [1, 3] oxazines as anticancer agents.

A series of novel 3-(1H-benzo[d]imidazol-2-yl)-3,4-dihydro-2H-benzo[e][1,3] oxazine analogues synthesized through a two-step synthetic protocol. The structure of the compounds were established by interpretation 1H NMR, 13C NMR and Mass spectral data recorded after purification. All the title compounds 4a-k were screened for their in vitro anti-cancer activity against two breast cancer cell lines MCF 7 and MDA-MB-231 by using Doxorubicin as standard reference. Compound 4e displayed superior activity against both the cell lines MCF-7 and MDA-MB-231 with IC50 values of 8.60 ± 0.75 and 6.30 ± 0.54 µM respectively, compared to the Doxorubicin IC50 value of 9.11 ± 0.54 and 8.47 ± 0.47 µM. Compound 4i also indicated good activity with IC50 value of 9.85 ± 0.69 µM on par with Doxorubicin against MCF-7 cells. Compound 4g demonstrated best activity on par with standard reference to IC50 value of 8.52 ± 0.62 µM against MDA-MB-231 cell line. And all other compounds demonstrated good to moderate activity compared to Doxorubicin. Docking studies against EGFR showed that all the compounds have very good binding affinities towards the target. The predicted drug-likeness properties of all compounds enable them to be used as therapeutic agents.

Synthesis, Crystal Structure, DFT, and Anticancer Activity of Some Imine-Type Compounds via Routine Schiff Base Reaction: An Example of Unexpected Cyclization to Oxazine Derivative.

The synthesis, characterization, and anticancer properties of three imine-type compounds 1-3 and an unexpected oxazine derivative 4 are presented. The reaction of p-dimethylaminobenzaldehyde or m-nitrobenzaldehyde with hydroxylamine hydrochloride afforded the corresponding oximes 1-2 in good yields. Additionally, the treatment of benzil with 4-aminoantipyrine or o-aminophenol was investigated. Routinely, the Schiff base (4E)-4-(2-oxo-1,2-diphenylethylideneamino)-1,2-dihydro-1,5-dimethyl-2-phenylpyrazol-3-one 3 was obtained in the case of 4-aminoantipyrine. Unexpectedly, the reaction of benzil with o-aminophenol proceeded with cyclization to produce the 2,3-diphenyl-2H-benzo[b][1,4]oxazin-2-ol 4. The structures of compounds 3 and 4 were unambiguously determined by single crystal X-ray diffraction. Hirshfeld analysis of molecular packing revealed the importance of the O…H (11.1%), N…H (3.4%), C…H (29.4%), and C…C (1.6) interactions in the crystal stability of 3. In the case of 4, the O…H (8.8%), N…H (5.7%), and C…H (30.3%) interactions are the most important. DFT calculations predicted that both compounds have a polar nature, and 3 (3.4489 Debye) has higher polarity than 4 (2.1554 Debye). Different reactivity descriptors were calculated for both systems based on the HOMO and LUMO energies. The NMR chemical shifts were calculated and were found well correlated with the experimental data. HepG2 growth was suppressed by the four compounds more than MCF-7. The IC50 values of 1 against HepG2 and MCF-7 cell lines were the lowest, and it is considered the most promising candidate as an anticancer agent.

Synthesis and characterisation of phenanthroline-oxazine ligands and their Ag(I), Mn(II) and Cu(II) complexes and their evaluation as antibacterial agents.

A series of phenanthroline-oxazine ligands were formed by a cyclisation reaction between L-tyrosine amino acid esters and 1,10-phenanthroline-5,6-dione (phendione). The methyl derivative of the phenanthroline-oxazine ligand 1 was complexed with Ag(I), Mn(II) and Cu(II) to form [Ag(1)2]ClO4, [Mn(1)3](ClO4)2 and [Cu(1)3](ClO4)2. The activity of these metal complexes was tested against the bacteria Escherichia coli and Staphylococcus aureus. Each of the metal complexes was more active than 1 against S. aureus and the Mn(II) and Cu(II) complexes also showed greater activity than 1 towards E. coli. The effect of increasing the length of the alkyl moiety on the phenanthroline-oxazine ligands and their corresponding tris homoleptic Cu(II) complexes was investigated. In all cases both the ligands and their complexes were more active against Gram-positive S. aureus than against Gram-negative E. coli. Differences in the lipophilicity of the ligands and their corresponding Cu(II) complexes did alter the antibacterial activity, with the hexyl and octyl derivatives and their complexes showing the greatest activity and comparing well with clinically used antibiotics. The most active Cu(II) complexes and their respective ligands were also active against Methicillin-resistant S. aureus (MRSA). In vivo toxicity studies, conducted using the Galleria mellonella model, showed that all of the compounds were well tolerated by the insect larvae.

Cycloaddition of 4-Acyl-1H-pyrrole-2,3-diones Fused at [e]-Side and Cyanamides: Divergent Approach to 4H-1,3-Oxazines.

4-Acyl-1H-pyrrole-2,3-diones fused at [e]-side with a heterocyclic moiety are suitable platforms for the development of a hetero-Diels-Alder-reaction-based, diversity-oriented approaches to series of skeletally diverse heterocycles. These platforms are known to react as oxa-dienes with dienophiles to form angular 6/6/5/6-tetracyclic alkaloid-like heterocycles and are also prone to decarbonylation at high temperatures resulting in generation of acyl(imidoyl)ketenes, bidentate aza- and oxa-dienes, which can react with dienophiles to form skeletally diverse products (angular tricyclic products or heterocyclic ensembles). Based on these features, we have developed an approach to two series of skeletally diverse 4H-1,3-oxazines (tetracyclic alkaloid-like 4H-1,3-oxazines and 5-heteryl-4H-1,3-oxazines) via a hetero-Diels-Alder reaction of 4-acyl-1H-pyrrole-2,3-diones fused at [e]-side with cyanamides. The products of these transformations are of interest for drug discovery, since compounds bearing 4H-1,3-oxazine moiety are extensively studied for inhibitory activities against anticancer targets.

An Oxazine-Based Fluorogenic Probe with Changeable π-Conjugation to Eliminate False-Positive Interference of Albumin and Its Application to Sensing Aminopeptidase†N.

Many fluorophores/probes suffer from the interference of albumin in biosystems. Herein, we propose an effective strategy to overcome this interference by virtue of both an albumin-insensitive fluorophore and its changeable π-conjugation, and demonstrate the strategy by designing an oxazine-based fluorogenic probe for aminopeptidase N (APN). The modification on the N atom in the oxazine fluorophore with alanine through a cleavable linker locks the resulting probe in a non-conjugated, colorless and non-fluorescent state, so the non-specific interaction of albumin produces no spectroscopic response. APN can selectively cleave the alanine moiety, restoring the large π-conjugation and strong fluorescence. The capability of the probe to eliminate the albumin influence has been demonstrated by imaging APN in different cell lines, and by quantitatively determining APN in human serum and mouse urine. The present strategy may be useful for developing more specific fluorogenic probes for other enzymes.

Novel pyrano 1,3 oxazine based ligand inhibits the epigenetic reader hBRD2 in glioblastoma.

Glioblastoma (GBM) is the most common primary brain malignancy, rarely amenable to treatment with a high recurrence rate. GBM are prone to develop resistance to the current repertoire of drugs, including the first-line chemotherapeutic agents with frequent recurrence, limiting therapeutic success. Recent clinical data has evidenced the BRD2 and BRD4 of the BET family proteins as the new druggable targets against GBM. In this relevance, we have discovered a compound (pyrano 1,3 oxazine derivative; NSC 328111; NS5) as an inhibitor of hBRD2 by the rational structure-based approach. The crystal structure of the complex, refined to 1.5 Šresolution, revealed that the NS5 ligand significantly binds to the N-terminal bromodomain (BD1) of BRD2 at the acetylated (Kac) histone binding site. The quantitative binding studies, by SPR and MST assay, indicate that NS5 binds to BD1 of BRD2 with a KD value of ∼1.3 µM. The cell-based assay, in the U87MG glioma cells, confirmed that the discovered compound NS5 significantly attenuated proliferation and migration. Furthermore, evaluation at the translational level established significant inhibition of BRD2 upon treatment with NS5. Hence, we propose that the novel lead compound NS5 has an inhibitory effect on BRD2 in glioblastoma.

Development of polymer-based nanoparticles for zileuton delivery to the lung: PMeOx and PMeOzi surface chemistry reduces interactions with mucins.

In this paper, two amphiphilic graft copolymers were synthesized by grafting polylactic acid (PLA) as hydrophobic chain and poly(2-methyl-2-oxazoline) (PMeOx) or poly(2-methyl-2-oxazine) (PMeOzi) as hydrophilic chain, respectively, to a backbone of α,ß-poly(N-2-hydroxyethyl)-D,L-aspartamide (PHEA). These original graft copolymers were used to prepare nanoparticles delivering Zileuton in inhalation therapy. Among various tested methods, direct nanoprecipitation proved to be the best technique to prepare nanoparticles with the smallest dimensions, the narrowest dimensional distribution and a spherical shape. To overcome the size limitations for administration by inhalation, the nano-into-micro strategy was applied, encapsulating the nanoparticles in water-soluble mannitol-based microparticles by spray-drying. This process has allowed to produce spherical microparticles with the proper size for optimal lung deposition, and, once in contact with fluids mimicking the lung district, able to dissolve and release non-aggregated nanoparticles, potentially able to spread through the mucus, releasing about 70% of the drug payload in 24 h.

Coumarin-Annulated Ferrocenyl 1,3-Oxazine Derivatives Possessing In Vitro Antimalarial and Antitrypanosomal Potency.

A tailored series of coumarin-based ferrocenyl 1,3-oxazine hybrid compounds was synthesized and investigated for potential antiparasitic activity, drawing inspiration from the established biological efficacy of the constituent chemical motifs. The structural identity of the synthesized compounds was confirmed by common spectroscopic techniques: NMR, HRMS and IR. Biological evaluation studies reveal that the compounds exhibit higher in vitro antiparasitic potency against the chemosensitive malarial strain (3D7 P. falciparum) over the investigated trypanosomiasis causal agent (T. b. brucei 427) with mostly single digit micromolar IC50 values. When read in tandem with the biological performance of previously reported structurally similar non-coumarin, phenyl derivatives (i.e., ferrocenyl 1,3-benzoxazines and α-aminocresols), structure-activity relationship analyses suggest that the presence of the coumarin nucleus is tolerated for biological activity though this may lead to reduced efficacy. Preliminary mechanistic studies with the most promising compound (11b) support hemozoin inhibition and DNA interaction as likely mechanistic modalities by which this class of compounds may act to produce plasmocidal and antitrypanosomal effects.

In Vitro Blood-Brain Barrier Permeability and Cytotoxicity of an Atorvastatin-Loaded Nanoformulation Against Glioblastoma in 2D and 3D Models.

Inhibitors of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase of the family of statins have been suggested as therapeutic options in various tumors. Atorvastatin is a statin with the potential to cross the blood-brain barrier; however, the concentrations necessary for a cytotoxic effect against cancer cells exceed the concentrations achievable via oral administration, which made the development of a novel atorvastatin formulation necessary. We characterized the drug loading and basic physicochemical characteristics of micellar atorvastatin formulations and tested their cytotoxicity against a panel of different glioblastoma cell lines. In addition, activity against tumor spheroids formed from mouse glioma and mouse cancer stem cells, respectively, was evaluated. Our results show good activity of atorvastatin against all tested cell lines. Interestingly, in the three-dimensional (3D) models, growth inhibition was more pronounced for the micellar formulation compared to free atorvastatin. Finally, atorvastatin penetration across a blood-brain barrier model obtained from human induced-pluripotent stem cells was evaluated. Our results suggest that the presented micelles may enable much higher serum concentrations than possible by oral administration; however, if transport across the blood-brain barrier is sufficient to reach the therapeutic atorvastatin concentration for the treatment of glioblastoma via intravenous administration remains unclear.

Ultra-High to Ultra-Low Drug-Loaded Micelles: Probing Host-Guest Interactions by Fluorescence Spectroscopy.

Polymer micelles are an attractive means to solubilize water insoluble compounds such as drugs. Drug loading, formulations stability and control over drug release are crucial factors for drug-loaded polymer micelles. The interactions between the polymeric host and the guest molecules are considered critical to control these factors but typically barely understood. Here, we compare two isomeric polymer micelles, one of which enables ultra-high curcumin loading exceeding 50 wt.%, while the other allows a drug loading of only 25 wt.%. In the low capacity micelles, steady-state fluorescence revealed a very unusual feature of curcumin fluorescence, a high energy emission at 510 nm. Time-resolved fluorescence upconversion showed that the fluorescence life time of the corresponding species is too short in the high-capacity micelles, preventing an observable emission in steady-state. Therefore, contrary to common perception, stronger interactions between host and guest can be detrimental to the drug loading in polymer micelles.

Functional Brush Poly(2-ethyl-2-oxazine)s: Synthesis by CROP and RAFT, Thermoresponsiveness and Grafting onto Iron Oxide Nanoparticles.

Brush polymers are highly functional polymeric materials combining the properties of different polymer classes and have found numerous applications, for example, in nanomedicine. Here, the synthesis of functional phosphonate-ester-bearing brush polymers based on poly(2-oxazine)s is reported through a combination of cationic ring-opening polymerization (CROP) of 2-ethyl-2-oxazine and reversible addition-fragmentation chain transfer (RAFT) polymerization. In this way, a small library of well-defined (D ≤ 1.17) poly(oligo(2-ethyl-2-oxazine) methacrylate) P(OEtOzMA)n brushes with tunable lower critical solution temperature (LCST) behavior and negligible cell toxicity is prepared. Upon deprotection, the phosphonic acid end-group of the P(OEtOzMA)n brush enables the successful grafting-onto iron oxide nanoparticles (IONPs). Colloidal stability of the particle suspension in combination with suitable magnetic resonance imaging (MRI) relaxivities demonstrates the potential of these particles for future applications as negative MRI contrast agents.

Three-component reaction of o-aminophenol (o-phenylenediamine), dialkyl acetylenedicarboxylate and 3-phenacylideneoxindolines.

The acid-promoted three-component reaction of o-aminophenol or 2-aminoethanol with dialkyl acetylenedicarboxylate and 3-phenacylideneoxindolines in refluxing acetonitrile afforded functionalized oxindolinyl-substituted benzo[b]pyrrolo[1,2-d][1,4]oxazine or pyrrolo-[2,1-c][1,4]oxazine derivatives in good yields. However, using o-phenylenediamine only resulted in oxindolinyl-substituted 3,4-dihydroquinoxaline derivatives.

Probing of local polarity in poly(methyl methacrylate) with the charge transfer transition in Nile red.

The permittivity of polymers and its spatial distribution play a crucial role in the behavior of thin films, such as those used, e.g., as sensor coatings. In an attempt to develop a conclusive approach to determine these quantities, the polarity of the model polymer poly(methyl methacrylate) (PMMA) in 600 nm thin films on a glass support was probed by the energy of the charge transfer transition in the oxazine dye Nile red (NR) at 25 °C. The absorption and fluorescence spectra of NR were observed to shift to the red with increasing solvent polarity, because of the intramolecular charge transfer character of the optical transition. New types of solvatochromic plots of emission frequency against absorption frequency and vice versa afforded the Onsager radius-free estimation of the ground and excited states dipole moment ratio. With this approach the values of these dipole moments of 11.97 D and 18.30-19.16 D, respectively, were obtained for NR. An effective local dielectric constant of 5.9-8.3 for PMMA thin films was calculated from the solvatochromic plot and the fluorescence maximum of NR observed in the PMMA films. The fluorescence band of NR in the rigid PMMA films shifted to the red by 130 cm-1 with increasing excitation wavelength from 470 to 540 nm, while in a series of liquids the position of the emission maximum of NR remained constant within same range of the excitation wavelength. It is concluded that the fluorescence spectrum of NR in PMMA undergoes inhomogeneous broadening due to different surroundings of NR molecules in the ground state and slow sub-glass transition (T g) relaxations in PMMA.

Diastereoselective synthesis of fused cyclopropyl-3-amino-2,4-oxazine ß-amyloid cleaving enzyme (BACE) inhibitors and their biological evaluation.

The diastereoselective synthesis and structure activity relationship (SAR) of a series of fused cyclopropyl-3-amino-2,4-oxazine (2-oxa-4-azabicyclo[4.1.0]hept-3-en-3-amine)-containing BACE inhibitors is described. Through these efforts compound 2 was identified as a potent (cell IC50 = 15 nM) BACE inhibitor with acceptable ADME properties. When tested in vivo, compound 2 demonstrated a significant reduction of brain and cerebral spinal fluid (CSF) Aß40 levels (46% and 66%, respectively) in a rat pharmacodynamic study and thus represents a suitable starting point for the further development of in vivo efficacious compounds for the treatment of Alzheimer's disease.