Amide Nitrogen Research Articles

Conformational Properties of Aromatic Amides Bearing Imidazole Ring and Acid-Induced Trans–Cis Amide Switching

Aromatic amides bearing secondary amide bond exist in trans conformation both in the crystal and in solution, whereas the conformation of the N-methylated derivatives is cis in the crystal and predominantly cis in various solvents. The cis conformational preference of N-alkylated benzanilide provides access to aromatic foldamers such as oligo(N-alkyl-p-benzamide)s, which adopt dynamic helical structures. Here, the conformational properties of imidazole-substituted amide in the crystal and in solution were examined. Imidazole-substituted amides 2a and 4a existed mainly in the cis conformation in solution. The ratio of the cis conformer of N-methyl-N-(1-methyl-1H-imidazol-4-yl)benzamide (4a) was smaller than that of N,1-dimethyl-N-phenyl-1H-imidazole-2-carboxamide (2a) or N-methylbenzanilide, but the introduction of a substituent strongly affected the conformer ratio. Compounds 6a and 7a bearing an electron-withdrawing group on the imidazole ring existed predominantly in trans form. On the other hand, the introduction of an electron-withdrawing group on the phenyl ring or a bulky substituent on the amide nitrogen of 4a increased the ratio of cis conformer. Further, the major conformer of N-alkylated N-imidazolylamides was switched from cis to trans by the addition of acid. These results suggest that imidazole-substituted amides might be applicable as conformational switches in aromatic foldamers to enable environment-dependent structural change.

The Application of Nitrogen Source in Regulating Lignin Biosynthesis, Storage Root Development and Yield of Sweet Potato

The understanding of the effects of nitrogen sources on lignin synthesis in sweet potato during storage root formation is limited. In this study, we investigated the effects of different nitrogen source on sweet potato storage root formation and development, as well as lignin synthesis in potential storage roots. The sweet potato cultivars Shangshu 19 and Jixu 23 were used in field experiments in 2019 and 2020. Three treatments were tested: (a) no nitrogen fertilizer application (control); (b) 60 kg hm−2 ammonium nitrogen; and (c) 60 kg hm−2 amide nitrogen. The results indicate that during sweet potato storage root formation, ammonium nitrogen significantly enhanced root activity compared to that of the control. The ammonium nitrogen treatment promoted IbEXP1 and inhibited Ibkn1 and Ibkn2 expression during the early stages of storage root formation, then increased gibberellic acid and decreased zeatin riboside content, enhanced phenylalanine ammonia lyase and peroxidase activities, and promoted lignin synthesis in potential storage roots. The opposite effects of ammonium nitrogen treatment on gene expression, hormone contents, and enzyme activity were observed in the late stages of storage root formation. Relative to the control, the ammonium nitrogen treatment significantly increased the number of storage roots during canopy closure. The ammonium nitrogen treatment produced the highest storage root yield and number of storage roots per plant. These results indicated that the ammonium nitrogen can inhibit root lignin synthesis, then promote storage root formation and increase the yield of sweet potato.

Preferential eradication of gram-negative bacteria using peptide surrogates: cisions & reflections

Short surrogates of the pentapeptide K-A-A-A-K, centered on Freidinger’s lactam, were applied to eradicate E.coli (Gram-negative bacteria) and S. Aureus (Gram-positive microbe). It was found that it was easier to eliminate the gram-positive bacteria, which was influenced by the N-methylation of the amide nitrogen of 30 →31 (Table). However, The N-methylated surrogates were more efficient in eradicating the E. coli than the S. Aureus samples. We were able (Figure 14) to show that one structural change could make a remarkable difference in the eradication (MIC) of the different bacteria

TOTAL NITROGEN DETERMINATION IN AMMONIACAL, AMIDIC AND NITRATE NITROGEN CONTAINING FERTILIZERS BY THE RANEY CATALYST METHOD

This paper presents the optimized conditions for the determination of total nitrogen in ammoniacal, amidic, and nitrate nitrogen containing fertilizers by the Raney catalyst method using a Buchi K-436 speed digester and a Buchi K-360 distillation unit.

Investigation of the μ and κ-opioid receptor activation by eight new synthetic opioids using the [35S]-GTPγS assay: U-47700, isopropyl U 47700, U-49900, U-47931E, N-methyl U-47931E, U-51754, U-48520 and U-48800

Since their first occurrence in 2008, a rapid increase of new psychoactive substances (NPS) on the recreational drug market has been observed. One class of NPS are synthetic opioids, which poses a health risk due to the high affinity and high potency of most of these compounds for the opioid receptors. Four opioid receptor subtypes are known, the mü-opioid (MOR), the delta-opioid (DOR), the kappa-opioid (KOR) and the nociceptin receptor, which are G protein-coupled receptors (GCPRs). MOR and DOR agonists often express mood-enhancing and euphoric properties. However, opioid overdoses can lead to respiratory depression and result in death. Nevertheless, for many NPS, including new synthetic opioids, data on toxicological and toxicokinetic properties are scarce. The aim of the present study was to investigate eight structurally closely related U-opioids (U-47700, isopropyl U-47700, U-49900, U-47931E, N-methyl U-47931E, U-48520, U-51754, and U-48800) for their potential of MOR and KOR activation, due to the relative lack of pharmacological data for the U-opioids. The [35S]-GTPγS assay, was used to study receptor activation and is based on the exchange of GDP with radiolabelled GTP. This exchange is one of the first events of the GPCR-signal cascade. For each receptor two respective and well-studied compounds were chosen as reference compounds: hydromorphone and fentanyl for MOR, and U-69593 and U-50488 for KOR. Owing to their close structural similarity of the investigated U-compounds, structure activity relationships have also been derived. The most prevalent compound of this set, U-47700, was also the most potent compound of the test set at MOR, with an EC50 value of 111 nM. However, the two MOR reference compounds hydromorphone and fentanyl had lower EC50 values of 6.75 nM and 24.9 nM, respectively, hence, being 16 and 4 times more potent than U-47700. At KOR, U-51754 was the most potent substance out of the test set, with an EC50 value of 120 nM. Nevertheless, the two U-opioids U-69593 and U-50488, which have been used as KOR reference compounds, were 4 and 5 times more potent than U-51754 at KOR, with EC50 of 29.3 nM and 24.8 nM, respectively. The studied compounds can be categorized into the U-47700 and U-50488 group. It has been previously reported that the compounds of the U-47700 group show higher receptor binding affinities for MOR and compounds of the U-50488 group for KOR, hence the presence or absence of the methylene group has an influence on the receptor binding affinity at MOR and KOR. In general, our results on the receptor activation of MOR and KOR are in good alignment with reported receptor binding affinities, confirming that the U-47700 group has a higher affinity and activity at MOR and the U-50488 group at KOR. The following structural features were advantageous for activating MOR: two chlorine substituents in 3,4-position at the aromatic ring, the absence of the methylene group between the amide group and the aromatic ring, a methyl group at the amide nitrogen, and/or a dimethylamine residue at the amine nitrogen of the cyclohexane ring. Further, the following structural features were beneficial for KOR activation: a methylene group between the amide group and the aromatic ring, a pyrrolidine residue at the amine nitrogen of the cyclohexane ring, a methyl group at the amide nitrogen, and/or chlorine substitution in 3,4-position at the aromatic ring. While synthetic opioids are often considered more potent than conventional opioids, there are some occurring on the NPS market, which are less potent. Hence, performing these studies is important to identify the effect of structural alterations on the receptor activity and in understanding the potential risk to the public health.

Identification of the novel synthetic cannabinoid-type new psychoactive substance, CH-PIACA, in seized material

Synthetic cannabinoids (SCs) remain the largest class of new psychoactive substances (NPS) according to the European Monitoring Centre for Drugs and Drug Addiction (EMDCDDA) and while the number of new analogues that are reported for the first time each year declines, SCs are reported the most compared to other NPS classes. This decline can be seen as a result of legislative changes by different jurisdictions which have sometimes transitioned to a more generalized approach when controlling substances by defining common structural scaffolds rather than explicit structures. While the consequences of such legislative changes have been expected over the years, the introduction of so called “class-wide” bans has put further pressure on clandestine laboratories to synthesize compounds which are out of the scope of the legislation and thus these compounds are initially harder to detect and/or identify in forensic chemistry or medico-legal contexts in the absence of analytical data. Recently, a synthetic cannabinoid with an indole-3-acetamide core-linker scaffold, AD-18 (i.e. ADB-FUBIATA or ADB-FUBIACA), was reported for the first time in China in 2021. Here, an additional cannabinoid with the indole-3-acetamide scaffold, N-cyclohexyl-2-(1-pentyl-1H-indol-3-yl)acetamide (tentatively CH-PIACA) was structurally characterized using gas chromatography – mass spectrometry (GC-MS), liquid chromatography – high-resolution mass spectrometry (LC-HRMS) and nuclear magnetic resonance (NMR) spectroscopy. A beige powder in a zip-lock bag was seized by The Danish Customs Agency and subsampled by combining three aliquots of approximately 1 g after homogenization with a mortar and pestle. Sample solutions for GC-MS and UHPLC-QTOF-MS were prepared by dissolving the material in methanol and 25% methanol + 1% formic acid, respectively. For NMR, 3 mg of the powder was dissolved in DMSO-d6 and filtered into an NMR tube. Routine GC-MS analysis of the seized material yielded a single major peak at 22.156 min with a molecular ion at m/z 326.3 and fragment ions at m/z 200, 144 and 130 in the electron ionization mass spectrum (EI-MS). In addition, a major component was observed at 11.91 min in the UHPLC-QTOF-MS screening which had a precursor ion at m/z 327.2450 corresponding to a compound with a molecular formula of C21H30N2O. Similar product ions were observed in the electrospray ionization tandem MS (ESI-MS/MS) spectrum with m/z 245.1644, 200.1441, 144.0808, 130.0651, 100.1120 and 83.0853. NMR spectroscopy with 1H, 13 C, COSY, HMBC and HSQC indicated that the structure was likely to be a substituted indole with a pentyl chain and N-cyclohexylacetamide at the 1- and 3 positions. This structure was corroborated by the EI-MS and ESI-MS/MS data with the neutral loss of N-cyclohexyl-carboxamide (C7H13NO, 127.0997 Da) via cleavage of the bond between the α and β carbons forming m/z 200.1441, while the product ion at m/z 245.1644 corresponded to the loss of cyclohexene from the amide nitrogen. The loss of the N-cyclohexyl-carboxamide was also followed by the loss of the pentyl chain from the nitrogen of the indole ring to yield m/z 130.0651, while m/z 100.1120 corresponded to the cyclohexylammonium cation. The product ion at m/z 144.0808 was proposed to be due to the loss of both the N-cyclohexyl-carboxamide and cleavage of the pentyl chain to liberate 1-butene. A new SC with the indole-3-acetamide scaffold was identified in a seized material in Denmark and characterized using GC-MS, UHPLC-QTOF-MS and NMR spectroscopy. This marks the second SC with this scaffold that has been reported with further analogues anticipated to emerge in the near future.

Peptide backbone-copper ring structure: A molecular insight into copper-induced amyloid toxicity

Copper ions can promote amyloid diseases that are associated with amyloid peptides, such as type 2 diabetes (T2D), Alzheimer’s disease (AD), Parkinson’s disease (PD), and amyotrophic lateral sclerosis (ALS). However, the underlying molecular mechanism remains obscure. Here we present that Cu2+ is able to specifically bind to the backbone of T2D-related human islet amyloid polypeptide (hIAPP) by forming a ring structure, which causes the reduction of Cu2+ to Cu+ to produce reactive oxygen species (ROS) and the modulation of hIAPP aggregation. Nuclear magnetic resonance spectroscopy showed that Cu2+ bound to the backbone of a turn region, His18–Ser21, which is critical for hIAPP aggregation. Ab initio calculations and x-ray absorption fine structure analyses revealed that Cu2+ simultaneously bound with both the amide nitrogen and carbonyl oxygen on the peptide backbone, resulting in a ring structure, and causing the reduction of Cu2+ to Cu+ to form a hIAPP-Cu+ complex. 2′,7′-dichlorodihydrofluorescin diacetate fluorescence measurements further indicated that this complex led to enhanced ROS levels in rat insulinoma cells. Additionally, thioflavin T fluorescence and atomic force microscopy measurements denoted that the backbone-Cu ring structure largely modulated hIAPP aggregation, including the inhibition of hIAPP fibrillation and the promotion of peptide oligomerization. These findings shed new light on the molecular mechanism of Cu2+-induced amyloid toxicity involving both the enhancement of ROS and the modulation of hIAPP aggregation.

Bicyclostreptins are radical SAM enzyme-modified peptides with unique cyclization motifs.

Microbial natural products comprise diverse architectures that are generated by equally diverse biosynthetic strategies. In peptide natural products, amino acid sidechains are frequently used as sites of modification to generate macrocyclic motifs. Backbone amide groups, among the most stable of biological moieties, are rarely used for this purpose. Here we report the discovery and biosynthesis of bicyclostreptins-peptide natural products from Streptococcus spp. with an unprecedented structural motif consisting of a macrocyclic β-ether and a heterocyclic sp3-sp3 linkage between a backbone amide nitrogen and an adjacent α-carbon. Both reactions are installed, in that order, by two radical S-adenosylmethionine (RaS) metalloenzymes. Bicyclostreptins are produced at nM concentrations and are potent growth regulation agents in Streptococcus thermophilus. Our results add a distinct and unusual chemotype to the growing family of ribosomal peptide natural products, expand the already impressive catalytic scope of RaS enzymes, and provide avenues for further biological studies in human-associated streptococci.

QSAR Evaluations to Unravel the Structural Features in Lysine-Specific Histone Demethylase 1A Inhibitors for Novel Anticancer Lead Development Supported by Molecular Docking, MD Simulation and MMGBSA.

Using 84 structurally diverse and experimentally validated LSD1/KDM1A inhibitors, quantitative structure–activity relationship (QSAR) models were built by OECD requirements. In the QSAR analysis, certainly significant and understated pharmacophoric features were identified as critical for LSD1 inhibition, such as a ring Carbon atom with exactly six bonds from a Nitrogen atom, partial charges of lipophilic atoms within eight bonds from a ring Sulphur atom, a non-ring Oxygen atom exactly nine bonds from the amide Nitrogen, etc. The genetic algorithm–multi-linear regression (GA-MLR) and double cross-validation criteria were used to create robust QSAR models with high predictability. In this study, two QSAR models were developed, with fitting parameters like R2 = 0.83–0.81, F = 61.22–67.96, internal validation parameters such as Q2LOO = 0.79–0.77, Q2LMO = 0.78–0.76, CCCcv = 0.89–0.88, and external validation parameters such as, R2ext = 0.82 and CCCex = 0.90. In terms of mechanistic interpretation and statistical analysis, both QSAR models are well-balanced. Furthermore, utilizing the pharmacophoric features revealed by QSAR modelling, molecular docking experiments corroborated with the most active compound’s binding to the LSD1 receptor. The docking results are then refined using Molecular dynamic simulation and MMGBSA analysis. As a consequence, the findings of the study can be used to produce LSD1/KDM1A inhibitors as anticancer leads.

The ion-neutral complex-mediated fragmentation reaction in electrospray ionization tandem mass spectrometric analysis of N-phenyl-3-(phenylthio)propanamides.

Amides are the fundamental units of both peptides and proteins, and also important functional groups of medical chemicals. Investigation of the fragmentation mechanism of amides in the gas phase is scientifically important for structural analysis. However, understanding of this problem is still elusive. Protonated N-phenyl-3-(phenylthio)propanamide and its derivatives were investigated using positive ion tandem mass spectrometry (ESI-MS/MS) with an LCQ mass spectrometer. Accurate mass analysis was conducted with a micrOTOF-QII mass spectrometer. Density functional theory (DFT) calculations using the Gaussian 03 program and deuterium-labelling (D-labelling) experiments were performed to verify the proposed fragmentation mechanism. Interpretation of the fragment ions in the collision-induced dissociation mass spectra showed that the ionizing proton in the protonated ion transferred from the most thermodynamically favorable carbonyl oxygen to the dissociative protonation site at amide nitrogen or sulfur atom upon collisional activation. The dissociation of the amide or the C-S bond was induced by such proton transfer. An ion-neutral complex (INC) was generated via the dissociation of the amide bond. In the INC, it was observed that the carbocation of the ionic part attacked the ortho phenyl carbon atom adjacent to the sulfur atom, and proton transfer from the carbon atom to the nitrogen atom led to the formation of protonated aniline. The fragmentation mechanism of protonated N-phenyl-3-(phenylthio)propanamide and its derivatives was proposed and elucidated. All the compounds studied showed similar fragmentation pathways, and the competitive formation of two ions, RC9 H9 OS+ and C6 H8 N+ , was observed. The generation of protonated aniline is mediated by INC in ESI-MS/MS.

Synthesis, IR characterization and antioxidant capacity of Cu(II) complexes with amino acids and melatonin

In this paper, the reactions of anhydrous copper(II) chloride in methanolic solution with alanine, glycine, histidine, L-tryptophan, and melatonin were investigated and the resulting products were characterized by FTIR spectroscopy. Based on FTIR characterization, it was shown that these reaction conditions result in the formation of Cu(II) complexes with glycine and alanine, which are more complex structures than bis(glycinato) - and bis(alaninato) copper(II) complexes. Analysis of the FTIR spectrum of the histidine complex shows the participation of several groups in coordination at the Cu(II) center. The complex prepared with melatonin shows unusual changes in the spectral region of the amidic nitrogen bonds. The latter observation is very significant for very few known metal complexes of melatonin, while the synthesis of most of them is an experimentally demanding process with simultaneous control of several parameters. The antioxidant capacity of the synthesized complexes was examined, with the CEAC range from 121.6 to 734.4 µM. The lowest values of antioxidant capacity were recorded for the copper complex with tryptophan, while the highest values were recorded for the copper complex with alanine. A high antioxidant capacity of the copper complex with melatonin (673.8 µM) was also observed.

Synthesis, IR characterization and antioxidant capacity of Cu(II) complexes with amino acids and melatonin

In this paper, the reactions of anhydrous copper(II) chloride in methanolic solution with alanine, glycine, histidine, L-tryptophan, and melatonin were investigated and the resulting products were characterized by FTIR spectroscopy. Based on FTIR characterization, it was shown that these reaction conditions result in the formation of Cu(II) complexes with glycine and alanine, which are more complex structures than bis(glycinato) - and bis(alaninato) copper(II) complexes. Analysis of the FTIR spectrum of the histidine complex shows the participation of several groups in coordination at the Cu(II) center. The complex prepared with melatonin shows unusual changes in the spectral region of the amidic nitrogen bonds. The latter observation is very significant for very few known metal complexes of melatonin, while the synthesis of most of them is an experimentally demanding process with simultaneous control of several parameters. The antioxidant capacity of the synthesized complexes was examined, with the CEAC range from 121.6 to 734.4 µM. The lowest values of antioxidant capacity were recorded for the copper complex with tryptophan, while the highest values were recorded for the copper complex with alanine. A high antioxidant capacity of the copper complex with melatonin (673.8 µM) was also observed.

Ammonium stress promotes the conversion to organic nitrogen and reduces nitrogen loss based on restructuring of bacterial communities during sludge composting

This study aimed to clarify the conversion relationship between organic and inorganic nitrogen. The NH4Cl was used to enhance the inorganic nitrogen content. The key role of bacterial conversion of ammonium to organic nitrogen under ammonium stress was explored. Studies had shown that ammonium stress increased the amide nitrogen and bioavailable nitrogen content by 36.95% and 32.25%, respectively. Network and regression analyses showed that the microbial community structure was restructured by high ammonium and more bacteria were involved in the conversion of inorganic nitrogen to organic nitrogen(i.e., amide nitrogen, unknown nitrogen). Variation partition analysis and structural equation model showed that the bacterial community was the main contributor to organic nitrogen production(up to 67.4%), which reduced the nitrogen loss by 6.03%. These findings shed light on the poorly understood interaction between inorganic and organic nitrogen by clarifying the role of core bacterial communities in nitrogen conversion.

Effect of N-Methylation on Dopamine Surface Chemistry.

Dopamine (DA) surface chemistry has received significant attention because of its applicability in a wide range of research fields and the ability to graft functional molecules onto numerous solid surfaces. Various DA derivatives have been newly synthesized to identify key factors affecting the coating efficiency and to advance the coating system development. The oxidation of catechol into quinone followed by internal cyclization via the nucleophilic attack of primary amine is crucial for DA-based surface coating. Thus, it is expected that the amine group's nucleophilicity control directly affects the coating efficiency. However, it has not been systematically investigated, and most studies have been conducted with the focus on the transformation of amines into amides, despite such approaches decreasing the coating efficiency; the nitrogen in amides is less nucleophilic than that in free amines. In this study, we investigated the effect of N-alkylation on dopamine surface chemistry. N,N-Dimethyldopamine (DMDA) was newly synthesized, and the coating efficiency was systematically compared with DA and N-methyldopamine (MDA). DA N-monomethylation improved the coating rate by increasing the nitrogen nucleophilicity, whereas N,N-dimethylation dramatically decreased the DA surface coating property. In addition, MDA remained capable of universal surface coating and secondary reactions using the surface catechols. This study provides opportunities for developing coating materials with advanced functions and an improved coating rate.

Intramolecular cyclization of 15-carboxy-13-amide derivatives of chlorin e6 under the action of 2-Chloro-1-methylpyridinium iodide

We have shown the possibility of intramolecular cyclization with the participation of the carboxyl group at position 15 of the chlorin macrocycle with a primary or secondary amide group at position 13 through the formation of an imide bond under the action of 2-Chloro-1-methylpyridinium iodide; the imide bond can be used to form a seven-membered exocycle. Using this reaction, we synthesized a number of cycloimide derivatives of chlorophyll a. The proposed synthetic route can be carried out if the substituent at the amide nitrogen atom has a hydroxyl, dimethylaminomethyl or vinyl group, which opens up possibilities for further chemical modification of the obtained derivatives.

Convenient synthesis and evaluation of antioxidant property of functionalized spiro indolinone-dihydroquinazolinones

In the present study an efficient synthetic pathway has been developed for the library synthesis of diversely functionalized spiro indolinone-dihydroquinazolinones from easily available isatins and 2-aminobenzamides by acid catalyzed condensation at 70 °C in ethanol. The outcome of the ROS scavenging analysis over the synthesized spiro compounds displays significant variation in their respective antioxidant properties with the change of substituent at different positions. Noteworthy, the spiro compounds substituted with phenyl ring at nitrogen atom either in indolinone or dihydroquinazolinone moiety show a promising defensive capability towards OH (≈ 83% at 80 µM against control) and O2− (≈ 78% at 20 µM against epinephrine auto-oxidation). Almost every single spiro compound exhibits substantial reducing power, especially compounds containing dihydroquinazolinone moiety substituted with aromatic ring at amide nitrogen (N-3) exhibit remarkable reducing property. IC50 and TEAC (Trolox Equivalent Antioxidant Capacity) values reveal that the spiro compound substituted with phenyl ring to indolic nitrogen (N-1) possesses significant antioxidant potency (IC50 ≈ 22.67 µM) and substantial OH scavenging ability (TEAC ≈ 0.82) comparable to highly potent antioxidant Trolox.

Strategies to Control the Cis-Trans Isomerization of Peptoid Amide Bonds.

Peptoids are oligomers of N-substituted glycine units. They structurally resemble peptides but, unlike natural peptides, the side chains of peptoids are present on the amide nitrogen atoms instead of the α-carbons. The N-substitution improves cell-permeability of peptoids and enhance their proteolytic stability over natural peptides. Therefore, peptoids are ideal peptidomimetic candidates for drug discovery, especially for intracellular targets. Unfortunately, most peptoid ligands discovered so far possess moderate affinity towards their biological targets. The moderate affinity of peptoids for biomacromolecules is linked to their conformational flexibility, which causes substantial entropic loss during the peptoid-biomacromolecule binding process. The conformational flexibility of peptoids is caused by the lack of backbone chirality, absence of hydrogen bond donors (NH) in their backbone to form CO⋅⋅⋅HN hydrogen bonds and the facile cis-trans isomerization of their tertiary amide bonds. In recent years, many investigators have shown that the incorporation of specific side chains with unique steric and stereoelectronic features can favourably shift the cis-trans equilibria of peptoids towards one of the two isomeric forms. Such strategies are helpful to design homogenous peptoid oligomers having well defined secondary structures. Herein, we discuss the strategies developed over the years to control the cis-trans isomerization of peptoid amide bonds.

Investigation of the μ- and κ-opioid receptor activation by eight new synthetic opioids using the [35 S]-GTPγS assay: U-47700, isopropyl U-47700, U-49900, U-47931E, N-methyl U-47931E, U-51754, U-48520, and U-48800.

In 2009, new synthetic opioids appeared on the new psychoactive substances market. This class of new psychoactive substances generally poses a health risk due to the high affinity and potency of most of these compounds for the opioid receptors. It is known that overdoses can lead to respiratory depression and result in death. However, for many new synthetic opioids, data on toxicological and toxicokinetic properties are scarce. In the present study, eight U-opioids were investigated for their structure activity relationships at the μ- and κ-opioid receptors using a [35 S]-GTPγS assay. The potencies of the investigated U-opioids were lower than those of the reference compounds (μ-opioid receptor: hydromorphone, fentanyl; κ-opioid receptor: U-69593, U-50488). At the μ-opioid receptor, U-47700 showed the highest potency with an EC50 value of 111 nM, and at the κ-opioid receptor, U-51754 was found to be the most potent compound with an EC50 value of 120 nM. The following structural features were advantageous for activating the μ-opioid receptor: two chlorine substituents in 3,4-position at the aromatic ring, the absence of the methylene group between the amide group and the aromatic ring, a methyl group at the amide nitrogen, and/or a dimethylamine residue at the amine nitrogen of the cyclohexane ring. Further, the following structural features were beneficial for κ-opioid receptor activation: a methylene group between the amide group and the aromatic ring, a pyrrolidine residue at the amine nitrogen of the cyclohexane ring, a methyl group at the amide nitrogen, and/or a chlorine substitution at the 3,4-position of the aromatic ring.

Efficient Synthesis and Biological Evaluation of 6-Trifluoroethoxy Functionalized Pteridine Derivatives as EGFR Inhibitors.

Pteridine-based scaffolds have been widely prevalent in pharmaceuticals, such as kinase inhibitors targeting EGFR, FLT3 and PI3K/mTOR which are attractive targets for the anticancer therapy. This work aimed at designing and synthesizing 6-2,2,2-trifluoroethoxy functionalized pteridine-based derivatives for investigation of their anti-cancer activities as EGFR inhibitor. Pteridine-based derivatives were synthesized in 6 steps involving amination, bromination, cyclization, alkoxylation, chlorination and coupling reactions. Cellular anti-proliferative activities and inhibition activities on EGFR signaling of these pteridine derivatives in vitro were determined by the MTT assay and western blot analysis, respectively. Molecular docking simulation studies were carried out by the crystallographic structure of the erlotinib/EGFR kinase domain [Protein Data Bank (PDB) code: 1M17]. The compound 7m, with IC50 values of 27.40 μM on A549 cell line, exhibited comparable anti-proliferative activity relative to the positive control. Besides, western blots showed its obvious down-regulation of p-EGFR and p-ERK expression at 0.8 μM. The molecular docking model displayed a hydrogen bond between Met-769 amide nitrogen and N-1 in pteridine motif of 7m which lied at the ATP binding site of EGFR kinase domain. The inhibition of 7m on cellular growth was comparable to that of the positive control. The inhibitory activities of 7m on EGFR phosphorylation and ERK phosphorylation in A549 cell line were relatively superior to that of the positive control. Both results suggested that the antiproliferative activity of 7m against A549 cell line was caused by inhibition of EGFR signaling pathway, providing a new perspective for the modification of pteridine-based derivatives as EGFR inhibitor.

Effect of heparin drug loading on biodegradable polycaprolactone–iron pentacarbonyl powder blend stents fabricated by solvent cast 3D printing

PurposeThe purpose of this paper is to fabricate pre-existing geometries of the stents using solvent cast 3D printing (SC3P) and encapsulation of each stent with heparin drug by using aminolysis reaction.Design/methodology/approachThe iron pentacarbonyl powder and poly-ɛ-caprolactone blend (PCIP) were used to print stent designs of Art18z, Palmaz-Schatz and Abbott Bvs1.1. The properties of antithrombosis, anticoagulation and blood compatibility were introduced in the stents by conjugation of heparin drug via the aminolysis process. The aminolysis process was confirmed by energy dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy due to presence of amide group and nitrogen peak in the respective analysis. Biological studies were performed to depict the cell viability, hemocompatibility and antithrombotic properties. Besides, mechanical behaviors were analyzed to study the behavior of the stents under radial compression load and bending load.FindingsThe amount of heparin immobilized on the Art18z, Palmaz-Schatz and Abbott Bvs1.1 stents were 255 ± 27, 222 ± 30 and 212 ± 13 µg, respectively. The cell viability studies using L929 fibroblast cells confirmed the cytocompatibility of the stents. The heparinized SC3P printed stents displayed excellent thrombo-resistance, anticoagulation properties and hemocompatibility as confirmed by blood coagulation analysis, platelet adhesion test and hemolysis analysis. Besides, mechanical behavior was found in context of the real-life stents. All these assessments confirmed that the developed stents have the potential to be used in the real environment of coronary arteries.Originality/valueVarious customized shaped biodegradable stents were fabricated using 3D printing technique and encapsulated with heparin drug using aminolysis process.