Spectroscopic, DFT, and XRD Studies of Hydrogen Bonds in N-Unsubstituted 2-Aminobenzamides

Curcumin loaded waste biomass resourced cellulosic nanofiber cloth as a potential scaffold for regenerative medicine: An in-vitro assessment

This article demonstrates the development of nanofibrous cloths by electrospinning of renewable materials, i.e., curcumin-loaded 90% cellulose acetate (CA)/10% poly(ε-caprolactone) (PCL), for applications in regenerative medicine. The CA is derived from the biomass waste of the oil palm plantation (empty fruit bunch). The nanofiber scaffolds are characterized for the fiber morphology, microstructure, thermal properties, and wettability. The optimized smooth and bead-free electrospun fiber cloth contains 90% CA and 10% PCL in two curcumin compositions (0.5 and 1 wt%). The role of curcumin is shown to be two-fold: the first is its function as a drug and the second is its role in lowering the water contact angle and increasing the hydrophilicity. The hydrophilicity enhancements are related to the hydrogen bonding between the components. The enhanced hydrophilicity contributed to improve the swelling behavior of the scaffolds; the CA/PCL/Cur (0.5%) and the CA/PCL/Cur (1.0%) showed swelling of ~700 and 950%, respectively, in phosphate-buffered saline (PBS). The drug-release studies revealed the highest cumulative drug release of 60% and 78% for CA/PCL/Cur (0.5%) and CA/PCL/Cur (1.0%) nanofibers, respectively. The in-vitro studies showed that CA/PCL/Cur (0.5 wt%) and CA/PCL/Cur (1.0 wt%) nanofiber scaffolds facilitate a higher proliferation and expression of actin in fibroblasts than those scaffolds without curcumin for wound healing applications.

In Vitro Enzymatic and Kinetic Studies, and In Silico Drug-Receptor Interactions, and Drug-Like Profiling of the 5-Styrylbenzamide Derivatives as Potential Cholinesterase and β-Secretase Inhibitors with Antioxidant Properties

The 5-(styryl)anthranilamides were transformed into the corresponding 5-styryl-2-(p-tolylsulfonamido)benzamide derivatives. These 5-styrylbenzamide derivatives were evaluated through enzymatic assays in vitro for their capability to inhibit acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and β-secretase (BACE-1) activities as well as for antioxidant potential. An in vitro cell-based antioxidant activity assay involving lipopolysaccharides (LPS)-induced reactive oxygen species (ROS) production revealed that compounds 2a and 3b have the capability of scavenging free radicals. The potential of the most active compound, 5-styrylbenzamide (2a), to bind copper (II) or zinc (II) ions has also been evaluated spectrophotometrically. Kinetic studies of the most active derivatives from each series against the AChE, BChE, and β-secretase activities have been performed. The experimental results are complemented with molecular docking studies into the active sites of these enzymes to predict the hypothetical protein–ligand binding modes. Their drug likeness properties have also been predicted.

Spectroscopic, X-ray Diffraction and Density Functional Theory Study of Intra- and Intermolecular Hydrogen Bonds in Ortho-(4-tolylsulfonamido)benzamides

The conformations of the title compounds were determined in solution (NMR and UV-Vis spectroscopy) and in the solid state (FT-IR and XRD), complemented with density functional theory (DFT) in the gas phase. The nonequivalence of the amide protons of these compounds due to the hindered rotation of the C(O)–NH₂ single bond resulted in two distinct resonances of different chemical shift values in the aromatic region of their ¹H-NMR spectra. Intramolecular hydrogen bonding interactions between the carbonyl oxygen and the sulfonamide hydrogen atom were observed in the solution phase and solid state. XRD confirmed the ability of the amide moiety of this class of compounds to function as a hydrogen bond acceptor to form a six-membered hydrogen bonded ring and a donor simultaneously to form intermolecular hydrogen bonded complexes of the type N–H···O=S. The distorted tetrahedral geometry of the sulfur atom resulted in a deviation of the sulfonamide moiety from co-planarity of the anthranilamide scaffold, and this geometry enabled oxygen atoms to form hydrogen bonds in higher dimensions.

Crystal structure of 1-(4-chloro-2-hydroxy-5-iodophenyl)ethan-1-one, C8H6ClIO2

C8H6ClIO2, orthorhombic, Pbcn (no. 60), a = 13.3204(7) Å, b = 7.2517(4) Å, c = 18.5627(9) Å, V = 1793.07(16) Å3, Z = 8, Rgt(F) = 0.0195, wRref(F2) = 0.0483, T = 173 K.

Structural and Conformational Studies on Carboxamides of 5,6-Diaminouracils-Precursors of Biologically Active Xanthine Derivatives

8-Arylethynylxanthine derivatives are potent, selective adenosine A_2A receptor antagonists, which represent (potential) therapeutics for Parkinson's disease, Alzheimer's dementia, and the immunotherapy of cancer. 6-Amino-5-amidouracil derivatives are important precursors for the synthesis of such xanthines. We noticed an unexpected duplication of NMR signals in many of these uracil derivatives. Here, we present a detailed analytical study of structurally diverse 6-amino-5-carboxamidouracils employing dynamic and two-dimensional NMR spectroscopy, density functional theory calculations, and X-ray analysis to explain the unexpected properties of these valuable drug intermediates.

The interplay and strength of the π⋯HF, C⋯HF, F⋯HF and F⋯HC hydrogen bonds upon the formation of multimolecular complexes based on C2H2⋯HF and C2H4⋯HF small dimers

The conception of this theoretical research was idealized aiming to unveil the intermolecular structures of complexes formed by acetylene or ethylene and hydrofluoric acid. At light of computational calculations by using the B3LYP/6-311++G(d,p) method, the geometries of the C₂H₂⋯(HF), C₂H₂⋯2(HF), C₂H₂⋯4(HF), C₂H₄⋯(HF), C₂H₄⋯2(HF) and C₂H₄⋯4(HF) hydrogen-bonded complexes were fully optimized. Moreover, the Post-Hartree-Fock calculations MP2/6-311++G(d,p), MP2/aug-cc-pVTZ, MP4(SDQ)/6-311++G(d,p) and CCSD/6-311++G(d,p) also were also used. The infrared spectra were analyzed in order to identify the new vibrational modes and frequencies of the proton donors shifted to red region. Through the modeling of charge-fluxes on the basis of the Quantum Theory of Atoms In Molecules (QTAIM) and, by contradicting the expectation of the hydrofluorination mechanisms of acetylene or ethylene, C⋯HF was recognized as a new type of hydrogen bond instead of the already well known π⋯H. The calculations of the Natural Bonding Orbital (NBO) and Charges derived from the Electrostatic Potential Grid-based (ChElPG) were also applied to interpret the shifting frequencies as well as measuring of the punctual charge-transfer after the formation of the complexes. Finally, the determination of the stabilization energy was carried out through the arguments of the Fock matrix in NBO basis and through the supermolecule approach. Also it is worthwhile to notice that some algebraic formulations were used for determining the electronic cooperative effect (CE).

Physico-Mechanical, Morphological Properties of Polyvinyl Alcohol/Palm Kernel Shell/Coconut Kernel Shell Elastomeric Polymer Nanocomposites

In this study, the physico-mechanical and morphological properties of polyvinyl alcohol/palm kernel shell/coconut kernel shell elastomeric polymer nanocomposites (PVA/PKS/CKS EPNCs) were investigated. PVA/PKS/CKS EPNCs were prepared via solution casting method and the properties of the elastomeric polymer nanocomposites were characterized through Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), tensile testing and moisture absorption test. Test results showed that increasing the PVA content increased the mechanical properties of elastomeric polymer nanocomposites as well as provided better surface morphology. However, beyond certain percentage of PVA content, the moisture absorption increased too. Therefore, 55wt% of PVA/PKS/CKS EPNCs was chosen as the best elastomeric polymer nanocomposites as it had the best overall properties from the aspect of physico-mechanical, morphological and moisture absorption.

Theoretical Investigation of the Formation Mechanism of NH₃ and HCN during Pyrrole Pyrolysis: The Effect of H₂O

Coal is a major contributor to the global emission of nitrogen oxides (NO_x). The NO_x formation during coal utilization typically derives from the thermal decomposition of N-containing compounds (e.g., pyrrolic groups). NH₃ and HCN are common precursors of NO_x from the decomposition of N-containing compounds. The existence of H₂O has significant influences on the pyrrole decomposition and NO_x formation. In this study, the effects of H₂O on pyrrole pyrolysis to form NO_x precursors HCN and NH₃ are investigated using the density functional theory (DFT) method. The calculation results indicate that the presence of H₂O can lead to the formation of both NH₃ and HCN during pyrrole pyrolysis, while only HCN is formed in the absence of H₂O. The initial interaction between pyrrole and H₂O determines the N products. NH₃ will be formed when H₂O attacks the C₂ position of pyrrole with its hydroxyl group. On the contrary, HCN will be generated instead of NH₃ when H₂O attacks the C₃ position of pyrrole with its hydroxyl group. In addition, the DFT calculations clearly indicate that the formation of NH₃ will be promoted by H₂O, whereas the formation of HCN is inhibited.