Search Results (1,128)

In recent years, extensive research has focused on cannabidiol (CBD), a well-studied non-psychoactive component of the plant-derived cannabinoids. CBD has shown significant therapeutic potential for treating various diseases and disorders, including antioxidants and anti-inflammatory effects. Due to the promising therapeutic effect of CBD in a wide variety of diseases, synthetic derivatization of this compound has attracted the attention of drug discovery in both industry and academia. In the current research, we focused on the derivatization of CBD by introducing Schiff base moieties, particularly (thio)-semicarbazide and aminoguanidine motifs, at the 3-position of the olivetolic ring. We have designed, synthesized, and characterized new derivatives based on CBD’s framework, specifically aminoguanylhydrazone- and (thio)-semicarbazones-CBD-aldehyde compounds. Their antioxidant potential was assessed using FRAP and DPPH assays, alongside an evaluation of their effect on LDL oxidation induced by Cu²⁺ and AAPH. Our findings suggest that incorporating the thiosemicarbazide motif into the CBD framework produces a potent antioxidant, warranting further investigation. Full article

A curious and noticeable structural feature in Schiff bases from 2-aminoaldoses is the fact that imino tautomers arranged equatorially in the most stable ring conformation exhibit a counterintuitive reverse anomeric effect (RAE) in the mutarotational equilibrium, i.e., the most stable and abundant anomer is the equatorial one (β). As shown by our very recent research, this effect arises from the total or partial inhibition of the exo-anomeric effect due to the presence of an intramolecular hydrogen bond between the anomeric hydroxyl and the iminic nitrogen in the axial anomer (α). When the Schiff base adopts either an enamine structure or the imino group is protonated, the exo-anomeric effect is restored, and the axial α-anomer becomes the most stable species. Although the intramolecular H-bonding should appropriately be interpreted as a genuine stereoelectronic effect, the magnitude of the RAE could be affected by other structural parameters. Herein and through a comprehensive analysis of benzylidene, cinnamylidene, naphthalene, phenanthrene, and anthracene aldehydes, we show the robustness of the RAE effect, which is similar in extent to simple aldehydes screened so far, irrespective of the size and/or hydrophobicity of the substituent at the nitrogen atom. Full article

This paper reports the synthesis and structural characterization of a novel azide-bridged polymeric manganese (III) Schiff base complex, using 2-((allylimino)methyl)-6-ethoxyphenol as a ligand. The crystal structure of the synthesized compound, elucidated by single-crystal X-ray diffraction analysis, indicates that it crystallizes in the monoclinic space group P2₁/c. The complex is found to display an octahedral geometry in which the central manganese Mn(III) coordinates with two bidentate donor Schiff base ligands via oxygen and nitrogen atoms. In addition, the metallic centers are linked together to form a one-dimensional chain bridged by end-to-end azide ligands. To offer a more thorough characterization of the synthesized compound, the study incorporates experimental data from FT-IR, UV-Vis, and cyclic voltammetry, alongside computational results from Hirshfeld surface analysis and DFT calculations conducted for both the ligand and complex. The computational analyses provided valuable insights into the intrachain and interchain interactions within the crystal structure, clarified the conformational characteristics of the isolated ligand molecule, and aided in the interpretation of the experimental IR spectra. Furthermore, an assessment of the compound’s drug-like properties was conducted using activity spectra for substances (PASS) predictions, revealing potential pharmacological activities. Full article

Several novel copper (II) complexes of reduced Schiff bases containing fluoride substituents were prepared and structurally characterized by single-crystal X-ray diffraction. The complexes exhibited diverse structures, with the central atom in distorted tetrahedral geometry. The biological effects of the products were evaluated, specifically their cytotoxicity, antimicrobial, and antiurease activities, as well as affinity for albumin (BSA) and DNA (ct-DNA). The complexes showed marked cytotoxic activities in the HepG2 hepatocellular carcinoma cell line, considerably higher than the standard cisplatin. The cytotoxicity depended significantly on the substitution pattern. The best activity was observed in the complex with a trifluoromethyl group in position 4 of the benzene ring—the dichloro[(±)-trans-N,N′-bis-(4-trifluoromethylbenzyl)-cyclohexane-1,2-diamine]copper (II) complex, whose activity (IC₅₀ 28.7 μM) was higher than that of the free ligand and markedly better than the activity of the standard cisplatin (IC₅₀ 336.8 μM). The same complex also showed the highest antimicrobial effect in vitro. The affinity of the complexes towards bovine serum albumin (BSA) and calf thymus DNA (ct-DNA) was established as well, indicating only marginal differences between the complexes. In addition, all complexes were shown to be excellent inhibitors of the enzyme urease, with the IC₅₀ values in the lower micromolar region. Full article

Graphene oxide (GO) nanosheets were functionalized with Schiff base and reduced Schiff base. Covalent and non-covalent functionalized GO nanostructures have been tested for the removal of pesticides with different chemical structures and properties (e.g., Epoxiconazole, Dimethomorph, Cyprodinil, Chlorothalonil, Acetochlor, Trifluralin) from aqueous solutions. The structure and morphology characteristics of the prepared structures were analyzed using techniques such as solid-state nuclear magnetic resonance (SSNMR), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Results of the experiments showed that, although the non-covalent functionalization did not affect the adsorption properties of GO much, the covalent functionalization increased the adsorption capacity of GO against the mentioned pesticides. Full article

Fe-N-C materials have been regarded as one of the potential candidates to replace traditional noble-metal-based electrocatalysts for the oxygen reduction reaction (ORR). It is believed that the structure of carbon support in Fe-N-C materials plays an essential role in highly efficient ORR. However, precisely designing the morphology and surface chemical structure of carbon support remains a challenge. Herein, we present a novel synthetic strategy for the preparation of porous carbon spheres (PCSs) with high specific surface area, well-defined pore structure, tunable morphology and controllable heteroatom doping. The synthesis involves Schiff-based polymerization utilizing octaaminophenyl polyhedral oligomeric silsesquioxane (POSS-NH₂) and heteroatom-containing aldehydes, followed by pyrolysis and HF etching. The well-defined pore structure of PCS can provide the confinement field for ferroin and transform into Fe-N-C sites after carbonization. The tunable morphology of PCS can be easily achieved by changing the solvents. The surface chemical structure of PCS can be tailored by utilizing different heteroatom-containing aldehydes. After optimizing the structure of PCS, Fe-N-C loading on N,S-codoped porous carbon sphere (NSPCS-Fe) displays outstanding ORR activity in alkaline solution. This work paves a new path for fabrication of Fe-N-C materials with the desired morphology and well-designed surface chemical structure, demonstrating significant potential for energy-related applications. Full article

In this study, an AM-based continuous processing reactor system was designed, manufactured, and assembled on a laboratory scale for the generation of pharmaceutical substances with an improved process control. The developed AM-based (additively manufactured) continuous pharmaceutical reactor system for the synthesis of metronidazole derivatives aimed to optimize both the physical and the chemical processes with time savings. Using AM, we were able to build reactor subcomponents with complex designs and precise dimensions, which facilitated the precise control of the reaction parameters and reduced the amount of chemicals required compared to macroscale reactors. The assembly of the whole reactor system consisted of main reactor bodies, mixers, valves, heat exchangers, electrical motors, and a microcontroller system. The assembled reactor system revealed a continuous flow of reagents and ensured uniform mixing and reaction conditions, thereby increasing the process efficiency and product quality. Five metronidazole derivatives were synthesized via two continuous processes, involving metronidazole reduction and its subsequent reactions with terephthalic aldehyde and anthracen-9(10H)-one to form Schiff bases. The optimal conditions were determined as follows: compound A (72% yield, 120 min, 55 °C), compounds B and C (63% and 68% yield, respectively, 8 h, 65 °C), and compounds D and E (74% and 85% yield, respectively, 8 h, 45 °C). Full article

Transition metal complexes of nickel(II) with 5–bromo–N–(8–quinolyl)salicylaldimine (HqsalBr, HL¹); [Ni(qsalBr)₂] (1) and 3,5–dibromo–N–(8–quinolyl)salicylaldimine (HqsalBr₂, HL²); [Ni(qsalBr₂)₂] (3) including zinc(II) complex with HL¹, [Zn(qsalBr)₂] (2), have been synthesized and successfully characterized using various techniques, namely IR, NMR, mass spectrometry, thermogravimetric analysis (TGA), and single crystal X–ray crystallography. DFT calculations were employed to examine the structural and electronic parameters of the complexes at their optimized geometries. The complexes showed strong DNA-binding activities, assessed by UV-Vis and fluorescence spectroscopy, primarily through intercalation. Molecular docking investigations were carried out to provide profound insights into the interaction mechanisms of these complexes with DNA and lung cancer cells. These computational studies revealed that [Ni(qsalBr₂)₂] (3) exhibits the most favorable negative binding energies, −9.1 kcal/mol with DNA and −9.3 kcal/mol with cancer cells, facilitated by hydrogen bonding and hydrophobic interactions. Furthermore, the in vitro anticancer activity was evaluated against the A549 human lung adenocarcinoma cell line, with [Zn(qsalBr)₂] (2) exhibiting the highest potency against this cancer cell line. Full article

The chemical tolerance of ketoenamine covalent organic frameworks (COFs) is excellent; however, the tight crystal structure and low surface area limit their applications in the field of catalysis. In this work, a porous single-atom iron catalyst (FeSAC) with a core–shell structure and high surface area was synthesized by using Schiff base COF nanospheres as the core and ketoenamine COF nanosheets growth on the surfaces. Surface defects were created using sodium cyanoborohydride etching treatment to increase specific surface area. The dye degradation experiments by peroxymonosulfate (PMS) catalyzed by the FeSAC proved that methylene blue can be degraded with a degradation rate constant of 0.125 min⁻¹ under the conditions of 0.1 g L⁻¹ catalyst dosage and 0.05 g L⁻¹ peroxymonosulfate. The FeSAC/PMS system effectively degrades various pollutants in the pH range of 4–10 with over 80% efficiency for four cycles and can be recovered by soaking in iron salt solution. Free radical quenching experiments confirmed that singlet oxygen and superoxide radicals are the main active species for catalysis. Full article

Schiff bases are compounds that are widely distributed in nature and have practical value for industry and biomedicine. Another important use of Schiff bases is identifying metal ions and different molecules, including proteins. Their proneness to hydrolysis limits the utilization of Schiff bases to mainly non-aqueous solutions. However, by introducing –OH and –SH substituents to aromatic amine-bearing rings, it is possible to increase the resilience of the Schiff base to destruction in water. The present paper discusses how the hydroxyl or thiol group influences the spectral properties and kinetics of the hydrolysis and formation of Schiff bases derived from pyridoxal 5′-phosphate and aniline, 2-hydroxyaniline, and 2-mercaptoaniline using quantum chemical data. The spectral variation between different imines can be explained by taking into account the geometry and frontier molecular orbital alteration induced by the substituents. The changes in the hydrolysis rate are analyzed using the computed values of local reactivity indices. Full article

Nanotechnology has ushered in significant advancements in drug design, revolutionizing the prevention, diagnosis, and treatment of various diseases. The strategic utilization of nanotechnology to enhance drug loading, delivery, and release has garnered increasing attention, leveraging the enhanced physical and chemical properties offered by these systems. Polyamidoamine (PAMAM) dendrimers have been pivotal in drug delivery, yet there is room for further enhancement. In this study, we conjugated PAMAM dendrimers with chitosan (CS) to augment cellular internalization in tumor cells. Specifically, doxorubicin (DOX) was initially loaded into PAMAM dendrimers to form DOX-loaded PAMAM (DOX@PAMAM) complexes via intermolecular forces. Subsequently, CS was linked onto the DOX-loaded PAMAM dendrimers to yield CS-conjugated PAMAM loaded with DOX (DOX@CS@PAMAM) through glutaraldehyde crosslinking via the Schiff base reaction. The resultant DOX@CS@PAMAM complexes were comprehensively characterized using Fourier-transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), and dynamic light scattering (DLS). Notably, while the drug release profile of DOX@CS@PAMAM in acidic environments was inferior to that of DOX@PAMAM, DOX@CS@PAMAM demonstrated effective acid-responsive drug release, with a cumulative release of 70% within 25 h attributed to the imine linkage. Most importantly, DOX@CS@PAMAM exhibited significant selective cellular internalization rates and antitumor efficacy compared to DOX@PAMAM, as validated through cell viability assays, fluorescence imaging, and flow cytometry analysis. In summary, DOX@CS@PAMAM demonstrated superior antitumor effects compared to unconjugated PAMAM dendrimers, thereby broadening the scope of dendrimer-based nanomedicines with enhanced therapeutic efficacy and promising applications in cancer therapy. Full article

Monoclonal antibodies (Mabs) are widely used in a variety of fields, including protein identification, life sciences, medicine, and natural product chemistry. This review focuses on Mabs against naturally occurring active compounds. The preparation of Mabs against various active compounds began in the 1980s, and now there are fewer than 50 types. Eastern blotting, which was developed as an antibody staining method for low-molecular-weight compounds, is useful for its ability to visually represent specific components. In this method, a mixture of lower-molecular-weight compounds, particularly glycosides, are separated by thin-layer chromatography (TLC). The compounds are then transferred to a membrane by heating, followed by treatment with potassium periodate (KIO₄) to open the sugar moiety of the glycoside on the membrane to form an aldehyde group. Proteins are then added to form Schiff base bonds to enable adsorption on the membrane. A Mab is bound to the glycoside moiety on the membrane and reacts with a secondary antibody to produce color. Double Eastern blotting, which enables the simultaneous coloration of two glycosides, can be used to evaluate quality and estimate pharmacological effects. An example of staining by Eastern blotting and a component search based on the results will also be presented. A Mab-associated affinity column is a method for isolating antigen molecules in a single step. However, the usefulness of the wash fractions that are not bound to the affinity column is unknown. Therefore, we designated the wash fraction the “knockout extract”. Comparing the nitric oxide (NO) production of a glycyrrhizin (GL)-knockout extract of licorice with a licorice extract revealed that the licorice extract is stronger. Therefore, the addition of GL to the GL-knockout extract of licorice increased NO production. This indicates that GL has synergic activity with the knockout extract. The GL-knockout extract of licorice inhibited high-glucose-induced epithelial–mesenchymal transition in NRK-52E cells, primarily by suppressing the Notch2 pathway. The real active constituent in licorice may be constituents other than GL, which is the causative agent of pseudohyperaldosteronism. This suggests that a GL-knockout extract of licorice may be useful for the treatment of diabetic nephritis. Full article

Aggregation-induced emitters or AIEgens are generally signified by their stronger photoluminescence in aggregation than in the solution state. Due to high emission efficiency in aggregate and solid states and good processability, organic AIEgens drew attention to the development of advanced luminescent materials. However, as mesogenic materials self-assemble to a different molecular arrangement in different phases, achieving liquid crystallinity and AIE properties in the same molecule would provide a valuable tool to develop solvent-independent AIEgenic materials. With this goal, the present work reports the synthesis of new organic thermotropic liquid crystalline compounds exhibiting aggregation-induced emission (AIE). The synthesized compounds exhibit strong green luminescence in a solid state which sharply quenches upon entering smectic mesophase by heating. This is in addition to the exhibition of dispersion medium (solvent)-dependent emission, thus providing a dual mode of AIE. The mesogenic property of the synthesized compounds was studied by XRD, POM, and DSC. The AIE was studied by fluorescence spectroscopy and variable temperature fluorescence microscopy. A DFT study was carried out to gain an insight into the AIEgenic behavior of the material. Full article

A new hydrazone Schiff base bridging ligand (H₂L_Schiff (E)-N′-((1-hydroxynaphthalen-2-yl)methylene)pyrazine-2-carbohydrazide) and L/D-proline were used to construct a pair of homochiral Dy₆ cluster complexes, [Dy₆(CO₃)(L-Pro)₆(L_Schiff)₄(HL_Schiff)₂]·5DMA·2H₂O (L-1, L-HPro = L-proline; DMA = N,N-dimethylacetamide) and [Dy₆(CO₃)(D-Pro)₆(L_Schiff)₄(HL_Schiff)₂]·5DMA·2H₂O (D-1, D-HPro = D-proline), which show a novel triangular Dy₆ topology. Notably, the fixation of CO₂ in the air formed a carbonato central bridge, playing a key role in assembling L-1/D-1. Magnetic measurements revealed that L-1/D-1 displays intramolecular ferromagnetic coupling and magnetic relaxation behaviours. Furthermore, L-1/D-1 shows a distinct magneto-optical Faraday effect and has a second harmonic generation (SHG) response (1.0 × KDP) at room temperature. The results show that the immobilization of CO₂ provides a novel pathway for homochiral multifunctional 4f cluster complexes. Full article

In this work, we describe the synthesis of novel Ruthenium (II) complex-based salen Schiff bases. The obtained Ruthenium (II) complexes are characterized using usual spectroscopic and spectrometric techniques, viz., IR, UV-Vis, NMR (¹H and ¹³C), powder X-ray diffraction, and HRMS. Further techniques, such as DTA-TGA and elemental analysis, are used to well establish the structure of the obtained complexes. Octahedral geometries are tentatively proposed for the new Ru(II) complexes. The measured molar conductance for the Ruthenium (II) complexes shows their electrolytic nature (4.24–4.44 S/m). The new Ru(II) complexes are evaluated for their antioxidant and antibacterial activities. The DPPH radical scavenging, FRAP, and total antioxidant capacity (TAC) assays show that the obtained complexes are more potent than the used positive control. They also exhibit promising antibacterial responses against pathogen bacteria: [RuH₂L³Cl₂] exhibits an important inhibition against Bacillus subtilis DSM 6633, with an inhibition zone of 21 ± 1.41 mm with an MIC value of 0.39 mg/mL, and Proteus mirabilis INH, with 16.50 ± 0.70 mm and an MIC value of 0.78 mg/mL, while [RuH₂L²Cl₂] exerts interesting antibacterial effects versus Bacillus subtilis DSM 6633 (21 ± 1.41 mm) and Proteus mirabilis INH (25.5 ± 0.70 mm) with equal MIC values of 0.97 mg/mL. Full article