Salicylaldehyde Research Articles

Molybdenum Containing Catalysts Grafted on Functionalized Hydrous Zirconia Nano-particles for Epoxidation of Alkenes

Hydrous zirconia nanoparticles were covalently functionalized by 3-(trimethoxysilyl)-propylamine and salicyl aldehyde to graft different molybdenum containing catalysts. Bis-acetylacetonato-di-oxo-molybdenum(VI) and some molybdenum containing Keggin type heteropolyacids were used for this purpose. The prepared catalysts have been characterized by means of FT-IR spectroscopy, PXRD pattern, thermal analysis, elemental analysis and scanning electron microscopy. Then all of them were used for the epoxidation of cis-cyclooctene. The catalytic procedures were subsequently investigated for each catalyst and followed by Gas–Liquid Chromatography. They are also applied repeatedly in the optimum reaction conditions to reveal their recycling ability. Then these conditions were used for successful epoxidation of other linear and non-linear alkenes. Hydroxyl covered hydrous zirconia nanoparticles was covalently functionalized using 3-(trimethoxysilyl)-propylamine and salicyl aldehyde to support bis-acetylacetonato-di-oxo-molybdenum(VI) or impound Keggin type heteropolyanions. The supported catalysts were then applied to the epoxidation of cis-cyclooctene, and the product yields were studied by Gas Liquid Chromatography. The catalytic procedures of these catalysts were optimized for the parameters involved such as the solvent and oxidant.

Characterization of the In Vivo and In Vitro Metabolites of Linarin in Rat Biosamples and Intestinal Flora Using Ultra-High Performance Liquid Chromatography Coupled with Quadrupole Time-of-Flight Tandem Mass Spectrometry.

Linarin, a flavone glycoside, is considered to be a promising natural product due to its diverse pharmacological activities, including analgesic, antipyretic, anti-inflammatory and hepatoprotective activities. In this research, the metabolites of linarin in rat intestinal flora and biosamples were characterized using ultra-high-performance liquid chromatography/quadrupole time-of-flight mass spectrometry (UPLC/Q-TOF-MS/MS). Three ring cleavage metabolites (4-hydroxybenzoic acid, 4-hydroxy benzaldehyde and phloroglucinol) were detected after linarin was incubated with rat intestinal flora. A total of 17 metabolites, including one ring cleavage metabolite (phloroglucinol), were identified in rat biosamples after oral administration of linarin. These results indicate that linarin was able to undergo ring fission metabolism in intestinal flora and that hydrolysis, demethylation, glucuronidation, sulfation, glycosylation, methylation and ring cleavage were the major metabolic pathways. This study provides scientific support for the understanding of the metabolism of linarin and contributes to the further development of linarin as a drug candidate.

Synthesis of Novel 1,4-Naphthoquinones Possessing Indole Scaffolds Using In(OTf)₃ in Solvent-Free Conditions.

Novel 1,4-naphthoquinones possessing indole scaffolds were prepared by the reaction of 2-hydroxy-1,4-naphthoquinone-substituted salicylic aldehydes and indoles using In(OTf)3 as a catalyst. The method has the advantages of simple operation, mild reaction conditions, and friendly environment.

Ratiometric Fluorescence Platform Based on Modified Silicon Quantum Dots and Its Logic Gate Performance.

A novel optical nanoprobe based on silicon quantum dots (SiQDs) has been assembled through a one-pot low-temperature (40 °C) treatment by using 3-(aminopropyl)trimethoxysilane (APTMS) and ascorbic acid (AA) as two precursors. The water-soluble SiQDs demonstrate intense green luminescence in aqueous environment and the excitation-dependent feature has been explored. Meanwhile, the incorporation of salicylaldehyde (SA) serves to suppress the emission of SiQDs effectively via nucleophilic reaction and an "on-off" change is observed. Furthermore, the addition of Zn2+ can lead to evolution of emission peaks, and the green band at 500 nm gradually shifts toward the blue side at 455 nm. The corresponding ratiometric signal changes ( I455/ I500) can accurately determine the Zn2+ concentration and the limit of detection is calculated to be 0.17 μM in the linear range between 1 and 100 μM. In this research, a molecular logic gate (AND) system has been well established by using SA and Zn2+ as two inputs. The fluorescence emission changes based on SiQDs will shed new light on the development of functional sensors at the nanoscale level.

Serine/Threonine Ligation: Origin, Mechanistic Aspects, and Applications.

Synthetic proteins are expected to go beyond the boundary of recombinant DNA expression systems by being flexibly installed with site-specific natural or unnatural modification structures during synthesis. To enable protein chemical synthesis, peptide ligations provide effective strategies to assemble short peptide fragments obtained from solid-phase peptide synthesis (SPPS) into long peptides and proteins. In this regard, chemoselective peptide ligation represents a simple but powerful transformation realizing selective amide formation between the C-terminus and N-terminus of two side-chain-unprotected peptide fragments. These reactions are highly chemo- and regioselective to tolerate the side-chain functionalities present on the unprotected peptides, highly reactive to work with millmolar or submillimolar concentrations of the substrates, and operationally simple with mild conditions and accessible building blocks. This Account focuses on our work in the development of serine/threonine ligation (STL), which originates from a chemoselective reaction between an unprotected peptide with a C-terminal salicylaldehyde (SAL) ester and another unprotected peptide with an N-terminal serine or threonine residue. Mechanistically, STL involves imine capture, 5- endo-trig ring-chain tautomerization, O-to- N [1,5] acyl transfer to afford the N, O-benzylidene acetal-linked peptide, and acidolysis to regenerate the Xaa-Ser/Thr linkage (where Xaa is the amino acid) at the ligation site. The high abundance of serine and threonine residues (12.7%) in naturally occurring proteins and the good compatibility of STL with various C-terminal residues provide multiple choices for ligation sites. The requisite peptide C-terminal SAL esters can be prepared from the peptide fragments obtained from both Fmoc-SPPS and Boc-SPPS through four available methods (a safety-catch strategy based on phenolysis, direct coupling, ozonolysis, and the n + 1 strategy). In the synthesis of proteins (e.g., ACYP enzyme, MUC1 glycopeptide 40-mer to 80-mer, interleukin 25, and HMGA1a with variable post-translational modification patterns), both C-to- N and N-to- C sequential STL strategies have been developed through selection of temporal N-terminal protecting groups and proper design of the switch-on/off C-terminal SAL ester surrogate, respectively. In the synthesis of cyclic peptide natural products (e.g., daptomycin, teixobactin, cyclomontanin B, yunnanin C) and their analogues, intramolecular head-to-tail STL has been implemented on linear peptide SAL ester precursors containing four to 10 amino acid residues with good efficiency and minimized oligomerization. As a thiol-independent chemoselective ligation complementary to native chemical ligation, STL provides an alternative tool for the chemical synthesis of homogeneous proteins with site-specific and structure-defined modifications and cyclic peptide natural products, which lays foundation for chemical biology and medicinal studies of those molecules with biological importance and therapeutic potential.

Synthesis of benzimidazole sweat fingerprint fluorescent developer and fluorescent effect

In this paper, benzimidazole fluorescent compounds (compound 1 and compound 2) containing hydroxymethyl and carboxyl substituents were synthesized by replacing salicylaldehyde and substituted ortho- phenylenediamine.By measuring the spectral properties of these fluorescent compounds, the influence of different substituents on the fluorescence properties of these fluorescent compounds was investigated and the fluorescence effect of these fluorescent compounds as a fluorescent latent agent for sweat fingerprinting was also investigated.The obtained hydroxymethyl and carboxyl substituted benzimidazole sweat latent fingerprints have good adsorption performance, remarkable fluorescence effect and strong stability, therefore, they can be widely used.This research also expands the research and application range of benzimidazole derivatives and it has very important research value in the field of criminal detection technology.

ИССЛЕДОВАНИЕ КОМПЛЕКСООБРАЗОВАНИЯ ЖЕЛЕЗА (III) С (Е)-2-ГИДРОКСИ-3-((2-ГИДРОКСИБЕНЗИЛИДЕН)(АМИНО) БЕНЗОЛСУЛЬФОКИСЛОТОЙ

A new organic reagent (e)-2-hydroxy-3-((2-hydroxybenzylidene)(amino)benzenesulphonic acid was synthe-sized on the basis of salicylic aldehyde. The dissociation constant of the reagent was determined using a pH-metric method in a water-ethanol medium: pK1 = 8.47 ± 0.03, pK2= 9.38 ± 0.04. The complexation of Fe(III) with (e)-2-hydroxy-3-((2-hydroxybenzylidene)(amino)benzenesulphonic acid was studied in the presence of diantipyrylphenylmethane (DAPM) and 8-hydroxyquinoline. Optimal conditions for the complexation were established. The main spectrophotometric characteristics of the complexes, such as pHopt, λopt, molar absorption coefficient, the compositions of the complexes and the interval where Beer's law holds, were calculated. The study of iron (III) complexation with the reagent showed that diverse-ligand complex-es are formed in the presence of DAPM and 8-hydroxyquinoline. During this reaction, bathochromic shifts are observed in the absorption spectrum, with the maximum yield shifting to the acidic medium compared to single-ligand complexes. The effect of individual ions and masking agents on the formation of binary and diverse-ligand iron (III) complexes was investigated, showing that the selectivity of the reaction increases in the presence of diantipyrylphenylmethane and 8-hydroxyquinoline. The developed technique was used to determine the microquantities of iron in bread and wheat bran.

Synthesis and photophysical properties of functionalized fluorescent 4H-chromenes and benzo[a]chromenophenazines as Fe3+ and Cu2+ ion sensor

An efficient Amberlite resin catalyzed one-pot, multicomponent reaction of 1,2-phenylenediamine, 2-hydroxynaphthalene-1,4-dione, 2-hydroxy benzaldehydes, and 1,3-diketones in EtOH/H2O (1/1, v/v) as solvent to obtain the fluorescent 4H-chromenes and benzo[a]chromenophenazines has been achieved. The structure of compounds 5 g and 6e were confirmed from single crystal XRD analysis. Photophysical properties such as solvatochromism, absorption, emission, Stocks shift and quantum yield have been evaluated. The emission spectra suggested that these are blue emissive fluorescent compounds. Further, 4H-chromenes and benzo[a]chromenophenazines act as fluorescent chemosensor for the detection of metal-ions. Among the screened compounds, 4H-chromene derivative 5a and benzo[a]chromenophenazine 6a have been found to be good metal ion sensors for the detection of Fe3+ and Cu2+ ions.

Determination of Stability for imines derived from carbonyl compounds by conductivity measurements

The project explained for the first time, how conductivity method was used in the determination of stability of some imines derived from mother compounds 2-acetyl pyridine, 3 or 4 –hydroxy benzaldehyde, and others.
 The method as found, simple precise and fast for the determination of stability of imines in 10% ethanol aqueous medium, as measured by evaluation of their conductance. Different conductance values for 10-2 M imine solutions in the range (5.53-180) μmho were collected experimentally as interpreted and discussed.

Synthesis and biological imaging of fluorescent polymeric nanoparticles with AIE feature via the combination of RAFT polymerization and post-polymerization modification

In recent years, florescent polymeric nanoparticles (FPNs) containing aggregation-induced emission (AIE) fluorogens have received great intention for their potential applications in biological imaging and theranostic nanomedicine. Herein, we have developed AIE-active FPNs through a combination of reversible addition-fragmentation chain transfer (RAFT) polymerization and post-polymerization modification strategies. The salicylaldehyde (SA) containing zwitterionic copolymers are fabricated via RAFT polymerization and further modified by benzophenone hydrazone (BPH) via Schiff base reaction. The obtained AIE-active amphiphilic copolymers BPH-poly(FHMA-co-MPC) can self-assemble in aqueous solution with the hydrophobic fluorogens aggregating together to form the core and the hydrophilic chains to form the protective shell. BPH-poly(FHMA-co-MPC) and the resulting FPNs are characterized by 1H nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy and fluorescence spectroscopy. Results demonstrate that BPH-poly(FHMA-co-MPC) are successfully synthesized and as-prepared BPH-poly(FHMA-co-MPC) FPNs exhibit desirable morphology and size, good dispersibility, high brightness, remarkable photostability and large Stokes shifts. More importantly, through cytotoxicity test and cell uptake behavior, these BPH-poly(FHMA-co-MPC) FPNs show low toxicity and excellent cell dyeing behavior. Taken together, we have developed a facile and effective method for the fabrication of AIE-active FPNs, which display great potential for biomedical applications.

BIOACTIVE FRACTION OF TROPIDIA CURCULIOIDES, A RARE ORCHID OF ARUNACHAL PRADESH, INDIA: PHYTOCHEMICAL PROFILE AND MARKER COMPOUNDS

Objective: Chemical profiling of the most active fraction of Tropidia curculioides, isolation and characterization of marker compounds along with the evaluation of biological activity. Methods: The most active Et2O fraction of roots of T. curculioides (TC) was analyzed by gas chromatography coupled with a mass selective detector. Repetitive chromatography followed by high-performance liquid chromatography of the active fraction afforded three major compounds. The structure of the compounds was established by nuclear magnetic resonance and mass spectral analysis. Antibacterial activity of the compounds was determined by agar well diffusion method against five multidrug-resistant (MDR) clinical isolates while minimum inhibitory concentration (MIC) and minimum bactericidal concentration were determined by microdilution method. Scanning electron microscopy was performed with compound 2 against Escherichia coli cells at MIC (15 μg/ml).Results: Analysis of the gas chromatography–mass spectrometry (GC–MS) spectra revealed that the isolated compounds constituted 27.16% of the total constituents. Two other chemical classes, namely, saturated fatty acids and sterol constituted 38.04% and 12.49%, respectively. The structure of the compounds was characterized as 4-hydroxy benzaldehyde (1), bisphenol F (2), and 3,5-dihydroxy-4-methoxybenzoic acid (3). The most significant bacteriostatic and bactericidal activity against E. coli comparable to that of tetracycline and gentamicin was observed with compound 2. Microscopic study confirmed that compound 2 affects integrity of cell membrane severely, causing death of the bacterium. Compound 1 and 3 showed moderate to good antibacterial activity against E. coli and Enterococcus sp. Cell cytotoxicity of the compounds was well within permissible limit. This is the first report of compounds in TC.Conclusion: The study identified three marker compounds from the less polar fraction of the roots of TC with significant antibacterial activity. The GC–MS spectra with marker compounds could be treated as the chemical fingerprinting of the bioactive fraction. The outcome justifies the use of the plant in traditional medicine.

Synthesis and study the behavior of liquid crystalline phases of new heterocyclic compound from folic acid

This work includes syntheses of new heterocyclic compounds of folic acid, The p-hydroxy benzaldehyde reaction with (pentanol, hexanol and heptanol) to produce (4-pentloxy, 4-hexaloxy and 4-hepteloxy) benzaldehyde, and compounds (p-hydroxy,p-chloro,p-nitro, 4-N,N-dimethyl) benzaldehyde and Vanillin reaction of folic acid with to produce Schiff bases. The Schiff base of benzaldehyde and Folic acid reaction with (4-pentloxy, 4- hexaloxy and4- hepteloxy) to produce Ester. The compounds have been identified using (FT-IR and 1H NMR). The misomorphic phases were identified by polarized light microscope (POM) and measured transition temperatures for compound by differrntion scanning calorimeter (DSC) then study of liquid crystal where it was found that compounds of (1-8) gave liquid crystalline properties, where the compounds (1,2,3,5,6,7and8) gave the nematic phase, but the compound (4) gave the smectic phase in addition to the nematic phase, while compounds (9,10and11) where oily compounds and showed not liquid crystalline properties.

Capillary electrophoresis method for the discrimination between natural and artificial vanilla flavor for controlling food frauds.

A capillary electrophoresis method was developed for the determination of coumarin (COUM), ethyl vanillin (EVA), p-hydroxybenzaldehyde (PHB), p-hydroxybenzoic acid (PHBA), vanillin (VAN), vanillic acid (VANA) and vanillic alcohol (VOH) in vanilla products. The measured concentrations are compared to values obtained by liquid chromatography (LC) method. Analytical results, method precision, and accuracy data are presented and limits of detection for the method ranged from 2 to 5μg/mL. The results obtained are used in monitoring the composition of vanilla flavorings, as well as for confirmation of natural or non-natural origin of vanilla in samples using four selected food samples containing this flavor.

Physical and Chemical Methods Used for Determination of Structures of Some Imines Derived from Different Carbonyl Compounds

The project is concerned with the preparation of fifteen imines derived from 2-acetyl pyridine ,3 or 4 –hydroxy benzaldehyde and m-anisaldehyde with aromatic primary amines by standard method . These imines include namely ,hydroxylamine hydrochloride,o,m,p-amino phenols ,4-amino naphthol ,bromo or chloro aniline and p-anisidine . The main aims of the study is the determination of structures of these imines by the available physical method ,namely ,the melting points ,boiling points , U.V and IR spectra . Some chemical tests for functional groups are also included .This seems important from chemistry point of view as in the elucidation of tautomerism reactions happen in some oximes and phenolic oximes . Finally ,the influence of inter molecular hydrogen bonding on association (polymerization) of imines was also discussed

Molecular and Crystal Structure of the Condensation Product of 2-(7-Bromo-2-Oxo-5-Phenyl-3H-1,4-Benzdiazepin-1-Yl)Acetohydrazide (Gidazepam) with Salicylic Aldehyde

Hydrazone [HydrHSal]∙Н2О is synthesized for the first time by the interaction of 2-(7-bromo-2-oxo-5- phenyl-3H-1,4-benzdiazepin-1-yl)acetohydrazide (gidazepam) with salicylic aldehyde and characterized by the elemental analysis, thermogravimetry, mass, electron, IR, and NMR spectroscopic techniques. The molecular and crystal structure is determined by single crystal X-ray diffraction.

Synthesis and studies on structural, optical and nonlinear optical properties of novel organic inter-molecular compounds: 4-chloro-3-nitroaniline−3-hydroxy benzaldehyde and urea−4-dimethylaminopyridine

Two novel organic inter-molecular compounds (IMCs), (3-(4-chloro-3-nitrophenylimino) methyl) phenol) (CNMP) and urea ̶ 4-dimethylaminopyridine complex (UDMAP), have been synthesized by solid state reaction. These two IMCs were identified by phase diagram study of CNA−HB and U−DMAP systems. The single crystals of newly obtained IMCs were grown by slow solvent evaporation technique at room temperature. Both the IMCs were further studied for their thermal, spectral, single crystal XRD for their atomic packing in molecule, crystallinity, optical and nonlinear optical behaviour. In both the cases, melting point of inter-molecular compounds was found to be higher than that of their parent components, CNMP was found to be thermally stable up to 158 °C while UDMAP was stable up to 144 °C, which indicate their extra stability than their parents. The single crystal XRD studies confirmed that CNMP has crystallized in orthorhombic unit cell with non-centrosymmetric space group P212121 while UDMAP has crystallized in monoclinic unit cell with centrosymmetric space group C2/c. The absorption spectrum of CNMP was found to be in between the absorption of parents, while broadening of peak and red shift was observed in UDMAP as compared to the parents. Second order nonlinear optical property of CNMP and UDMAP was studied using Kurtz Perry powder technique and intense green light emission was observed with CNMP on excitation with 1064 nm of Nd:YAG laser while no emission was observed with UDMAP.

Flame-retarding epoxy resin with an efficient P/N/S-containing flame retardant: Preparation, thermal stability, and flame retardance

To further study the effect of the phosphorus, sulfur, and nitrogen-containing flame retardant on epoxy resin, a DOPO-based phenol derivative 4-[(benzothiazolyl 2-amino)(6-oxido-6H-dibenz[c,e][1,2]oxaphosphorin-6-yl) methyl] phenol namely D-P-A, was successfully synthesized from 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), p-hydroxybenzaldehyde (PHBA), and 2-aminobenzothiazole (ABZ), and used to flame retard epoxy resin (EP). As expected, D-P-A imparted flame retardance to epoxy resin. For example, with 7.5 wt% loading of D-P-A, epoxy thermoset passed a UL-94 V-0 rating, and got a LOI value of 29.6%. Besides, D-P-A played an effective role in inhibiting heat release of EP, that EP/7.5% D-P-A showed a peak of heat release rate (PHRR) of 713 kW/m2 much lower than 1137 kW/m2 of EP. However, it decomposed in advance owing to the lower thermal stability of D-P-A. Finally, through Scanning electron microscopy (SEM), Raman spectra and X-ray photoelectron spectroscopy (XPS) and pyrolysis-gas chromatograph/mass spectrometer (Py-GC/MS), it disclosed that D-P-A exerted its flame-retardant activity both in the vapor and condensed phase.

Hairy and Slippery Polyoxazoline-Based Copolymers on Model and Cartilage Surfaces.

Comb-like polymers presenting a hydroxybenzaldehyde (HBA)-functionalized poly(glutamic acid) (PGA) backbone and poly(2-methyl-2-oxazoline) (PMOXA) side chains chemisorb on aminolized substrates, including cartilage surfaces, forming layers that reduce protein contamination and provide lubrication. The structure, physicochemical, biopassive, and tribological properties of PGA-PMOXA-HBA films are finely determined by the copolymer architecture, its reactivity toward the surface, i.e. PMOXA side-chain crowding and HBA density, and by the copolymer solution concentration during assembly. Highly reactive species with low PMOXA content form inhomogeneous layers due to the limited possibility of surface rearrangements by strongly anchored copolymers, just partially protecting the functionalized surface from protein contamination and providing a relatively weak lubrication on cartilage. Biopassivity and lubrication can be improved by increasing copolymer concentration during assembly, leading to a progressive saturation of surface defects across the films. In a different way, less reactive copolymers presenting high PMOXA side-chain densities form uniform, biopassive, and lubricious films, both on model aminolized silicon oxide surfaces, as well as on cartilage substrates. When assembled at low concentrations these copolymers adopt a "lying down" conformation, i.e. adhering via their backbones onto the substrates, while at high concentrations they undergo a conformational transition, assuming a more densely packed, "standing up" structure, where they stretch perpendicularly from the substrate. This specific arrangement reduces protein contamination and improves lubrication both on model as well as on cartilage surfaces.

Cyclic Polymer Grafts That Lubricate and Protect Damaged Cartilage

AbstractTissue‐reactive graft copolymers were designed to protect the cartilage against enzymatic degradation and restore its lubrication properties during the early stages of osteoarthritis (OA). The copolymers feature a poly(glutamic acid) (PGA) backbone bearing hydroxybenzaldehyde (HBA) functions and cyclic poly(2‐methyl‐2‐oxazoline) (PMOXA) side chains. PGA‐PMOXA‐HBA species chemisorb on the degraded tissue via Schiff bases and expose the biopassive and lubricious PMOXA cyclic grafts at the interface. The smaller hydrodynamic radius by cyclic PMOXA side chains coupled to the intrinsic absence of chain ends generate denser and more lubricious films on cartilage when compared to those produced by copolymers bearing linear PMOXA. Topology effects demonstrate how the introduction of cyclic polymers within tissue‐reactive copolymers substantially improve their tribological and biopassive properties, suggesting a plethora of possible applications for cyclic macromolecules in biomaterials formulations.

Cyclic Polymer Grafts That Lubricate and Protect Damaged Cartilage.

Tissue-reactive graft copolymers were designed to protect the cartilage against enzymatic degradation and restore its lubrication properties during the early stages of osteoarthritis (OA). The copolymers feature a poly(glutamic acid) (PGA) backbone bearing hydroxybenzaldehyde (HBA) functions and cyclic poly(2-methyl-2-oxazoline) (PMOXA) side chains. PGA-PMOXA-HBA species chemisorb on the degraded tissue via Schiff bases and expose the biopassive and lubricious PMOXA cyclic grafts at the interface. The smaller hydrodynamic radius by cyclic PMOXA side chains coupled to the intrinsic absence of chain ends generate denser and more lubricious films on cartilage when compared to those produced by copolymers bearing linear PMOXA. Topology effects demonstrate how the introduction of cyclic polymers within tissue-reactive copolymers substantially improve their tribological and biopassive properties, suggesting a plethora of possible applications for cyclic macromolecules in biomaterials formulations.