Schiff Base Formation Research Articles

Synthesis, Characterization and Biological Activities of Schiff Bases and Their Transition Metal Complexes

Schiff bases are aldehyde or ketone derivatives that are made by condensation of primary amines and carbonyl compounds and have their carbonyl organization (C = O) replaced by an imine or azomethine organization (>C = N-). Schiff bases are a key ligand elegance in coordination chemistry and are widely used in a variety of fields. Metallic buildings have extra organic action than the relating ligands. Schiff base complexes in particular are particularly intriguing due to their stability, electron-donating potential, photochromic, optical nonlinearity properties, and biological interest. The coordination of Schiff bases with steel ions serves as the foundation for each one. With -NH2 and -COOH coordination sites, amino acids are functionally important in many biological processes and form Schiff bases that easily coordinate with metallic ions when combined with aldehydes or ketones. The majority of Schiff bases derived from amino acids and their metallic complexes exhibit specific pharmacological properties. This assess centers around research related with Schiff base buildings of amino corrosive subordinates throughout the course of recent years. We spotlight the antimicrobial, anticancer and cell reinforcement amino acids of a couple of Schiff base mixtures with nitrogen, oxygen and sulfur contributors and different metallic particles.

Synthesis, Characterization and Anticancer Activity of Chitosan Schiff Base / PVP Gold Nano Composite in Treating Esophageal Cancer Cell Line

In the present paper, chitosan Schiff base has been synthesized from chitosan’s reaction with the salicyldehyde. The AuNPs was manufacture by extract of onion peels as a reducing agent. The Au NPs that have been prepared were characterized through the UV-vis spectroscopy, XRD analyses and SEM microscopy. The polymer blends of the chitosan Schiff base / PVP has been prepared through using the approach of solution casting. Chitosan Schiff base / PVP Au nano-composites was prepared. Nano composites and polymer blends have been characterized by FTIR which confirm the formation of Schiff base by revealing a new band of absorption at 1651cm-1 as a result of the (C=N) imine group. SEM, DSC and TGA confirms the thermal stability of the prepared polymer blends and nanocomposites, nano composites have shown good results in inhibiting esophageal cancer cell lines, IC50 of nanocomposite = 21.56 µg / mL.

Enaminoketones - functional derivatives based on 7-hydroxy-3′,3′-dimethyl-3′<i>H</i>-spiro[chromen-2,1′-isobenzofuran]-8-carbaldehyde with aromatic amines. physicochemical studies and biological activity

This research focuses on studying derivatives of 2-oxaindane spiropyran by its condensation with aromatic amines. The results showed that all the synthesized compounds are enaminoketones form in both solution and solid state. This is explained by the fact that during the formation of Schiff bases, the proton of the 7-hydroxyl group of the benzopyran part migrates to the azomethine nitrogen, which leads to the transition of the cyclic form of spiropyran into the corresponding enaminoketone. In the DMSO solution, the enaminoketones dynamic equilibrium of the E , Z -isomeric forms were observed. The structure of enaminoketone based on 3,4-dimethylaniline was proved by the X-ray diffraction method. The synthesized compounds were studied for their in vitro anticancer activity against human hepatocellular carcinoma (HepG2), breast carcinoma (MCF-7), lung cancer (A549), and carcinoma cells (KB). Enaminoketone with R = 3,4-СH3Ph is characterized by the highest activity, with IC50 values of 13.38 μM (KB). The results in vitro antioxidant activity test using 1,1-diphenyl-2-picrylhydrazyl (DPPH) indicated that enaminoketones were inactive.

Lipid Peroxidation Products Influence Calpain-1 Functionality In Vitro by Covalent Binding

The objective of the current study was to evaluate the effects of lipid peroxidation products, malondialdehyde (MDA), hexenal, and 4-hydroxynonenal (HNE), on calpain-1 function, and liquid chromatography and tandem mass spectrometry (LC-MS/MS) identification of adducts on calpain-1. Calpain-1 activity slightly increased after incubation with 100 μM MDA but not with 500 and 1000 μM MDA. However, calpain-1 activity was lowered by hexenal and HNE at 100, 500, and 1000 μM. No difference in calpain-1 autolysis was observed between the control and 1000 μM MDA. However, 1000 μM hexenal and HNE treatments slowed the calpain-1 autolysis. Adducts of MDA were detected on glutamine, arginine, lysine, histidine, and asparagine residues via Schiff base formation, while HNE adducts were detected on histidine, lysine, glutamine, and asparagine residues via Michael addition. These results are the first to demonstrate that lipid peroxidation products can impact calpain-1 activity in a concentration-dependent manner and may impact the development of meat tenderness postmortem.

Niobium doped triazine based covalent organic frameworks for supercapacitor applications

Covalent organic frameworks (COFs) are gaining high importance in energy storage systems due to their uniform porosity and versatile functionality. The present work deals with the fabrication of triazine-based COF through Schiff base formation. The method involves the polycondensation reaction between melamine and terephthalaldehyde. In addition, the COF was also decorated with Niobium to generate Nb@COF. The morphological, elemental mapping, X-ray photoelectron spectroscopy, C13 NMR results show the effective doping of Nb to the COF and provide insights into the nature of bond formation. The obtained experimental XRD results are in good agreement with Materials Studio simulated results. COF and Nb@COF have been used for supercapacitor applications in a three-electrode system. Enhanced specific capacitance was observed in Nb@COF (367 F g−1) compared to pure COF (244 F g−1) at a scan rate of 2 mV s−1. The superior electrochemical performance in Nb@COF could be due to the increased porosity and interlayer spacing. COF and Nb@COF exhibited good stability towards charge and discharge and managed to retain 82 and 89 % specific capacitance, respectively even at 5000 cycles. COF and Nb@COF were assembled in a coin cell and fabricated an asymmetric supercapacitor device as negative and positive electrodes, respectively. The results obtained were satisfactory and shows a specific capacitance of 87 F g−1 at a scan rate of 2 mV s−1.The good stability, specific capacitance and reliability of Nb@COF indicate its potential application in energy storage devices.

The Catalytic Mechanism of Acetoacetate Decarboxylase: A Detailed Study of Schiff Base Formation, Protonation States, and Their Impact on Catalysis.

The enzyme acetoacetate decarboxylase (AAD) has a crucial function in the process of decarboxylating the substrate acetoacetate (AA). It has been extensively studied over the years, but its exact catalytic mechanism has remained partly unsolved due to the difficulty in assessing reaction intermediates. In this study, we combine molecular dynamics and electronic structure calculations to rediscover its catalytic mechanism. Our results show that the presence of the substrate, the acetoacetate, significantly influences the electrostatic potential of the active site. Furthermore, our simulations show that the decarboxylation reaction can take place by means of a direct proton transfer instead of via an enamine intermediate, which is thought to be strictly necessary. This work provides new insights into the role of the electrostatic interactions on the catalytic activity of AAD and for the first time connects it to the catalytic mechanism of other decarboxylases.

Highly selective Schiff base functionalized silatrane based receptor as Sn(II) ion chemosensor: Synthesis, photophysical, DFT and docking studies

This article illustrates the successful formation of Schiff base of 3-methyl-2-thiophenecarboxyaldehyde based silanes and their corresponding silatranes and silocanes, which were thoroughly characterized by NMR (1H and 13C) and mass spectrometry. Compound 3a selectively detect Sn(II) metal ion over other relevant metal cations by UV–Visible and fluorometric spectroscopic experiments with low limit of detection (LOD) values of 3.725 × 10−8 M and 4.32 × 10−9 M and binding constant values of 0.479 × 107 M−1 and 1.1802 × 1010 M−1, respectively. Job's plot supports the 1:1 stoichiometric binding of compound 3a to Sn(II) metal ion. Pharmacokinetic properties of the synthesized drugs were also studied using MOLINSPIRATION and ADMET (absorption, distribution, metabolism, excretion, and toxicity) software, and they gave satisfactory results. Good anti-oxidant properties were shown by compound 3a with IC50 value 15 ± 2.07. However, antioxidant therapy has potent benefit in treatment of malaria [1]. As a result, the protein of malaria Plasmodium falciparum was employed in a molecular docking experiment with compound 3a to investigate the compound's potential anti-malarial activity, and it produced extremely good results with a binding energy of -6.43 Kcalmol−1. Furthermore, the compound 3a's recovery of Sn(II) in water samples was tested with a recovery percentage greater than 95 which suggests it can be employed in real time applications.

PARP1 Incises Abasic Sites and Covalently Cross-links to 3'-DNA Termini via Cysteine Addition Not Reductive Amination.

Poly [ADP-ribose] polymerase 1 (PARP1) is a ubiquitous nuclear enzyme that plays multifaceted roles in the cellular response to DNA damage. Previous studies demonstrated that PARP1 incises the most frequently formed DNA lesion, the apurinic/apyrimidinic (AP) site, and in the process is trapped as a DNA-PARP1 cross-link at the 3'-terminus. The covalent linkage was proposed to be composed of a secondary amine resulting from formal reductive amination of an initially formed incision product. PARP1 cysteine residues were proposed to reduce the initially formed Schiff base. Here, we report evidence to support a different mechanism in which DNA-PARP1 cross-links result from cysteine addition to incised AP sites.

G-C3N4 based Chitosan Schiff base bio Nanocomposite for water purification

A novel adsorbent material for the removal of Copper and chromium metal ions from aqueous solution was prepared by modifying chitosan. Cross linked chitosan material was prepared using vanillin as a crosslinking agent and further it was incorporated with graphitic-C3N4 to obtain the polymeric matrix. The composite material thus obtained was characterized using various characterization techniques such as FTIR, TGA, SEM and XRD. A peak at 1658 cm−1 indicates the formation of Schiff base and the peaks at 2θ = 9°, 15°, 21° and 24° indicates the incorporation of g-C3N4 and the increased crytallinity of the composite material. Adsorption studies were done in order to obtain the maximum capacity of the adsorbent for the Copper and Chromium ions which were found to be 166.66 and 250 mgg−1 respectively. The adsorption isotherm best fitted a Langmuir model and the adsorptive process was found to have pseudo second-order kinetics showing the chemical sorption type. Thermodynamic studies indicated that the adsorption process was spontaneous and endothermic in nature.

Electrodeposited Carbonyl Functional Polymers as Suitable Supports for Preparation of the First-Generation Biosensors.

The aim of this electrochemical study was to ascertain which type of electrochemically deposited carbonyl functionalized polymer represents the most suitable electrode substrate for direct covalent immobilization of biological catalysts (enzymes). For this purpose, a triad of amperometric biosensors differing in the type of conductive polymers (poly-vanillin, poly-trans-cinnamaldehyde, and poly-4-hydroxybenzaldehyde) and in the functioning of selected enzymes (tyrosinase and alkaline phosphatase) has been compared for the biosensing of neurotransmitters (dopamine, epinephrine, norepinephrine, and serotonin) and phenyl phosphates (p-aminophenyl phosphate and hydroquinone diphosphate). The individual layers of the polymers were electrochemically deposited onto commercially available screen-printed carbon electrodes (type C110) using repetitive potential cycling in the linear voltammetric mode. Their characterization was subsequently performed by SEM imaging and attenuated total reflectance FTIR spectroscopy. Molecules of enzymes were covalently bonded to the free carbonyl groups in polymers via the Schiff base formation, in some cases even with the use of special cross-linkers. The as-prepared biosensors have been examined using cyclic voltammetry and amperometric detection. In this way, the role of the carbonyl groups embedded in the polymeric structure was defined with respect to the efficiency of binding enzymes, and consequently, via the final (electro)analytical performance.

The 4-Hydroxynonenal-Protein Adducts and Their Biological Relevance: Are Some Proteins Preferred Targets?

It is well known that oxidative stress and lipid peroxidation (LPO) play a role in physiology and pathology. The most studied LPO product with pleiotropic capabilities is 4-hydroxynonenal (4-HNE). It is considered as an important mediator of cellular signaling processes and a second messenger of reactive oxygen species. The effects of 4-HNE are mainly attributed to its adduction with proteins. Whereas the Michael adducts thus formed are preferred in an order of potency of cysteine > histidine > lysine over Schiff base formation, it is not known which proteins are the preferred targets for 4-HNE under what physiological or pathological conditions. In this review, we briefly discuss the methods used to identify 4-HNE-protein adducts, the progress of mass spectrometry in deciphering the specific protein targets, and their biological relevance, focusing on the role of 4-HNE protein adducts in the adaptive response through modulation of the NRF2/KEAP1 pathway and ferroptosis.

Lysine and Arginine Reactivity and Transformation Products during Peptide Chlorination.

Chlorine reactions with peptide-bound amino acids form disinfection byproducts and contribute to pathogen inactivation by degrading protein structure and function. Peptide-bound lysine and arginine are two of the seven chlorine-reactive amino acids, but their reactions with chlorine are poorly characterized. Using N-acetylated lysine and arginine as models for peptide-bound amino acids and authentic small peptides, this study demonstrated conversion of the lysine side chain to mono- and dichloramines and the arginine side chain to mono-, di-, and trichloramines in ≤0.5 h. The lysine chloramines formed lysine nitrile and lysine aldehyde at ∼6% yield over ∼1 week. The arginine chloramines formed ornithine nitrile at ∼3% yield over ∼1 week but not the corresponding aldehyde. While researchers hypothesized that the protein aggregation observed during chlorination arises from covalent Schiff base cross-links between lysine aldehyde and lysine on different proteins, no evidence for Schiff base formation was observed. The rapid formation of chloramines and their slow decay indicate that they are more relevant than the aldehydes and nitriles to byproduct formation and pathogen inactivation over timescales relevant to drinking water distribution. Previous research has indicated that lysine chloramines are cytotoxic and genotoxic to human cells. The conversion of lysine and arginine cationic side chains to neutral chloramines should alter protein structure and function and enhance protein aggregation by hydrophobic interactions, contributing to pathogen inactivation.

Retinal-phospholipid Schiff-base conjugates and their interaction with ABCA4, the ABC transporter associated with Stargardt disease

N-retinylidene-phosphatidylethanolamine (N-Ret-PE), the Schiff-base conjugate formed through the reversible reaction of retinal (Vitamin A-aldehyde) and phosphatidylethanolamine, plays a crucial role in the visual cycle and visual pigment photoregeneration. However, N-Ret-PE can react with another molecule of retinal to form toxic di-retinoids if not removed from photoreceptors through its transport across photoreceptor membranes by the ATP-binding-cassette transporter ABCA4. Loss-of-function mutations in ABCA4 are known to cause Stargardt disease (STGD1), an inherited retinal degenerative disease associated with the accumulation of fluorescent di-retinoids and severe loss in vision. A larger assessment of retinal-phospholipid Schiff-base conjugates in photoreceptors is needed, along with further investigation of ABCA4 residues important for N-Ret-PE binding. In this study we show that N-Ret-PE formation is dependent on pH and phospholipid content. When retinal is added to liposomes or photoreceptor membranes, 40 to 60% is converted to N-Ret-PE at physiological pH. Phosphatidylserine and taurine also react with retinal to form N-retinylidene-phosphatidylserine and N-retinylidene-taurine, respectively, but at significantly lower levels. N-retinylidene-phosphatidylserine is not a substrate for ABCA4 and reacts poorly with retinal to form di-retinoids. Additionally, amino acid residues within the binding pocket of ABCA4 that contribute to its interaction with N-Ret-PE were identified and characterized using site-directed mutagenesis together with functional and binding assays. Substitution of arginine residues and hydrophobic residues with alanine or residues implicated in STGD1 significantly reduced or eliminated substrate-activated ATPase activity and substrate binding. Collectively, this study provides important insight into conditions which affect retinal-phospholipid Schiff-base formation and mechanisms underlying the pathogenesis of STGD1.

Decolorization of dye effluents via immobilized glycoprotein peroxidase on post-consumer polystyrene foam

Development of sustainable approaches to manage industrial wastes such as plastic waste and dye effluents is a major research endeavor, owing to escalating environmental and health concerns arising from discharge of such wastes into water bodies. In this context, this study aims to convert packaging waste of expanded polystyrene foam (EPS) into effective biocatalyst for enzymatic degradation of dye effluent. Briefly, crushed EPS were decorated with amine groups via chlorosulfonation followed by conjugation of branched polyethylenimine. Carbohydrate rich turnip peroxidase (TPOD) was purified to homogeneity from Brassic rapa roots followed by periodate oxidation to introduce reactive dialdehyde groups. Such oxidized TPOD glycoprotein was covalently immobilized on aminated EPS through Schiff base formation. Immobilized TPOD exposed noticeable tolerance toward elevated temperatures (80 °C) that qualifies it as viable biocatalyst for decolorization of dye effluents that is frequently hot. Indeed, immobilized TPOD could successfully decolorize methyl orange (90 %) and crystal violet (96 %) within 2 h. Due to the floating nature of EPS, the immobilized TPOD was simply separated by skimming and reused in fifteen subsequent catalytic cycles. Ultimately, this work demonstrates the conversion of post-consumer EPS into a value-added biocatalyst for the ecofriendly enzymatic treatment of dye effluents.

Study on Maillard reaction mechanism by quantum chemistry calculation

The Maillard reaction is a high-temperature reaction of amino acids and carbohydrates to produce macromolecular substances such as melanoidins and intermediate reducing ketones, aldehydes, and volatile compounds. At present, only very limited researches involved the reaction mechanisms of Maillard reaction, which causes a lot of confusion in understanding numerous food processes. The detailed calculations of Maillard reaction are urgently needed. The density functional theory (DFT) method (M06-2X/6-311G*) was used to deeply explore the specific mechanism of the primary and intermediate stages of Maillard reaction for a selected model system. The results show that the basic reaction processes in primary stage are the formation of Schiff-base by the condensation of amino and carbonyl groups, and then, Schiff-base tautomerization twice through proton transfer to generate Amadori rearrangement products. In the intermediate stage, two main reaction paths, 1-2 and 2-3 enolization, were comprehensively investigated. The first route finally generates 5-hydroxymethylfurfural through isomerization, dehydration, hydrolysis, elimination, and condensation, and the second route products dicarbonyl compounds through isomerization and elimination and then Strecker degradation forms aldehydes through condensation, decarboxylation, hydrolysis, and elimination. The results show that both paths are involved in complex reactions, some are lower barrier reactions, and some higher barrier reactions. An important aspect is that water catalysis is critical in all of these reactions; it is present in most processes. Our study deepens the understanding of the Maillard reaction from molecular level and facilitate the regulation of some harmful products.

Development of self-healing vanillin/PEI hydrogels for tissue engineering

Self-healing materials recover mechanical damages to expand the lifetime of the material provided. In this study, self-healing hydrogels have been successfully prepared using a novel and simple technique. Vanillin is a natural monomer, used as a bio-based cross-linker for UV-induced bonding and Schiff-base bonding. Methacrylate-functionalized vanillin (M-VAN) is covalently integrated with the polymer matrix. While M-VAN supports polymer matrix with its vinyl group, its aldehyde functionality helps the formation of dynamic covalent imine bonds via Schiff-base formation. The hydrogel showed excellent self-healing ability overnight under physiological conditions without external addition. In addition, the hydrogel surface was modified by collagen and its cell viability was investigated. The prepared scaffolds showed good cell viability of 124% and 163% compared to the control sample. The developed self-healing material reveals that it has possible uses for future biomedical applications and tissue engineering studies due to the self-healing mechanism taking place under ambient conditions.

Uncovering quality changes of salted bighead carp fillets during frozen storage: The potential role of time-dependent protein denaturation and oxidation

This study aimed to find the specific relationship between quality traits and myofibrillar proteins (MPs) alteration of salted fish during frozen storage. Protein denaturation and oxidation occurred in frozen fillets, with the denaturation occurring before oxidation. In the pre-phase of storage (0-12 weeks), protein structural changes (secondary structure and surface hydrophobicity) were closely related to the water-holding capacity (WHC) and textural properties of fillets. The MPs oxidation (sulfhydryl loss, carbonyl and Schiff base formation) were dominated and associated with changes in pH, color, WHC, and textural properties during the later stage of frozen storage (12-24 weeks). Besides, the brining at 0.5 M improved the WHC of fillets with less undesirable changes in MPs and quality traits compared to other concentrations. The 12 weeks was an advisable storage time for salted frozen fish and our results might provide an available suggestion for fish preservation in aquatic industry.

Spectrophotometric method for the Determination of Sulfathiazole Drug by Schiff's base Formation

This research involves the development of simple, sensitive and rapid spectrophotometric method for determination of sulfathiazole (STHZ) in aqueous solution. The method is based on the Schiff's base formation between the primary amino group of sulfathiazole and aldehyde group of the p-dimethyl aminobenzaldehyde reagent (p-DMAB) to produce a yellow colored complex having maximum absorption at 451 nm at pH 2.2. Beer's law is obeyed in the concentration range 2-24μg/ml of sulfathiazole , with a molar absorptivity 11259 L.mol-1.cm-1 and sandal index of 0.023 μg.cm-2 . The average recovery is 99.925%, relative standard deviation 0.68-0.81% and D.L of 0.1534 μg/ml . This method has been applied successfully to determination of sulfathiazole in veterinary injection liquid solution (bio prime).

A strong, antimildew, and fully bio-based adhesive fabricated by soybean meal and dialdehyde chitosan

It is still a great challenge to develop soybean protein adhesives with high strength and antimildew properties through a sustainable and facile strategy. Herein, water-soluble dialdehyde chitosan (DCS) was obtained by oxidizing chitosan (CS) and used to crosslink soybean meal (SM) to fabricate protein adhesives via the Schiff base reaction. This strategy is simple, all-biomass, and without additional crosslinkers. Owing to the covalent imine bonds and non-covalent hydrogen bonds interactions, the adhesion strength of SM/DCS-4 adhesive reached 1.47 MPa, satisfying the requirement for Type II interior plywood (≥ 0.7 MPa). More importantly, the protein adhesives showed excellent antimildew properties due to the amino and aldehyde groups of DCS and the Schiff base formation. The SM/DCS-4 adhesive exhibited long shelf life (7 d), which is beneficial for industrial applications. This study helps in preparing green and fully bio-based adhesives from agricultural and fishery wastes.

Selective Schiff base formation via gas-phase ion/ion reactions to enable differentiation of isobaric lipids in imaging mass spectrometry.

The separation and identification of lipids in complex mixtures are critical to deciphering their cellular functions. Failure to resolve isobaric compounds (e.g., via high mass resolution or tandem mass spectrometry) can result in incorrect identifications in mass spectrometry experiments. In imaging mass spectrometry, unresolved peaks can also result in composite images of multiple compounds, giving inaccurate depictions of molecular distributions. Gas-phase ion/ion reactions can be used to selectively react with specific chemical functional groups on a target analyte, thereby extracting it from a complex mixture and shifting its m/z value to an unobstructed region of the mass range. Herein, we use selective Schiff base formation via a novel charge inversion ion/ion reaction to purify phosphatidylserines from other isobaric (i.e., same nominal mass) lipids and reveal their singular distributions in imaging mass spectrometry. The selective Schiff base formation between singly deprotonated phosphatidylserine (PS) lipid anions and doubly charged N,N,N',N'-tetramethyl-N,N'-bis(6-oxohexyl)hexane-1,6-diaminium (TMODA) cations is performed using a modified commercial dual source hybrid Fourier transform ion cyclotron resonance (FTICR) mass spectrometer. This process is demonstrated using the isobaric lipids [PS 40:6 - H]- (m/z 834.528) and [SHexCer d38:1 - H]- (m/z 834.576), which produces [PS 40:6 + TMODA - H - H2O]+ (m/z 1186.879), and [SHexCer d38:1 + TMODA-H]+ (m/z 1204.938) product ions following the gas-phase charge inversion reaction. These product ions differ by roughly 18Da in mass and are easily separated by low mass resolution analysis, while the isobaric precursor ions require roughly 45,000 mass resolving power (full-width at half maximum) to separate. Imaging mass spectrometry using targeted gas-phase ion/ion reactions shows distinct spatial distributions for the separated lipid product ions relative to the composite images of the unseparated precursor ions.