A Review on the Antimicrobial Activity of Schiff Bases: Data Collection and Recent Studies

Antiviral Potential and In Silico Insights of Polyphenols as Sustainable Phytopharmaceuticals: A Comprehensive Review

Polyphenols, particularly flavonoids, are reported to have health-promoting, disease-preventing abilities and several polyphenols having a wide spectrum of antiviral activities can be explored for preventive and/or therapeutic purposes. We have compiled the updated literature of diverse polyphenols active against common viral diseases, including herpes, hepatitis, influenza, rota and SARS-corona-viruses. The antiviral activity of bioactive polyphenols depends on the hydroxyl and ester groups of polyphenol molecules, as compounds with five or more hydroxyl groups and three specific methoxy groups showed antiviral potential, like anti-rabies activity. This comprehensive review will explore selective polyphenols isolated from common ethnomedicinal or food plants. Comparing bioactivities of structurally related polyphenols and using bioinformatics studies, we have explored the three most promising phyto-antivirals, including chrysin, resveratrol and quercetin, available in many foods and medicinal plants. Quercetin showed a maximum interaction score with human genes. We also explore the intricate structure-activity relationship between these polyphenols and pathogenic viruses with their mechanisms of antiviral action in selected virus models. Here, we report the promising potential of some phyto-polyphenols in the management of viral diseases through an in-depth analysis of the structure and bioactivity of these compounds.

Synthesis and Fungicidal Activities of Coumarin Derivatives as Succinate Dehydrogenase Inhibitors

Succinate dehydrogenase inhibitors (SDHIs) have been developed to the fastest growing family of fungicides. To develop novel succinate dehydrogenase (SDH) inhibitors, 27 novel non-amides coumarin derivatives were designed, synthesized, and characterized. The bioassay revealed that most of the target compounds exhibited significant antifungal activity against Botrytis cinerea in vitro. Notably, compounds 1a and 2c with EC50 values of 0.92 and 0.52 µg/mL, respectively, which were better than that of positive control chlorothalonil (EC50 = 3.14 µg/mL). Moreover, in vivo antifungal assay results showed that compound 2c could observably inhibit the growth of B. cinerea on Kuerla pears with remarkable protective at a dosage of 200 µg/mL. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) investigation indicated that compound 2c significantly damaged the cell structures of B. cinerea mycelium. Three-dimensional quantitative structure-activity relationship (3D-QSAR) models were analyzed for structure-activity relationships of all target compounds. Furthermore, molecular docking revealed that compound 2c was able to bind closely to the receptor protein of SDH. Enzyme activity analysis also further verified its inhibitory effect. These results demonstrated that compound 2c may be potential candidate for novel SDH inhibitors, and these results afforded further valuable reference for SDHIs discovery.

Spectroscopic, docking, antiproliferative, and anticancer activity of novel metal derivatives of phenylacetohydrazide Schiff base on different human cancer cell lines

In the last two decades, many Schiff bases have been investigated due to the importance of their metal complexes in the medical field and drug industry. The Schiff base metal complexes have several applications as anticancer agents because they have a high binding ability to nucleic acids (DNA and RNA). The Schiff base H2L, derived from the condensation of 2-phenylacetohydrazide and 2-hydroxynaphthaldehyde, was reacted with Fe2+, Zn2+, Cd2+, and Pt2+ to form the unique metal complexes [Fe(HL)2], [Zn2(HL)2](CH3COO)2, [Cd2(HL)2](CH3COO)2, and [Pt(H2L)Cl2]. Various analytical and spectroscopic techniques were used to characterize the newly reported compounds. The elemental and spectroscopic analysis revealed that the platinum complex was a square planar with 2.5 water molecules in the crystal lattice, whereas the iron complex had an octahedral geometry. The thermogravimetric analysis demonstrated the stability of the complexes and validated the dimerization of zinc and cadmium complexes. DFT calculations were investigated to obtain the optimized structure of the ligand and its complexes. Biological screening and molecular docking studies of the ligand and complexes were reported to explore their potential application as therapeutic drugs. Among the tested complexes, [Cd2(HL)2](CH3COO)2 complex showed the best cytotoxic effect, especially on the human colorectal cancer cell line (HCT116, IC50 = 0.329 µg/ml) as compared to normal human skin fibroblast (HSF, IC50 = 5.240 µg/ml) and selectivity index (SI) = 15.93. It represents a promising anticancer drug compared to Cisplatin (IC50 = 2.25µg/ml, SI = 4.92). The biological studies and molecular docking were correlated to each other.

Tryptamine-Derived Schiff Bases: Potent Antimicrobial Agents and Evaluation of Cytotoxicity, ADME and DNA Binding Properties

Inspired by the fact that the introduction of indole pharmacophore in organic scaffolds could enable interesting pharmacological properties, the series of novel tryptamine-derived Schiff bases was synthetized. Tryptamine was used as a source of indole pattern, as well as an example of biogenic amines which chemical transformations lead to the compounds with prominent biological activities. The obtained results for antimicrobial activity against a range of bacterial and fungal strains and cytotoxic activities have revealed that Schiff base TSB4 combining the tryptamine and p-nitro aryl patterns in the structure showed better antifungal activity at low concentrations than standard drug Fluconazole, while compound TSB6 with molecular scaffold composed from tryptamine and quinoline moieties showed certain cytotoxic effect on HCT-116 cell line with a strongly expressed selectivity about healthy fibroblast cells, MRC-5. For these two selected compounds, additional ADME analysis and DNA interactions were performed. to obtain better insight into their pharmacokinetics and determination of binding mode for DNA molecules. As results suggested, strong binding of examined compounds to CT-DNA was observed, while the ADME screening showed that selected compounds possess suitable physicochemical properties for oral bioavailability and druglikeness.

Fe3O4@SiO2/Schiff-base/Zn (II) nanocomposite functioning as a versatile antimicrobial agent against bacterial and fungal pathogens

Antimicrobial resistance (AMR) presents a critical global health issue, necessitating novel therapeutic strategies to manage bacterial and fungal infections. This study explores the development and evaluation of multifunctional Fe3O₄@SiO₂/Schiff-base/Zn (II) magnetic nanocomposite (MNC) with enhanced antimicrobial properties. The synthesized MNC combines the magnetic characteristics of Fe₃O₄ magnetic nanoparticles (MNPs) with the antimicrobial properties of Schiff-base ligand functionalized with Zn (II) ions. The preparation involved the coprecipitation of Fe₃O₄, coating with SiO₂ via a modified Stöber method, and subsequent functionalization with Schiff-base/Zn (II) complex. Comprehensive characterization using FT-IR, XRD, SEM, TEM, DLS, EDX, VSM, and TGA confirmed successful synthesis, structural integrity, and superparamagnetic behavior of the MNPs and MNC. The antifungal and antibacterial activities were assessed against six Candida species and four bacterial strains using broth microdilution methods. The Fe₃O₄@SiO₂/Schiff-base/Zn (II) MNC exhibited significant inhibitory effects, with MIC values of 8-64 µg/mL for Candida species and 64-512 µg/mL for bacteria, demonstrating potent antimicrobial efficacy. The MTT assay indicated biocompatibility across various concentrations, except for slight cytotoxicity at 256 µg/mL after five days. To our knowledge, this is the first report integrating Zn (II) Schiff-base ligands into magnetic nanoparticles to achieve a versatile platform for both antimicrobial and biofilm inhibition applications.

A quinoline derivative exerts antineoplastic efficacy against solid tumour by inducing apoptosis and anti-angiogenesis both in vitro and in vivo

Cancer is a heterogeneous and multicomplex disease with the highest morbidity and mortality rate. The targeting of tumour progression with drugs is a very well-established treatment strategy. Despite these, due to the failure of commonly used drugs in combating cancer, new drugs need to be screened and established for better therapeutic approach. With this rationale, the current investigation was aimed to develop quinoline compound (QC) derivatives as anti-tumour molecules. In this extended study, a series of QC analogues were subjected to anti proliferative assays through cell-based screening and evaluated its mechanism of action through apoptotic and anti-angiogenic assays. The change in cell behaviour was assessed through gene expression analysis using qRT-PCR and immunoblot analysis. Further, in vivo solid tumour model was developed and the anti-tumour potential of QC-4 was verified with gene expression studies. The results suggested that QC-4 exhibited significant cytotoxic effect, particularly against human lung adenocarcinoma cell lines and murine Ehrlich Ascites Carcinoma cells. The QC-4 induced condensation, nuclear damage and changes in membrane integrity resulted in apoptosis and neovascularisation inhibition. The modulation of apoptotic and angiogenic genes such as BAX, BAD, p53 and MMP-2 and 9 further supported the molecular cause of cytotoxicity induced by QC-4. The regression of in vivo solid tumour with extended survivability warranted the in vitro results and the gene expression patterns were additionally supportive. Overall, the QC-4 analogue exhibits the anti-neoplastic with a multi-target approach, reserving its capacity to be developed into a new class of the anticancer molecules.

Exploring 1,2,3-triazole-Schiff's base hybrids as innovative EGFR inhibitors for the treatment of breast cancer: In vitro and in silico study

EGFR inhibitors are a class of targeted therapies utilized in the management of certain tumor kinds such as NSCLC and breast cancer. Series of 1,2,3-triazole-Schiff's base hybrids were designed, synthesized, and estimated for their antitumor effect toward breast cancer cells, MCF-7 and MDA-MB-231. The safety and selectivity of the new compounds were tested using normal cell (WI-38). Analogs 4a, 4b, and 5f demonstrated significant antitumor effects toward both MCF-7 and MDA-MB-231 with IC50 range of 5.61-18.01 µM in comparison to Doxorubicin (6.72 µM). Moreover, they proved considerable selectivity toward the tested cancer cells (SI values of 4.36-5.33). The superior compounds were investigated for EGFR inhibition where compounds 4b and 5f showed the highest EGFR inhibition effect with IC50 equal 0.16 and 0.15 µM, respectively utilizing Gefitinib as reference (IC50 = 0.081 µM). Further mechanistic studies for hybrid 5f in MDA-MB-231 cells, exhibited cell cycle arrest at G2/M phase by 29.85 % that was accompanied by the elevation of apoptosis percent by 48-fold more than the control. The apoptosis studies indicated that hybrid 5f was able to upregulate Bax (9.43 folds) while downregulate Bcl-2 (0.27) with substantial remarkable elevation of Bax/Bcl-2 ratio (35:1). Furthermore, it upregulated both caspases 8 and 9 by 2.93 and 6.54-fold, respectively. Molecular modeling studies showed the good binding affinity of compounds 4b and 5f with EGFR kinase active site explaining their potent biological effects. Drug likeness and ADMET features of compounds 4b and 5f demonstrated that they represent promising drug like candidates against breast cancer.

Sustainable synthesis of benzimidazole-based Schiff base using reusable CaAl2O4 nanophosphors catalyst: Insights into metal(II) complexes and DNA interactions

This article presents a new and facile method for the synthesis of Schiff base compounds with a benzimidazole group using a low-cost and reusable calcium aluminate nanophosphorus catalyst (CaAl2O4). This approach avoids harmful solvents and reactants, supporting a more environmentally friendly synthesis process. The catalyst maintained its activity and heterogeneity over four cycles with minimal loss of efficiency. The synthesis process was straightforward and eliminated the need for column chromatography. The Schiff base ligand (HL=(E)-N-((6-(thiophen-2-yl)pyridin-2-yl)methylene)-1H-benzo[d]imidazol-2-amine)) was synthesized by the reaction of 6-(thiophen-2-yl)pyridine-2-carbaldehyde with 1H-benzimidazole-2-amine. Subsequently, metal(II) complexes of Co(II), Ni(II), and Cu(II) were prepared using this ligand. Structural analysis of both the ligand and its metal complexes was carried out using various physicochemical and spectroscopic methods. Ni(II) and Co(II) complexes were found to adopt an octahedral geometry, while the Cu(II) complex exhibited a square-planar structure. Binding studies with calf thymus DNA (CT-DNA) at pH 7.2 were performed using UV-visible spectroscopy, viscosity measurements, and thermal denaturation studies and showed that the metal complexes intercalate into the DNA and produced a distinct binding pattern. Molecular docking simulations with AutoDock Vina provided insights into the interaction of these complexes with the B-DNA dodecamer. Furthermore, the ligand and its metal complexes showed UV-visible photonuclease activity against pUC19 DNA. Agarose gel electrophoresis showed that the metal complexes exhibit photoinduced nuclease activity, confirming their ability to cleave DNA upon exposure to light.

Chitosan-Based Schiff Bases (CSBs) and Their Metal Complexes: Promising Antimicrobial Agents

The scientific interest in the chemical modification of chitosan to increase its solubility and application has led to its conjugation with Schiff bases, which are interesting scaffolds endowed with diverse biological properties. The resultant chitosan-based Schiff bases (CSBs) are widely studied in scientific literature due to the myriad of activities exerted, both catalytic and biological, including anticancer, anti-inflammatory, antioxidant, and especially antimicrobial ones. Antimicrobial resistance (AMR) is one of the major public health challenges of the twenty-first century because it represents a threat to the prevention and treatment of a growing number of bacterial, parasitic, viral, and fungal infections that are no longer treatable with the available drugs. Thus, in this review, we present a brief outline of the biological activities of CSBs as well as their complexes with metals, with a particular focus on the recent literature regarding the antimicrobial effect of these captivating derivatives.

A Formyl Chromone Based Schiff Base Derivative: An Efficient Colorimetric and Fluorescence Chemosensor for the Selective Detection of Hg2+ Ions

A novel chromone-based Schiff base L was designed and synthesized by condensing an equimolar amount of 3-formyl chromone and 2,4-dinitro phenyl hydrazine. Schiff base L was developed as a potent colorimetric and fluorescent molecular probe to recognize Hg2+ ions over other competitive metal ions. In the presence of Hg2+, Schiff base L displays a naked-eye detectable color change under day and UV365 nm light. Various UV-Vis and fluorescence studies of L were performed in the absence and presence of Hg2+ to determine the sensitivity and the sensing mechanism. With high selectivity and specificity, the detection limit and association constant of L for Hg2+ were estimated at 1.87 µM and 1.234 × 107 M-1, respectively. The developed sensor L was applied to real soil samples for the detection of Hg2+.

A Captivating Potential of Schiff Bases Derivatives for Antidiabetic Activity

A double bond between the nitrogen and carbon atoms characterizes a wide class of compounds known as Schiff bases. The flexibility of Schiff bases is formed from several methods and may be combined with alkyl or aryl substituents. The group is a part of organic compounds, either synthetic or natural, and it serves as a precursor and an intermediate in drugs that have therapeutic action. The review focuses on molecular docking and structure-activity relationship (SAR) analysis for antidiabetic effects of the different nonmetal Schiff bases. Many studies have found that Schiff bases are used as linkers in an extensive range of synthesized compounds and other activities. Thus, this current study aims to give the scientific community a thoughtful look at the principal ideas put forward by investigators regarding antidiabetic actions exhibited by certain Schiff-based derivatives, as this review covered many aspects, including docking and SAR analysis. For individuals who intend to create novel antidiabetic compounds with Schiff bases as pharmacophores or physiologically active moieties, it will be an invaluable informational resource.

Highly Sensitive and Selective Detection of Hg2+ ions and Antibacterial Activity Using a Schiff-base Derivative

A simple and highly effective Schiff-base fluorescent chemosensor (S1) was synthesized and characterized by 1HNMR and fluorescence spectroscopy. The synthesized chemosensor was applied for the selective and sensitive detection of Hg2+ ions. The chemosensor exhibited a strong 'turn-on' fluorescence response in a CH3OH/H2O (1:9, v/v) solution due to complex formation (S1-Hg2+) which block photo induce electron transfer (PET). The chemosensor showed significant sensitivity with very low detection limit of 2.0 ppb, making it suitable for trace-level Hg2+ detection. Furthermore, the S1-Hg2+ complex demonstrated excellent antibacterial activity against various Gram-positive and Gram-negative bacterial strains, broadening its utility beyond sensing. This dual-functional system offers significant potential in environmental and biomedical applications.

Evaluation of Quinazolin-2,4-Dione Derivatives as Promising Antibacterial Agents: Synthesis, In Vitro, In Silico ADMET and Molecular Docking Approaches

A series of new quinazolin-2,4-dione derivatives incorporating amide/eight-membered nitrogen-heterocycles 2a-c, in addition, acylthiourea/amide/dithiolan-4-one and/or phenylthiazolidin-4-one 3a-d and 4a-d. The starting compound 1 was prepared by reaction of 4-(2,4-dioxo-1,4-dihydro-2H-quinazolin-3-yl)-benzoyl chloride with ammonium thiocyanate and cyanoacetic acid hydrazide. The reaction of 1 with strong electrophiles, namely, o-aminophenol, o-amino thiophenol, and/or o-phenylene diamine, resulted in corresponding quinazolin-2,4-dione derivatives incorporating eight-membered nitrogen-heterocycles 2a-d. Compounds 3a-d and 4a-d were synthesized in good-to-excellent yield through a one-pot multi-component reaction (MCR) of 1 with carbon disulfide and/or phenyl isocyanate under mild alkaline conditions, followed by ethyl chloroacetate, ethyl iodide, methyl iodide, and/or concentrated HCl, respectively. The obtained products were physicochemically characterized by melting points, elemental analysis, and spectroscopic techniques, such as FT-IR, 1H-NMR, 13C-NMR, and MS. The antibacterial efficacy of the obtained eleven molecules was examined in vitro against two Gram-positive bacterial strains (Staphylococcus aureus and Staphylococcus haemolyticus). Furthermore, Computer-Aided Drug Design (CADD) was performed on the synthesized derivatives, standard drug (Methotrexate), and reported antibacterial drug with the target enzymes of bacterial strains (S. aureus and S. haemolyticus) to explain their binding mode of actions. Notably, our findings highlight compounds 2b and 2c as showing both the best antibacterial activity and docking scores against the targets. Finally, according to ADMET predictions, compounds 2b and 2c possessed acceptable pharmacokinetics properties and drug-likeness properties.

Injectable hemostatic hydrogel adhesive with antioxidant, antibacterial and procoagulant properties for hemorrhage wound management

In emergencies, uncontrolled severe bleeding can result in undesired complications and even death of the injured. Designing advanced hemostatic agents is a potential solution for emergency hemostasis, yet it remains challenging to realize the persistent adhesion in a wet wound environment. In this study, based on dynamic reversible Schiff base bond and photo-initiated double-bond polymerization, a novel injectable hemostatic hydrogel (L-COC) consisting of methacrylated carboxymethyl chitosan (CMCSMA), oxidized konjac glucomannan (OKGM) and (+)-catechin hydrate (CH) was synthesized for emergency hemostasis. To our delight, the incorporated CH imparted enhanced blood procoagulantion to the L-COC hydrogel by intensifying the hydrogel-red blood cell interactions. As a result, the hemostatic effect of the engineered L-COC hydrogel was significantly superior to that of fluid gelatin SurgifloTM for liver bleeding wounds in rats (Blood loss: 0.62 ± 0.11 g (L-COC), 0.90 ± 0.08 g (SurgifloTM); hemostasis time: 69.0 ± 2.9 s (L-COC), 84.0 ± 2.2 s (SurgifloTM)). With the favorable antioxidant and antibacterial activities, as well as multifunctional properties, the bio-adhesive L-COC hydrogel and the underlying design principles may facilitate further development of practical hemostatic hydrogels.

Schiff Base-Based Molybdenum Complexes as Green Catalyst in the Epoxidation Reaction: A Minireview

Epoxides are class of cyclic ether and have been extensively used in petrochemicals and pharmaceuticals industries as raw materials. Due to this reasons, development of the synthetic strategy of epoxides are getting enormous interest among the research chemists. In terms of "development of the synthetic strategy", the use of a catalyst, especially, Schiff base-based complex is of potential interest due to alternative easy routes and significant advances in metal-mediated pathways giving rise to diverse degree of substrate-reagent interactions. In addition, the synthetic strategy that follows the 12 principles of green chemistry, particularly (i) reduce the use of organic solvent, especially toxic solvents, and (ii) increasing the use of catalysts to obtain selective and quick processes in terms of atom economy, are of great attention now a days. The present review encompasses the Schiff base-based molybdenum complexes as green catalyst in the epoxidation reaction. Molybdenum complexes have grown interest owing to lower cost, environmental protection and commercialization as well as its abundance in different metalloenzymes. On the other hand, molybdenum complexes speed up the O-O bond break of tert-butylhydroperoxide (TBHP); as a result, it accelerates the oxygen transfer process from TBHP to the olefin. This review mainly focused on the catalytic activity of molybdenum-based Schiff base complexes for the epoxidation reaction in water/solvent free condition.

Unveiling Fluorescence Spectroscopy, Molecular Docking and Dynamic Simulations: Interactions Between Protein and 2, 4-Dinitrophenylhydrazine Schiff Base

In this study, we aimed to explore the interaction mechanism between bovine serum albumin (BSA) and a Schiff base compound derived from 2,4-dinotrophenyl hydrazine (L) using various spectroscopic techniques. The interaction between BSA and synthesizing molecule can provide insights into binding affinity, conformational changes and potential applications in drug delivery or biochemistry. The interaction between BSA and L was studied by using UV-Vis and fluorescence titration analysis. The fluorescence quenching emission was observed at 343 nm, upon addition of L to the buffer solution of BSA. The binding between BSA and ligand is static in nature using fluorescence quenching emission. The thermodynamic parameters were calculated from the temperature-dependent binding constants (i.e., ∆H = -0.318 kcal/mol, ∆G = -7.857 kcal/mol and ∆S = 0.023 kcal/mol), which indicated that the protein-ligand complex formation between L and BSA is mainly due to the electrostatic interactions. The experimental and theoretical results showed excellent agreement with respect to the mechanism of binding and binding constants. The molecular docking and molecular dynamic analysis experiments were performed to establish the interaction between protein and ligand.

Synthesis of biologically active cefpodoxime and vanillin-based schiff base metal complexes with the detailed biological evaluations

Schiff bases of existing antimicrobial drugs are an area, which is still to be comprehensively explored to improve drug efficiency against consistently resisting bacterial species. In this study, we have targeted a new and eco-friendly method of condensation reaction that allows the "green synthesis" as well as improved biological efficacy. The transition metal complexes of cefpodoxime with well-enhanced biological activities were synthesized. The condensation reaction product of cefpodoxime and vanillin was further reacted with suitable metal salts of [Mn (II), Cu (II), Fe (II), Zn (II), and Ni (II)] with 1:2 molar ratio (metal: ligand). The characterization of all the products were carried out by using UV-Visible, elemental analyzer, FTIR, 1H-NMR, ICP-OES, and LC-MS. Electronic data obtained by UV-Visible proved the octahedral geometry of metal complexes. The biological activities Schiff base ligand and its transition metal complexes were tested by using in-vitro anti-bacterial analysis against various Gram-negative, as well as Gram-positive bacterial strains. Proteinase and protein denaturation inhibition assays were utilized to evaluate the products in-vitro anti-inflammatory activities. The in vitro antioxidant activity of the ligand and its complexes was evaluated by utilizing the 2,2-diphenyl-1-picrylhydrazyl (DPPH) in-vitro method. The final results proved metal complexes to be more effective against bacterial microorganisms as compared to respective parent drug as well as their free ligands. Patch Dock, a molecular docking tool, was used to dock complexes 1a-5e with the crystal structure of GlcN-6-P synthase (ID: 1MOQ). According to the docking results, complex 2b exhibited a highest score (8,882; ACE = -580.43 kcal/mol) that is well correlated with a high inhibition as compared to other complexes which corresponds to the antibacterial screening outcomes.

Glutaraldehyde crosslinked ternary carboxymethylcellulose/polyvinyl alcohol/polyethyleneimine film with enhanced mechanical properties, water resistance, antibacterial activity, and UV-shielding ability without any UV absorbents

Despite the plethora of methods reported for fabricating ultraviolet (UV) shielding films using various UV absorbers to date, it remains a major challenge for the development of novel UV shielding films that simultaneously exhibit excellent transparency. In this work, a novel composite film (GA-x-CMC/PVA/PEI) is fabricated by integrating anionic carboxymethylcellulose (CMC), cationic polyethyleneimine (PEI), and polyvinyl alcohol (PVA) via electrostatic and hydrogen bond interactions and further cross-linking with glutaraldehyde (GA). Herein, PVA expands hydrogen bonding networks, reduces film haze, and enhances its mechanical strength. GA acts as a crosslinker in producing Schiff bases with PEI and acetals with CMC and PVA. The synthesized GA-x-CMC/PVA/PEI composite film possesses a notable amount of unsaturated -CH=N- bonds of Schiff base, resulting from the condensation of PEI and GA, which exhibit superior shielding efficiency against both UV-A and UV-B rays while maintaining exceptional transparency, visibility, and simultaneously enhancing mechanical properties and thermal stability. Notably, increasing the content of PEI leads to almost complete shielding of the entire UV spectrum (<400 nm) due to the increasing of the number of -CH=N- unsaturated bonds. Furthermore, the obtained film without any UV-shielding additives has exceptional mechanical properties, hydrophobicity, and antibacterial properties, rendering it a wide application prospect.

Synthesis of Ferrocenyl Chalcone-Containing Aminourea Schiff Bases and Their Detection on Tryptophan

In this paper, 1-phenyl-3-ferrocenylenone aminourea Schiff bases were synthesized by a novel method. A multifunctional molecular probe (Probe A) of 1-phenyl-3-ferrocenylenone, carbon-based solid acid, aminourea, and anhydrous ethanol was synthesized by adding them to a vessel at elevated temperatures and refluxing for the synthesis of a multifunctional molecular probe (Probe A) of 1-phenyl-3-ferrocenylenone aminourea Schiff base, and it was found that it recognizes tryptophan (Trp) in solution, and that the catalyst can be reused more than five times after recycling. This method is characterised by low cost, high efficiency, green environment and no waste acid. Fluorescence and UV spectra show that probe A specifically recognizes tryptophan (Trp) without interference by other amino acids or pH and time does not affect it within 45 min. The lowest limit of detection for Trp was 1.307 × 10- 4 mol/L for probe A. The binding ratios of probe A to Trp were measured to be 1:1 by Job's plotting method, respectively. The complexation constant of probe A with Trp was found to be 2.733 × 107 L/mol according to the Benesi-Hildebrand equation. The bonding mechanism was explored through IR spectroscopy and ¹H NMR titration.

An Integrated All-Natural Conductive Supramolecular Hydrogel Wearable Biosensor with Enhanced Biocompatibility and Antibacterial Properties

Conductive hydrogels exhibit tremendous potential for wearable bioelectronics, biosensing, and health monitoring applications, yet concurrently enhancing their biocompatibility and antimicrobial properties remains a long-standing challenge. Herein, we report an all-natural conductive supramolecular hydrogel (GT5-DACD2-B) prepared via the Schiff base reaction between the biofriendly dialdehyde cyclodextrin and gelatin. The potent antibacterial agent fusidic acid (FA) is incorporated through host-guest inclusion, enabling 100% inhibition of Staphylococcus aureus proliferation. The biocompatibility of our hydrogel is bolstered with tannic acid (TA) facilitating antibacterial effects through interactions with gelatin, while borax augments conductivity. This supramolecular hydrogel not only exhibits stable conductivity and rapid response characteristics but also functions as a flexible sensor for monitoring human movement, facial expressions, and speech recognition. Innovatively integrating biocompatibility, antimicrobial activity, and conductivity into a single system, our work pioneers a paradigm for developing multifunctional biosensors with integrated antibacterial functionalities, paving the way for advanced wearable bioelectronics with enhanced safety and multifunctionality.

Exploring biological activities of novel Schiff bases derived from amlodipine and in silico molecular modeling studies

Aim: Calcium channel antagonists are of considerable interest in treating elevated blood pressure and its pathologies.Materials & methods: Schiff base derivatives of amlodipine were produced to check its urease inhibition potentials as well antibacterial and antioxidant activities. Structural illustration along with chemical characterization were achieved by spectral techniques (1H NMR, FTIR, 13C NMR) and docking studies also performed.Results & conclusion: 3g displayed remarkable anti-hypertensive activity compared with parent drug. 3b, 3f and 3g showed urease inhibition potentials. These compounds can aid as lead for further investigations since they exhibited comparable or superior interactions.

Recent Development of Functional Bio-Based Epoxy Resins

The development of epoxy resins is mainly dependent on non-renewable petroleum resources, commonly diglycidyl ether bisphenol A (DGEBA)-type epoxy monomers. Most raw materials of these thermoset resins are toxic to the health of human beings. To alleviate concerns about the environment and health, the design and synthesis of bio-based epoxy resins using biomass as raw materials have been widely studied in recent decades to replace petroleum-based epoxy resins. With the improvement in the requirements for the performance of bio-based epoxy resins, the design of bio-based epoxy resins with unique functions has attracted a lot of attention, and bio-based epoxy resins with flame-retardant, recyclable/degradable/reprocessable, antibacterial, and other functional bio-based epoxy resins have been developed to expand the applications of epoxy resins and improve their competitiveness. This review summarizes the research progress of functional bio-based epoxy resins in recent years. First, bio-based epoxy resins were classified according to their unique function, and synthesis strategies of functional bio-based epoxy resins were discussed, then the relationship between structure and performance was revealed to guide the synthesis of functional bio-based epoxy resins and stimulate the development of more types of functional bio-based epoxy resins. Finally, the challenges and opportunities in the development of functional bio-based epoxy resins are presented.

Photocatalyzed Synthesis of a Schiff Base via C-N Bond Formation: Benzyl Alcohol as Sustainable Surrogates of Aryl Aldehydes

The advancement of photocatalytic techniques has enabled green chemical synthesis through visible-light-mediated photochemical oxidation under mild conditions. A novel approach under visible-light conditions was facilitated by eosin-Y for the reaction between substituted benzyl alcohols and anilines, resulting in the synthesis of diverse Schiff bases. This innovative method is emphasized for its environmentally friendly nature, lack of metal catalysts, cost-effectiveness, and nontoxic characteristics.

Bio-Based Thermosetting Resins: From Molecular Engineering to Intrinsically Multifunctional Customization

Recent years have witnessed a growing interest in bio-based thermosetting resins in terms of environmental concerns and the desire for sustainable industrial practices. Beyond sustainability, utilizing the structural diversity of renewable feedstock to craft bio-based thermosets with customized functionalities is very worthy of expectation. There exist many bio-based compounds with inherently unique chemical structures and functions, some of which are even difficult to synthesize artificially. Over the past decade, great efforts are devoted to discovering/designing functional properties of bio-based thermosets, and notable progress have been made in antibacterial, antifouling, flame retardancy, serving as carbon precursors, and stimuli responsiveness, among others, largely expanding their application potential and future prospects. In this review, recent advances in the field of functional bio-based thermosets are presented, with a particular focus on molecular structures and design strategies for discovering functional properties. Examples are highlighted wherein functionalities are facilitated by the inherent structures of bio-based feedstock. Perspectives on issues regarding further advances in this field are proposed at the end.

Tungsten Oxide Dispersed on Silica as Robust and Readily Available Oxo/Imido Heterometathesis Catalyst

Continuing our investigation of catalytic oxo/imido heterometathesis as novel water-free method for C=N bond construction, we report here the application of classical transition metal oxides dispersed on silica (MOx/SiO2, M=V, Mo, W) as cheap, robust and readily available alternative to the catalysts prepared via Surface Organometallic Chemistry (SOMC). The oxide materials demonstrated activity in heterometathetical imidation of ketones, WO3/SiO2 being the most efficient. We also describe a new well-defined supported W imido complex (≡SiO)W(=NMes)2(Me2Pyr) (Mes=2,4,6-Me3C6H2, Me2Pyr=2,5-dimethylpyrrolyl) and characterize it with SOMC protocols, which allowed us to identify the position of W on the oxo/imido heterometathesis activity scale (Mo Collapse

Key Words

• imido
• imines
• metathesis
• supported catalysts
• tungsten

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MESH Headings Collapse

Grants

• 19-73-10163 Russian Science Foundation
• 075-00277-24-00 Ministry of Science and Higher Education of the Russian Federation

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Affiliation(s)

Nikolai S Bushkov A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilov str., 28, 119334, Moscow, Russia
Andrey V Rumyantsev A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilov str., 28, 119334, Moscow, Russia Chemistry Department, Moscow State University, Vorob'evy Gory, 1, 119992, Moscow, Russia
Anton A Zhizhin A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilov str., 28, 119334, Moscow, Russia
Tatyana V Strelkova A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilov str., 28, 119334, Moscow, Russia
Roman A Novikov N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky prosp., 47, 119991, Moscow, Russia
Evgenii I Gutsul A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilov str., 28, 119334, Moscow, Russia
Rina U Takazova A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilov str., 28, 119334, Moscow, Russia
Dinara K Kitaeva A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilov str., 28, 119334, Moscow, Russia
Nikolai A Ustynyuk A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilov str., 28, 119334, Moscow, Russia
Pavel A Zhizhko A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilov str., 28, 119334, Moscow, Russia
Dmitry N Zarubin A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilov str., 28, 119334, Moscow, Russia

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Lipid-based nanosystems for wound healing

INTRODUCTION

Wounds, resulting from traumas, surgery, burns or diabetes, are important medical problems due to the complexity of wound healing process regarding healing times and healthcare costs. Nanosystems have emerged as promising candidates in this field thank to their properties and versatile applications in drugs delivery.

AREAS COVERED

Lipid-based nanosystems (LBN) are described for wound treatment, highlighting their different behaviors when interacting with the cutaneous tissue. The role of nanosystems in delivering mostly natural compounds on skin as well as the technological and engineering strategies to increase their efficiency in wound healing effect are reviewed. Finally, in vitro, ex-vivo and in vivo studies are reported.

EXPERT OPINION

LBN have shown promise in addressing the challenges of wound healing as they can improve the stability of drugs used in wound therapy, leading to higher efficacy and fewer adverse effects as compared to traditional formulations. LBNs being involved in the inflammatory and proliferation stages of the wound healing process, enable the modification of wound healing through multiple ways. In addition, the use of new technologies, including 3D bioprinting and photobiomodulation, may lead to potential breakthroughs in wound healing. This would provide clinicians with more potent forms of therapy for wound healing.

Discovery of new Schiff bases of the disalicylic acid scaffold as DNA gyrase and topoisomerase IV inhibitors endowed with antibacterial properties

DNA gyrase and topoisomerase IV show great potential as targets for antibacterial medicines. In recent decades, various categories of small molecule inhibitors have been identified; however, none have been effective in the market. For the first time, we developed a series of disalicylic acid methylene/Schiff bases hybrids (5a-k) to act as antibacterial agents targeting DNA gyrase and topoisomerase IV. The findings indicated that the new targets 5f-k exhibited significant antibacterial activity against Gram-positive and Gram-negative bacteria, with efficacy ranging from 75% to 115% of the standard ciprofloxacin levels. Compound 5h demonstrated the greatest efficacy compared to the other compounds tested, with minimum inhibitory concentration (MIC) values of 0.030, 0.065, and 0.060 μg/mL against S. aureus, E. coli, and P. aeruginosa. 5h had a MIC value of 0.050 μg/mL against B. subtilis, which is five times less potent than ciprofloxacin. The inhibitory efficacy of the most potent antibacterial derivatives 5f, 5h, 5i, and 5k against E. coli DNA gyrase was assessed. The tested compounds demonstrated inhibitory effects on E. coli DNA gyrase, with IC50 values ranging from 92 to 112 nM. These results indicate that 5f, 5h, 5i, and 5k are more effective than the reference novobiocin, which had an IC50 value of 170 nM. Compounds 5f, 5h, 5i, and 5k were subjected to additional assessment against E. coli topoisomerase IV. Compounds 5h and 5i, which have the highest efficacy in inhibiting E. coli gyrase, also demonstrated promising effects on topoisomerase IV. Compounds 5h and 5i exhibit IC50 values of 3.50 µM and 5.80 µM, respectively. These results are much lower and more potent than novobiocin's IC50 value of 11 µM. Docking studies demonstrate the potential of compound 5h as an effective dual inhibitor against E. coli DNA gyrase and topoisomerase IV, with ADMET analysis indicating promising pharmacokinetic profiles for antibacterial drug development.

Designing and synthesis of injectable hydrogel based on carboxymethyl cellulose/carboxymethyl chitosan containing QK peptide for femoral head osteonecrosis healing

Femoral head necrosis is a debilitating disorder that typically caused by impaired blood supply to the hip joint. In this study, a novel injectable hydrogel based on Oxidized Carboxymethyl Cellulose (OCMC)-Carboxymethyl Chitosan (CMCS) polymers containing an angiogenesis stimulator peptide (QK) with a non-toxic crosslinking interaction (Schiff based reaction) was synthesized to enhance angiogenesis following femoral head necrosis in an animal model. The physicochemical features of fabricated injectable hydrogel were analyzed by FTIR, swelling and degradation rate, rheometry, and peptide release. Also, the safety and efficacy were evaluated following an in vitro hydrogel injection study and an avascular necrosis (AVN) animal model. According to the results, the hydrogel exhibited an appropriate swelling ratio and water uptake (>90 %, 24 h) as well as a suitable degradation rate over 21 days accompanied by a continuous peptide release. Also, data showed that hydrogels containing QK peptide boosted the proliferation, differentiation, angiogenesis, and osteogenic potential of both Bone Marrow mesenchymal Stem Cells (BM-MSCs) and human umbilical vein endothelial cells (HUVECs) (****p < 0.0001 and ***p < 0.001, respectively). Furthermore, molecular and histological evaluations significantly demonstrated the overexpression of Runx2, Osteocalcin, Collagen I, VEGF and CD34 genes (**p < 0.01 and ***p < 0.001, respectively), and also femoral head necrosis was effectively prohibited, and more blood vessels were detected in defect area by OCMC-CMCS hydrogel containing QK peptide (bone trabeculae >9000, ***p < 0.001). In conclusion, the findings demonstrate that OCMC-CMCS-QK injectable hydrogel could be considered as an impressive therapeutic construct for femoral head AVN healing.

Current Perspectives on Biological Screening of Newly Synthetised Sulfanilamide Schiff Bases as Promising Antibacterial and Antibiofilm Agents

Growing resistance to antimicrobials, combined with pathogens that form biofilms, presents significant challenges in healthcare. Modifying current antimicrobial agents is an economical approach to developing novel molecules that could exhibit biological activity. Thus, five sulfanilamide Schiff bases were synthesized under microwave irradiation and characterized spectroscopically and in silico. They were evaluated for their antimicrobial and antibiofilm activities against both Gram-positive and Gram-negative bacterial strains. Their cytotoxic potential against two cancer cell lines was also determined. Gram-positive bacteria were susceptible to the action of these compounds. Derivatives 1b and 1d inhibited S. aureus's growth (MIC from 0.014 mg/mL) and biofilm (IC from 0.029 mg/mL), while compound 1e was active against E. faecalis's planktonic and sessile forms. Two compounds significantly reduced cell viability at 5 μg/mL after 24 h of exposure (1d-HT-29 colorectal adenocarcinoma cells, 1c-LN229 glioblastoma cells). A docking study revealed the increased binding affinities of these derivatives compared to sulfanilamide. Hence, these Schiff bases exhibited higher activity compared to their parent drug, with halogen groups playing a crucial role in both their antimicrobial and cytotoxic effects.

Comparative study on Antibacterial efficacy of a series of chromone sulfonamide derivatives against drug-resistant and MDR-isolates

Sulfonamide derivatives have numerous pharmaceutical applications having antiviral, antibacterial, antifungal, antimalarial, anticancer, and antidepressant activities. The structural flexibility of sulfonamide derivatives makes them an excellent candidate for the development of new multi-target agents, although long-time exposure to sulfonamide drugs results in many toxic impacts on human health. However, sulfonamides may be functionalized for developing less toxic and more competent drugs. In this work, sulfonamides including Sulfapyridine (a), Sulfathiazole (b), Sulfamethoxazole (c), and Sulfamerazine (d) are used to synthesize Schiff bases of 7-hydroxy-4-methyl-2-oxo-2H-chromene-8-carbalde-hyde (1a-1d). The synthesized compounds were spectroscopically characterized and tested against hospital isolates of three Gram-positive (Methicillin-resistant Staphylococcus aureus PH217, Ampicillin-resistant Coagulase-negative Staphylococcus aureus, multidrug-resistant (MDR) Enterococcus faecalis PH007R) and two Gram-negative bacteria (multidrug-resistant Escherichia coli, and Salmonella enterica serovar Typhi), compared to the quality control strains from ATCC (S. aureus 29213, E. faecalis 25922, E. coli 29212) and MTCC (S. Typhi 734). Two of the four Schiff bases 1a and 1b are found to be more active than their counterpart 1c and 1d; while 1a have showed significant activity by inhibiting MRSA PH217 and MDR isolates of E. coli at the minimum inhibitory concentration (MIC) of 150 μg/mL and 128 μg/mL with MBC of 1024 µg/mL, respectively. On the other hand, the MIC of 1b was 150 μg/mL against both S. aureus ATCC 29213 and Salmonella Typhi MTCC 734, compared to the control antibiotics Ampicillin and Gentamycin. Scanning electron microscopy demonstrated the altered surface structure of bacterial cells as a possible mechanism of action, supported by the in-silico molecular docking analysis.

New Water-Soluble (Iminomethyl)benzenesulfonates Derived from Biogenic Amines for Potential Biological Applications

In this paper, a highly efficient and straightforward method for synthesizing novel Schiff bases was developed by reacting selected biogenic amines with sodium 2-formylbenzene sulfonate and sodium 3-formylbenzene sulfonate. 1H and 13C NMR, IR spectroscopy, and high-resolution mass spectrometry were used to characterize the new compounds. The main advantages of the proposed procedure include simple reagents and reactions carried out in water or methanol and at room temperature, which reduces time and energy. Moreover, it was shown that the obtained water-soluble Schiff bases are stable in aqueous solution for at least seven days. Additionally, the antioxidant and antimicrobial activity of synthesized Schiff bases were tested.

Antidiabetes and antioxidant potential of Schiff bases derived from 2-naphthaldehye and substituted aromatic amines: Synthesis, crystal structure, Hirshfeld surface analysis, computational, and invitro studies

Three Schiff bases were synthesised by the condensation reaction between 2-napthaldehyde and aromatic amines to afford (E)-N-mesityl-1-(naphthalen-2-yl)methanimine (L1), (E)-N-(2,6-dimethylphenyl)-1-(naphthalen-2-yl)methanimine (L2) and (E)-N-(2,6-diisopropylphenyl)-1-(naphthalen-2-yl)methanimine (L3). The synthesised compounds were characterised using UV-visible, NMR (13C & 1H), and Fourier transform infrared spectroscopic methods while their purity was ascertained by elemental analysis. Structural analysis revealed that the naphthalene ring is almost coplanar with the imine functional group as evident by C1-C10-C11-N1 torsion angles of 176.4(2)° and 179.4(1)° in L2 and L3, respectively. Of all the various intermolecular contacts, H⋯H interactions contributed mostly towards the Hirshfeld surfaces of both L2 (58.7 %) and L3 (69.7 %). Quantum chemical descriptors of L1 - L3 were determined using Density Functional Theory (DFT) and the results obtained showed that the energy band gap (ΔE) for L1, L2 and L3 are 3.872, 4.023 and 4.004 eV respectively. The antidiabetic potential of the three compounds were studied using α-amylase and α-glucosidase assay. Compound L1 showed very promising antidiabetic activities with IC50 values of 58.85 μg/mL and 57.60 μg/mL while the reference drug (Acarbose) had 405.84 μg/mL and 35.69 μg/mL for α-amylase and α-glucosidase respectively. In-silico studies showed that L1 docking score as well as binding energies are higher than that of acarbose, which are recognized inhibitors of α-amylase together with α-glucosidase. Further insight from the RMSF, RMSD and RoG analysis predicted that, throughout the simulation L1 showcased evident influence on the structural stability of α-amylase. The antioxidant potential of the compounds was carried out using nitric oxide (NO), ferric reducing ability power (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) assays. The compounds exhibited good to fairly antioxidant properties with L1 as well as L3 having IC50 values of 70.91 and 91.21 μg/mL respectively for NO scavenging activities assay, which comparatively outshined acarbose (reference drug) with IC50 value of 109.95 μg/mL. Pharmacology and pharmacokinetics approximations of L1 - L3 showed minimal violation of Lipinski's Ro5 and this projects them to be less toxic and orally bioavailable as potential templates for the design of therapeutics with antioxidant and antidiabetic activities.

Small Schiff Base Molecules-A Possible Strategy to Combat Biofilm-Related Infections

Microorganisms participating in the development of biofilms exhibit heightened resistance to antibiotic treatment, therefore infections involving biofilms have become a problem in recent years as they are more difficult to treat. Consequently, research efforts are directed towards identifying novel molecules that not only possess antimicrobial properties but also demonstrate efficacy against biofilms. While numerous investigations have focused on antimicrobial capabilities of Schiff bases, their potential as antibiofilm agents remains largely unexplored. Thus, the objective of this article is to present a comprehensive overview of the existing scientific literature pertaining to small molecules categorized as Schiff bases with antibiofilm properties. The survey involved querying four databases (Web of Science, ScienceDirect, Scopus and Reaxys). Relevant articles published in the last 10 years were selected and categorized based on the molecular structure into two groups: classical Schiff bases and oximes and hydrazones. Despite the majority of studies indicating a moderate antibiofilm potential of Schiff bases, certain compounds exhibited a noteworthy effect, underscoring the significance of considering this type of molecular modeling when seeking to develop new molecules with antibiofilm effects.

Design, preparation and characterization of magnetic nanoparticles functionalized with chitosan/Schiff base and their use as a reusable nanocatalyst for the green synthesis of 1H-isochromenes under mild conditions

In this study, a Schiff base complex magnetic nanocatalyst was designed and prepared. The structure of the Fe3O4@CS-SB-CaMgFe2O4 nanocatalyst was characterized using FT-IR spectroscopy, XRD, VSM, FE-SEM, EDX, elemental mapping, BET, and TGA techniques. The synthesis of 1H-isochromene compounds has attracted the attention of chemists due to their biological and medicinal properties. The 1H-isochromene derivatives were synthesized in the presence of the Fe3O4@CS-SB-CaMgFe2O4 nanocatalyst with excellent efficiency and short reaction time as well as according to the rules of green chemistry. This reaction was carried out using Fe3O4@CS-SB-CaMgFe2O4 as a catalyst to develop a simple method with low activation energy at room temperature under optimal conditions. This catalyst provides a promising route for the synthesis of 1H-isochromene multiple times through its recyclability without significant loss of catalytic activity. This nanocatalyst possesses several advantages, including cost-effectiveness, facile separation, environmental friendliness, and recyclability, for the efficient production of 1H-isochromenes. The obtained compounds were further analyzed using spectroscopic techniques, such as melting point, FT-IR, 1H NMR, and 13C NMR analyses, to confirm their structures. The spectra of the synthesized compounds were recorded and analyzed, and a plausible mechanism for their synthesis was proposed. The characterization results and structural elucidation provide valuable insights into the preparation of these compounds.

Novel Penicillin Derivatives Against Selected Multiple-drug Resistant Bacterial Strains: Design, Synthesis, Structural Analysis, In Silico and In Vitro Studies

INTRODUCTION

The rising numbers of multiple drug-resistant (MDR) pathogens and the consequent antibacterial therapy failure that resulted in severe medical conditions push to illustrate new molecules with extended activity against the resistant strains. In this manner, chemical derivatization of known antibiotics is proposed to save efforts in drug discovery, and penicillins serve as an ideal in this regard.

METHODS

Seven synthesized 6-aminopenicillanic acid-imine derivatives (2a-g) were structure elucidated using FT-IR, 1H NMR, 13C NMR, and MS spectroscopy. In silico molecular docking and ADMET studies were made. The analyzed compounds obeyed Lipinski's rule of five and showed promising in vitro bactericidal potential when assayed against E. coli, E. cloacae, P. aeruginosa, S. aureus, and A. baumannii. MDR strains using disc diffusion and microplate dilution techniques.

RESULTS

The MIC values were 8 to 32 μg/mL with more potency than ampicillin, explained by better membrane penetration and more ligand-protein binding capacity. The 2g entity was active against E. coli. This study was designed to find new active penicillin derivatives against MDR pathogens.

CONCLUSION

The products showed antibacterial activity against selected MDR species and good PHK, PHD properties, and low predicted toxicity, offering them as future candidates that require further preclinical assays.

Schiff Bases: A Captivating Scaffold with Potential Anticonvulsant Activity

One of the most important organic compounds, also known as a Schiff base, imine, or azomethine, has been associated with several biological processes. The group is a component of both natural or synthetic chemicals and functions as both a precursor and an intermediary in the synthesis of therapeutically active substances. The review highlights the various non-metal Schiff bases' structure-activity relationship (SAR) studies, general model, docking, and design approach for anticonvulsant actions. Schiff bases serve as linkers in numerous synthetic compounds with a variety of activities, according to the findings of several investigations. As a result, the current review will give readers a thorough understanding of the key ideas put forth by different researchers regarding the anticonvulsant properties of Schiff bases. It will serve as a valuable information source for those planning to synthesize new anticonvulsant molecules that contain Schiff bases as pharmacophores or biologically active moieties.

Developing a new multi-featured chitosan-quinoline Schiff base with potent antibacterial, antioxidant, and antidiabetic activities: design and molecular modeling simulation

A new chitosan Schiff base was developed via the reaction of chitosan (CH) with 2-chloro-3-formyl-7-ethoxy quinoline (Q) derivative. The alteration in the chemical structure and morphology of CHQ derivative was confirmed by 1H NMR, FT-IR spectroscopy and SEM analysis. The antibacterial activity was considerably promoted with increasing quinoline concentration up to 1 M with maximal inhibition reached 96 and 77% against Staphylococcus haemolyticus and Escherichia coli, respectively. Additionally, CHQ derivative afforded higher ABTS·+ radical scavenging activity reached 59% compared to 13% for native chitosan, approving its acceptable antioxidant activity. Moreover, the developed CHQ derivative can stimulate the glucose uptake in HepG-2 and yeast cells, while better inhibition of α-amylase and α-glucosidase was accomplished with maximum values of 99.78 and 92.10%, respectively. Furthermore, the molecular docking simulation clarified the binding mode of CHQ derivative inside the active site of α-amylase and α-glucosidase, suggesting its potential use as diabetes mellitus drug. The DFT calculations indicated an improvement in the electronic properties of CHQ with a lower energy band gap reached 4.05eV compared to 5.94eV for CH. The cytotoxicity assay revealed the safety of CHQ towards normal HSF cells, hypothesizing its possible application as non-toxic antibacterial, antioxidant, and antidiabetic agent for biomedical applications.

Bacteriostatic Pickering emulsions stabilized by whey protein isolate-vanillin nanoparticles: Fabrication, characterization and stability in vitro

The purpose of this work was to prepare Pickering emulsion stabilized by bacteriostatic whey protein isolate-vanillin (WPI-Van) nanoparticles as a carrier for encapsulating vitamin E. The particle size, ζ potential, PDI were used to study the optimal preparation conditions of nanoparticles. The results showed that the optimal preparation condition was achieved at WPI/Van mass ratio of 3:1. FTIR spectra demonstrated the complexation of WPI and Van. SEM image showed spherical and slightly rough surface of nanoparticles. Inhibitory effects of nanoparticles on E. coli and S. aureus were also observed. After storage of 21 days at 4 °C, the retention rate of vitamin E in the emulsions remained 43% higher than that of unencapsulated vitamin E. Moreover, the release rate of vitamin E encapsulated in emulsions in the small intestine was 81%, indicating excellent bioaccessibility. The research can provide a new insight for production and application of antibacterial Pickering emulsions.

Synthesis of Schiff Bases Based on Chitosan and Heterocyclic Moiety: Evaluation of Antimicrobial Activity

Schiff bases of chitosan (CS) were prepared by reaction of four different heterocyclic compounds, namely, 1,3-dimethyl-2,4,6-trioxohexahydropyrimidine-5-carbaldehyde (M1), 3-acetyl-2H-chromen-2-one (M2), 5-chloro-3-methyl-1-phenyl-1H-pyrazole-4-carbaldehyde (M3), and 4-oxo-4H-chromene-3-carbaldehyde (M4), with CS using thermal and ultrasound approaches. CS Schiff base formation was confirmed by using FT-IR, XRD, and TGA. Characteristic data show that amino groups in chitosan reacted with the functional group in the heterocyclic compound to form the Schiff base. CS Schiff bases show thermal stability more than pure CS. The antimicrobial activity of Schiff bases was tested against +ve Gram bacteria and -ve Gram bacteria. The result shows that Schiff bases prepared by temperature and ultrasound methods possess high antimicrobial activity against +ve Gram bacteria and -ve Gram bacteria; in comparison, Schiff bases produced by the ultrasound method have higher antimicrobial activity. The Schiff base (CSM4U), prepared by the ultrasound method by reaction of CS with 4-oxo-4H-chromene-3-carbaldehyde, exhibited higher antimicrobial activity than Gentamicin as an antibacterial agent. The inhibition range caused by CSM4U was between 19 and 27 mm. Moreover, CSM4U also acted as an antifungal agent, causing an inhibition zone of 21 mm for both Candida albicans and Candida tropicalis, which was higher than that of Terbinafine.

Part-II: an update of Schiff bases synthesis and applications in medicinal chemistry-a patent review (2016-2023)

INTRODUCTION

Schiff bases are compounds with characteristic features of azomethine linkage (-C=N-). Schiff bases are capable of coordinating with metal ions via azomethine nitrogen. Schiff base derivatives and their metal complexes are known for intriguing novel therapeutic properties. In organic synthesis, the Schiff base reaction is prime in creating the C-N bond. Synthetic accessibility and structural diversity are the salient features for facile synthesis of Schiff base hybrids via a condensation reaction between an aldehyde/ketone and primary amines.

AREA COVERED

This review aims to provide a comprehensive overview of the commendable medicinal applications of Schiff base derivatives and their metal complexes patented from 2016 to 2023.

EXPERT OPINION

Schiff base derivatives are exceptional molecules for their assorted applications in medicinal chemistry. Several Schiff base products are marketed as drugs, and plenty of room is available for the purposive synthesis of new compounds in a diverse pool of disciplines. Expansion in the derivatization of Schiff bases in innumerable directions with multitudinous applications makes them 'magical molecules.' These compounds have proved extraordinary, from medicinal chemistry to other fields outside medicine. This review covers the therapeutic importance of Schiff base derivatives and aims to cover the patents published in recent years (2016-2023).

Crystal Structure, Hirshfeld Surface Analysis, and Biological Activities of Schiff-Base Derivatives of 4-Aminoantipyrine

Eight Schiff bases, synthesized by the reaction of 4-aminoantipyrine with different cinnamaldehydes, were studied in the solid state by using vibrational spectroscopy (IR) and X-ray diffraction techniques. The analysis was extended to the solution phase through ultraviolet-vis, fluorescence spectroscopy, and cyclic voltammetry. Finally, the crystal structures of four compounds (3b, 3d, 3g, and 3h) were determined and studied. In addition to the experimental study, theoretical calculations using the semiempirical method PM6/ZDO were performed to understand better the compound's molecular properties, UV-vis, and infrared spectra. The primary difference is the angular conformation of the terminal phenyl rings around the corresponding linking C-N and C-C σ-bonds. Furthermore, as a result of extended bonding, the > C=N- azomethine group-containing Cpyr-N=(CH)-(CR)=(CH)-Cbz chain (with R=H for 3b, 3d, and 3h, and R=CH3 for 3g) is planar, nearly coplanar, with the mean plane of the pyrazole ring. Hirshfeld surface (HS) analysis was used to investigate the crystal packing and intermolecular interactions, which revealed that intermolecular C-H···O and C-H···N hydrogen bonds, π···π stacking, and C-H···π and C=O···π interactions stabilize the compounds. The energy contributions to the lattice energies of potential hydrogen bonds were primarily dispersive and repulsive. All derivatives were tested in vitro on LPS-stimulated mouse macrophages to assess their ability to suppress the LPS-induced inflammatory responses. Only a slight reduction in the level of NO production was found in activated macrophages treated with 3h. Additionally, the derivatives were tested for antimicrobial activity against several clinical bacteria and fungi strains, including three biofilm-forming microorganisms. Nevertheless, only Schiff base 3f showed interesting antibacterial activities with minimum inhibitory concentration (MIC) values as low as 15.6 μM against Enterobacter gergoviae. On the other hand, Schiff base 3f and, to a lesser extent, 3b and 3h showed antifungal activity against clinical isolates of Candida. The lowest MIC value was for 3f against Candida albicans (15.6 μM). It is interesting to note that the same Schiff bases exhibit the highest activity in both biological evaluations.

Antibacterial Activity of Quinoline-Based Derivatives against Methicillin-Resistant Staphylococcus aureus and Pseudomonas aeruginosa: Design, Synthesis, DFT and Molecular Dynamic Simulations

Bacterial virulence becomes a significant challenge for clinical treatments, particularly those characterized as Multi-Drug-Resistant (MDR) strains. Therefore, the preparation of new compounds with active moieties could be a successful approach for eradication of MDR strains. For this purpose, newly synthesized quinoline compounds were prepared and tested for their antimicrobial activity against Methicillin-Resistant Staphylococcus Aureus (MRSA) and Pseudomonas Aeruginosa (PA). Among the synthesized derivatives, compounds 1-(quinolin-2-ylamino)pyrrolidine-2,5-dione (8) and 2-(2-((5-methylfuran-2-yl)methylene)hydrazinyl)quinoline (12) were shown to possess the highest antimicrobial activity with the minimum inhibitory concentration with the values of 5±2.2 and10±1.5 μg/mL towards Pseudomonas aeruginosa without any activity towards MRSA. Interestingly, compounds 2-(2-((1H-indol-3-yl)methylene)hydrazinyl)quinoline (13) and 2-(4-bromophenyl)-3-(quinolin-2-ylamino)thiazolidin-4-one (16c) showed significant inhibition activity against Staphylococcus aureus MRSA and Pseudomonas aeruginosa. Compound 13 (with indole moiety) particularly displayed excellent bactericidal activity with low MIC values 20±3.3 and 10±1.5 μg/mL against Staphylococcus aureus MRSA and Pseudomonas aeruginosa, respectively. Effects molecular modelling was used to determine the mode of action for the antimicrobial effect. The stability of complexes formed by docking and target-ligand pairing was evaluated using molecular dynamics simulations. The compounds were also tested for binding affinity to the target protein using MM-PBSA. Density-functional theory (DFT) calculations were also used to investigate the electrochemical properties of various compounds.

Unusual reaction of (E)-2-[(benzo[d]thia-zol-2-yl-imino)-meth-yl]-5-(di-ethyl-amino)-phenol with tri-phenyl-borane: crystal structures and optical properties

The mol-ecular and crystal structure of (E)-2-[(benzo[d]thia-zol-2-yl-imino)-meth-yl]-5-(di-ethyl-amino)-phenol (C18H19N3O2S, Et2N-Bz) and its unexpected reaction product with tri-phenyl-borane, 2,2-diphenyl-1,3-dioxa-2-borata-1,2-di-hydro-naphthalene [systematic name: N,N-diethyl-2,2-diphenyl-2H-1,3λ3,2λ4-ben-zodioxaborinin-7-amine, C23H24BNO2, (I)] are described. For Et2N-Bz, the hydroxyl group is involved in an intra-molecular hydrogen bond with the imino nitro-gen atom and the C=N bond displays an E configuration. The crystal packing is characterized by layers of inversion dimers parallel to the (10) plane and chains of mol-ecule in the a-axis direction formed through C-H⋯O inter-actions. Complex (I) crystallizes with two mol-ecules (A and B) in the asymmetric unit, which differ in the orientation of the ethyl groups. The 1,3-dioxa-2-borata-1,2,3,4-tetra-hydro-naphthalene ring displays a slight envelope conformation with the boron atom as the flap. In the crystal packing, chains of alternating A and B mol-ecules formed by C-H⋯O hydrogen bonds run in the b-axis direction. The UV-vis absorption and emission properties of the compounds are discussed and their aggregation-induced emission properties are further investigated.

Synthesis of new imine-/amine-bearing imidazo[1,2-a]pyrimidine derivatives and screening of their cytotoxic activity

Imidazo[1,2-a]pyrimidine derivatives bearing imine groups (3a-e) were successfully synthesized in moderate to good yields using microwave-assisted heating. Corresponding amine derivatives (4a-e) were also obtained by the reduction reaction of the imine derivatives (3a-e). All synthesized products were characterized by FT-IR, 1H NMR, 13C NMR, and LC-MS spectroscopic techniques. In silico ADMET, Lipinski, and drug-likeness studies of the compounds were conducted and all were found to be suitable drug candidates. The cytotoxicity of the potential drug molecules was screened against the breast cancer cell lines MCF-7 and MDA-MB-231 and the healthy model HUVEC by the sulforhodamine B method. According to the antiproliferative studies, compounds 3d and 4d showed remarkable inhibition of MCF-7 cells with IC50 values of 43.4 and 39.0 μM and of MDA-MB-231 cells with IC50 values of 35.9 and 35.1 μM, respectively. In particular, compound 3d selectively inhibited the proliferation of MCF-7 1.6-fold and MDA-MB-231 2.0-fold relative to healthy cells. Moreover, the apoptotic mechanism studies indicated that compound 4d induced apoptosis by moderately increasing the ratio of Bax/Bcl-2 genes. Imidazo[1,2-a]pyrimidine derivative 3d, a promising cytotoxic agent, may be helpful in the discovery of new and more efficient anticancer agents for breast cancer treatment.

Fabrication of Antibacterial and Antioxidant ZnO-Impregnated Amine-Functionalized Chitosan Bio-Nanocomposite Membrane for Advanced Biomedical Applications

Developing a variety of safe and effective functioning wound dressings is a never-ending objective. Due to their exceptional antibacterial activity, biocompatibility, biodegradability, and healing-promoting properties, functionalized chitosan nanocomposites have attracted considerable attention in wound dressing applications. Herein, a novel bio-nanocomposite membrane with a variety of bio-characteristics was created through the incorporation of zinc oxide nanoparticles (ZnONPs) into amine-functionalized chitosan membrane (Am-CS). The developed ZnO@Am-CS bio-nanocomposite membrane was characterized by various analysis tools. Compared to pristine Am-CS, the developed ZnO@Am-CS membrane revealed higher water uptake and adequate mechanical properties. Moreover, increasing the ZnONP content from 0.025 to 0.1% had a positive impact on antibacterial activity against Gram-positive and Gram-negative bacteria. A maximum inhibition of 89.4% was recorded against Escherichia coli, with a maximum inhibition zone of 38 ± 0.17 mm, and was achieved by the ZnO (0.1%)@Am-CS membrane compared to 72.5% and 28 ± 0.23 mm achieved by the native Am-CS membrane. Furthermore, the bio-nanocomposite membrane demonstrated acceptable antioxidant activity, with a maximum radical scavenging value of 46%. In addition, the bio-nanocomposite membrane showed better biocompatibility and reliable biodegradability, while the cytotoxicity assessment emphasized its safety towards normal cells, with the cell viability reaching 95.7%, suggesting its potential use for advanced wound dressing applications.

Strategies for Improving Selectivity and Sensitivity of Schiff Base Fluorescent Chemosensors for Toxic and Heavy Metals

Toxic cations, including heavy metals, pose significant environmental and health risks, necessitating the development of reliable detection methods. This review investigates the techniques and approaches used to strengthen the sensitivity and selectivity of Schiff base fluorescent chemosensors designed specifically to detect toxic and heavy metal cations. The paper explores a range of strategies, including functional group variations, structural modifications, and the integration of nanomaterials or auxiliary receptors, to amplify the efficiency of these chemosensors. By improving selectivity towards targeted cations and achieving heightened sensitivity and detection limits, consequently, these strategies contribute to the advancement of accurate and efficient detection methods while increasing the range of end-use applications. The findings discussed in this review offer valuable insights into the potential of leveraging Schiff base fluorescent chemosensors for the accurate and reliable detection and monitoring of heavy metal cations in various fields, including environmental monitoring, biomedical research, and industrial safety.

AIEgen orthopalladated hybrid polymers for efficient inactivation of the total coliforms in urban wastewater

Monitorable AIE polymers with a bioactive pattern are employed in advanced biomedical applications such as functional coatings, theranostic probes, and implants. After the global COVID-19 pandemic, interest in developing surfaces with superior antimicrobial, antiproliferative, and antiviral activities dramatically increased. Many formulations for biocide surfaces are based on hybrid organic/inorganic materials. Palladium (II) complexes display relevant activity against common bacteria, even higher when compared to their uncoordinated ligands. This article reports the design and synthesis of two series of orthopalladated polymers obtained by grafting a cyclopalladated fragment on two different O, N chelating Schiff base polymers. Different grafting percentages were examined and compared for each organic polymer. The fluorescence emission in the solid state was explored on organic matrixes and grafted polymers. DFT analysis provided a rationale for the role of the coordination core. The antibacterial response of the two series of hybrid polymers was tested against the total coliform group of untreated urban wastewater, revealing excellent inactivation ability.

Synthesis, spectroscopic characterization, density functional theory study, antimicrobial and antioxidant activities of curcumin and alanine-curcumin Schiff base

In this work, a novel Schiff-base derived from curcumin and L-Alanine was synthesized under microwave conditions in excellent yield. The structural characterization has been carried out from their elemental analyses, FTIR, UV-Vis and 13C-NMR and 1H-NMR spectral techniques. The Schiff base (Cur-Ala) and curcumin (Cur) have been screened for their antimicrobial activity toward some pathogens clinically important microorganisms: Bacillus subtilis, Escherichia coli and Staphylococcus aureus, Aspergillus niger and Candida albicans. Result found that the Schiff base was more active than the curcumin. The antibacterial and antifungal activities of Cur-Ala can be attributed to its greatest dipole moment, as shown by theoretical calculations. Also, the antioxidant activity of Schiff base and curcumin were studied by DPPH, cupric ion reducing antioxidant capacity and o-phenanthroline techniques. Results indicate that Cur-Ala and Cur show more antioxidant activities than the standard antioxidants (BHT and BHA). Quantum chemical parameter calculations of Cur-Ala and Cur have been investigated by DFT using B3LYP/6-31G (d,p) basis set method to calculate the optimized structure, atomic charges, MESP, global reactivity descriptors and thermomolecular proprieties of both molecules.Communicated by Ramaswamy H. Sarma.

Synthesis, Characterization, Theoretical and Experimental Anticancer Evaluation of Novel Cocrystals of 5-Fluorouracil and Schiff Bases against SW480 Colorectal Carcinoma

The chemotherapeutic agent known as 5-fluorouracil (5-FU) is an artificial fluoropyrimidine antimetabolite that has been widely used for its antineoplastic properties. Cocrystals of 5-fluorouracil (5-FU) with five different Schiff bases (benzylidene-urea (BU), benzylidene-aniline (BA), salicylidene-aniline (SA), salicylidene-phenylhydrazine (SPH), and para-hydroxy benzylideneaniline (HBA)) are reported in this study. The newly synthesized cocrystals were analyzed by FTIR and PXRD. In this study, we investigated the antitumor efficacy of 5-FU derivatives in SW480 colon cancer cells via MTT assay at varying dose concentrations. Molecular docking was performed to predict the binding mechanism of TS with various 5-FU complexes. FTIR revealed the presence of respective functional groups in the prepared cocrystals. The frequencies (v) of N-H (3220.24 cm^-1) and carbonyl groups (1662.38 cm^-1) in the spectrum of 5-FU shifted considerably in all derivative cocrystal new interactions. There was a noticeable transformation in the PXRD peak of 5-FU at 2θ = 28.37° in all derivatives. The novelty of the present study lies in the fact that 5-FU-BA showed an anticancer potential IC₅₀ (6.4731) far higher than that of 5-FU (12.116), almost comparable to that of the reference drug doxorubicin (3.3159), against SW480 cancel cell lines, followed by 5-Fu-HBA (10.2174). The inhibition rates of 5-FU-BA and 5-FU-HBA were highest among the derivatives (99.85% and 99.37%, respectively) in comparison with doxorubicin (97.103%). The results revealed that the synthesized 5-FU cocrystals have promising antitumor efficacy compared with previously reported 5-FU and 5-FU. The activities of the cocrystals were rationalized by a molecular modeling approach to envisage binding modes with the target cancer protein.