Synthesis, Characterization, and Antimicrobial Evaluation of Schiff Base-mixed Ligand Complexes with Divalent Metal Ions Derived from Amoxicillin and Vanillin/Nicotinamide.

INTRODUCTION: This study focuses on the development of novel antimicrobial agents. A Schiff base ligand, 6-(2-(4-hydroxy-3-methoxybenzylideneamino)-2-(4-hydroxyphenyl)acetamido)-3,3-dimethyl-7-oxo- 4-thia-1-azabicyclo [3.2.0] heptane-2-carboxylic acid, synthesized through the condensation of amoxicillin and vanillin in methanol, served as the foundation. Polydentate mixed ligand complexes were then formed by reacting the Schiff base with metal ions (Fe(II), Co(II), Ni(II), Cu(II), and Zn(II)) and nicotinamide in specific ratios. METHODS: Characterization involved various techniques, such as 1H-NMR, FT-IR, UV-Vis, and elemental analysis for the ligand, and Atomic Absorption, FT-IR, UV-Vis, magnetic susceptibility, and conductance measurements for the Schiff base-metal ion complexes. RESULTS: Quantum chemical features of both ligands and metal complexes were computed, refining their electronic and molecular structures theoretically. Antimicrobial activity against Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Salmonella typhi, Acinetobacter baumannii, and Pseudomonas aeruginosa was assessed for the starting materials, ligands, and synthesized complexes, revealing significant effects on certain species. In-silico binding modes with Escherichia coli (PDB ID: 5iq9) were determined through molecular docking. CONCLUSION: This study underscores the potential applications of the Schiff base ligands and their metal complexes in developing new antimicrobial agents.

New Sustainable Synthetic Routes to Cyclic Oxyterpenes Using the Ecocatalyst Toolbox.

Cyclic oxyterpenes are natural products that are mostly used as fragrances, flavours and drugs by the cosmetic, food and pharmaceutical industries. However, only a few cyclic oxyterpenes are accessible via chemical syntheses, which are far from being ecofriendly. We report here the synthesis of six cyclic oxyterpenes derived from ß-pinene while respecting the principles of green and sustainable chemistry. Only natural or biosourced catalysts were used in mild conditions that were optimised for each synthesis. A new generation of ecocatalysts, derived from Mn-rich water lettuce, was prepared via green processes, characterised by MP-AES, XRPD and TEM analyses, and tested in catalysis. The epoxidation of ß-pinene led to the platform molecule, ß-pinene oxide, with a good yield, illustrating the efficacy of the new generation of ecocatalysts. The opening ß-pinene oxide was investigated in green conditions and led to new and regioselective syntheses of myrtenol, 7-hydroxy-α-terpineol and perillyl alcohol. Successive oxidations of perillyl alcohol could be performed using no hazardous oxidant and were controlled using the new generation of ecocatalysts generating perillaldehyde and cuminaldehyde.

Design, Synthesis, Biological Evaluation and In Silico Study of Benzyloxybenzaldehyde Derivatives as Selective ALDH1A3 Inhibitors.

Aldehyde dehydrogenase 1A3 (ALDH1A3) has recently gained attention from researchers in the cancer field. Several studies have reported ALDH1A3 overexpression in different cancer types, which has been found to correlate with poor treatment recovery. Therefore, finding selective inhibitors against ALDH1A3 could result in new treatment options for cancer treatment. In this study, ALDH1A3-selective candidates were designed based on the physiological substrate resemblance, synthesized and investigated for ALDH1A1, ALDH1A3 and ALDH3A1 selectivity and cytotoxicity using ALDH-positive A549 and ALDH-negative H1299 cells. Two compounds (ABMM-15 and ABMM-16), with a benzyloxybenzaldehyde scaffold, were found to be the most potent and selective inhibitors for ALDH1A3, with IC50 values of 0.23 and 1.29 µM, respectively. The results also show no significant cytotoxicity for ABMM-15 and ABMM-16 on either cell line. However, a few other candidates (ABMM-6, ABMM-24, ABMM-32) showed considerable cytotoxicity on H1299 cells, when compared to A549 cells, with IC50 values of 14.0, 13.7 and 13.0 µM, respectively. The computational study supported the experimental results and suggested a good binding for ABMM-15 and ABMM-16 to the ALDH1A3 isoform. From the obtained results, it can be concluded that benzyloxybenzaldehyde might be considered a promising scaffold for further drug discovery aimed at exploiting ALDH1A3 for therapeutic intervention.

Vanillin enones as selective inhibitors of the cancer associated carbonic anhydrase isoforms IX and XII. The out of the active site pocket for the design of selective inhibitors?

New C-glycosides and α,ß-unsaturated ketones incorporating the 4-hydroxy-3-methoxyphenyl (vanillin) moiety as inhibitors of carbonic anhydrase (CA, EC 4.2.1.1) isoforms have been investigated. The inhibition profile of these compounds is presented against four human CA (hCA) isozymes, comprising hCAs I and II (cytosolic, ubiquitous enzymes) and hCAs IX and XII (tumour associated isozymes). Docking analysis of the inhibitors within the active sites of these enzymes has been performed and is discussed, showing that the observed selectivity could be explained in terms of an alternative pocket out of the CA active site where some of these compounds may bind. Several derivatives were identified as selective inhibitors of the tumour-associated hCA IX and XII. Their discovery might be a step in the strategy for finding an effective non-sulfonamide CA inhibitor useful in therapy/diagnosis of hypoxic tumours or other pathologies in which CA isoforms are involved.

Rhodaelectro-catalyzed access to chromones via formyl C-H activation towards peptide electro-labeling.

Chromones represent a privileged scaffold in medicinal chemistry and are an omnipresent structural motif in natural products. Chemically encoded non-natural peptidomimetics feature improved stability towards enzymatic degradation, cell permeability and binding affinity, translating into a considerable impact on pharmaceutical industry. Herein, a strategy for the sustainable assembly of chromones via electro-formyl C-H activation is presented. The rational design of the rhodaelectro-catalysis is guided by detailed mechanistic insights and provides versatile access to tyrosine-based fluorogenic peptidomimetics.

Synthesis of new Hantzsch adducts showing Ca2+ channel blockade capacity, cholinesterase inhibition and antioxidant power.

Background: Alzheimer's disease is a chronic neurodegenerative chronic disease with a heavy social and economic impact in our developed societies, which still lacks an efficient therapy. Method: This paper describes the Hantzsch multicomponent synthesis of twelve alkyl hexahydro-quinoline-3-carboxylates, 4a-l, along with the evaluation of their Ca2+ channel blockade capacity, cholinesterase inhibition and antioxidant power. Results: Compound 4l showed submicromolar inhibition of butyrylcholinesterase, Ca2+ channel antagonism and an antioxidant effect. Conclusion: Compound 4l is an interesting compound that deserves further investigation for Alzheimer's disease therapy.

Synthesis and Biological Activities of Novel (Z)-/(E)-Anisaldehyde-Based Oxime Ester Compounds.

In search of novel natural product-based bioactive molecules, twenty (ten pairs) novel (Z)-/(E)-anisaldehyde-based oxime ester compounds were designed and synthesized by using anisaldehyde as starting material. Structural characterization of the target compounds was carried out by NMR, FT-IR, ESI-MS, and elemental analysis. Their herbicidal and antifungal activities were preliminarily tested. As a result, at 50 µg/mL, compound (E)-5b exhibited excellent to good inhibition rates of 92.3 %, 79.2 %, and 73.9 %, against Rhizoctonia solani, Fusarium oxysporum f. sp. cucumerinum, and Bipolaris maydis, respectively, better than or comparable to that of the positive control chlorothalonil. In addition, at 100 µg/mL, compounds (E)-5b, (E)-5f, (Z)-5f and (E)-5d exhibited excellent to good inhibition rates of 85.8 %, 82.9 %, 78.6 % and 64.2 %, respectively, against the root-growth of rape (B. campestris), much better than that of the positive control flumioxazin. The bioassay result also showed that the synthesized compounds had obvious differences in antifungal and herbicidal activities between (Z)- and (E)-isomers. Preliminary structure-activity relationship was also discussed by theoretical calculation.

Molecular docking, synthesis and anticancer activity of thiosemicarbazone derivatives against MCF-7 human breast cancer cell line.

BACKGROUND: The aim of this study was to synthesize and evaluate anticancer activity of 2-hydroxy benzaldehyde and 4-hydroxy benzaldehyde thiosemicarbazone (2-HBTSc and 4-HBTSc) against MCF-7 breast cancer cell line. MATERIALS AND METHODS: The ligands were prepared and characterized by UV vis, IR and NMR. MTT assay was used to assess viability of cells. RNA isolation, extraction and cDNA synthesis were done. Then all groups were subjected to RT-qPCR using Gene expression specific primers. Also, western blot protein expression and molecular docking were done. Two-way ANOVA with Tukey post-hoc test was employed to test the significance using GraphPad Prism. RESULTS: The IC50 values were 3.36µg/ml and 3.60µg/ml for 2-HBTSc and 4-HBTSc treated MCF-7 tumor cells respectively. Tumor cell growth inhibition ranged from 38 to 49.27% in 4-HBTSc treated cells, and 19 to 25% in 2-HBTSc treated cells with increase in doses 5 µg/ml to 20 µg/ml. The protein and gene expression result showed a significant upregulation in tumor suppressor and apoptosis inducing genes while, oncogene activity was significantly downregulated. Specifically, BRCA2 and pRB gene showed the highest expression in 4-HBTSc and 2-HBTSc treated cells respectively. Conversely, RAS oncogene was downregulated significantly. Docking result showed that both 2-HBTSc and 4-HBTSc have the potential to inhibit Estrogen Receptor Alpha Ligand Binding Domain, Human 17-Beta-hydroxysteroid dehydrogenase type 1 mutant protein and Human Topoisomerase II alpha that are expressed more during Breast Cancer. CONCLUSION: The findings of this study imply that the test compound has potential for further study.

Unified synthesis and assessment of tumor cell migration inhibitory activity of optically active UTKO1, originally designed moverastin analog.

UTKO1 is a synthetic analog of a natural tumor cell migration inhibitor, moverastin, isolated from microbial extracts of Aspergillus sp. 7720. UTKO1 was initially developed as a mixture of the stereoisomers. In this study, a concise and unified synthesis of the 4 optically active stereoisomers of UTKO1 was achieved from a known optically pure dihydro-α-ionone through a 5-step sequence. The key transformation in the synthesis was a Nozaki-Hiyama-Kishi (NHK) reaction between an optically active enoltriflate and a known aldehyde to install the chiral allylic hydroxy group at C2'. Simple chromatographic separation of the 2 diastereomers with regard to the allylic hydroxy group was possible by the derivatization into the corresponding acetals with Nemoto's optical resolution reagent, (S)- or (R)-5-allyl-2-oxabicyclo[3.3.0]octene (ALBO). All 4 synthetic stereoisomers of UTKO1 exhibited comparable tumor cell migration inhibitory activity.

Efficient Biosynthesis of Vanillin from Isoeugenol by Recombinant Isoeugenol Monooxygenase from Pseudomonas nitroreducens Jin1.

Currently, the biotechnological preparation of fragrances using natural materials attracted growing attention. Enzymatic synthesis of vanillin from isoeugenol by recombinant isoeugenol monooxygenase from Pseudomonas nitroreducens Jin1 was systematically investigated herein. With series of work on the construction of recombinant E. coli over-expressing isoeugenol monooxygenase, optimization of the culture conditions for enzyme production and reaction process for converting isoeugenol into vanillin, an increase of 22-fold in the enzyme activity (2050 U/L) was obtained, and the conversion was significantly increased at high substrate concentration with the aid of magnetic chitosan membrane for product isolation in situ. Under optimal conditions, the product concentration and space-time yield reached 252 mM and 115 g/L/d, respectively, and vanillin was obtained in 82.3% yield and > 99% purity in the gram preparative scale. The developed bioprocess showed application potential for efficient preparation of vanillin from inexpensive natural resources.

Exploration of Structure-Activity Relationship of Aromatic Aldehydes Bearing Pyridinylmethoxy-Methyl Esters as Novel Antisickling Agents.

Aromatic aldehydes elicit their antisickling effects primarily by increasing the affinity of hemoglobin (Hb) for oxygen (O2). However, challenges related to weak potency and poor pharmacokinetic properties have hampered their development to treat sickle cell disease (SCD). Herein, we report our efforts to enhance the pharmacological profile of our previously reported compounds. These compounds showed enhanced effects on Hb modification, Hb-O2 affinity, and sickling inhibition, with sustained pharmacological effects in vitro. Importantly, some compounds exhibited unusually high antisickling activity despite moderate effects on the Hb-O2 affinity, which we attribute to an O2-independent antisickling activity, in addition to the O2-dependent activity. Structural studies are consistent with our hypothesis, which revealed the compounds interacting strongly with the polymer-stabilizing αF-helix could potentially weaken the polymer. In vivo studies with wild-type mice demonstrated significant pharmacologic effects. Our structure-based efforts have identified promising leads to be developed as novel therapeutic agents for SCD.

Photoactivatable Odorants for Chemosensory Research.

The chemosensory system of any animal relies on a vast array of detectors tuned to distinct chemical cues. Odorant receptors and the ion channels of the TRP family are all uniquely expressed in olfactory tissues in a species-specific manner. Great effort has been made to characterize the molecular and pharmacological properties of these proteins. Nevertheless, most of the natural ligands are highly hydrophobic molecules that are not amenable to controlled delivery. We sought to develop photoreleasable, biologically inactive odorants that could be delivered to the target receptor or ion channel and effectively activated by a short light pulse. Chemically distinct ligands eugenol, benzaldehyde, 2-phenethylamine, ethanethiol, butane-1-thiol, and 2,2-dimethylethane-1-thiol were modified by covalently attaching the photoremovable protecting group (8-cyano-7-hydroxyquinolin-2-yl)methyl (CyHQ). The CyHQ derivatives were shown to release the active odorant upon illumination with 365 and 405 nm light. We characterized their bioactivity by measuring activation of recombinant TRPV1 and TRPA1 ion channels expressed in HEK 293 cells and the electroolfactogram (EOG) response from intact mouse olfactory epithelium (OE). Illumination with 405 nm light was sufficient to robustly activate TRP channels within milliseconds of the light pulse. Photoactivation of channels was superior to activation by conventional bath application of the ligands. Photolysis of the CyHQ-protected odorants efficiently activated an EOG response in a dose-dependent manner with kinetics similar to that evoked by the vaporized odorant amyl acetate (AAc). We conclude that CyHQ-based, photoreleasable odorants can be successfully implemented in chemosensory research.

Synthesis, molecular docking and anti-diabetic studies of novel benzimidazole-pyrazoline hybrid molecules.

Pyrazoline and benzimidazoles derivatives have been widely studied due to their potential applications in the medicinal field. In this research project, we have hybridized these two heterocyclic systems in the same molecule. A new series of compounds, 2-((3,5-diaryl-4,5-dihydro-1H-pyrazol-1-yl)methyl)-1H-benzo[d]imidazole (5a-i) were synthesized through a multistep reaction. In the first step, chalcones 3a-i were prepared by coupling of various acetophenones and benzaldehydes under alkaline conditions. These chalcones were cyclized with hydrazine hydrate to form a series of pyrazolines which were finally coupled with 2-chloromethyl-1H-benzimidazole to get a new series of titled hybrid molecules. The structures of these compounds were elucidated by spectral (1H NMR and 13C NMR) analysis. The anti-diabetic potential of these compounds was studied by screening them for their α-glucosidase inhibition activity. The SAR was established through molecular docking analysis. Compound 5d appeared as effective inhibitor with IC50 = 50.06µM as compared to reference drug (acarbose) having IC50 = 58.8µM.

Synthesis and in vitro evaluation of vanillin derivatives as multi-target therapeutics for the treatment of Alzheimer's disease.

A number of novel naphthalimido and phthalimido vanillin derivatives were synthesised, and evaluated as antioxidants and cholinesterase inhibitors in vitro. Antioxidant activity was assessed using DPPH, FRAP, and ORAC assays. All compounds demonstrated enhanced activity compared to the parent compound, vanillin. They also exhibited BuChE selectivity in Ellman's assay. A lead compound, 2a (2-(3-(bis(4-hydroxy-3-methoxybenzyl)amino)propyl)-1H-benzo[de]isoquinoline-1,3(2H)-dione), was identified and displayed strong antioxidant activity (IC50 of 16.67 µM in the DPPH assay, a 25-fold increase in activity compared to vanillin in the FRAP assay, and 9.43 TE in the ORAC assay). Furthermore, 2a exhibited potent BuChE selectivity, with an IC50 of 0.27 µM which was around 53-fold greater than the corresponding AChE inhibitory activity. Molecular modelling studies showed that molecules with bulkier groups, as in 2a, exhibited better BuChE selectivity. This work provides a promising basis for the development of multi-target hybrid compounds based on vanillin as potential AD therapeutics.

A bioinspired microreactor with interfacial regulation for maximizing selectivity in a catalytic reaction.

We report a bioinspired emulsion microreactor composed of an electrical double layer to mimic the functions of cell membranes. This "artificial cell" can modulate the phase-oriented transport of reagents at the oil-liquid interface via the electrical double layer, affording a powerful tool to optimize the selectivity in a catalytic reaction.

A non-anhydrous, minimally basic protocol for the simplification of nucleophilic 18F-fluorination chemistry.

Fluorine-18 radiolabeling typically includes several conserved steps including elution of the [18F]fluoride from an anion exchange cartridge with a basic solution of K2CO3 or KHCO3 and Kryptofix 2.2.2. in mixture of acetonitrile and water followed by rigorous azeotropic drying to remove the water. In this work we describe an alternative "non-anhydrous, minimally basic" ("NAMB") technique that simplifies the process and avoids the basic conditions that can sometimes limit the scope and efficiency of [18F]fluoride incorporation chemistry. In this approach, [18F]F- is eluted from small (10-12 mg) anion-exchange cartridges with solutions of tetraethylammonium bicarbonate, perchlorate or tosylate in polar aprotic solvents containing 10-50% water. After dilution with additional aprotic solvent, these solutions are used directly in nucleophilic aromatic and aliphatic 18F-fluorination reactions, obviating the need for azeotropic drying. Perchlorate and tosylate are minimally basic anions that are nevertheless suitable for removal of [18F]F- from the anion-exchange cartridge. As proof-of-principle, "NAMB" chemistry was utilized for the synthesis of the dopamine D2/D3 antagonist [18F]fallypride.

4-(4-Chloro-2-oxo-3(1H-phenanthro[9,10-d]imidazol-2-yl)-2H-chromen-6-yl) benzaldehyde as a fluorescent probe for medical imaging: linear and nonlinear optical properties.

This study presents the full theoretical optical and biological characteristics of a new fluorescent probe based on the phenanthroimidazole backbone (PB5). The aldehyde group was selected as the active group to bind to the protein during conjugation. The new fluorescent probe is based on the phenanthroimidazole backbone; however, unlike previously presented works, as the chromophore part, it contains the first introduction of the 4-chloro-2H-chromen-2-one part. In order to achieve the best cognitive aspect, the study included not only the dye itself but also the concanavalin A conjugate. The linear and non-linear optical properties and biological activities described in this study clearly indicate that the presented dye is a promising material as a fluorescent probe in medical imaging.

Synthesis, Molecular Docking, and Preliminary Evaluation of 2-(1,2,3-Triazoyl)benzaldehydes As Multifunctional Agents for the Treatment of Alzheimer's Disease.

We described here our results on the use of thiourea as a ligand in the copper catalysed azide-alkyne cycloaddition (CuAAC) of 2-azidobenzaldehyde with alkynes. Reactions were performed reacting 2-azidobenzaldehyde with a range of terminal alkynes using 10 mol % of copper iodide as a catalyst, 20 mol % of thiourea as a ligand, triethylamine as base, DMSO as solvent at 100 °C under nitrogen atmosphere. The corresponding 2-(1H-1,2,3-triazoyl)-benzaldehydes (2-TBH) were obtained in moderated to excellent yields and according our experiments, the use of thiourea decreases the formation of side products. The obtained compounds were screened for their binding affinity with multiple therapeutic targets of AD by molecular docking: ß-secretase (BACE), glycogen synthase kinase (GSK-3ß) and acetylcholinesterase (AChE). The three compounds with highest affinity, 5 a (2-(4-phenyl-1H-1,2,3-triazol-1-yl)benzaldehyde), 5 b (2-(4-(p-tolyl)-1H-1,2,3-triazol-1-yl)benzaldehyde), and 5 d (2-(4-(4-(tert-butyl)phenyl)-1H-1,2,3-triazol-1-yl)benzaldehyde) were selected and evaluated on its antioxidant effect, in view of select the most promising one to perform the in vivo validation. Due the antioxidant potential ally to the affinity with BACE, GSK-3ß and AChE, compound 5 b was evaluated in a mouse model of AD induced by intracerebroventricular injection of streptozotocin (STZ). Our results indicate that 5 b (1 mg/kg) treatment during 20 days is able to reverse the cognitive and memory impairment induced by STZ trough the modulation of AChE activity, amyloid cascade and GSK-3ß expression.

5-Trifluoromethyl-2-formylphenylboronic Acid.

2-Formylphenylboronic acids display many interesting features, not only from synthetic but also from an application as well as structural points of view. 5-Trifluoromethyl-2-formyl phenylboronic acid has been synthesized and characterized in terms of its structure and properties. The presence of an electron-withdrawing substituent results in a considerable rise in the acidity in comparison with its analogues. In some solutions, the title compound isomerizes with formation of the corresponding 3hydroxybenzoxaborole. Taking into account the probable mechanism of antifungal action of benzoxaboroles, which blocks the cytoplasmic leucyl-tRNA synthetase (LeuRS) of the microorganism, docking studies with the active site of the enzymes have been carried out. It showed possible binding of the cyclic isomer into the binding pocket of Candida albicans LeuRS, similar to that of the recently approved benzoxaborole antifungal drug (AN2690, Tavaborole, Kerydin). In case of Escherichia coli LeuRS, the opened isomer displays a much higher inhibition constant in comparison with the cyclic one. The antimicrobial activity of the title compound was also investigated in vitro, showing moderate action against Candida albicans. The compound reveals higher activity against Aspergillus niger as well as bacteria such as Escherichia coli and Bacillus cereus. In case of Bacillus cereus, the determined Minimum Inhibitory Concentration (MIC) value is lower than that of AN2690 (Tavaborole). The results confirm potential of 2-formylphenylboronic acids as antibacterial agents and give a hint of their possible mechanism of action.

Synthesis of Galectin Inhibitors by Regioselective 3'-O-Sulfation of Vanillin Lactosides Obtained under Phase Transfer Catalysis.

Vanillin-based lactoside derivatives were synthetized using phase-transfer catalyzed reactions from per-O-acetylated lactosyl bromide. The aldehyde group of the vanillin moiety was then modified to generate a series of related analogs having variable functionalities in the para- position of the aromatic residue. The corresponding unprotected lactosides, obtained by Zemplén transesterification, were regioselectively 3'-O-sulfated using tin chemistry activation followed by treatment with sulfur trioxide-trimethylamine complex (Men3N-SO3). Additional derivatives were also prepared from the vanillin's aldehyde using a Knoevenagel reaction to provide extended α, ß-unsaturated carboxylic acid which was next reduced to the saturated counterpart.