In vitro binding studies of organotin(IV) complexes of 1,2-bis(1H-benzimidazol-2-yl)ethane-1,2-diol with CT-DNA and nucleotides (5′-GMP and 5′-TMP): Effect of the ancillary ligand on the binding propensity

The chiral benzimidazole ligand, 1,2-Bis(1H-benzimidazol-2-yl)ethane-1,2-diol, L, exhibiting coordination mode with an oxygen atom of alcohol group directed towards the metal ion and another -OH group with different molecular axis directed away from the metal center was utilized as a building block for organotin complexes [C₁₈H₁₉N₄O₂SnCl], [C₂₈H₂₃N₄O₂SnCl] and [C₅₂H₄₂N₄O₂Sn₂] (1-3). Complexes 1 and 3 exhibit a pentacoordinate geometry while the complex 2 reveals hexacoordinated environment around the Sn(IV) metal ions as evidenced by ¹¹⁹Sn NMR studies. The DNA binding ability of benzimidazole ligand and their organotin(IV) complexes 1-3 were examined by employing different biophysical methods. The absorption titration of the complexes with CT-DNA reveal significant hyperchromic effect together with strong bathochromic shift of 4-5 nm which infer substantial binding of the complexes with CT-DNA. The intrinsic binding constant K_b values of the complexes 1-3 were found to be 2.16 ± 0.04 × 10⁴, 3.47 ± 0.04 × 10⁴ and 4.60 ± 0.04 × 10³ M⁻¹, respectively, suggesting pronounced binding of complex 2 with DNA double helix. The mechanism of binding of the complexes was further ascertained by the interaction studies of these complexes with nucleotides (5′-GMP and 5′-TMP) using absorption spectroscopy suggesting a clear preference for 5′-GMP binding which was further authenticated by NMR (¹H and ³¹P NMR) studies.     

Flavonoids as Potential Anti-Inflammatory Molecules: A Review

Hydroxylated polyphenols, also called flavonoids, are richly present in vegetables, fruits, cereals, nuts, herbs, seeds, stems, and flowers of numerous plants. They possess numerous medicinal properties such as antioxidant, anti-cancer, anti-microbial, neuroprotective, and anti-inflammation. Studies show that flavonoids activate antioxidant pathways that render an anti-inflammatory effect. They inhibit the secretions of enzymes such as lysozymes and β-glucuronidase and inhibit the secretion of arachidonic acid, which reduces inflammatory reactions. Flavonoids such as quercetin, genistein, apigenin, kaempferol, and epigallocatechin 3-gallate modulate the expression and activation of a cytokine such as interleukin-1beta (IL-1β), Tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and interleukin-8 (IL-8); regulate the gene expression of many pro-inflammatory molecules such s nuclear factor kappa-light chain enhancer of activated B cells (NF-κB), activator protein-1 (AP-1), intercellular adhesion molecule-1 (ICAM), vascular cell adhesion molecule-1 (VCAM), and E-selectins; and also inhibits inducible nitric oxide (NO) synthase, cyclooxygenase-2, and lipoxygenase, which are pro-inflammatory enzymes. Understanding the anti-inflammatory action of flavonoids provides better treatment options, including coronavirus disease 2019 (COVID-19)-induced inflammation, inflammatory bowel disease, obstructive pulmonary disorder, arthritis, Alzheimer’s disease, cardiovascular disease, atherosclerosis, and cancer. This review highlights the sources, biochemical activities, and role of flavonoids in enhancing human health.     

Screening of peptide affinity tags using immobilised metal affinity chromatography in 96-well plate format

A method for high throughput screening of Green Fluorescent Proteins carrying metal binding tags in bacteria was developed. A random four amino acids tag-peptide library was successfully generated in E. coli. A 96-microtiter plate assembled with metal-iminodiacetic acid small cryogel columns was used for library screening. For the first time we were able to simultaneously screen a metal binding peptide tags library obtained from E. coli against different metal ions. From screening 25 different tags, three clones were able to bind to all metal ions studied (Ni2+, Zn2+, Co2+ and Cd2+). It was clearly demonstrated that the new construct could facilitate the screening of large peptide libraries.     

Intramolecular cross-dehydrogenative coupling of benzaldehyde derivatives: A novel and efficient route to benzocyclic ketones

Benzocyclic ketones are not only found throughout many natural products and synthetic pharmaceutically active compounds but also used as versatile building blocks in organic synthesis. In view of their importance, many researchers have been working to explore novel and efficient synthetic routes for this class of carbonyl compounds. Recently, cross-dehydrogenative coupling reactions have emerged as one of the most versatile and powerful synthetic strategies to construct various carbon-carbon and carbon-heteroatom bonds. In this regard, direct acylation of (hetero)arenes with aldehydes through C(sp²)-H activation opened up a new page on the synthesis of the titled compounds. In this focus-review, we discuss the most representative and important reports on the synthesis of cyclic diaryl ketones through intramolecular cross-dehydrogenative coupling reactions of corresponding benzaldehydes with emphasis on the mechanistic aspects of the reactions.     

Preparation, crystal structures, and magnetic features for a series of dinuclear [Ni(II)Ln(III)] Schiff-base complexes: evidence for slow relaxation of the magnetization for the Dy(III) derivative

A series of dinuclear [Ni(II)Ln(III)] Schiff-base complexes (using a Schiff-base dicompartmental ligand derived from o-vanillin [H(2)valpn = 1,3-propanediylbis(2-iminomethylene-6-methoxy-phenol)]) with Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, and a hydroxo-bridged tetranuclear [Ni(II)Yb(III)] are reported. The crystal structures have been solved for 10 dinuclear complexes revealing four arrangements for the dinuclear units, which are modulated by the coordinated solvent molecules and the nitrato-anion interactions. The magnetic behaviors have been investigated, and the nature of the Ni(II)-Ln(III) exchange interaction has been emphasized by comparison with the behavior of the related [Zn(II)Ln(III)] derivatives. This allowed for establishing that the interaction within these compounds is antiferromagnetic with the 4f ions of the beginning of the Ln series and turns ferromagnetic from Gd(III) toward the end of the series. AC susceptibility investigations clearly show the occurrence of slow relaxation processes of the magnetization close to 2 K for the dinuclear [Ni(II)Dy(III)] complex.     

Synthesis,characterization, crystal structure and electrochemical behavior of a nickel(II) complex of 5,6-dihydro-2H-pyran-3-aldehyde thiosemicarbazone

A new Ni^II complex of 5,6-dihydro-2H-pyran-3-aldehyde thiosemicarbazone (HDPTSC) has been synthesized and characterized by microanalyses, magnetic susceptibility, molar conductance measurements and by spectral methods (i.r., u.v.–vis., ¹H-n.m.r.). The structure of [Ni(DPTSC)₂] · B DMF has been solved using X-ray diffraction and found to be highly symmetrical with a trans -arrangement of the two bidentate ligands. The thiosemicarbazone coordinates as an anionic ligand via the thiosemicarbazone moietys azomethine nitrogen and thiolate sulfur [on loss of the N2 hydrogen]. The electrochemical behavior of the ligand and its Ni^II complex, determined by cyclic voltammetry, shows that the redox process of the ligand was highly irreversible, whereas the redox process of the Ni^II complex was observed as a one electron transfer process in a quasi-reversible and diffusion-controlled reaction.     

Macroporous gels prepared at subzero temperatures as novel materials for chromatography of particulate-containing fluids and cell culture applications

Macroporous gels (MGs) with a broad variety of morphologies are prepared using the cryotropic gelation technique, i. e. gelation at subzero temperatures. These highly elastic hydrophilic materials can be produced from practically any gel-forming system with a broad range of porosity extending from elastic and porous gels with pore sizes up to 1.0 microm to elastic and sponge-like gels with pore sizes up to 100 microm. The versatility of the cryogelation technique is demonstrated by use of different chemical reactions (hydrogen bond formation, chemical cross-linking of polymers, free radical polymerization) mainly in an aqueous medium. Appropriate control over solvent crystallization (formation of solvent crystals) and rate of chemical reaction during the cryogelation allows the reproducible preparation of cryogels with tailored properties. Different approaches, such as chemical modification of reactive groups, grafting of the pore surface with an appropriate polymer, or direct copolymerization with functional monomers are used for control of the surface chemistry of MGs. Typically, MGs with pore sizes up to 1.0 microm are produced in the shape of beads and MGs with pore size up to 100 microm are prepared as monoliths, discs, and sheets. The difference in porous structure of MGs defines the main applications of these porous materials. Elastic beaded MGs are mostly used as carriers for cell and enzyme immobilization or for capture of low-molecular weight targets from particulate-containing fluids in expanded-bed mode. However, the elastic and sponge-like MG monoliths with interconnected pores measuring hundreds of mum have been successfully used as monolithic columns for chromatography of particulate-containing fluids (crude cell homogenates, viruses, whole cells, wastewater effluents) and as three-dimensional scaffolds for mammalian cell culture applications.     

Varying the metal/metal ratio in related Cu–Ca complexes

We demonstrate with the help of structural determinations and spectroscopic data that the nuclearity of Cu–Ca complexes derived from compartmental Schiff base ligands does not depend on the ionic radius of calcium. The main factors governing these reactions are the different affinities of the calcium ions for the anionic species present in solution: the tetradentate O₂O₂ coordination site of the ligand and the nitrato ions. Because these affinities do vary upon going from calcium to lanthanide ions, it is not possible to use the template effect of the trinuclear Cu–Ca–Cu complexes in order to prepare the corresponding Cu–Ln–Cu complexes.     

Microwave-assisted regioselective N-alkylation of cyclic amidines

A simple and efficient methodology for regioselective alkylation of exocyclic nitrogen of cyclic amidines was developed by microwave-assisted heating in the presence of amines. Novel N-alkylated 3,4-dihydropyrazino[2,1-b]quinazolin-6-ones were prepared in good yields. The reaction occurred via a transamination (addition-elimination) process involving a first attack of the amine on the electrophilic carbon of the amidine function.