Synthesis and antioxidant activities of transition metal complexes based 3-hydroxysalicylaldehyde-S-methylthiosemicarbazone

Poly(p-phenylene)-based membranes with cerium for chemically durable polymer electrolyte fuel cell membranes

A poly(p-phenylene)-based multiblock polymer is developed with an oligomeric chain extender and cerium (CE-sPP-PPES + Ce3+) to realize better performance and durability in proton exchange membrane fuel cells. The membrane performance is evaluated in single cells at 80 °C and at 100% and 50% relative humidity (RH). The accelerated stability test is conducted 90 °C and 30% RH, during which linear sweep voltammetry and hydrogen permeation detection are monitored periodically. Results demonstrate that the proton conductivity of the pristine hydrocarbon membranes is superior to that of PFSA membranes, and the hydrogen crossover is significantly lower. In addition, a composite membrane containing cerium performs similarly to a pristine membrane, particularly at low RH levels. Adding cerium to CE-sPP-PPES + Ce3+ membranes improves their chemical durability significantly, with an open circuit voltage decay rate of only 89 μV/h for 1000 h. The hydrogen crossover is maintained across accelerated stability tests, as confirmed by hydrogen detection and crossover current density. The short-circuit resistance indicates that membrane thinning is less likely to occur. Collectively, these results demonstrate that a hydrocarbon membrane with cerium is a potential alternative for fuel cell applications.

Biologically potent organotin(iv) complexes of N-acetylated β-amino acids with spectroscopic, X-ray powder diffraction and molecular docking studies†

Twelve novel organotin(iv) complexes (1–12) of N-acetylated β-amino acids (L₁–L₈) were synthesized and characterized by elemental analysis, FTIR, multinuclear (¹H, ¹³C, ¹¹⁹Sn) NMR, EI-MS and powder XRD techniques. The XRD results determined lattice parameters, average particle size, and intrinsic strain and confirmed the crystalline nature of complexes as face centered cubic phases. Molecular docking analysis using a catalytic pocket of the α-glucosidase enzyme indicated that most of the compounds displayed a well-fitted orientation and occupied important amino acids in the enzyme's catalytic pocket. Furthermore, in vitro α-glucosidase inhibitory activity results revealed that L₁ and complexes 4, 6 and 10 showed the highest activity with IC₅₀ values of 21.54 ± 0.45, 37.96 ± 0.81 and 35.20 ± 1.02, respectively, compared to standard acarbose with an IC₅₀ value of 42.51 ± 0.21. In addition, in vivo antidiabetic activity of selected compounds using alloxan induced diabetic rabbits showed that L₄ and complexes 4, 6, 10, 12 showed significant activities like standard metformin. Anti-bacterial activity against the selected Gram-positive and Gram-negative bacterial strains has the following order Escherichia coli > Pseudomonas aeruginosa > Staphylococcus aureus > Bacillus subtilis. Similarly, antioxidant activity by the DPPH scavenging method was also studied with following results: triorganotin > diorganotin > ligands.

Novel organotin(iv) complexes of N-acetylated β-amino acids were synthesized and characterized by different techniques. The molecular docking, in vitro α-glucosidase inhibitory, and in vivo antidiabetic activity studies were carried out.

An Iron(III)-S-methylthiosemicarbazone Complex: Synthesis, Spectral Characterization, and Antioxidant Potency Measured by CUPRAC and DPPH Methods

An iron(III) complex, [Fe(L1)Cl].H2O, was synthesized by template condensation reaction of 1,1,1-Trifluoroacetylacetone-S-methylthiosemicarbazone hydrogen iodide (L) and 2,3-dihydroxybenzaldehyde in the presence of iron(III) ions. The complex was characterized by IR, ESI MS and X-ray diffraction techniques. Free radical scavenging (FRS) ability and antioxidant capacity of the S-methylthiosemicarbazone and the iron(III) complex were evaluated through DPPH and CUPRAC methods, respectively. The complex exerted better than the S-methylthiosemicarbazone in both TEAC and FRS% values. In addition, iron(III) complex was found to be 3.1 times more antioxidant than the reference ascorbic acid according to the CUPRAC method.

Synthesis and antioxidant activities of new nickel(II) complexes derived from 4-benzyloxysalicylidene-S-methyl/propyl thiosemicarbazones

Six nickel(II) complexes of the N₂O₂ chelating thiosemicarbazones were synthesized using N¹-4-benzyloxysalicylidene-S-methyl/propyl thiosemicarbazone and methoxy-substitute-salicylaldehydes in the presence of Ni(II) ion by template reaction. The structures of thiosemicarbazones and nickel(II) complexes were characterized by elemental analysis, UV-Vis, IR, and ¹H-NMR spectroscopies. The structure of the N¹-4-benzyloxysalicylidene-S-propyl thiosemicarbazone ( 2 ) was determined by X-ray single-crystal diffraction method. The total antioxidant capacities of synthesized compounds were evaluated by using cupric reducing antioxidant capacity (CUPRAC) method. The thiosemicarbazones exhibited more potent antioxidant capacity than Ni(II) complexes. Trolox equivalent antioxidant capacity (TEAC) of 1c was found highest in tested nickel(II) complexes. In addition, antioxidant activities of tested compounds were evaluated by using the hydroxyl radical, DPPH radical, and ABTS radical scavenging abilities of these compounds.

Glycoprotein levels and oxidative lung injury in experimental diabetes: effect of oxovanadium(IV) complex based on thiosemicarbazone

Diabetes mellitus (DM) is chronic and metabolic disorder, which is mainly attributed by hyperglycemia. Vanadium salts and their oxo-complexes have been shown to possess insulin-mimetic and anti-diabetic activities in animal models and diabetic patients. The main goal of this study was to investigate the protective effect of oxovanadium(IV) complex based on thiosemicarbazone (VOL) [L: (N(1)-2,4-dihydroxybenzylidene-N-(4)-2-hydroxybenzylidene-S-methyl-isothiosemicarbazidato-oxovanadium(IV)] on glycoprotein components levels and oxidative lung injury of streptozotocin (STZ)-induced diabetic rats. Male Swiss albino rats were separated into four groups. Group I (n = 5): Control (normal) animals, Group II (n = 5): Control animals administered with VOL, Group III (n = 6): STZ-induced diabetic animals, and Group IV (n = 5): STZ-induced diabetic rats treated with VOL. VOL was given to the experimental animals by gavage at a dose of 0.2 mM/kg body weight every day for 12 days. Diabetes was induced by single intraperitoneal injection of STZ (65 mg/kg body weight). On the 12th day, lung tissue samples were taken. Glycoprotein components, advanced oxidation protein products, protein carbonyl, hydroxyproline levels, and prolidase, arginase, xanthine oxidase, catalase, superoxide dismutase, glutathione peroxidase, glutathione reductase, glutathione-S-transferase and adenosine deaminase activities significantly increased whereas aryl esterase, paraoxonase-1, carbonic anhydrase, Na⁺/K⁺-ATPase activities remarkably decreased in lung tissue of diabetic rats. Treatment with VOL reversed these effects showing a beneficial effect. The present study shows that VOL has a protective effect against diabetes-induced lung damage as well as on abnormal glycoprotein component levels.

Protective Effects of an Oxovanadium(IV) Complex with N2O2 Chelating Thiosemicarbazone on Small Intestine Injury of STZ-Diabetic Rats

Vanadium compounds are being investigated as potential therapeutic agents in the treatment of many health problems, primarily diabetes. We aimed to provide the effect of N(1)-4-hydroxysalicylidene-N(4)-salicylidene-S-methyl-isothiosemicarbazidato-oxovanadium(IV) (VOL) on small intestinal injury in experimental male diabetic rats. Four groups were created of 3.0-3.5-month-old rats. The rats were made diabetic by a single dose of streptozotocin (STZ) at 65 mg/kg and grouped as follows: control animals, VOL-given control animals, STZ-induced diabetic animals and STZ-induced diabetic animals given VOL. A daily dose of 0.2 mM/kg vanadium complex was administered orally for 12 days after the inducement of diabetes. On the 12th day, small intestine tissue samples were taken. According to the data obtained from the biochemical analysis, reduced glutathione (GSH) level, catalase (CAT), glutathione peroxidase (GPx), glutathione-S-transferase (GST), superoxide dismutase (SOD), Na⁺/K⁺-ATPase and paraoxanase (PON) activities were increased, whereas sialic acid (SA), xanthine oxidase (XO) and disaccharidases (maltase and saccharidase) activities were decreased in the small intestine tissue of VOL-treated diabetic rats. Microscopic examinations revealed a remarkable decrease in the mucosal necrotic areas, discontinuity in the brush border, deterioration of the villi integrity and oedema inside the villi, but with a mild decrease in the inflammatory cells, deterioration and loss of integrity of the gland in the small intestine of VOL-treated diabetic rats. Moreover, VOL treatment markedly decreased the proliferation of villus cells and especially inflammatory cells in the small intestine of diabetic rats. According to the obtained data, the administration of VOL is a potentially convenient strategy to reducing small intestine injury in diabetic rats.

Spectral, Molecular Modeling, and Biological Activity Studies on New Schiff's Base of Acenaphthaquinone Transition Metal Complexes

The newly synthesized Schiff's base derivative, N-allyl-2-(2-oxoacenaphthylen-1(2H)-ylidene)hydrazine-1-carbothioamide, has been characterized by different spectral techniques. Its reaction with Co(II), Ni(II), and Zn(II) acetate led to the formation of 1 : 1 (M:L) complexes. The IR and NMR spectral data revealed keto-thione form for the free ligand. On chelation with Co(II) and Ni(II), it behaved as mononegative and neutral tridentate via O, N¹, and S donors, respectively, while it showed neutral bidentate mode via O and N¹ atoms with Zn(II). The electronic spectra indicated that all the isolated complexes have an octahedral structure. The thermal gravimetric analyses confirmed the suggested formula and the presence of coordinated water molecules. The XRD pattern of the metal complexes showed that both Co(II) and Ni(II) have amorphous nature, while Zn(II) complex has monoclinic crystallinity with an average size of 9.10 nm. DFT modeling of the ligand and complexes supported the proposed structures. The calculated HOMO-LUMO energy gap, ΔE_H-L, of the ligand complexes was 1.96–2.49 eV range where HAAT < Zn(II) < Ni(II) < Co(II). The antioxidant activity investigation showed that the ligand and Zn(II) complex have high activity than other complexes, 88.5 and 88.6%, respectively. Accordingly, the antitumor activity of isolated compounds was examined against the hepatocellular carcinoma cell line (HepG2), where both HAAT and Zn(II) complex exhibited very strong activity, IC₅₀ 6.45 ± 0.25 and 6.39 ± 0.18 μM, respectively.

Exploring the antioxidant activity of thiaflavan compounds: a quantum chemical study

Conceptual DFT tools (HAT, SPLET, SET-PT, aromaticity index,…) have been used to explore the antioxidant activity of thiaflavan compounds, and predict which derivate should be the best one.

Synthesis and biological screening of thiosemicarbazones of substituted 3-acetylcoumarins having d-glucose moiety

Thiosemicarbazones 5a-j were synthesized with yields of 45-68% by condensation of 3-acetylcoumarins 3a-j and tetra-O-acetyl-β-d-thiosemicarbazide 4. All obtained thiosemicarbazones were screened for anti-microorganic activities against bacteria (B. subtilis, S. aureus, S. epidermidis, E. coli, P. aeruginosa, K. pneumoniae, S. typhimurium) and fungi (A. niger, C. albicans, S. cerevisiae, and A. flavus). Some compounds had significant inhibitory activity with MICs of 0.78-3.125 μM in comparison with 5a, including 5e,h,i for S. aureus, and 5c,f,i for S. epidermidis (Gram-(+) bacteria), 5c,f,g for E.coli, 5f for K. pneumoniae, 5b,c,g for P. aeruginosa, and 5i for S. typhimurium (Gram-(-) bacteria), 5d,h,i for A. niger, 5i for A. flavus, 5b,d,e,h for C. albicans, and 5i for S. cerevisiae. Compounds exhibited excellent activity against tested microorganism with MIC = 0.78 μM, including 5h,i (against S. aureus), 5h (against C. albicans), and 5i (against S. cerevisiae).

Cu(ii) salen and 1,2,4-triazole complexes from thiosemicarbazone: synthesis, physicochemical and structural properties and cytotoxic activities

The complexes were synthesized from reaction of salicylaldehydethiosemicarbazone and ethylenediamine in the presence of CuCl₂.

Antibacterial and antioxidant activities for natural and synthetic dual-active compounds

Antimicrobial resistance is widely recognized as a grave threat to global health in the 21st century, since the past decades have seen a dramatic increase in human-pathogenic bacteria that are resistant to one or multiple antibiotics. New antimicrobial agents are urgently required, particularly in the treatment of chronic infections such as cystic fibrosis, often associated with persistent colonization by drug-resistant pathogens and epithelial damage by pulmonary oxidative stress. In such events, it would be favourable to find agents that could have antioxidant and antibacterial activities combined in one molecule. The discovery of compounds that can show a dual-target activity considerably increased in the last years, reflecting the growing confidence that this new approach could lead to better therapeutic solutions for complex multigenic diseases. The aim of this review is to report those natural and synthetic compounds displaying significant antioxidant and antibacterial activities. In recent years there has been a growing attention on plant-derived antimicrobials as an alternative to antibiotics, for their efficacy and low tendency in developing bacterial resistance. Moreover, it was found that some natural products could enhance the activity of common antibiotics displaying a synergistic effect. We then report some selected synthetic compounds with an in-built capacity to act on two targets or with the combination in a single structure of two pharmacophores with antioxidant and antibacterial activities. Recent literature instances were screened and the most promising examples of dual-active antibacterial-antioxidant molecules were highlighted.

Synthesis and evaluation of in vivo antioxidant, in vitro antibacterial, MRSA and antifungal activity of novel substituted isatin N-(2,3,4,6-tetra-O-acetyl-β-d-glucopyranosyl)thiosemicarbazones

Some new isatin N-(2,3,4,6-tetra-O-acetyl-β-d-glucopyranosyl)thiosemicarbazones 4a-t with different substituents at 1-, 5- and 7-positions of isatin ring have been synthesized by reaction of N-(2,3,4,6-tetra-O-acetyl-β-d-glucopyranosyl)thiosemicarbazide 2 with corresponding isatins 3a-t. Compounds 4a-t were evaluated in vivo for antioxidant activity and in vitro for anti-microorganism activities. The MIC values were found for Gram positive bacteria (MIC = 1.56-6.25 μM), for Gram negative bacteria (MIC = 12.5 μM), and for fungi Aspergillus niger (MIC = 3.12-12.5 μM), Fusarium oxysporum (MIC = 6.25-12.5 μM) and Saccharomyces cerevisiae (MIC = 6.25-12.5 μM). Regarding the antioxidant activity, the SOD, GHS-Px and catalase activities of 4c-i and 4m-r were MIC = 10.57-10.85, 0.27-0.93 and 345.45-399.75 unit/mg protein, respectively. Compounds 4e-h had MIC values of 0.78, 1.56, and 3.12 μM for three clinical MRSA isolates. Compound 4e showed the selective cytotoxic effects against some cancer (LU-1, HepG2, MCF7, P338, SW480, KB) cell lines and normal fibroblast cell line NIH/3T3.

cis-Dioxomolybdenum(VI) complexes of a new ONN chelating thiosemicarbazidato ligand; synthesis, characterization, crystal, molecular structures and antioxidant activities

5-Chloro-4-methyl-2-hydroxybenzophenone S-propyl-4-phenyl-thiosemicarbazone (H2L) and its cis-dioxomolybdenum(VI) complexes, in the general formula [MoO2(L)R-OH)] (R: methyl, 1; ethyl, 2; n-propyl, 3; n-butyl, 4; n-pentyl, 5), were synthesized and characterized by micro analysis, electronic, infrared and (1)H and (13)C NMR spectra. The crystal structures of complexes, 1 and 3, have been solved by direct methods (SIR92) and refined to the residual indexes R1=0.098 and R1=0.052 respectively. Complexes 1 and 3 are crystallized in the triclinic space group P-1 with Z=2. The crystal study of complex 1 showed the first example of intermolecular hydrogen bond for this type of molybdenum-thiosemicarbazone complexes. The hydrogen bond is between the hydroxyl proton of attached alcohol and an oxo oxygen (in MoO2(2+) unit) of another complex molecule, and its bond distance (1.767(1)Å) is shorter than from the σ-coordination bonds in complex 1. Antioxidant activities of the compounds were determined by using 1,1-diphenyl-2-picrylhydrazyl (DPPH) method. Ligand showed 23.61% DPPH radical scavenging activity at 250 mg/L concentration. Cupric Reducing Antioxidant Capacity (CUPRAC) was also evaluated and trolox-equivalent antioxidant capacity (TEAC) values were found for ligand, 1 and 3 as 0.51, 0.33 and 0.30 respectively.

Iron(iii) and nickel(ii) complexes as potential anticancer agents: synthesis, physicochemical and structural properties, cytotoxic activity and DNA interactions

The iron complex 3 was cytotoxic at low concentrations in K562 cells and could damage the DNA, specifically the adenine base.