Kinetics and Mechanism of Oxidation of 1-Phenylsemicarbazide by Peroxydisulphate

Kinetics of oxidation of 1-phenylsemicarbazide (PSC) by peroxydisulphate ion (PDS) have been carried out where by the pseudo first order condition was verified at large excess of PDS concentration. The rate of the reaction was followed spectrophotometrically, The stoichiometry was found to be 1:1 where 1-phenylazoformamide is the oxidation product. The effect of acidity on the rate of oxidation was investigated for different temperatures. The parameters of activation ΔG*, ΔH* and ΔS* were computed for both hydrogen ion depedent and hydrogen ion independent reaction pathes. A free radical mechanism was proposed.     

Potential Mechanisms Involved in the Protective Effect of Dicaffeoylquinic Acids from Artemisia annua L. Leaves against Diabetes and Its Complications

Diabetes mellitus is a chronic disease affecting the globe and its incidence is increasing pandemically. The use of plant-derived natural products for diabetes management is of great interest. Polar fraction of Artemisia annua L. leaves has shown antidiabetic activity in vivo. In the present study, three major compounds were isolated from this polar fraction; namely, 3,5-dicaffeoylquinic acid (1); 4,5-dicaffeoylquinic acid (2), and 3,4- dicaffeoylquinic acid methyl ester (3), using VLC-RP-18 and HPLC techniques. The potential protective effects of these compounds against diabetes and its complications were investigated by employing various in vitro enzyme inhibition assays. Furthermore, their antioxidant and wound healing effectiveness were evaluated. Results declared that these dicaffeoylquinic acids greatly inhibited DPPIV enzyme while moderately inhibited α-glucosidase enzyme, where compounds 1 and 3 displayed the most prominent effects. In addition, compound 3 showed pronounced inhibition of α-amylase enzyme. Moreover, these compounds markedly inhibited aldose reductase enzyme and exerted powerful antioxidant effects, among which compound 3 exhibited the highest activity implying a notable potentiality in impeding diabetes complications. Interestingly, compounds 2 and 3 moderately accelerated scratch wound healing. Our findings suggest that these dicaffeoylquinic acids can be promising therapeutic agents for managing diabetes and its complications.     

An Efficient Synthesis of Thiazolidine‐4‐ones with Antitumor and Antioxidant Activities

Reaction of 3‐aroyl‐1‐arylthioureas with dimethyl but‐2‐ynedioate in dichloromethane and catalyzed by triphenylphosphine at ?5°C led to (Z)‐methyl 2‐[(Z)‐2‐(4‐aroylimino)‐4‐oxo‐3‐aryl‐1,3‐thiazolidin‐5‐ylidene]acetates in good yields. The mechanism is discussed. X‐ray structure analysis of one thiazolidine derivative is described. Antitumor and antioxidant activities have been investigated. One derivative of 1,3‐thiazolidine showed moderate antiproliferative in vitro activity against hepatocellular carcinoma Hep‐G2, whereas another 1,3‐thiazolidine introduced effective antioxidant activity compared to ascorbic acid.     

A Novel Potentiometric Detection Strategy for the Determination of Amlodipine Besylate Based on Functionalized Particles

A novel potentiometric strategy based on functionalized magnetite nanoparticles and microparticles were compared with the classical potentiometric strategy. This strategy provided nano‐ and microsized particles that were highly dispersed and coated with ionophore and plasticizer to promote an in situ cooperative ion‐pairing interaction between the ionophore and the analyte present in inner solution of sensor membrane, compared to the classical technique. Three amlodipine (AML) sensors were constructed using functionalized nanoparticles in sensor 1; microparticles in sensor 2, as ionophores, and the polymeric membrane ionophoric property in sensor 3.     

Eremophilane esters of Robinsonecio gerberifolius and their rearranged products. Study of the coupling constants (2)J(H, H), (3)J(H, H) and (4)J(H, H)

In the course of the basic hydrolysis of four eremophilane esters isolated from Robinsonecio gerberifolius, some rearrangements, eliminations, and additions occurred. Five compounds were obtained, three of them not previously described. Additionally, a new sesquiterpene was produced by autooxidation of compound 1. The (1)H and (13)C NMR spectra of these compounds were completely assigned by utilization of HMQC, HMBC, COSY, DEPT, and NOESY techniques. The long-range coupling constants of the peroxide 10 are reported, and all its coupling constants (2)J(H, H), (3)J(H, H), and (4)J(H, H) are calculated at the B3LYP/6-31G(d,p) level of theory. Their magnitude is explained in terms of electronic delocalization and the additivity of stereoelectronic effects.     

Comparative study of 2-hydroxy propyl beta cyclodextrin and calixarene as ionophores in potentiometric ion-selective electrodes for neostigmine bromide

Three novel neostigmine bromide (NEO) selective electrodes were investigated with 2-nitrophenyl octyl ether as a plasticiser in a polymeric matrix of polyvinyl chloride (PVC). Sensor 1 was fabricated using tetrakis(4-chlorophenyl)borate (TpClPB) as an anionic exchanger without incorporation of an ionophore. Sensor 2 used 2-hydroxy propyl β-cyclodextrin as an ionophore while sensor 3 was constructed using 4-sulfocalix-8-arene as an ionophore. Linear responses of NEO within the concentration ranges of 10⁻⁵ to 10⁻², 10⁻⁶ to 10⁻² and 10⁻⁷ to 10⁻² mol L⁻¹ were obtained using sensors 1, 2 and 3, respectively. Nernstian slopes of 51.6 ± 0.8, 52.9 ± 0.6 and 58.6 ± 0.4 mV/decade over the pH range of 4-9 were observed. The selectivity coefficients of the developed sensors indicated excellent selectivity for NEO. The utility of 2-hydroxy propyl β-cyclodextrin and 4-sulfocalix[8]arene as ionophores had a significant influence on increasing the membrane sensitivity and selectivity of sensors 2 and 3 compared to sensor 1. The proposed sensors displayed useful analytical characteristics for the determination of NEO in bulk powder, different pharmaceutical formulations, and biological fluids (plasma and cerebrospinal fluid (CSF)) and in the presence of its degradation product (3-hydroxyphenyltrimethyl ammonium bromide) and thus could be used for stability-indicating methods.     

Design and synthesis of novel antimicrobial acyclic and heterocyclic dyes and their precursors for dyeing and/or textile finishing based on 2-N-acylamino-4,5,6,7-tetrahydro-benzo[b]thiophene systems

A series of novel polyfunctionalized acyclic and heterocyclic dye precursors and their respective azo (hydrazone) counterpart dyes and dye precursors based on conjugate enaminones and/or enaminonitrile moieties were synthesized. The dyes and their precursors are based on 2-cyano-N-(3-cyano-4,5,6,7-tetrahydrobenzo[b]thiophen-2-yl)-acetamide, 2-ethoxycarbonyl-N-(3-cyano-4,5,6,7-tetrahydrobenzo[b]thiophen-2-yl)-acetamide or 2-phenylcarbamoyl-N-(3-cyano-4,5,6,7-tetrahydrobenzo[b]thiophen-2-yl)-acetamide systems as precursors. The latter compounds were used to synthesize polyfunctional thiophene-, thiazole-, pyrazole, pyridine-, pyrimidine-, oxazine-, as well as acyclic moieties. The dyes and dye precursors were characterized by elemental analysis and spectral methods. All dyes and their precursors were screened in vitro and evaluated for both their antibacterial and antifungal activities. MIC data of the novel dye systems and their respective precursors showed significant antimicrobial activity against most tested organisms. Some compounds exhibited comparable or even higher efficiency than selected standards. Dyes were applied at 5% depth for disperse dyeing of nylon, acetate and polyester fabrics. Their spectral characteristics and fastness properties were measured and evaluated.     

Complexes of hydrazide Schiff bases

Summary 1,2-Diphenyl-2-(benzoylhydrazino)ethanol (DBE) and 1,2-diphenyl-2-(p-nitrobenzoylhydrazino)ethanol (DPNBE) form complexes of general formulae [M(H₂L)₂]X₂ and [M₂L₂] (where M = Co or Ni, H₂L and L are the neutral and dibasic forms of the ligands and X = Cl or NO₃). The analytical, spectral, magnetic and physical studies show the complexes to be of two types, namely monomeric cationic species prepared in neutral media and neutral binuclear oxygen-bridged species formed in alkaline solution. The ligands are tridentate, coordinating through carbonyl (or enolic) oxygen, azomethine nitrogen and alcoholic oxygen atoms.     

Molecular Imprints Frozen by Strong Intermolecular Interactions in Place of Cross-Linking

A new way to freeze molecular imprints in a polymer material is reported. So far, molecular imprinted polymers (MIP) involve copolymerization of a functional monomer and large amounts of cross-linking agent, which keeps the template shape memory in rigid molecular imprints. MIP materials are prepared herein without cross-linking agent. Stiff chains of polyaniline grafted on a solid support as a brush-like material achieve the necessary rigidity. Differential adsorption to imprinted and non-imprinted materials provides evidence of molecular imprints. A correct adsorption isotherm for mobile adsorbed layers (Volmer isotherm) is introduced instead of the popular but inadequate Langmuir isotherm. Non-selective adsorption is entropic, whereas adsorption to molecular imprints has an enthalpic contribution coming from specific interactions. Fast adsorption kinetics are a definite benefit with regards to applications such as chromatographic separations and chemical sensors.     

Conductivity study by complex impedance spectroscopy of solid solution AgxK1 − xNb4AsO13 (x = 0.2 and 0.62): effect of the substitution of K+ by Ag+ cations on the ionic conduction properties

Journal of Solid State Electrochemistry - Crystals of Ag0.2K0.8Nb4AsO13 (I) and Ag0.62K0.38Nb4AsO13 (II) were synthesized by a solid-state reaction. Both of them crystallize in the orthorhombic...