No abstract

No abstract

No abstract

A number of novel catechol-and phenol-containing Schiff bases with thiophenol or mercaptobenzimidazole groups have been synthesized. Electrochemical studies of the target compounds were carried out in order to establish the primary centres involved in redox reactions, and the mechanism of oxidative transformations. The antioxidant activities of the compounds were determined using different assays. Compounds combining the catechol group with the mercaptobenzimidazole or benzothiazoline cycles exhibit more pronounced antioxidant activity in the concerning tests. However, a significant promoting effect on the process of lipid peroxidation of rat brain homogenates was found in the presence of catechols. Antibacterial and cytotoxic effects of Schiff bases can be caused by the possibility of ROS and o-benzoquinones generation. It was established that some compounds have a moderate bacteriostatic effect against Staphylococcus aureus strains. Schiff bases with catechol and heterocyclic groups exhibit a good antiproliferative activity (IC 50 < 10 μM) towards MCF-7, HTC-116 and A549 cell lines.

The determination of gold in natural minerals in the range n × 10 -4 to n × 10 -6 % is an important and relatively complex analytical problem. The chemical composition of natural matrices significantly complicates the determination of trace gold by modern physicochemical methods. Therefore, different methods are used for the preseparation and preconcentration of gold from the matrix for improving the reliability and accuracy of the analysis of natural samples. Chelating polymer adsorbents are most promising in efficiency, rapidity, and simplicity [1][2][3].Chelating polymer adsorbents are characterized by the presence of chemically active groups in the polymer matrix; these groups can interact with metal ions present in the solution to form chelates or ion associates. The adsorbent properties are primarily determined by the nature of functional analytical groups introduced into the matrix. They also depend on the physical and chemical properties of the polymer matrix (styrenedivinylbenzene copolymers of different cross-linking degrees and macroporosities), analyte nature, and sorption conditions.In this work, the results of studying the physicochemical and analytical properties of some new chelating polymer adsorbents bearing aminoazo functional analytical groups are studied, and the possibilities for their use for the preconcentration and spectroscopic determination of gold in natural mineral samples are assessed.EXPERIMENTAL Solutions, reagents, and apparatus. Gold and platinum-group metal solutions with the concentration 1 mg/mL were prepared by dissolving exact portions of metals in aqua regia. Other solutions were prepared by dissolving chemically pure salts in HCl. Working solutions were prepared by diluting the stock solutions with 1 M HCl. High-purity grade acids were used.Concentrates were incinerated in an Sh-450 muffle furnace. An ADV-200 analytical balance and MM-2A magnetic stirrers were used. Gold(III) in solutions was analyzed on a Perkin-Elmer 403 atomic-absorption spectrometer. Some measurements were performed on a VG Plasma Quard ICP-MS spectrometer (England).Adsorbents were synthesized according to the scheme described in [4]. The synthesized chelating polymer adsorbents were dark brown powders insoluble in water, acids, alkalis, and organic solvents. The procedure for the synthesis of poly(styrene-azo-2-aminobenzene) is given below as an example. Polystyrene 30/100, where the numerator denotes the amount of divinylbenzene (g) and the denominator indicates the amount of the pore-forming agent benzene (1 g per 100 g of monomer mixture), was used for the synthesis.Synthesis of poly(styrene-azo-2-aminobenzene). Macroporous styrene-divinylbenzene amino copolymer hydrochloride (48 g, 0.3 mol) was placed in a 1-L beaker, mixed with 400 mL of water and 60 mL of concentrated HCl, and cooled with liquid nitrogen in an ice bath (from 0 to +5 ° C). Next, aminopolystyrene was diazotized with a solution of 14 g (0.2 mol) NaNO 2 in 50 mL of water for 2 h under stirring. Red-brown granules of aminopolystyrene...