Volume 70, Issue 5

Physical, enzymatic and chemical methods were used to develop an efficient procedure for preparing gelatine hydrogels of appropriate strength and elastic properties for applications as enzyme carriers. The concentrations of the crosslinking enzyme (transglutaminase), the initial amount of gelatine, the production time and the effect of additional crosslinking with glutaraldehyde were examined. As a result, the following conditions were selected: 0.1 g cm –3 solution of gelatine, 0.01 g cm –3 of transglutaminase (mTGase), a minimum of 2 h incubation at 4°C and an additional step of crosslinking with 1.0 vol. % of glutaraldehyde. Next, the absorption properties and storage stability of hydrogels so obtained were determined. From these results, it was observed that, with the exception of the physical gel, the remaining materials presented a relatively high resistance to hydrolytic degradation and retained their original spatial structure without any visible damages. The immobilisation experiments indicated gelatine-based hydrogels crosslinked with transglutaminase as suitable for use as matrices for the entrapment of enzymes, which catalyse the conversion of low-molecular mass compounds. In addition to the potential for effective re-use in subsequent batch processes, the essential advantage of the immobilised β -galactosidase obtained in the current study is a marked reduction in its volume under storage conditions of long duration, without any significant decline in catalytic activity.

A variety of aromatic nitro compounds were chemoselectively reduced to the corresponding anilines using conveniently prepared nanosized CdS as a photocatalyst under the sunlight and blue LED irradiation. The results demonstrated that synthesized CdS nanostructures have the potential to provide a promising visible light driven photocatalyst for chemoselective reduction of nitro aromatics in the presence of nitrile and carbonyl groups to the corresponding amines under both sunlight and blue LED irradiation. Photoreduction of nitro aromatics by the prepared nanosized CdS with high surface area was faster than when using the commercially available CdS under both sunlight and LED irradiation. Nanosized CdS photocatalyst was prepared by a simple method without any capping agent. X-ray diffraction (XRD), energy dispersive spectrometry (EDAX), transmission electron microscopy (TEM), scanning electron microscopy (SEM), N 2 absorption–desorption, diffuse reflectance spectroscopy (DRS), and flat band potential methods were employed for the characterization, which revealed that the prepared CdS nanoparticles have a well-resolved cubic structure with the size of around 10–30 nm and a band gap of 2.37 eV.

A heterogeneous polyvinylpolypyrrolidone supported Brønsted acidic catalyst ([PVPP-BS]HSO 4 ) was used to synthesize butyrate in this paper. The prepared catalysts were characterized by FT-IR, TG, and FESEM and their catalytic activity in butyric acid esterification with benzyl alcohol was investigated. The influencing factors such as the amount of catalyst, reaction temperature, and reaction time were carefully studied. Under the optimized condition with the butyric acid to benzyl alcohol mole ratio of 1 : 1.2 and the reaction temperature of 130°C, the yield of benzyl butyrate reached 96.8 % within 4 h in the presence of 8 mass % of catalyst. Moreover, the catalyst could be reused six times without noticeable drop in activity. This catalyst was also used to synthesize other kinds of butyrates achieving the butyrate yield above 90 %.

In this experiment, the behaviour of ten pesticides on field-sprayed blackcurrants ( Ribes nigrum ) after washing, juicing and cooking was investigated. The concentration level changes in two acaricides (fenazaquin, propargite), three insecticides (alpha-cypermethrin, deltamethrin and lambda-cyhalothrin) and five fungicides (boscalid, bupirimate, difenoconazole, pyraclostrobin, thiophanatemethyl) were quantified. Analysis was carried out using the QuEChERS method followed by chromatographic analysis based on LC-MS/MS. The matrix effects ranged from –(17.4 ± 8.1) % to (15.9 ± 7.8) %. The limits of detection and limits of quantification were 0.003 mg kg −1 and 0.01 mg kg −1 , respectively. The mean recoveries of the analytes ranged between 71 % and 109 %. The processing factors of all the blackcurrant products were determined. Washing reduced the pesticide residues up to 71 %. Juicing significantly reduced all the pesticide residues (processing factors (PFs) ranged 0.14–0.47). Cooking resulted in a decrease in residues up to 82 %. The residue levels of alpha-cypermethrin, deltamethrin and lambda-cyhalothrin in blackcurrant jam increased, and PFs > 1 were noted as PF = 1.38, 1.66 and 1.04, respectively. Cluster analysis was performed to find any similarity in the behaviour of pesticides after processing. The results confirmed that solubility, polarity and mode of action could be used to explain differences in the behaviour of pesticides.

Phyllanthus amarus ( P. amarus ) is a herbal plant used in the treatment of various diseases such as hepatitis, diabetes, and cancer. Efficiency of its bioactive compounds extraction and therefore the biological activity of the extracts are significantly influenced by both solvent character and extraction method. This study is aimed at the determination of the influence of six various solvents (water, acetonitrile, ethanol, methanol, ethyl acetate, and dichloromethane) and nine different extraction methods (conventional, ultrasound-assisted, microwave-assisted, and six novel methods) on the extraction efficiency and antioxidant capacity of P. amarus . The results indicated that water extracted the maximal amount of phenolics from P. amarus and had the highest antioxidant capacity, while microwave-assisted extraction provided the highest yields of phenolics and saponins, and the highest antioxidant capacity with the lowest energy consumption when compared to the other extraction methods. These findings implied that water and microwave-assisted extraction are recommended as the most effective solvent and method for the extraction of bioactive compounds from P. amarus for potential application in the pharmaceutical and nutraceutical industries.

Eucalyptus species have found their place in traditional medicine and pharmacological research and they have also been shown to possess a large number of phenolic compounds and antioxidants. The present study sought to implement conventional extraction to yield maximal total phenolic content (TPC), total flavonoid content (TFC), proanthocyanidins, antioxidants, and saponins from E. robusta using different solvents. The most suitable extraction solvent was further employed for extracting phytochemicals from E. saligna, E. microcorys , and E. globulus to select the Eucalyptus species with the greatest bioactive compound content. The results emphasised the efficiency of water in extracting TPC ((150.60 ± 2.47) mg of gallic acid equivalents per g), TFC ((38.83 ± 0.23) mg of rutin equivalents per g), proanthocyanidins ((5.14 ± 0.77) mg of catechin equivalents per g), and antioxidants ABTS ((525.67 ± 1.99) mg of trolox equivalents (TE) per g), DPPH ((378.61 ± 4.72) mg of TE per g); CUPRAC ((607.43 ± 6.69) mg of TE per g) from E. robusta . Moreover, the aqueous extract of E. robusta had the highest TPC, TFC and antioxidant values among the other Eucalyptus species tested. These findings highlighted the efficiency of conventional extraction in extracting natural bioactive compounds from Eucalyptus species for pharmaceutical and nutraceutical applications.

The application of membrane capacitive deionisation was investigated for treating model water samples and real waste waters from the textile industry. For the pre-treatment of waste waters, nanofiltration was integrated in order to prevent scaling and fouling of membranes and electrodes during membrane capacitive deionisation. Different conditions were applied when treating water samples with membrane capacitive deionisation with the aim of optimising conditions for high desalination efficiency and, consequently, for conductivity reduction. The conductivity of waste waters with high salt concentrations was reduced to the required value, below 1.5 mS cm − 1 .The desalination rates achieved as much as 95 %, depending on the initial conductivity and the different ions present in the water samples. In addition, chemometric characterisation of the samples was performed in order to determine the existence of significant correlations between the monitored parameters: the presence of various ions (Na + , K + , Ca 2+ , Mg 2+ , Cl − , Br − , F − , SO42−, NO3−${\rm{SO}}_{\rm{4}}^{{\rm{2}} - } ,\,{\rm{NO}}_3^ - $), desalination and water recovery, the duration of each phase and the flow of the solution during each phase. A model for desalination rate prediction was designed using multiple linear regression. It was established that the model values accorded well with the experimental values - the differences between model and experimental values were less than 1 %.

Olefins and paraffins are important basic chemical raw materials with so similar molecular structure and volatility that their separation is a difficult and energy-consuming process. Liquid–liquid equilibrium (LLE) data were determined for ternary systems of: 1-hexene + hexane + solvent at 25°C, 30°C, and 35°C, and N-formylmorpholine (NFM), N-methyl-2-pyrrolidone (NMP), 7-butyrolactone (GBL), and 1-methylimidazole (1-MEI) as the solvents studied. Liquid–liquid equilibrium data for each system were correlated to the NRTL (Non-Random Two Liquid) equation and the interaction parameters presented. The calculated results agree well with the experimental data.

The separation of two systems containing minimum boiling azeotropes (acetone-methanol and tetrahydrofuran (THF)-water) was performed using extractive distillation with a heavy boiling mixed entrainer consisting of two compounds. The entrainer constituents did not form new azeotropes with each other and with the components of the original mixture. An analysis of the mixed entrainer influence on the vapor-liquid equilibrium (VLE) and relative volatility provides an understanding of the cases in which the separation by extractive distillation (ED) in the presence of the mixed entrainer revealed energy benefits over their individual constituents. New results for application of the mixed entrainer monoethanolamine (MEA)-ethylene glycol (EG) and dimethyl-sulphoxide (DMSO)-glycerol for the separation of THF-water and acetone-methanol, respectively, are presented for the first time. The individual selective agents were chosen from the efficient entrainers discussed in the literature. The calculations were performed using the platform Aspen Plus 7.3. Different extractive distillation flowsheets are provided for the zeotropic mixed agents, viz. with two or three columns. For the ED of the binary mixtures investigated, the structures of the different separation schemes, the operating parameters of the columns, and the energy consumptions are presented and compared. The application of the mixed entrainer MEA-EG fed into the ED column with pre-mixing can be recommended, providing up to 1.7 % of energy saving for acetone-methanol separation. In the case of THF-water, the mixed entrainer DMSO-glycerol provides 0.8 % of energy saving. The separate inputs of the individual constituents of the mixed entrainer led to a significant increase in the energy consumptions of the flowsheet because of the third regeneration column, hence this flowsheet cannot be recommended for use in the separation of both mixtures.

The removal of non-reactive iron for different combinations of Fe 2+ and tannic acid in iron-gall inks, via calcium phytate solutions, was studied. In parallel, the non-reactive iron removal kinetics was investigated using the pseudo first-order and second-order kinetic models. The results showed that the use of a dilute solution of calcium phytate to wash the impregnated paper strips removed the non-reactive iron from iron-gall inks in approximately 15 min in stoichiometric and non-stoichiometric combinations of iron and tannic acid. A second washing of the paper strips after an accelerated ageing, showed a distinct kinetic behaviour, with iron removal taking place simultaneously but apparently via a different mechanism. The use of a reference calcium phytate solution exhibited the same behaviour, suggesting that the use of dilute solutions as iron removal agents would represent less damage to historical documents. The results of kinetic modelling showed that all the combinations of Fe 2+ and tannic acid used fitted the pseudo first-order kinetic model, when dilute and reference phytate solutions were tested as iron-desorbing agents.

para -Benzylamine substituted oligophenol was synthesized via enzymatic oxidative polycondensation of 4-(benzylamino)phenol (BAP). Polymerization involved only the phenolic moiety without oxidizing the sec -amine (benzylamine) group. Chemoselective polycondensation of BAP monomer using HRP enzyme yielded oligophenol with sec -amine functionality on the side-chain. Effects of various factors including solvent system, reaction pH and temperature on the polycondensation were studied. Optimum polymerization process with the highest yield (63 %) and molecular weight ( M n = 5000, degree of polymerization ≈ 25) was achieved using the EtOH/ buffer (pH 5.0; 1 : 1 vol. ratio) at 25 °C in 24 h under air. Characterization of the oligomer was accomplished by 1 H NMR and 13 C NMR, Fourier transform infrared spectroscopy (FT-IR), gel permeation chromatography (GPC), ultraviolet-visible spectroscopy (UV-Vis), cyclic voltammetry (CV) and thermogravimetric analysis (TGA). The polymerization process involved the elimination of hydrogen from BAP, and phenolic-OH end groups of the oligo(BAP), confirmed using 1 H NMR and FT-IR analyses. The oligomer backbone possessed phenylene and oxyphenylene repeat units, and the resulting oligomer was highly soluble in common organic solvents such as acetone, CHCl 3 , 1,4-dioxane, N,N -dimethylformamide (DMF), tetrahydrofurane (THF) and dimethylsulfoxide (DMSO). Oligo(BAP) was thermally stable and exhibited 5 % and 50 % mass loss determined by thermogravimetric analysis at 247°C and 852°C, respectively.

The influence of 1 H -benzotriazole, 5-methyl-1 H -benzotriazole and 5-chloro-1 H -benzotriazole on copper corrosion in an acidic sulphate medium was studied, as well as the influence of chloride ions on the corrosion behaviour of copper. The methods used were potentiodynamic measurements, open circuit potential and mass loss. The results show that the examined compounds possess good inhibitory properties in an acidic medium. The potentiodynamic polarisation results indicate that the degree of copper protection against corrosion depends on the concentration of Cl − ions and the concentration of organic compounds. The adsorption of these compounds on the copper surface follows the Langmuir adsorption isotherm.

Electrophilic aromatic substitution is one of the most thoroughly studied reactions in organic chemistry. In the present paper, the 5-brominated spirobrassinol methyl ethers VII, VIII were obtained by electrophilic substitution of the aromatic core of indoline at the C-5 position in the presence of various brominating agents. The same products were also prepared from 5-bromoindole ( IX ) following the sequence for the synthesis 1-methoxyspirobrassinol methyl ether ( V ) from indoline. In addition, the new related 5-bromospiroindoline derivatives XX–XXIII were synthesised and their biological activity on human tumour cell lines was examined. The presence of bromine in the indole or indoline skeleton at the C-5 position resulted in the partial increase in anticancer activity on leukaemia cell lines (Jurkat, CEM). The structures of the newly prepared products were determined by 1 H and 13 C NMR spectroscopy, including HSQC, HMBC, COSY, NOESY and DEPT measurements.

N-Phenylpyrazine-2-carboxamides (anilides of pyrazinoic acids with simple substituents in various positions) were previously shown to possess significant biological activities in vitro, markedly anti-mycobacterial and photosynthesis-inhibiting activity. Based on structure-activity relationships (SAR) extracted from previously published series, 25 new anilides of non-substituted pyrazinoic acid (POA), 5-CH 3 -POA, 6-Cl-POA, 5- tert -butyl-POA and 5- tert -butyl-6-Cl-POA were designed and synthesised. The phenyl part was substituted with simple hydrophobic substituents chosen from methyl and halogens. 5- tert -Butyl-N-(5-fluoro-2-methylphenyl)pyrazine-2- carboxamide ( 9 ), N-(3-chloro-4-methylphenyl)-5-methylpyrazine-2-carboxamide ( 12 ), 6-chloro-N- (3-chloro-4-methylphenyl)pyrazine-2-carboxamide ( 13 ) and 6-chloro-N-(5-iodo-2-methylphenyl)pyrazine-2-carboxamide ( 18 ) possessed whole cell anti-mycobacterial activity in vitro against Mycobacterium tuberculosis H37Rv with minimum inhibitory concentration (MIC) of around 10 μ M. Importantly, no cytotoxicity in the HepG2 model was detected in vitro at the concentrations tested and the estimated IC 50 values were in hundreds of μ M, indicating promising selectivity. N-(3-Chloro-4-methylphenyl)pyrazine-2-carboxamide ( 11 ) and N-(4-chloro-2-iodophenyl)pyrazine- 2-carboxamide ( 21 ) exerted significant activity against Mycobacterium kansasii with MIC 12.6 μ M and 8.7 μ M, respectively. No activity was detected against Mycobacterium avium. SAR were in accordance with those observed for the derivatives previously published.

The use of catalysts in the activation of carboxyl groups towards nucleophilic attack and the protection of other functional groups by suitable protecting groups are standard and necessary procedures in amide bond formation. In contrast to the usual methods, various new compounds, amides of APTES ((3-aminopropyl)triethoxysilane, 3-triethoxysilylpropylamine) and carboxyphenylboronic acids, as well as the amides of aniline and carboxyphenylboronic acids, were obtained in good yields by a one-step synthesis under mild conditions without using any coupling reagents or additional catalysts.

Anovel Hg 2+ ion induced reversible ring contraction was achieved employing the intramolecular reaction of isobutylene with an aromatic hydroxyl group of cyclophane; reversibility of the reaction was facilitated by excess addition of NaBH 4 which also resulted in complexation. The ring contraction and expansion was monitored by UV-VIS absorption, and by fluorescence and 1 HNMR spectra. Switchable fluorescence behavior (on–off–on) was observed when the ring-size was tuned from a 19-membered ring to an 18-membered and vice versa. This fine tuning has the potential to be applied in the construction of new supramolecular devices.