STUDIA CHEMIA - Issue no.2 / 2017 Tom 2 - Table of contents

The present study aimed to describe the basic pharmacokinetics of zolpidem and its metabolite zolpidem phenyl-4-carboxylic acid after a single oral dose of 5 mg zolpidem. Six competing kinetic models were created in order to analyze the experimental data obtained from the 20 healthy volunteers enrolled in a clinical study. Based on rational model discrimination criteria (Akaike index value), the best one was chosen and further used for a better understanding of the kinetics of zolpidem and its metabolite in the body after administration. The kinetic model considers that zolpidem absorption process follows a first-order kinetics and during this stage it is partially metabolized (pre-systemic metabolism) to its main metabolite. The kinetics of both zolpidem and its metabolite is characterized by bicompartmental distribution and first order kinetics of both elimination and systemic metabolism.

Keywords: zolpidem, zolpidem phenyl-4-carboxylic acid, compartmental pharmacokinetic analysis

Fixed-dose combinations of an angiotensin II receptor antagonist (telmisartan) and a thiazide diuretic (hydrochlorothiazide) provide an effective antihypertensive therapy while promoting patient compliance with the convenience of once-daily single dose administration. The current study investigated two capillary electrophoretic methods: a capillary zone electrophoresis (CZE) and micellar electrokinetic capillary chromatography one (MEKC) for the simultaneous determination of hydrochlorothiazide and telmisartan. In order to optimize the analytical conditions, efforts were focused on establishing the influence of several experimental parameters on the separation: buffer composition, concentration and pH, applied voltage, temperature, injection pressure and time. The separation of the two analytes can be achieved by CZE using a 25 mM phosphate buffer at pH 2.50 and by MEKC using a 50 mM borate buffer at pH 9.50 containing 25 mM sodium dodecyl sulfate as surfactant. The analytical performance of the two methods was verified in terms of their linearity, precision, accuracy and robustness, and the methods were applied for the determination of the analytes from fixed-dose combinations.

Keywords: hydrochlorothiazide, telmisartan, fixed dose combinations, capillary electrophoresis, pharmaceutical preparations

The purpose of the present study was to develop a simple, rapid and reproducible analytical method for the determination of Nisonicotynoyl- N´-(3-fluorobenzal)hydrazone (SH2) - a synthesized by us halogenated isoniazid derivative with high tuberculostatic activity, in aqueous phase, on the basis of RP-HPLC-PDA and UV/VIS spectrophotometric investigations. Despite of the high linearity (R2 0.9984) of the UV/VIS spectrophotometric method applied, the significantly higher LOQ and LOD values indicated its unsuitability for detection and quantification of low Nisonicotynoyl- N´-(3-fluorobenzal)hydrazone concentrations (< 10 μg/mL). The proposed RP-HPLC-PDA method with mobile phase ACN/phosphate buffer (60:40, v/v) offered short retention time (3.1 min), high precision (RSD 3.50 %) and linearity (R2 0.9898). It characterized with satisfactory LOD (0.346 μg/mL) and LOQ (1.05 μg/mL) values and allowed the qualitative detection of SH2 E/Z-isomer.

Keywords: N-isonicotynoyl-N´-(3-fluorobenzal)hydrazone, RP-HPLC-PDA, UV/VIS, aqueous phase

In our research we investigate the accumulation extent of the inorganic contaminants accessing the aquatic food chain, including zooplankton and fish species through model experiments. In this paper we discuss the preliminary experiments considering the measurement of iron and manganese accumulated in Artemia sp. after hatched and reared in metal contaminated model media. The goal is to develop the sample preparation and analytical methods required for the determination of metals adsorbed in the studied organisms. We proved that rinsing the zooplankton organisms three times with 2 mL per grams (wet weight Artemia) of rinsing solution prior to the sample preparation process decreased the possibility of analytical error. European Reference Material of fish tissue (ERM®-BB422) was used to validate the applied sample preparation and atomic spectrometric methods. The average recovery value for the measured elements by open system digestion with conventional heating was 96% and 92% with microwave digestion. With MP-AES 99% and 92% were gained, respectively. According to our results no significant difference occurred between the digestion in open system with conventional heating and microwave assisted digestion as well as the cost effective microwave plasma atomic emission spectrometry (MPAES) proved to be appropriate for the routine quantitative analysis of adsorbed elements in zooplankton organisms and fish tissues.

Keywords: zooplankton, fish tissue, sample preparation, elemental analysis, atomic emission spectrometry

Carbon nanotube-triethanolamine and carbon nanotubedendrimer structures were obtained from carboxyl functionalized nanotubes (SW-, DW-, MW-COOH). The synthesized compounds were characterized by elemental analysis, scanning transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy (STEM-EDX). The toxicity of the obtained derivatized carbon nanostructures was tested on human immortalized keratinocyte cell line (HaCaT). The viability of the cells was determined using the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium-bromide (MTT) cell proliferation assay.

Keywords: carbon nanotube, dendrimer, biological activity, MTT assay, HaCaT

Multi-walled carbon nanotubes (MWCNTs) surfaces have been characterized by FTIR and SEM techniques. The adsorption performance of MWCNTs was investigated for the removal of ammonium ions from wastewater. The effect of contact time, temperature and initial ions concentration on the adsorption of ammonium ions by MWCNTs were studied and optimized. The results showed a high adsorption capacity of 129 mg/g according to Langmuir isotherm model and removal efficiency of 95%. In addition, the adsorption kinetic and equilibrium data were fitted to the pseudo–second–order model. The potential application of MWCNTs for adsorption of ammonium ions from wastewater was successfully accomplished using a batch adsorption technique.

Keywords: Carbon nanotubes; Removal; Adsorption; Kinetics; Isotherm; Ammonium ions; Langmuir

The aim of this study is to investigate the effect of various wax type warm mix additives on the rheological properties of Chemically Stabilized Rubber Bitumen (CSRB). The rubber bitumen samples were prepared by the modified wet process (HU 226481) and the bitumen tests were carried out according to the relevant standards. Two types of warm mix additives (polypropylene wax - produced by thermal cracking of polypropylene and Fischer-Tropsch wax) with different concentrations (1.0%, 3.0%, 5.0%, 7.0% by weight) were used in our research. The influence of these warm mix additives on the rheological properties was evaluated by Dynamic Shear Rheometer (DSR) test. Multiple-stress creep and recovery (MSCR) test was also used for the determination of percent recovery and non-recoverable creep compliance of wax-modified and neat asphalt rubber samples. According to the results of DSR tests the addition of the Fischer-Tropsch wax resulted a higher complex modulus (thereby stiffness) and favourable higher recovery values based on MSCR tests unlike the addition of polypropylene wax.

Keywords: warm mix additive, asphalt rubber, rheological properties, MSCR

In the present study the purification of finely dispersed oil contaminated water (100 ppm crude oil; doil droplets < 2 μm) was investigated by using coagulation/flocculation process, membrane separation and combined methods. As coagulant, polyaluminum chloride (Bopac) iron(III) chloride and aluminum(III) chloride, while as flocculant anionic polyelectrolyte were applied. For the membrane separation, hydrophilic polyethersulfone (PES) microfilter (d=0.2 μm) was used, while for the determination of the purification efficiencies turbidity, chemical oxygen demand and extractable oil content were measured. The utilization of Bopac polyaluminum chloride coagulant (by setting Al3+ content to 20 ppm) resulted in high purification efficiency (96.7%). The extra addition of 1 ppm anionic polyelectrolyte lead to the increase in efficiency up to 98.8%. Due to the effective destabilization of oil in water emulsion the flux highly increased during the microfiltration of the emulsion, since both irreversible and reversible membrane resistances were greatly reduced.

Keywords: oil contaminated waters, coagulation, flocculation, Bopac, membrane filtration

The study presents the preliminary research on possibility to use the calcium sulphate waste (CSW) as replacing of sand in the cement mortar. The waste was chemically and mineralogical characterized. Four compositions of mortar without and with 7.5 %, 18.78 % and 37.50 % waste were prepared. The X-ray powder diffraction evidenced the main mineral compounds in mortar as hydration products of calcium silicates (CSH) with a low index of crystallinity and different oxide ratio CaO:SiO2:H2O, quartz, calcite, anhidrite and gypsum. Optical microscopy reveals that the samples contains aggregates as quartz, muscovite and rocks, especially of metamorphic origin (quartzite, micaschists, and quartzitic schists) embedded in a fine matrix resulted by hydration reactions of cement compounds or reactions of waste components with other compounds from system. The corrosion properties of mortar, at different CSW concentrations, on rebar, were investigated by polarization measurements and electrochemical impedance spectroscopy. The results revealed that at 7.5 % addition of waste anticorrosion properties are improved. As expected, the mechanical resistances (compressive and flexural strenght) decrease with increasing of waste in mortar composition.

Keywords: waste materials, corrosion, reinforced mortar steel, electrochemical techniques, mechanical properties

Density functional theory (DFT) studies were performed on representative zigzag models of boron nitride nanotubes (BNNTs) with different structural sizes. To achieve minimized-energy structures and their properties, first, optimization calculations were performed at the B3LYP/6- 311G* theoretical level for all models. Subsequently, density of states (DOS) plots, nuclear magnetic resonance (NMR) spectroscopy chemical shielding, natural bonding orbital (NBO) and nuclear quadrupole resonance (NQR) spectroscopy parameters were calculated. The results indicated that the values of energy gap, polarity and electrical charge detect the effects of structural growth in diameter and length.

Keywords: Boron nitride; Nanotube; Density functional theory; Tubular size

In this study, a QSPR study relating topological indices to the entropy of 69 benzene derivatives is reported. The entropy values were calculated at HF level of theory (6-31 G basis sets) by Gussian 98. Multiple linear regression (MLR) provided good models with three to seven independent variables. The best model obtained is based on three descriptors: Randić, Wiener and Szeged topological indices

Keywords: Topological indices; benzene derivatives; QSPR; MLR method.

The present study aims to investigate the influence of the temperature on the radical scavenging capacity (measured by the 2, 2- azinobis (3-ethylbenzothiazolyne-6-sulphonic acid) diammonium salt radical cation assay) and ferric reducing antioxidant power (FRAP) of Cornelian cherry fruit extract. The impact of the thermal treatment was investigated by monitoring these parameters at 75°C and comparing the obtained values to those resulted by refrigerated storage of the extract. The Cornelian Cherry extract showed a great stability of the antioxidant activity after 10 days of storage at 75°C (ca. 29% loss of antioxidant capacity).

Keywords: Cornelian cherries, antioxidant activity, thermal stability

Acetylated derivative (47%) of Bacillus licheniformis -amylase (BLA) was prepared using acetic anhydride and its molecular properties including chemical stability were studied with the help of CD spectroscopy, analytical gel filtration and enzymatic activity measurements. Acetylated BLA preparation was found homogeneous with respect to charge and size based on electrophoretic and chromatographic results. Expansion in the molecular size of the modified BLA was evident from the decrease in its elution volume on Superdex 200 column as well as Stokes radius determination. Near-UV CD spectra suggested significant change in the tertiary structure of the acetylated BLA, whereas secondary structures remained unaltered, as judged from the far-UV CD spectra. Acetylated BLA displayed greater chemical stability against urea denaturation as revealed by the increase in the mid-point (Cm) of the denaturation curve and significant retention of biological activity at different urea concentrations. These results indicated greater conformational stability of acetylated BLA in the presence of urea.

Keywords: Bacillus licheniformis α-amylase, acetylation, chemical stability, urea denaturation

New proteins as molecular targets in development of therapies are discovered every day. However, study of their interactions with other proteins or binding partners in complex cellular environments has its limits. Therefore, high-yield production of these proteins in heterologous systems is a valid necessity, while obtaining these proteins linked to suitable fluorescent markers represents a step ahead in protein-protein interaction studies and cellular or subcellular localization. In this study, we present production of human SMAC/Diablo recombinant protein with EGFP as a fusion partner. High-yield expression of the fusion protein was carried out in E. coli Rosetta™(DE3)pLysS strain, and an acceptable purity of the protein was obtained after affinity chromatography purification and gel filtration. The obtained protein can be further used in protein-protein interaction studies, whereas our method represents a cost-effective and efficient production method for EGFP-fused proteins, applicable for a number of therapeutically important polypeptides.

Keywords: SMAC/Diablo, apoptosis, heterologous expression, EGFP fusion proteins

The article discloses the main results of our new investigation of Platland tree, a.k.a. Sunland baobab, the largest known African baobab. Our recent research was motivated by the three successive splits of 2016 and 2017, which determined the collapse and demise of the stems that have built the main unit of the tree. According to our new findings concerning the architecture of large and old baobabs, we established that Platland tree has a double closed-ring shaped structure and consists of two units/rings that close two separate false cavities. The larger unit was composed of five fused stems, out of which four toppled and died, while the fifth stem is already broken. The smaller unit, which is still standing, consists of three fused stems. We also determined that the larger unit had an age of 800 yr, while the smaller unit is 1100 yr old.

Keywords: AMS radiocarbon dating, Adansonia digitata, tropical trees, ringshaped structure, age determination, false cavity.

The article reports the AMS (accelerator mass spectrometry) radiocarbon dating results of Sagole Big tree, a giant African baobab from Limpopo, South Africa. Several wood samples were collected from the walls of its inner cavity and dated by radiocarbon. The age values along the cavity samples increase with the distance into the wood. This anomaly shows that the cavity is a false one. The oldest sample segment had a radiocarbon date of 781 ± 29 BP, which corresponds to a calibrated age of 740 ± 15 yr. We estimate that the oldest part of the Sagole baobab has an age of 800-900 yr. We determined that the tree has a closed ring-shaped structure, which consists of a large unit with six fused stems and of two additional leaning stems.

Keywords: AMS radiocarbon dating, Adansonia digitata, tropical trees, ringshaped structure, age determination, false cavity.

A series of new N'-benzylidene-N-(thiazolyl)acetohydrazide derivatives was obtained by the acetylation of 2-(2-benzylidenehydrazinyl)thiazole derivatives using acetic anhydride. The antimicrobial activity of the new and parent compounds was screened against Gram-positive and Gram-negative bacteria using agar well diffusion method. 4-Methyl-2-[2-(4-hidroxibenzylidene)-hydrazinyl)- thiazole was identified as the most efficient, with a broad activity spectrum against both Gram positive and Gram negative bacteria.

Keywords: acetohydrazide, thiazole, antimicrobial

Aromatic plants are widely used in food preparation for aroma and fragrance, but they are also a good source of amino acids and fatty acids. Three indigenous species, Basil (Ocimum basilicum), mint (Mentha piperita) and sage (Salvia officinalis) which are traditionally used in medicine and food, were characterized and compared in terms of volatile extracts, amino acids, fatty acids contents and antioxidant activities. The gas chromatographic–mass spectrometry (GC–MS) method is a suitable technique for the characterization of the compounds of the herbs extracts. Antioxidant activity was measured using extracts ability to scavenge DPPH radicals. Linalool was found the major compound in basil, menthol in mint and α-thujone in sage. The dominant amino acids identified in the plants extracts were glutamic acid and aspartic acid in basil and mint, while proline was found in high concentration in sage and mint. The total free fatty acids (TFA) were highest in mint, followed by sage and basil. The essential omega 3 alpha-linolenic acid (ALA) was identified in all three extracts. All samples exhibited antioxidant activity, sage extract having the highest antioxidant activity.

Keywords: Ocimum basilicum, Mentha piperita, Salvia officinalis, volatile compounds, amino acids, fatty acids

The Amfissis cultivar olive fruits grown in the region of Larissa, central Greece, were studied for the changes in total polyphenol content, phenolic fractions and antioxidant capacity during maturation period (four months). It has been established that the total phenol content and antioxidant capacity, change in broad ranges depending on the ripening stage of fruits. The content of total phenols in the Amfissis cultivar during maturation varied from 3.9 to 11.9 mg (GAE) g-1 FW. The highest content of total phenols has been found in the harvest stage (December). The content of flavonoid phenols ranges from 3.12 to 9.47 mg (GAE) g-1 FW. The highest content of flavonoid phenols was determined the time period of the harvesting. The content of non-flavonoid phenols during ripening of olive fruit ranges from 0.78 to 2.43 mg (GAE) g-1 FW. The highest content of NFP was determined the time period of the harvesting (black color). The inhibition concentration (IC50) of extract during maturation of the olive fruit in all stages ranges from (735 to 130) mg/l. The lowest inhibition concentration (highest antioxidant capacity) was observed in the collection stage of the olive fruits. The obtained results have a direct impact on the harvesting date of the table cultivar Amfissis, influencing the sensory properties and the quality of the olive fruit.

Keywords: Antioxidant activity FRAP; Olives, Amfissis; Total phenols