Crystal structures and characterization of two divalent metal selenates templated by dabco, (C6H14N2)[MII(H2O)6](SeO4)2 (MII: NiII, ZnII)

International audienceTwo new organic-inorganic hybrid materials have been synthesized and crystallographically characterized. Both compounds, (C6H14N2)[Ni(H2O)6](SeO4)2 (I) and (C6H14N2)[Zn(H2O)6](SeO4)2 (II), crystallize isotypically in the monoclinic system, space group P21/c, with the following unit cell parameters: a = 12.4045(3), b = 11.9360(3), c = 12.8366(3) Å, β = 108.518(2)°, V = 1802.18(8) Å3, Z = 4 for compound (I) and a = 12.7839(2), b = 11.9153(4), c = 12.3814(2) Å, β = 108.264(5)°, V = 1790.97(7) Å3, Z = 4 for the zinc related phase. Their supramolecular structure consists of metallic cation octahedrally coordinated by six water molecules [MII(H2O)6]2+, selenate anions (SeO4)2- and dabcodiium cation (C6H14N2)2+ linked together via two types of hydrogen bonds, Ow-H...O and N-H...O only. The thermal decomposition of these supramolecular compounds takes place in several steps leading to the formation of metal oxide. The magnetic measurements show that the nickel based compound is predominantly paramagnetic with weak antiferromagnetic interactions at low temperature

Valorization of Moroccan clay: Application to the adsorption of cobalt ions contained in wastewater synthesized

In this study, we were able to reduce the content of cobalt ions Co2+ contained in wastewater by the natural clay of El Oulja-Sale region Moroccan as an inorganic adsorbent. The different effects of the experimental parameters on the adsorption kinetics were studied, namely, the different masses of adsorbent, the initial concentrations of cobalt ions, the contact time, the rate of stirring and the pH of prepared solutions. The results of the studied parameters in the removal of cobalt ions have been recorded in the following values: 3 g per mass of adsorbent, 200 mg/l of the concentration of cobalt ions, 400 tr/min of speed agitation, 2 fortunes for the contact time and pH equal to 6. According to the adsorption kinetics study and according to the adsorption equations of Langmuir and Freundlich whose linear forms, it was shown that the maximum amount adsorbed of the studied ions metals have been validated by the linear models of Langmuir and Freundlich isotherms

Understanding the effects of roasting on antioxidant components of coffee brews by coupling on-line ABTS assay to high performance size exclusion chromatography

INTRODUCTION: Coffee is a widely consumed beverage containing antioxidant active compounds. During roasting the phytochemical composition of the coffee bean changes dramatically and highly polymeric substances are produced. Besides chlorogenic acids that are already present in green coffee beans, melanoidins show antioxidant capacity as well. OBJECTIVE: To employ post‐column derivatisation by coupling high performance size exclusion chromatography (HPSEC) to an antioxidant assay to investigate the effect of roasting on the properties of antioxidant active compounds in coffee brews. METHODOLOGY: We have investigated the antioxidant capacity of Coffea arabica (Arabica) and C. canephora (Robusta) beans that were roasted over the full spectrum of roast conditions (four roasting speeds to three roast degrees) by comparing the results from HPSEC coupled on‐line to the ABTS assay with those from two batch assays, Folin Ciocalteu (FC) and oxygen radical absorbance capacity (ORAC) assay. RESULTS: The antioxidant capacity showed a general decrease towards slower and darker roasted coffee for all three assays, indicative of heat degradation of active compounds. Hence, low molecular weight (LMW) compounds such as chlorogenic acids (CGAs) decreased progressively already from relatively mild roasting conditions. In contrast, high molecular weight (HMW) compounds (e.g. melanoidins) increased from light to dark roast degrees with lowering magnitude towards slower roasting profiles. CONCLUSION: By coupling HPSEC on‐line to the ABTS assay we were able to separately quantify the contribution of HMW and LMW compounds to the total antioxidant capacity, increasing our understanding of the roast process. © 2016 The Authors. Phytochemical Analysis Published by John Wiley & Sons Ltd

Coordinate and redox interactions of epinephrine with ferric and ferrous iron at physiological pH

Coordinate and redox interactions of epinephrine (Epi) with iron at physiological pH are essential for understanding two very different phenomena - the detrimental effects of chronic stress on the cardiovascular system and the cross-linking of catecholamine-rich biopolymers and frameworks. Here we show that Epi and Fe3+ form stable high-spin complexes in the 1:1 or 3:1 stoichiometry, depending on the Epi/Fe3+ concentration ratio (low or high). Oxygen atoms on the catechol ring represent the sites of coordinate bond formation within physiologically relevant bidentate 1:1 complex. Redox properties of Epi are slightly impacted by Fe3+. On the other hand, Epi and Fe2+ form a complex that acts as a strong reducing agent, which leads to the production of hydrogen peroxide via O-2 reduction, and to a facilitated formation of the Epi-Fe3+ complexes. Epi is not oxidized in this process, i.e. Fe2+ is not an electron shuttle, but the electron donor. Epi-catalyzed oxidation of Fe2+ represents a plausible chemical basis of stress-related damage to heart cells. In addition, our results support the previous findings on the interactions of catecholamine moieties in polymers with iron and provide a novel strategy for improving the efficiency of cross-linking.Supplementary material: [http://cherry.chem.bg.ac.rs/handle/123456789/3040

Polyphénols de l'alimentation (extraction, interactions avec les ions du fer et du cuivre, oxydation et pouvoir antioxydant)

Les polyphénols sont des métabolites secondaires des plantes abondants dans l'alimentation. Les extraire des végétaux dans des conditions douces et efficaces et mieux comprendre leurs mécanismes d'oxydation et d'activité abntioxydantes constituent des enjeux scientifiques importants qui sont à la base de ce travail. Dans une première partie, la réactivité de polyphénols communs et représentatifs des principales classes (quercétine, rutine, acide caféique, acide gallique, catéchine) avec les ions de métaux de transition d'intérêt biologique (Fe'', Fe''', Cu', Cu'') a été étudiée par spectroscopie UV-visible (études cinétiques) par CLHP-SM (analyse de productions d'oxydation) et au moyen de divers tests colorimétriques permettant de préciser l'état redox des ions métalliques et la production éventuelle de H2O2. En milieu neutre (tampon phosphate), la complexation est généralement rapide et conduit à des complexes relativement stables avec les ions du fer (malgré l'autoxydation rapide de Fe'' en Fe'''). En revanche, les complexes des ions du cuivre (en particulier Cu') sont capables d'activer rapidement O2 avec formation de H2O2, oxydation du polyphénol et maintien du cuivre au degré d'oxydation I. En milieu acide, la complexation n'a pas lieu mais Fe''' est assez réactif pour oxyder les polyphénols sans consommation de O2. L'activité antioxydante des polyphénols a également été étudiée par leur capacité à inhiber la peroxydation de l'acide linoléique initiée par Cu''/H2O2. La seconde partie porte sur l'extraction à l'eau des ployphénols du thé vert sous irradiation micro-ondes en comparaison avec un chauffage conventionnel. Après optimisation de la température et de la durée d'extraction, le procédé sous micro-ondes s'est révélé plus efficace que le procédé conventionnel, en particulier pour l'extraction des flavanols et des acides hydroxycinnamiquesPolyphénols are plant secondary métabolites which are abundant in the diet. Their extraction from plants using mild and efficient processes and a better understanding of the mechanisms of their oxidation and antioxidant activity are important scientific goal, which underline this work. In a first part, the reactivity of some polyphénols both common et representative of the main classes (quercetin, rutin, caffeic acid, gallic acid, catechine) with transition metal ions of biological interest (Fe'', Fe''', Cu', Cu'') was studied by UV-visible spectroscopy (kinetic studies) pa rHPLC-MS (analysis of oxydation products) and via colorimetric tests for the determination of the redox state ot he metal ions and the possible production of H2O2. In neutral medium (phosphate buffer), the binding is generally fast and leads to relatively stable complexes with iron ions (despite the fast autoxidation of Fe'' into Fe'''). By contrast, copper complexes (in particular Cu'-complexes) are able to rapidly activate O2 with H2O2 formation and oxidation of the polyphenol ligand, the copper ions being maintained at the redox state I. In acidic conditions, metal-polyphenol binding does not take place but Fe''' is réactive enough to oxidize the polyphenols without O2 consumption. The antioxidant activity of the selected polyphenols was also studied by their capacity to inhibit the peroxidation of linoleic acid induced by Cu''/H2O2. The second part deals with the water extraction of green tea polyphenols under microwave irradiation in comparison with conventional heating. After optimization of temperature and extraction time, the microwave-assisted process came up as more efficient than the conventional process, particularly for the extraction fo flavanols and hydroxycinnamic acidsAVIGNON-BU Centrale (840072102) / SudocSudocFranceMoroccoFRM

Extractability of water-soluble soil organic matter as monitored by spectroscopic and chromatographic analyses

International audienceCold and hot water processes have been intensively used to recover soil organic matter, but the effect of extraction conditions on the composition of the extracts were not well investigated. Our objective was to optimize the extraction conditions (time and temperature) to increase the extracted carbon efficiency while minimizing the possible alteration of water extractable organic matter of soil (WEOM). WEOM were extracted at 20A degrees C, 60A degrees C, or 80A degrees C for 24 h, 10-60 min, and 20 min, respectively. The different processes were compared in terms of pH of suspensions, yield of organic carbon, spectroscopic properties (ultraviolet-visible absorption and fluorescence), and by chromatographic analyses. For extraction at 60A degrees C, the time 30 min was optimal in terms of yield of organic carbon extracted and concentration of absorbing and fluorescent species. The comparison of WEOM 20A degrees C, 24 h; 60A degrees C, 30 min; and 80A degrees C, 20 min highlighted significant differences. The content of total organic carbon, the value of specific ultraviolet absorbance (SUVA(254)), the absorbance ratio at 254 and 365 nm (E (2)/E (3)), and the humification index varied in the order: WEOM (20A degrees C, 24 h) < WEOM (80A degrees C, 20 min) < WEOM (60A degrees C, 30 min). The three WEOM contained common fluorophores associated with simple aromatic structures and/or fulvic-like and common peaks of distinct polarity as detected by ultra performance liquid chromatography. For the soil chosen, extraction at 60A degrees C for 30 min is the best procedure for enrichment in organic chemicals and minimal alteration of the organic matter

Divalent Copper Selenate Complex: Two Types of Octahedral Coordination in the Unit Cell and Disordered 1,4-Diazabicyclo[2.2.2]octane

International audienceThe new hybrid compound (C6H14N2)[Cu(H2O)(6)][Cu(SeO4)(2)(H2O)(4)](2) crystallizes in the monoclinic system, space group P2(1)/n, with the unit cell parameters: a = 7.2469(2) angstrom, b = 9.5360(2) angstrom, c = 22.1919(5) angstrom, and beta = 95.789(2)degrees. The structure was solved by conventional direct methods. The R and wR values for 76142 measured reflections were 0.0337 and 0.0625, respectively. Within the structure of this new compound, the transition metal adopts two types of octahedral coordination. Indeed, Cu1 is coordinated by four water molecules and two selenate groups to form the tetraaquadiselenatocuprate(II) anion [Cu(SeO4)(2)(H2O)(4)](2-), whereas Cu2 adopts another octahedral environment formed by six water molecules, but three of them crystallographically independent. The Cu1 and Cu2 atoms display the socalled (4+1+1) and (4+2) type of coordination, respectively, that has often been observed in other compounds containing the same transition metal, which is consistent with a Jahn-Teller distortion. The crystal structure of the title complex consists of isolated metallic polyhedra and disordered dabcodiium cations linked together by two types of hydrogen bond, OW-H center dot center dot center dot O and N-H center dot center dot center dot O, only. The thermogravimetric analysis shows that the dehydration of the compound takes place in four steps. The decomposition leads to the copper oxide in the last stage

Water hydrochemistry of Lake Boudaroua in the Moroccan Prerifwest Mediterranean region

In order to assess the quality of surface water of Boudaroua Lake, located in the Moroccan Pre-rif.The water quality parameters was used to evaluate the potential presence of toxicity of this ecosystem. To this end, samples and hydrochemical analyzes were carried out for five permanent stations around the Lake, during the study period (July 2019, October 2019, January 2020). The study was based on 11 parameters, namely, turbidity (TUR), dissolved oxygen (O2), total hardness (DT), calcium (Ca2+),magnesium(Mg2+), sodium (Na+),potassium (K+), ammonium (NH+4), chloride(Cl−), sulfate( SO2−4), nitrate (NO-3)were considered. The results obtained of these physicochemical parameters have been compared with the Moroccan standard (MS) for surface water and with the World Health Organization (WHO). The results indicated that the values of the physicochemical parameters varies significantly seasonally due to precipitation rate variation. In addition the impact of Agricultural pollution resulting from the excessive use of fertilizers that enter the lake through waterways, such as ammonium NH+4, and dissolved oxygen (O2) its value reaching respectively 1.09 mg/L ,12 mg/L remains above standards (MS) and (WHO) which could harm the ecosystem of the lake