Activité antioxydante de quelques plantes utilisées dans la région de Tiassalé (Côte d’Ivoire) dans le maintien de la santé de la peau

Skin health is a concern for many people. This aim of this study is to evaluate in vitro the antioxidant activity of 10 plants used in cosmetopoeia for the maintenance of skin health. To achieve this objective, 30 extracts were tested using 2,2'-diphenyl-1-picrylhydrazyl radical (DPPH) and 2,2'-azino-bis (3-ethylbenzothiazoline-6) acid. -sulfonic) (ABTS + •) assays. The extracts studied were rich in total polyphenols, flavonoids, gallic tannins and alkaloids. For the DPPH reduction, 7 extracts including 5 methanolic and 2 aqueous extracts showed a percentage of inhibition similar to that of Vitamin C (95.79 ± 10.53%) used as a control. With ABTS, 11 extracts (5 methanol, 3 aqueous and 3 hexane) gave reduction percentages close to Trolox (95.97 ± 8.51%). These active plants could play a role in the maintaining of skin

Hydrogénation du citral sur catalyseurs bimétalliques Rh-Ge et Pt-Ge supportés sur oxyde de titane

L'objectif de ce travail était de préparer des catalyseurs bimétalliques Rh-Ge et Pt-Ge supportés sur un oxyde réductible (TiO2) dans le but d'associer l'effet bimétallique à l'effet de support réductible en hydrogénation sélective d'un aldéhyde , -insaturé, le citral. Les catalyseurs sont préparés par une réaction d'oxydoréduction de surface, la "réduction catalytique" dont le principe est de modifier un catalyseur monométallique parent par réaction superficielle entre l'hydrogène activé sur le premier métal (Rh ou Pt) et le cation du deuxième métal (Ge). L'analyse élémentaire des différents échantillons Rh-Ge/TiO2 et Pt-Ge/TiO2 met en évidence un dépôt de germanium croissant avec la concentration en germanium introduite en solution, confirmant ainsi la possibilité d'utiliser cette technique pour préparer de tels systèmes. L'existence d'interactions entre les métaux des catalyseurs bimétalliques Rh-Ge/TiO2 et Pt-Ge/TiO2 est confirmée par les mesures d'activités pour la réaction modèle de déshydrogénation du cyclohexane, ainsi que par l'adsorption de la molécule sonde CO suivie par infrarouge (IRTF). De plus, ces caractérisations ont montré que le germanium modifie plus profondément les propriétés catalytiques du platine que celles du rhodium. Ce travail sur l'hydrogénation sélective du citral en présence de catalyseurs Rh-Ge/TiO2 et Pt-Ge/TiO2 a montré que les effets bimétallique et de support réductible peuvent être associés pour promouvoir la sélectivité en alcools insaturés. Cependant, ces catalyseurs sont moins actifs que des catalyseurs bimétalliques plus chargés en germanium présentant une sélectivité en alcools insaturés pratiquement comparable obtenue par un simple effet bimétallique après réduction à 300C. Cet effet bimétallique sur oxyde de titane est supérieur à celui observé sur supports silice et alumine, montrant ainsi l'intérêt de cet oxyde pour préparer des catalyseurs bimétalliques en forte interaction.The objective of this work is to prepare the Rh-Ge and Pt-Ge bimetallic catalysts supported on reducible oxide (TiO2) in order to associate the bimetallic effect to the reducible support on selective hydrogenation an a,b-unsaturated aldehyde (citral). The bimetallic catalysts are prepared by surface redox reaction, the "catalytic reduction" method. The elemental analysis of Rh-Ge/TiO2 and Pt-Ge/TiO2 bimetallic catalysts shows that the amount of germanium deposited on the Rh/TiO2 and Pt/TiO2 parent catalysts increases with the germanium content of the solution. The presence of interaction between the metals in the bimetallic catalysts is confirmed by cyclohexane dehydrogenation and infrared spectroscopy of adsorbed CO. This study confirms that the bimetallic effect and the reducible support effect can be associated to promote the formation of unsaturated alcohols.POITIERS-BU Sciences (861942102) / SudocSudocFranceF

Histone Deacetylase Inhibitors: Synthesis of Tetrapeptide Analogue SAHA/TPX

The inhibition of HDAC (histone deacetylase) activity by specific inhibitors induces growth arrest, differentiation and apoptosis of transformed or several cancer cells. Some of these inhibitors are in clinical trial at phase I or phase II. The discovery and development of specific HDAC inhibitors are helpful for cancer therapy. In this paper we describe the synthesis of simple inhibitor B hybrid analogue suberoylanilide hydroxamic acid (SAHA), trapoxin B (TPX B) in as little as five steps. This compound is interesting lead for the design of potent inhibitors of histone deacetylase

Selective hydrogenation of citral to unsaturated alcohols over mesoporous Pt/Ti-Al2O3 catalysts. Effect of the reduction temperature and of the Ge addition

International audiencePt/y%Ti-Al2O3 (y corresponding to the atomic percent of Ti in alumina, in the range 10-33%), and derived bimetallic Pt-Ge/10%Ti-Al2O3 nanocomposite catalysts were synthesized, characterized, and reduced either at 300 degrees C and 500 degrees C (this latter temperature being performed in order to generate strong metal-support interactions, i.e. a SMSI effect). The materials were characterized in detail with techniques including elemental analysis, X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and nitrogen physisorption to evaluate their structural and textural properties. Due to the templating approach used, well-defined mesopore structures with high surface areas and mesopore volumes are obtained for all materials. The SMSI effect, evaluated using a structure insensitive model reaction, i.e. the cyclohexane dehydrogenation, is observed to be more pronounced on the Pt/y%Ti-Al2O3 catalysts with y = 20 and 33% than on a Pt/TiO2 P25 (Degussa P25 titania) sample, showing the beneficial effect of Ti fine dispersion through incorporation in alumina matrix on the generated metal-support interaction. During citral hydrogenation reaction, the selectivity toward unsaturated alcohols (UA: nerol and geraniol) is related to Ti and/or Ge loadings on the nanocomposite, as well as reduction temperature. Both SMSI effect and Ge addition promote the UA selectivity leading to similar values than on Pt/TiO2 P25 sample. (C) 2011 Elsevier B.V. All rights reserved

Design and Synthesis of Small Molecules Based on a Substructural Analysis of the Histone Deacetylase Inhibitors TSA and SAHA

Inhibitors of histone deacetylases (HDACs) are patent inducers of differentiation and bear considerable potential as drugs for chemoprevention and treatment of cancer. In this paper, we have investigated three synthetic, inhibitors A1a,b, A2a. Analogue hybrid trichostatine A (TSA), suberoylanilide hydroxamic acid SAHA, in order to seek new histone deacetylases (HDACs) inhibitors

Catalytic performances of large pore Ti-SBA15 supported Pt nanocomposites for the citral hydrogenation reaction

International audiencePt/x% Ti-SBA15 catalysts (x corresponding to the wt.% TiO2 loading in the Ti-SiO2 composite, in the range 25-60%) were synthesized by titanium precursor grafting in preformed mesoporous silica. Materials were characterized by several techniques, including elemental analysis, XRD, TEM and N-2-sorption isotherms to achieve structural and textural properties description. Different pore sizes were obtained for the SBA15 materials, by using or not hexane as swelling agent. The catalytic performances of these original materials were evaluated for the selective hydrogenation of citral (alpha, beta-unsaturated aldehyde), and compared with those of Pt/SBA and Pt/TiO2 P25 reference catalysts. Pt/x% Ti-SBA15 catalysts present high specific surface, with TiO2 nanoparticles and Pt-0 clusters located inside the hexagonal mesopore structure of silica. During citral hydrogenation, the selectivity towards unsaturated alcohols (nerol and geraniol) varies as a function of the support nature as follows: Pt/x% Ti-SBA15 > Pt/TiO2 P25 >> Pt/SBA. The results are discussed in term of variable metal-support interaction (SMSI) generated by the partial reduction of TiO2 species, this SMSI effect being reported more important over anatase TiO2 nanoparticles dispersed inside the mesostructure than over large crystals encountered in the classical P25 support

A fully bio-sourced adsorbent of heavy metals in water fabricated by immobilization of quinine on cellulose paper

International audienceThe fabrication of a fully bio-sourced adsorbent of Cd(II) by covalent immobilization of quinine on cellulose paper is described. The double bond of commercially available quinine was converted to a terminal alkyne function which was reacted with cellulose paper, chemically modified with azide functions, through a 1,3-dipolar cycloaddition, leading to Cell-Quin. The adsorption efficiency of Cell-Quin was investigated to determine the optimal pH, contact time and dose of adsorbent, ultimately leading to high levels of removal. The mechanism of adsorption of Cell-Quin was deeply rationalized through kinetic experiments and isotherm modeling. We also showed that Cell-Quin could adsorb other heavy metals such as Cu(II), Pb(II), Ni(II) and Zn (II)

Citral hydrogenation over Rh and Pt catalysts supported on TiO2: Influence of the preparation and activation protocols of the catalysts

International audienceDuring citral hydrogenation, the products distribution obtained on Rh/TiO2 and Pt/TiO2 catalysts depends on their preparation and activation protocols: (i) the unsaturated alcohols (the intended products) are formed in higher quantity on samples reduced at 500 degrees C and more notably with Pt/TiO2 catalyst; (ii) samples prepared by impregnation of the metallic precursor salt in HCl medium and activated at 300 degrees C are the only ones to lead to the formation of isopulegol as by-product. On the catalysts activated at 500 degrees C, these results can be explained by the presence of the SMSI effect beneficial to hydrogenate selectively the C=O bond of citral towards unsaturated alcohols

Biodiesel production from palm oil using sulfonated graphene catalyst

International audienceIn this study we report on sulfonated graphene, obtained by chemical exfoliation of inexpensive graphite and functionalization of the resulting graphene sheets with benzene sulfonic acid, as a new active catalyst for the transesterification of palm oil with methanol into biodiesel. The experimental conditions for obtaining fatty acid methyl esters were carefully optimized through the evaluation of several parameters including the catalyst loading, temperature, reaction time and methanol-to-oil molar ratio. Of particular relevance, we noticed that an excess of methanol was required to allow high transesterification yield, but an excessive dilution proved to be deleterious for the reaction yield due to lower interactions between the reactants and the catalyst. The heterogeneous catalyst showed a high thermal robustness and was successfully recycled without significant erosion of the reaction yield. Our catalytic system yields biodiesel with a high purity (>98%) after a single filtration and do not produce aqueous waste. (C) 2017 Elsevier Ltd. All rights reserved

Cellulose paper azide as a molecular platform for versatile click ligations: application to the preparation of hydrophobic paper surface

International audienceA cellulose paper sheet, chemically modified with azide functions, is described to be a versatile molecular platform for copper-catalyzed 1,3-dipolar cycloaddition with terminal alkynes. This 3-step methodology was carefully optimized at each stage of the process with the support of experimental and physical evidences. Our approach allows the surface coverage of structurally diverse molecular architectures through a covalent grafting with non-hydrolysable chemical linkers. This robust linkage is highlighted with the surface hydrophobization of cellulose paper through the click ligation of cholesterol units as renewable and inexpensive hydrophobic agents. The resulting water-resistant and water-repellent paper-based material shows powerful oleophilicity properties and displays a high contact angle of 139.6°