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

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

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

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°

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 grafted with polyamines as powerful adsorbent for heavy metals

International audienceThe preparation of new adsorbents for heavy metals consisting of cellulose paper grafted with polyamine moieties is described. The tosylation of pristine cellulose paper allowed the subsequent displacement of the tosylated leaving groups with either ethylenediamine or spermine provided the corresponding cellulose-based polyaminated adsorbents Cell-Ed and Cell-Sperm, respectively. Optimizations related to the influence of experimental conditions (time and pH) on the adsorption processes associated to detailed studies devoted to the understanding of the mechanism of adsorption through kinetic experiments and isotherm modeling provided a rational understanding for the removal Cu(II) and Pb(II). Interestingly, Cell-Sperm also displayed outstanding adsorption properties for other metal cations such as Cd(II), Zn(II) and Fe(II). [GRAPHICS]

Graphene-catalyzed transacetalization under acid-free conditions

International audience1,2- and 1,3-Diols are readily protected as cyclic acetals and ketals through a graphene-catalyzed transacetalization process. The methodology features an atom economic procedure since quasi-stoichiometric conditions have been developed. Unlike prior systems, the graphene-catalyzed transacetalization is performed under Bronsted and Lewis acid-free conditions and without solvent. Our method has been applied to several volatile compounds that are unsuitable for complex work-up and extensive purification steps. The very unusual catalytic properties of graphene for transacetalization reactions are ascribed to molecular charge transfer between graphene and substrates. (C) 2016 Elsevier Ltd. All rights reserved