Activités anti-radicalaires de l'huile essentielle et des extraits bruts de Thymus numidicus Poiret., Algérie

Thymus numidicus Poiret. (Lamiaceae) est une plante largement utilisée en médecine traditionnelle algérienne pour ses propriétés thérapeutiques. Le but de ce travail est d'évaluer l'activité antioxydante de l'huile essentielle ainsi que plusieurs extraits bruts (dichlorométhane, méthanol, méthanol-eau 5:1 v/v, et l'infusé) du Thymus numidicus Poiret. récolté à Annaba (Algérie). L'activité antioxydante a été estimée par deux méthodes photométriques, la méthode de DPPH et celle de réduction du peroxyde d'hydrogène. Les résultats ont révélé que les deux extraits méthanol et méthanol-eau 5:1 ont exercé une forte activité de piégeage des radicaux libres DPPH en comparaison avec le BHT ainsi qu'une haute capacité de blocage du peroxyde d'hydrogène en comparaison avec les contrôles positifs de l'acide gallique et l'acide caféique.Mots-clés : Thymus numidicus, extraits bruts, activité antioxydante. Anti-radical activities of essential oil and crude extracts of Thymus numidicus Poiret., AlgeriaThymus numidicus Poiret. (Lamiaceae) is a plant widely used in Algerian traditional medicine. The aim of this work was to assess the antioxidant activity of the volatile compounds as well as different crude extracts (dichloromethane, methanol, methanol-water 5:1 v/v, infusion) of the endemic Thymus numidicus Poiret. collected from Annaba city (Algeria). The antioxidant activity was estimated by two fluorimetric methods, the DPPH method and the hydrogen peroxide scavenging method. The results revealed that methanol and methanol water 5:1 v/v extracts exerted very high free radical scavenging activity compared to the well-known butylated hydroxytoluene (BHT) and high hydrogen peroxide blocking activity than positive controls gallic acid and caffeic acid.Keywords : Thymus numidicus, crude extracts, anioxidant activity

Core-shell carbon-polymer quantum dot passivation for near infrared perovskite light emitting diodes

High-performance perovskite light-emitting diodes (PeLEDs) require a high quality perovskite emitter and appropriate charge transport layers to facilitate charge injection and transport within the device. Solution-processed n-type metal oxides represent a judicious choice for the electron transport layer (ETL); however, they don't always present suitable surface properties and energetics in order to be compatible with the perovskite emitter. Moreover, the emitter itself exhibits poor nanomorphology and defect traps that compromise the device performance. Here we modulate the surface properties and interface energetics of the tin oxide (SnO2) ETL with the perovskite emitter by using an amino functionalized difluoro{2-[1-(3,5-dimethyl-2H-pyrrol-2-ylidene-N)ethyl]-3,5-dimethyl-1H-pyrrolato-N}boron (BDP) compound and passivate the defects present in the perovskite with carbon-polymer core-shell quantum dots (PCDs) inserted into the perovskite precursor. Both these approaches synergistically improve the perovskite layer nanomorphology and enhance the radiative recombination. These properties resulted in the fabrication of near infrared (NIR) PeLEDs based on formamidinium lead iodide (FAPbI3) with a high radiance of 92 W sr-1 m-2, an external quantum efficiency (EQE) of 14% and reduced efficiency roll-off

Organisation of long aliphatic monocarboxylic acids in β-cyclodextrin channels: Crystal structures of the inclusion complexes of tridecanoic acid and (Z)-tetradec-7-enoic acid in β-cyclodextrin

In the crystalline state, infinite channels of β-cyclodextrin dimers host infinite arrays of self associated linear aliphatic monocarboxylic acids, thus enclosing the hydrophilic carboxy ends inside the hydrophobic channels

Crystal structure of the inclusion complex of the antibacterial agent triclosan in {\ss}-cyclodextrin and NMR study of its molecular encapsulation in positively and negatively charged cyclodextrins

The inclusion complexes of triclosan with native cyclomaltoheptaose (beta-cyclodextrin, betaCD) as well as with negatively and positively charged derivatives are studied. The structure of the inclusion complex betaCD/triclosan in the crystalline state [P1, a=15.189(5), b=15.230(6), c=16.293(6), alpha=91.07(4), beta=91.05(3) gamma=100.71(3)] comprises two crystallographically independent host macrocycles A and B. The packing results in betaCD dimers that align head-to-head and form infinite channels along the c-axis. Only one guest molecule statistically disordered over two positions, (the dichlorophenyl ring in the cavities of either A or B) corresponds to each dimer (a 2:1 host/guest complex). The enclosed dichlorophenyl ring enters the dimer through the primary side, whereas the hydrophilic chlorophenol ring extends in the space between dimers. Water molecules in five positions are also enclosed in the intradimer region, arranged on a plane perpendicular to the sevenfold axis of betaCD. The NMR spectroscopic studies in aqueous solution show the presence of both 1:1 and 2:1 betaCD/triclosan complexes. In the first case, two different 1:1 complexes are simultaneously present, each with either ring entering the narrow primary side of one betaCD molecule. In the 2:1 complex both rings of triclosan are included in two independent betaCD hosts, a precursor to the supramolecular arrangement found in the crystalline form. In the case of the negatively charged sodium heptakis[6-deoxy-6-(3-thiopropionate)]-betaCD, the NMR studies at pH 7.9 show a complete inclusion of triclosan inside the host in two orientations, one for the non-ionized (phenol) and reverse for the ionized (phenolate) form. Finally, for the positively charged heptakis(6-aminoethylamino-6-deoxy)-betaCD, inclusion of triclosan is possible only when the pH is raised to 10 and it is concluded that both aromatic rings are alternatively inside the cavity. However in that case also, inclusion of the entire guest in the elongated cavity is suggested

The self-association of the drug acemetacin and its interactions and stabilization with β-cyclodextrin in aqueous solution as inferred from NMR spectroscopy and HPLC studies

Strongly concentration dependent, 1H NMR chemical shifts of the non-steroidal anti-inflammatory drug acemetacin sodium salt (sodium [1-(4-chlorobenzoyl)-5-methoxy-2-methylindol-3-yl]acetoxyacetate), were observed in aqueous solution. Self-titration and nOe experiments, point to a self-association model where stacking takes place via the indole portion of the drug. In addition, conformational isomerism (atropisomerism) of the anti to syn form was confirmed. Further increase of the concentration eventually led to stable chemical shifts and nearly simultaneous appearance of microcrystals. In the presence of βCD, 1:1 inclusion complexation occurred through the p-chlorobenzoyl part of the drug, whereas with excess βCD the indole part seemed to participate to a minor degree. The anti isomer is suggested to be involved in the inclusion process. In addition, aggregation of acemetacin was also evident, as competing with the conformational and inclusion equilibria. The present case demonstrates that many competitive processes are simultaneously active in a seemingly simple system. The measurements were strongly dependent upon the pH and use of buffered solutions was mandatory. Finally, for the quantitative analysis of acemetacin in the presence of βCD, a special HPLC method was developed. The stability of the drug, studied by the identification of the degradation products and the pseudo-first order rate of hydrolysis, was found to be unaffected by the presence of βCD. © 2002 Elsevier Science Ltd. All rights reserved