Étude phytochimique et évaluation de l’activité anti-oxydante de Thymus CIliatus ssp. Coloratus

Thymus ciliatus ssp. Coloratus, plante aromatique, spontanée et répandue en régions méditerranéennes et dans le nord de l’Algérie est très utilisée par les populations locales pour ses vertus médicinales. Les tests phytochimiques appliqués au Thymus ciliatus ssp coloratus ont montré la présence de quelques familles de composés chimiques et notamment les flavonoïdes. L'activité antioxydante in vitro de l’extrait de flavonoïdes a été évaluée par la technique de réduction du fer « FRAP » (ferric reducing antioxydant power) et par le test de DPPH. La première méthode a montré que la fraction acétate d’éthyle de la partie aérienne a une capacité à réduire le fer plus marquée que celles de l’acide ascorbique et le BHA et que celle des racines, est nettement inférieure. Quant aux fractions butanoliques des flavonoïdes de la partie aérienne et des racines, elles ont une capacité à réduire le fer largement inférieure à celles de l’acide ascorbique et le BHA. L’activité antioxydante, obtenue par la second procédé et relative à la fraction acétate d’éthyle des flavonoïdes de la partie aérienne de la plante est plus importante (I.C₅₀=0,85 mg/mL) que celles obtenues à partir d’antioxydants utilisés dans les industries alimentaire et pharmaceutique en l’occurrence l’acide ascorbique (I.C₅₀ = 1,12 mg/mL) et le BHA (I.C₅₀=1,61 mg/mL).Mots-clés : Thymus coloratus, activité antioxydant, flavonoïde, FRAP, DPPH.Phytochemical study and evaluation of the antioxidant activity of thymus ciliatus ssp. Coloratus Thymus ciliatus ssp. coloratus, aromatic plant, spontaneous and widespread in the Mediterranean and in northern Algeria is widely used by local people for its medicinal properties. Phytochemical tests applied for Thymus sciliatus ssp coloratus showed the presence of several families of chemical compounds including flavonoïds. The in vitro antioxidant activity of flavonoïds extract was evaluated by the iron reduction technique "FRAP" (ferric reducing antioxidant power) and DPPH test. The first method showed that the ethyl acetate fraction of the aerial part has an ability to reduce the iron greater than ascorbic acid and BHA and the roots, is significantly lower. As for butanol fractions of flavonoïds from the aerial part and roots, they have an ability to reduce iron significantly lower than those of ascorbic acid and BHA. The antioxidant activity obtained by the second method and on the ethyl acetate fraction of flavonoïds from the aerial part of the plant is more important (I.C₅₀ = 0.85 mg / mL) than those obtained from 'antioxidants used in food and pharmaceutical industries namely ascorbic acid (I.C₅₀ = 1.12 mg / mL) and BHA (I.C₅₀ = 1.61 mg / mL).Keywords : Thymus coloratus, antioxidant activity, flavonoïd, FRAP, DPPH

Pesticide exposure in honey bees results in increased levels of the gut pathogen Nosema

Global pollinator declines have been attributed to habitat destruction, pesticide use, and climate change or some combination of these factors, and managed honey bees, Apis mellifera, are part of worldwide pollinator declines. Here we exposed honey bee colonies during three brood generations to sub-lethal doses of a widely used pesticide, imidacloprid, and then subsequently challenged newly emerged bees with the gut parasite, Nosema spp. The pesticide dosages used were below levels demonstrated to cause effects on longevity or foraging in adult honey bees. Nosema infections increased significantly in the bees from pesticide-treated hives when compared to bees from control hives demonstrating an indirect effect of pesticides on pathogen growth in honey bees. We clearly demonstrate an increase in pathogen growth within individual bees reared in colonies exposed to one of the most widely used pesticides worldwide, imidacloprid, at below levels considered harmful to bees. The finding that individual bees with undetectable levels of the target pesticide, after being reared in a sub-lethal pesticide environment within the colony, had higher Nosema is significant. Interactions between pesticides and pathogens could be a major contributor to increased mortality of honey bee colonies, including colony collapse disorder, and other pollinator declines worldwide

Structure-Thermal Conductivity Tentative Correlation for Hybrid Aerogels Based on Nanofibrillated Cellulose-Mesoporous Silica Nanocomposite

Hybrid aerogels have been prepared by freeze-drying technique after mixing water dispersions of cellulose microfibers or cellulose nanofibers and silica (SiO2) of type SBA-15 (2D-hexagonal). The prepared composites were characterized by different analysis techniques such as SEM, hot-filament, DMA, etc. These composites are compared to those previously prepared using nanozeolites (NZs) as mineral charge. The morphology studied by SEM indicated that both systems have different structures, i.e., individual fibers for cellulose microfibers WP-based aerogels and films for nanofibrillated cellulose NFC-based ones.... These differences seem to be driven by the charge of the particles, their aspect ratio and concentrations. These hybrid materials exhibit tunable thermal conductivity and mechanical properties. The thermal conductivity values range between ~18 to 28 mW. m–1. K–1and confirm the superinsulation ability of these fibrous aerogels. Synergism on the thermal insulation properties and mechanical properties was shown by adjunction of mineral particles to both cellulose-based aerogels by reaching pore size lower than 100 nm. It significantly reduces the thermal conductivity of the hybrid aerogels as predicted by Knudsen et al. Furthermore, the addition of mineral fillers to aerogels based on cellulose microfibers induced a significant increase in stiffness

Etude de la conception de parois pour véhicules utilitaires isothermes

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Influence of the Processes Extraction on Essential Oil of Origanum glandulosum Desf.

International audienceEssential oils obtained from Origanum glandulosum Desf. using supercritical carbon dioxide, micro wavedistillation, hydrodistillation and solvent ethanol were analyzed with GC/MS. The extraction with pressurized CO2 was performed at 15°C and 67 bar. The major valuable component extracted was thymol (63.8, 75.3, 55.6 and 82.4%), respectively, wile the p-cymene and -tepinene were revealed only in CO2 extract, microwavedistillation and hydrodistillation (13.7, 6.0 and 12.5%) and (6.8, 8.4 and 11.2%), respectively

Weighing risk factors associated with bee Colony Collapse Disorder by classification and regression tree Analysis

Colony collapse disorder (CCD), a syndrome whose defining trait is the rapid loss of adult worker honey bees, Apis mellifera L., is thought to be responsible for a minority of the large overwintering losses experienced by U.S. beekeepers since the winter 2006-2007. Using the same data set developed to perform a monofactorial analysis (PloS ONE 4: e6481, 2009), we conducted a classification and regression tree (CART) analysis in an attempt to better understand the relative importance and interrelations among different risk variables in explaining CCD. Fifty-five exploratory variables were used to construct two CART models: one model with and one model without a cost of misclassifying a CCD-diagnosed colony as a non-CCD colony. The resulting model tree that permitted for misclassification had a sensitivity and specificity of 85 and 74%, respectively. Although factors measuring colony stress (e.g., adult bee physiological measures, such as fluctuating asymmetry or mass of head) were important discriminating values, six of the 19 variables having the greatest discriminatory value were pesticide levels in different hive matrices. Notably, coumaphos levels in brood (a miticide commonly used by beekeepers) had the highest discriminatory value and were highest in control (healthy) colonies. Our CART analysis provides evidence that CCD is probably the result of several factors acting in concert, making afflicted colonies more susceptible to disease. This analysis highlights several areas that warrant further attention, including the effect of sublethal pesticide exposure on pathogen prevalence and the role of variability in bee tolerance to pesticides on colony survivorship

Evaluation of the MRSA Sensitivity to Essential Oils Obtenained from four Algerian Medicinal Plants.

International audienceIn this work, we evaluated the anti-MRSA activity of essential oils obtained from four Algerian medicinal plants which are: Ammoides verticillata, Origanum vulgare subsp. glandulosum, Lavandula multifida, and Thymus munbyanus subsp. ciliatus. The anti-MRSA activity was evaluated by the technique of agar diffusion and determination of MICs. We also studied the kinetics of destruction of these oils against MRSA strain ATCC 43300. The four essential oils showed a good anti-MRSA activity. Oils with the highest activity are; Origanum vulgare subsp. glandulosum, Thymus munbyanus subsp. ciliatus, Lavandula multifida and Ammoides verticillata respectively. The kinetics of destruction of all essential oils against MRSA ATCC 43300 strain is dependent on concentration. The Concentration 1% allows a total destruction; while the concentration 0.5% was bactericidal only with Origanum vulgare, whereas the concentration 0.25% and 0.125% have had a low destruction respectively. We concluded that the essential oils can be used as an anti-MRSA