Chemical Composition, Antioxidant and Antibacterial Properties of Essential Oil from Ocotea Auriculiformis Kost. (Lauraceae) Leaves, Endemic of Madagascar

Plants constitute an important source of secondary metabolites in which essential oils are well-known for their use in various domains such as pharmacy, therapeutic, cosmetology and foods. In vitro antimicrobial and antioxidant properties of Ocotea auriculiformis Kost. (Lauraceae) leaves essential oil is demonstrated and its chemical composition is reported in the present study. The essential oil from Ocotea auriculiformis Kost. (Lauraceae) leaves, an endemic plant of Madagascar was extracted by hydrodistillation method. Chemical composition using GC, GC/ MS and NMR13C methods showed that the essential oil contained around 47 products in which 93.95% were identified. Known compounds are constituted by 74.7% of hydrocarbons and 19.25% of oxygenated products. The essential oil is rich in sesquiterpene and monoterpene. In vitro antibacterial capacity of the essential oil was assessed by disc method against human and food pathogens. Bacillus cereus and Streptococcus pneumoniae were very sensitive to the essential oil with 11 mm and 25 mm of inhibition zone respectively. The MIC of the essential oil was 1mg/mL for Bacillus cereus and 0.25 mg/mL for Streptococcus pneumoniae. MBC values were 2.5 mg/mL and 0.5 mg/mL, respectively. The ratio MBC/MIC for both strains was inferior to 4 concluding hence that the essential oil has bactericidal effect against the two sensitive strains. In vitro antioxidant capacity of the essential oil was performed according to qualitalive (TLC) and quantitative (measure of DPPH radical scavengening) methods. The essential oil showed antioxidant activity with IC50 value of 0.35 mg/mL

Biocontrol of potato wilt by selective rhizospheric and endophytic bacteria associated with potato plant

Ralstonia solanacearum is the causative agent of wilt disease in plants, which constitutes a severe problem to agricultural crops, particularly for potato production in Madagascar. The present study focuses on the isolation, in vitro and in vivo assays of potential rhizospheric and endophytic bacteria associated with healthy potato plant, capable to inhibit the growth of Ralstonia solanacearum for controlling potato bacterial wilt. A total of 77 bacteria strains were isolated from six soil rhizospheric samples and six vegetal material samples of healthy potatoes in the district of Antsirabe II. Forty of them were telluric actinomycetes, 25 were endophytic actinomycetes and 12 were fluorescent Pseudomonas spp. An additional 30 phytopathogenic isolates were obtained from six rhizopsheric soil samples of diseased potatoes. Morphological, cultural, biochemical characterization and molecular identification with the Ralstonia solanacearum specific primers 759/760 revealed that 24 of the pathogenic isolates belong to the Ralstonia solanacearum species, biovar two; the causal agent of potato bacterial wilt. Isolates from healthy plants were, then, examined in vitro and in vivo for their antagonistic activity against Ralstonia solanacearum strain for their potential to improve potato plant growth. In vitro antagonism of actinomycete and Pseudomonas isolates against Ralstonia solanacearum development was performed using agar diffusion technique, while in vivo tests were conducted under greenhouse conditions. Ten antagonistic strains including two Pseudomonas, four telluric actinomycetes, and four endophytic actinomycetes inhibited the tested Ralstonia strain. Four strains, E7, E13 (endophytic actinomycete from root potatoes), S25 (telluric actinomycetes) and P7 (fluorescent Pseudomonas), showed high antagonistic activity against the pathogen with zones of inhibition from 23 to 40 mm. Of the fours strains tested in greenhouse, E7 significantly reduced (p < 0.05) the percentage of Ralstonia solanacearum that infected plants by 72.04%. The isolates E13 and S25 have also been demonstrated to improve plant growth by increase of plant height to 44.63% and 44.84%, fresh weight to 68.75% and 75.85% and dry weight to 86.17% and 115.42%, respectively compared with non-treated control. Morphological and cultural characterization of these three active isolates showed that they belong to the genus Streptomyces. The antagonism of these isolates against Ralstonia solanacearum according to in vitro and in vivo tests results, along with their high efficiency as regards the improvement of plant development, suggests that these three actinomycete strains E7, E13 and S25 could be useful for biocontrol of potato bacterial wilt.Key words: Potato, Ralstonia, Actinomycetes, Pseudomonas, Biocontrol

Biological Properties of Actinomycetes Isolated from Marine Sponges in Madagascar

Marine actinomycetes are well known as a potential provider of novel bioactive compounds and currently considered as an important source of natural substances with unique chemical diversity. In this study, 20 marine actinomycetes were isolated from three Demospongia collected in the South East coast of Madagascar. Cultural, morphological, physiological and biochemical characteristics of the isolates showed that they belong to the genus Streptomyces. The Antimicrobial activity of the strains was performed using the agar cylinder technique against pathogens bacteria, yeast and fungi. It resulted that 90% of the isolates showed activity against at least one or more of the test germs. The isolates were more active against Gram-positive bacteria than Gram-negative bacteria. Simultaneously, ethanol extracts of the isolates were tested for their antioxidant activity using DPPH (1,1-Diphenyl-2-picrylhydrazyl) free radical scavenging test. Among tested extracts, those of Streptomyces M9 and M17 showed antioxidant activity against DPPH free radical with IC50 values of 12.8µg/ml and 12.4µg/ml, respectively

SUIVI TEMPOREL DE LA VARIATION DU NIVEAU D’EAU DU LAC TSIMANAMPETSOTSA A PARTIR DES DONNEES D’ALTIMETRIE LIDAR DU SATELLITE ICESAT

   Pendant sa période de fonctionnement, le satellite lidar ICESat a récolté des données sur la surface de la terre entre 80° et -80° de latitude. Il a permis d’avoir plusieurs points de mesures altimétriques sur le lac Tsimanampetsotsa sur plusieurs campagnes de mesure. Pour chaque campagne, nous avons trouvé que les dispersions des mesures altimétriques faites par ICESat sur le lac sont faibles. Les mesures sur le niveau du lac sont donc homogènes avec des moyennes qui varient de 4,9 m à 6,8 m et des écart-types qui sont inférieurs à 1 m. En observant la variation au cours du temps du niveau moyen du lac Tsimanampetsotsa, on trouve une légère tendance à la baisse du niveau d’eau. Entre 2004 à 2009, le niveau du lac a perdu 0,60 m

Estrogen Receptor Alpha as a Key Target of Red Wine Polyphenols Action on the Endothelium

BACKGROUND: A greater reduction in cardiovascular risk and vascular protection associated with diet rich in polyphenols are generally accepted; however, the molecular targets for polyphenols effects remain unknown. Meanwhile evidences in the literature have enlightened, not only structural similarities between estrogens and polyphenols known as phytoestrogens, but also in their vascular effects. We hypothesized that alpha isoform of estrogen receptor (ERalpha) could be involved in the transduction of the vascular benefits of polyphenols. METHODOLOGY/PRINCIPAL FINDINGS: Here, we used ERalpha deficient mice to show that endothelium-dependent vasorelaxation induced either by red wine polyphenol extract, Provinols, or delphinidin, an anthocyanin that possesses similar pharmacological profile, is mediated by ERalpha. Indeed, Provinols, delphinidin and ERalpha agonists, 17-beta-estradiol and PPT, are able to induce endothelial vasodilatation in aorta from ERalpha Wild-Type but not from Knock-Out mice, by activation of nitric oxide (NO) pathway in endothelial cells. Besides, silencing the effects of ERalpha completely prevented the effects of Provinols and delphinidin to activate NO pathway (Src, ERK 1/2, eNOS, caveolin-1) leading to NO production. Furthermore, direct interaction between delphinidin and ERalpha activator site is demonstrated using both binding assay and docking. Most interestingly, the ability of short term oral administration of Provinols to decrease response to serotonin and to enhance sensitivity of the endothelium-dependent relaxation to acetylcholine, associated with concomitant increased NO production and decreased superoxide anions, was completely blunted in ERalpha deficient mice. CONCLUSIONS/SIGNIFICANCE: This study provides evidence that red wine polyphenols, especially delphinidin, exert their endothelial benefits via ERalpha activation. It is a major breakthrough bringing new insights of the potential therapeutic of polyphenols against cardiovascular pathologies

Red wine polyphenols prevent metabolic and cardiovascular alterations associated with obesity in Zucker fatty rats (Fa/Fa)

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Dimethylarginine metabolism during acute and chronic rejection of rat renal allografts

Background. Dimethylarginines are inhibitors of NO synthesis and are involved in the pathogenesis of vascular diseases. In this study, we ask the question if asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA) levels change during fatal and reversible acute rejection, and contribute to the pathogenesis of chronic vasculopathy