• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 15
  • 2
  • 2
  • 1
  • Tagged with
  • 21
  • 7
  • 6
  • 6
  • 5
  • 5
  • 4
  • 4
  • 4
  • 4
  • 4
  • 4
  • 4
  • 3
  • 3
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Desenvolvimento inicial de Dalbergia miscolobium

Sassaki, Regina Miyuki 05 March 1991 (has links)
Orientador : Gil Martins Felippe / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-07-13T22:43:07Z (GMT). No. of bitstreams: 1 Sassaki_ReginaMiyuki_M.pdf: 6702384 bytes, checksum: f8e329e233af72da1ed77bae777a053f (MD5) Previous issue date: 1991 / Resumo: As plantas respondem de maneira de acorda com as condições em que são crescidas. No cerrado, muitas adaptações são exigidas delas, principalmente na sua fase inicial, para o estabelecimento às condições adversas características, como as deficiências hídrica e de nutrientes. Estudou-se o desenvolvimento inicial, em condições semi-controladas, de Dalbergia miscolobium, uma espécie típica dos cerrados. Foram verificadas a germinação e a viabilidade de sementes armazenadas por diferentes períodos. O crescimento inicial na terra de cerrado foi estudado em termos de peso seco, altura e conteúdo de carboidratos, tendo sido comparado crescimento em casa de vegetação e no campo. Foram também verificados os efeitos de sombrite e da testa, e da remoção de cotilédones. Foi observado que árvores de D. miscolobium do cerrado de Itirapina, SP, produzem aproximadamente 75% de sementes boas, que germinam muito bem quando desidratadas após a coleta, apresentando longevidade entre dois e cinco anos. Sementes armazenadas nuas mostraram melhor germinação em relação ás sementes armazenadas com fruto intacto, assim como quando armazenadas à temperatura baixa (4ºC). durante o crescimento inicial de D. miscolobium, a parte aérea apresentou maio peso seco, principalmente após o 20º dia, quando houve maior expanção foliar ...Observação: O resumo, na íntegra, poderá ser visualizado no texto completo da tese digital / Abstract: Not informed. / Mestrado / Mestre em Ciências Biológicas
2

Germinação, desenvolvimento inicial, fenologia e distribuição espacial da espécie Dalbergia cearensis Ducke / Germination, early growth, phenology and spatial distrubution of species Dalbergia cearensis Ducke

Nogueira, Francisco Carlos Barboza January 2012 (has links)
NOGUEIRA, Francisco Carlos Barboza. Germinação, desenvolvimento inicial, fenologia e distribuição espacial da espécie Dalbergia cearensis Ducke. 2012. 138 f. Tese (Doutorado em ecologia e recursos naturais)- Universidade Federal do Ceará, Fortaleza-CE, 2012. / Submitted by Elineudson Ribeiro (elineudsonr@gmail.com) on 2016-05-27T19:10:48Z No. of bitstreams: 1 2012_tese_fcbnogueira.pdf: 1317824 bytes, checksum: 0c1c24c72f7eb12a700ae910ab7f86ad (MD5) / Approved for entry into archive by José Jairo Viana de Sousa (jairo@ufc.br) on 2016-05-27T21:01:21Z (GMT) No. of bitstreams: 1 2012_tese_fcbnogueira.pdf: 1317824 bytes, checksum: 0c1c24c72f7eb12a700ae910ab7f86ad (MD5) / Made available in DSpace on 2016-05-27T21:01:21Z (GMT). No. of bitstreams: 1 2012_tese_fcbnogueira.pdf: 1317824 bytes, checksum: 0c1c24c72f7eb12a700ae910ab7f86ad (MD5) Previous issue date: 2012 / The viable seed production, dispersal, germination and early growth of seedlings are events of the life cycle of angiosperms that are part of the regeneration niche. Understanding how these events occur before environmental factors such as temperature, light and humidity and how the young and adult individuals are spatially distributed in the environment, increases the probability of getting success in the establishment of plant species and their future growth. Dalbergia cearensis is an endemic species of xerophilous thorny forest (caatinga) of northeastern Brazil. Its wood is much appreciated for the production of finely crafted furniture and musical instruments. In this study, we tried to understand the morphology of its fruit, seeds, and seedlings, the influence of light and temperature on seed germination, phenology, and spatial distribution. Fruits of D. cearensis were described as samaras which have features to spread anemochorous dispersion. Its germination process is relatively fast, beginning after three days of sowing. Its seeds germinate in the presence and absence of light, with the highest percentage of germination reached at temperatures of 25, 30 and 35oC. The young plants of D. cearensis show greater shoot growth under shade and their roots grow in the full light. Your tree loses leaves during the dry season which runs from July to December. At the beginning of rains (December), it starts the issuance of leaf buds which happens until March. Its flowers appear with the rain constancy and can happen between November and January. The phenological peak of ripi fruit happens in May. The young and adult population placed in Private Reserve of Natural Patrimony Não Me Deixes Farm in Quixadá, Ceará shows aggregated distribution. The highest proportion of seeds dispersed is 3 meters away from the nearest adult. / A produção de sementes viáveis, dispersão, germinação e crescimento inicial de plântulas são eventos do ciclo de vida das angiospermas que fazem parte do Nicho de regeneração. Entender como esses eventos ocorrem diante de fatores ambientais como temperatura, luz e umidade e como os indivíduos jovens e adultos estão distribuídos espacialmente no ambiente, aumenta a probabilidade de obtermos sucesso no estabelecimento de espécies vegetais e de seus crescimentos futuros. Dalbergia cearensis é uma espécie endêmica da floresta xerófila espinhosa do nordeste do Brasil. Sua madeira é muito apreciada para a fabricação de móveis de fino acabamento e instrumentos musicais. Nesse estudo, procuramos compreender os aspectos morfológicos de seus frutos, sementes e plântulas, a influência da luz e temperatura na germinação das sementes, a fenologia e sua distribuição espacial. Os frutos de D. cearensis foram descritos como sâmaras que possuem características para dispersão anemocórica. Seu processo germinativo é relativamente rápido, iniciando-se após três dias da semeadura. Suas sementes germinam na presença e na ausência de luz, com as maiores porcentagens de germinação alcançadas nas temperaturas de 25, 30 e 35o C. As plantas jovens de D. cearensis mostram maior crescimento da parte aérea sob sombreamento e suas raízes crescem mais a plena luz. A sua árvore perde folhas durante o período seco que vai de julho a dezembro. Com o início das chuvas (dezembro) começa a emissão de brotos foliares que acontece até março. Suas flores surgem com o ritmo das chuvas e podem ocorrer entre novembro e janeiro. O pico fenológico de frutos maduros ocorre em maio. A população de indivíduos jovens e adultos localizada na Reserva Particular do Patrimônio Natural Fazenda Não me Deixes, em Quixadá, Ceará, apresenta distribuição agregada. A maior proporção de sementes dispersadas ocorre a 3 metros de distância dos adultos mais próximos.
3

Contribuição ao estudo fitoquímico de dalbergia ecastophyllum (l.) Taub. (fabaceae)

Maciel, Rafaela Dos Santos Soares 23 February 2016 (has links)
Submitted by Maike Costa (maiksebas@gmail.com) on 2017-09-11T13:37:48Z No. of bitstreams: 1 arquivototal.pdf: 4539317 bytes, checksum: 8b0c70f7cf6924075fe039736b510527 (MD5) / Made available in DSpace on 2017-09-11T13:37:48Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 4539317 bytes, checksum: 8b0c70f7cf6924075fe039736b510527 (MD5) Previous issue date: 2016-02-23 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Dalbergia ecastophyllum (L.) Taub., popularly known as “rabo-de-bugio” or “marmelo-do-mangue”, is a species of the Fabaceae family, with expressive commercial value, since propolis comes from resinous exudates present in the stem of this species. This study aimed to contribute the phytochemistry study of Dalbergia (Fabaceae) genus through the phytochemical study of D. ecastophyllum species. The plant material (leaves and roots) was collected in Rio Tinto - Paraiba and deposited in the Herbarium of the Department of Systematics and Ecology – UFPB with the 45738 code (JPB). For phytochemical study, the plant material after drying and pulverization, was subjected to extraction processes, partition and chromatography to isolate the chemical constituents. The chemical structures thereof were determined by spectroscopic methods and comparisons with literature data. The fractions of the leaves allowed isolation of 13²-17³-hydroxy-ethoxypheophorbide A, pheophytin A, phytol and isoquercitrin substances. Since fractions of the roots were isolated the cedrol, acetate morolic acid, daidzein, formononetin, β-sitosterol and stigmasterol; and 4-geranyl-3,5-dihydroxy-4'-methoxy-trans-stilbene. The latter substance was isolated for the first time in the literature. The ethyl acetate fraction of the leaves has excellent antioxidant activity against DPPH (IC50 = 0.85 ± 0.236 g/ml). / Dalbergia ecastophyllum (L.) Taub., popularmente conhecida como rabo-de-bugio ou marmelo-do-mangue, é uma espécie da família Fabaceae, de significativa importância comercial, visto que a própolis vermelha tem origem do exsudato resinoso presente no caule desta espécie. Este trabalho objetivou contribuir o estudo fitoquímico do gênero Dalbergia (Fabaceae) através do estudo fitoquímico da espécie D. ecastophyllum. Para tanto, o material vegetal (partes aéreas e raízes) foi coletado em Rio Tinto – Paraíba e depositado no Herbário do Departamento de Sistemática e Ecologia – UFPB com o código 45738 (JPB). Para o estudo fitoquímico, o material vegetal, após secagem e pulverização, foi submetido a processos de extração, partição e cromatografia para isolamento dos constituintes químicos. As estruturas químicas dos mesmos foram determinadas por métodos espectroscópicos e comparações com modelos da literatura. Das frações das partes aéreas foram isoladas as substâncias 13²-hidroxi-17³-etoxifeoforbídeo A, feoftina A, fitol e isoquercitrina. Já das frações das raízes foram isolados o cedrol, acetato de ácido morolique, daidzeina, formononetina, β-sitosterol e estigmasterol; e 4-geranil-3,5-dihidroxi-4’-metoxi-trans-stilbeno. Sendo este último isolado pela primeira vez na literatura. A fração acetato de etila das partes aéreas apresentam uma excelente atividade antioxidante frente ao DPPH (CE50 = 0,85 ± 0,236 μg/ml).
4

A propolis vermelha do nordeste do Brasil e suas caracteristicas quimicas e biologicas / The red propolis of the northeast of Brazil and its chemical and biological characteristics

Daugsch, Andreas 16 February 2007 (has links)
Orientador: Yong Kun Park / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-08T03:38:25Z (GMT). No. of bitstreams: 1 Daugsch_Andreas_D.pdf: 2046442 bytes, checksum: 6c7927a805842c622f8365909bcb5a1a (MD5) Previous issue date: 2007 / Resumo: Própolis contém substâncias resinosas coletadas pelas abelhas (Apis mellifera) de várias plantas. Ela é usada pelas abelhas para selar buracos e proteger a colméia. Própolis é usada na medicina popular desde 300 anos antes de Cristo. Numerosas propriedades biológicas têm sido encontradas nas própolis, incluindo anti-microbiana, citotoxidade, anti-herpes, anti-tumor, anti-HIV, e efeitos supressivos da toxicidade da dioxina. Anteriormente as própolis brasileira haviam sido classificadas em 12 grupos, baseado nas características físico-químicas. Foi também analisada as origens botânicas das principais própolis, como do grupo 3 que foi identificada sendo resina do botão floral de Populus (Salicaceae), do grupo 6 e 12 foi identificada sendo resina de folhas jovens de Hyptis divaricata (Lamiaceae) e Baccharis dracunculifolia (Asteracea), respectivamente. Própolis normalmente é uma resina amarela escura ou amarronzada. Recentemente, nós encontramos uma própolis vermelha em colméias localizadas ao longo do mar e costas de rios no nordeste brasileiro que foi classificada então como própolis do grupo 13. Foi observado que as abelhas coletavam o exudato vermelho da superfície de Dalbergia ecastophyllum (L) Taub. (Leguminosae). Através de análises químicas e histológicas foi comprovado a existência de um novo grupo de própolis de origem botânica Dalbergia ecastophyllum com alta atividade anti-microbiana e anti-radical livre / Abstract: Propolis contains resinous substances of various plants gathered by the honeybee (Apis mellifera). It is used by the bees to seal of holes and to protect the beehive. Propolis is used as a folk medicine since 300 BC. Numerous biological properties have been found including anti-microbial, cytotoxic, anti-herpes, antitumor, anti-HIV and suppressive effects towards dioxin toxicity. Previously, 12 groups of Brazilian propolis have been classified based upon physiochemical characteristics. It was also analyzed the botanical origins of the main própolis. Propolis G3 was identified to contain resins of the buds of Populus (Salicaceae). The botanical origin of propolis of group 6 and 12 was identified as the resins on young leaves of Hyptis divaricata (Lamiaceae) and Baccharis dracunculifolia (Asteracea), respectively. Propolis normally is a dark yellow or brownish resin. Recently, we found a red propolis in beehives along the see and river shores of northeastern Brazil that was classified as propolis group 13. It was observed that honeybees collected red exudates from the surface of Dalbergia ecastophyllum (L) Taub. (Leguminosae). Through chemical and histological analyses the existence of a new group of propolis with botanical origin of Dalbergia ecastophyllum and a high biological activity against microorganisms and free radicals was confirmed. / Doutorado / Doutor em Ciência de Alimentos
5

Estudo comparativo de diferentes extrações de propolis dos grupos 12 e 13 e suas atividades biologicas / Comparative study of different extractions of propolis groups 12 and 13

Moraes, Cleber Silveira 20 March 2007 (has links)
Orientador: Yong Kun Park / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-08T04:20:38Z (GMT). No. of bitstreams: 1 Moraes_CleberSilveira_M.pdf: 1307304 bytes, checksum: bcd25bcdff7cb297e4b623a9f7e51872 (MD5) Previous issue date: 2007 / Mestrado / Mestre em Ciência de Alimentos
6

Dalbergia and Albizia: Plantlet Production via Tissue Culture, Karyological Evaluation, and Seed Anatomy with Scanning Electron Microscopy

Ghosh, Nabarun 12 1900 (has links)
A publication by the National Academy of Sciences, USA (1979) outlined some of the research need for a great variety of economically important woody species whose remaining genetic resources need urgently to be collected and conserved. A viable regeneration system was established via tissue and cell suspension culture for Albizia falcataria and A. lebbeck, two important wood yielding leguminous tree species. The culture medium was standardized after several trials to obtain callus from the leaflet explants of these two tree species. The optimum use of casein hydrolysate (w/v) and coconut milk (v/v) in addition to 6-Benzylaminopurine and Indole-3-butyric acid could induce morphogenesis and somatic embryogenesis in the cultured tissue. This reports the first observation on somatic embryogenesis ofA. lebbeck using leaflets as the explants. Scanning Electron Microscopy and histological studies were done on the different stages plant development following standard techniques. Embryogenesis in suspension culture followed regeneration of plantlets in A. lebbeck. In A.falcaaria the regenerative process followed via organogenesis from the shoot buds developed on the leaf explants. After hardening the regenerated plants were transferred to the greenhouse. Some of the trees grew more than 25 feet tall within a few months outside the greenhouse. Karyotype of the three leguminous trees Albizia lebbeck, A. falcataria, and Dalbergia sissoo was analyzed. In D. sissoo, various chromosomal anomalies were observed in the cultured tissue. The abnormality indices and ploidy level varied with the age and the frequency of the subculture. In the aged culture the regenerative potential declined but was reinstated to some extent with the addition of two complex growth factors, coconut milk and casein hydrolysate. Seed anatomy of 26 species of 4 leguminous genera was studied with SEM. The main distinguishing anatomical features observed in the seed sections were uniseriate or multiseriate epidermis, epidermal projections, and number of rows and nature of columns of hypodermal layer, especially the nature of endosperm. Three species of Dalbergia, Acacia and Cassia and two species of Albizia are difficult to distinguish externally even with seed coat study under SEM, but this study with cross sections provided enough characteristic features to distinguish one from the other.
7

ASEXUAL PROPAGATION OF ARIZONA ROSEWOOD, VAUQUELINIA CALIFORNICA (TORR.) SARGENT.

Smith, Eileen Yvonne. January 1982 (has links)
No description available.
8

Effects of leaf litter diversity on nutrients and mosquito communities in Neotropical artificial tree holes

Komosinski, Rachel 31 July 2012 (has links)
Inputs from terrestrial habitats to aquatic habitats are important for structuring aquatic communities. Terrestrial producer diversity in the tropics may decline due to anthropogenic causes. I investigated how tree diversity affects aquatic communities. We used leaves from three timber-producing species (Dalbergia retusa, Pachira quinata, and Tectona grandis) to test the effects of leaf litter species composition and richness on invertebrate aquatic communities in Gamboa, Panama. We quantified macroinvertbrate species richness and abundances, leaf litter mass loss, and dissolved carbon to nitrogen ratios (C:N) after 4 weeks. We found that litter types differed in breakdown and C:N. Tectona grandis had lower dissolved C:N than both native species and supported the fewest number of invertebrates. C:N ratios declined with increasing litter diversity; however breakdown was not affected by litter richness. Mosquito abundance increased with litter species richness. Results of this study highlight the importance of diverse detritus in structuring aquatic treehole communities.
9

Estudo fitoquímico de Dalbergia ecastophyllum (L.) Taub. (Fabaceae) / Phytochemical Studies of Dalbergia ecastophyllum (L.) Taub. (Fabaceae).

Soares, Rafaela dos Santos 09 February 2012 (has links)
Made available in DSpace on 2015-05-14T12:59:43Z (GMT). No. of bitstreams: 1 ArquivoTotal.pdf: 5455916 bytes, checksum: ae9a50d359b6e994167f8e2b4e7150db (MD5) Previous issue date: 2012-02-09 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Dalbergia ecastophyllum (L.) Taub. (Fabaceae), popularly known as "rabo-de-bugio" or marmelo-do-mangue", it is a scandentia or semi-prostrate species, commonly found in estuaries, mangroves and dunes. It was observed that the bees collected a red exudate from the surface of the parts area of this species suggesting that this is the botanical origin of the red propolis. This study aimed to contribute to the chemotaxonomical knowledge of the genus Dalbergia and of the family Fabaceae through the phytochemical study of the species D. ecastophyllum. The plant material was collected in Rio Tinto - Paraíba and a voucher specimen was deposited in the Herbarium of the Department of Systematics and Ecology - UFPB with the code 45738 (JPB). For the phytochemical study, the plant material, after drying and pulverization, was subjected to extraction processes, and partition chromatography to isolate the chemical constituents. The chemical structures were determined by spectroscopic methods, such as IR and 1H NMR and 13C one and two-D, and comparisons with models of literature. From the hexane phase, the triterpene friedelin, two mixtures of steroids, non-glycosylated and glycosylated (β-sitosterol and stigmasterol) and a mixture of three triterpenes (lupeol, β-amyrin and germanicol) were obtained. From the dichloromethane phase two isoflavones, biochanin A and 2' - hydroxy - 5' - metoxibiochanin A were isolated and identified , this latter substance is being reported for the first time in the genus, thus contributing to the chemotaxonomy of the genus Dalbergia and family Fabaceae. / Dalbergia ecastophyllum (L.) Taub. (Fabaceae), popularmente conhecida como rabo-de-bugio ou marmelo-do-mangue, é uma espécie escandente ou semi-prostrada, encontrada associada a estuários, mangues e dunas. Foi observado que as abelhas coletavam o exsudato vermelho da superfície dessa espécie sugerindo ser essa é a origem botânica da própolis vermelha. Este trabalho objetivou contribuir para o conhecimento quimiotaxonômico do gênero Dalbergia e da família Fabaceae através do estudo fitoquímico da espécie D. ecastophyllum. Logo, o material vegetal foi coletado em Rio Tinto Paraíba e depositado no Herbário do Departamento de Sistemática e Ecologia UFPB com o código 45738 (JPB). Para o estudo fitoquímico, o vegetal, após secagem e pulverização, foi submetido a processos de extração, partição e cromatografia para isolamento dos constituintes químicos. A estrutura química dos mesmos foi determinada por métodos espectroscópicos, como: Infravermelho e Ressonância Magnética Nuclear de 1H e 13C uni e bidimensionais, além de comparações com modelos da literatura. Da fase hexânica obteve-se o triterpeno friedelina, duas misturas de esteroides não glicosilado e glicosilado (β-sitosterol e estigmasterol) e uma mistura com três triterpenos (lupeol, β-amirina e germanicol). Da fase diclorometano foi isolado e identificado dois isoflavonoides, o biochanin A e 2 -hidroxi-5 -metoxibiochanin A, sendo essa última substância relatada pela primeira vez no gênerol, contribuindo, portanto para a quimiotaxonomia do gênero Dalbergia e da família Fabaceae.
10

Inhibition du mécanisme de quorum sensing et de la formation de biofilm chez Pseudomonas aerugionsa par des composés bioactifs de Dalbergia trichocarpa (Fabaceae) / Dalbergia trichocarpa, source of natural compounds which affect quorum sensing mechanism and biofilm formation in Pseudomonas aeruginosa

Rasamiravaka, Tsiry 13 June 2014 (has links)
Depuis quelques décennies, les bactéries pathogènes multi-résistantes aux antibiotiques sont de plus en plus répandues dans le monde. Cette situation a suscité le besoin et l'intérêt de trouver des médicaments antibactériens avec de nouvelles cibles potentiels. La découverte des systèmes de communication de type quorum sensing (QS) régulant la virulence bactérienne représente une des cibles privilégiées pour contrôler les bactéries pathogènes autrement qu’en interférant avec leur croissance bactérienne. Dans l’écosystème naturel, un grand nombre d'organismes (Eucaryotes et Procaryotes) co-existent en synthétisant chacun de leur côté des métabolites secondaires. Les plantes, étant en permanence en contact avec des bactéries, synthétisent des métabolites secondaires capables d’inhiber l’expression des gènes de virulence chez les bactéries sans pour autant affecter ni leur croissance ni leur viabilité. Notre objectif a été de contribuer à la valorisation de la biodiversité malgache en identifiant des plantes et en y isolant les composés actifs présentant une capacité à perturber le mécanisme de QS chez P. aeruginosa PAO1, une bactérie pathogène opportuniste de l’homme, des animaux et des plantes. Dans ce but, nous avons tout d’abord réalisé un criblage d’activité anti-QS de différents flavonoïdes commerciaux. De ce criblage, la narigenine et la naringine ont été sélectionnées pour être les molécules de contrôle positif et négatif des tests d’activité anti-QS, respectivement. Par la suite, 4 espèces de Dalbergia endémique de Madagascar ont fait l’objet de criblage pour leur activité anti-QS. Ce travail a fait ressortir l’activité anti-QS très intéressante de l’écorce de D. trichocarpa à partir de laquelle nous avons isolée le composé actif nommé la coumarate de l’aldéhyde-oléanolique (OALC). Le contrôle naringénine et l’OALC ne présente aucun effets inhibiteurs sur la croissance bactérienne de P. aeruginosa PAO1 et sur l’expression du gène QS-indépendant aceA suggérant une activité d’inhibition spécifiquement liée au QS. Cependant, ces deux molécules présentent des spectres d’inhibition différente. En effet, les deux molécules diffèrent dans le sens que la naringenine n’inhibe pas l’expression du gène gacA et la motilité de type twitching contrairement à l’OALC. Ces résultats suggèrent que l’OALC et la naringénine représente des candidats potentiels pour des investigations in vivo quant à leur effet anti-QS et anti-biofilm sur des modèles infectieux d’organismes supérieurs. Par ailleurs, ils démontrent la richesse des plantes malgaches comme sources de nouvelles molécules anti-virulence ainsi que l’importance de telle investigation afin de renforcer notre arsenal thérapeutique en composé antibactérienne dans la lutte continuelle contre les bactéries pathogènes/Since few decades, multidrug resistant bacteria spread all over the world. This situation gives rise to the need and interest in finding antibacterial drugs with novel potent target. Discovery of communication system termed Quorum Sensing (QS) which regulate bacterial virulence factor represent privileged target in another way than interfering with bacterial growth. In natural ecosystem, many organisms (Eukaryotes and Prokaryotes) produce secondary metabolites. As plants are permanently in contact with bacteria, they have synthetized secondary metabolites which inhibit bacterial virulence gene expression without affecting bacterial viability. Our goal was to contribute to the valorization of Malagasy biodiversity and specifically to identify plants and isolate bioactive compound presenting ability to disrupt QS mechanism in P. aeruginosa, opportunistic pathogen bacteria in plants, animals and human. In this purpose, screening of commercial available flavonoids has been firstly carried out. From this screening, naringenin and naringin have been selected to be used as positive and negative QS inhibitor controls, respectively. Subsequently, Four Malagasy endemic Dalbergia species have been screened for their anti-QS activity. This work pointed out the interesting anti-QS activity of D. trichocarpa bark extract which led to the isolation of oleanolic aldehyde coumarate (OALC) as one major bioactive compound. At the concentration tested, naringenin and OALC did not affect P. aeruginosa PAO1 viability and didn’t reduce QS-independent aceA gene expression suggesting a specific anti-QS activity. However, these two compounds present different inhibition spectrum. Indeed, naringenin didn’t inhibit gacA gene expression and twitching motility contrarily to OALC. These results suggest that OALC and naringenin represent potent candidates for in vivo investigations in their anti-QS and anti-biofilm activity onto eukaryotes infectious model. Besides, this finding demonstrated the potent source for novel anti-virulence compounds of Malagasy flora and the importance of this kind of research to strengthen our antimicrobial therapeutic arsenal with the ongoing struggle against bacterial infection. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Page generated in 0.4919 seconds