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  • 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.
101

Ultrasensitive Measurements of Magnetism in Carbon-based Materials

Scozzaro, Nicolas Joseph January 2016 (has links)
No description available.
102

Antioxidant Activity of Ampelopsis Grossedentata Crude Extract and its Major Component Dihydromyricetin

Ye, Liyun 25 August 2011 (has links)
Oxidation limits the shelf life of many food products. Adding antioxidants to foods is the most common way to solve this problem. Reports on safety issues of synthetic food additives have raised consumer interest in "all natural" foods, without added antioxidants or with synthetic replaced with natural antioxidants. The natural antioxidants now in use are much more expensive and less potent than the synthetic antioxidants. Thus, effective and economical natural antioxidants are of great interest to researchers. Teng Cha is a type of herbal tea found in China that has reported high levels of antioxidants. Antioxidant activity of Teng Cha extract and its major component dihydromyricetin has been reported, but no studies have provided clear evidence for the antioxidant effectiveness of Tech Cha extracts. The goal of this study was to measure the antioxidant activity of Teng Cha extract and dihydromyricetin (DHM), a major component of Tech Cha extract. The DPPH assay was conducted and antioxidant activities of the crude extract and dihydromyricetin were evaluated in soybean oil based on the peroxide value, anisidine value, Totox value, headspace volatiles and headspace oxygen. Antioxidant effectiveness was also evaluated in a cooked beef model system. DHM was more potent than BHA in preventing soybean oil oxidation. The crude extract was not as effective as BHA and DHM, possibly because it contained transition metals. In cooked beef, DHM and the crude extract showed lower activity than BHA, possibly due to their low solubility. Overall, Teng Cha extract and DHM are potential natural food antioxidants for future applications. / Master of Science in Life Sciences
103

Biološka aktivnost novosintetisanih D-seko i D-homo-estratrienskih derivata u in vivo i in vitro uslovima / Biological activity of the newly synthesized D-secoand D-homoestratriene derivatives in in vivo and in vitro experiments

Jovanović-Šanta Suzana 08 October 2010 (has links)
<p>Sintetisana su nova jedinjenja, 16- i 17-supstituisani&nbsp;16,17-sekoestratrienski derivati i D-homoestranski&nbsp;derivati, polazeći od 3-benziloksi-17-hidroksi-16,17-sekoestra-1,3,5(10)-trien-16-nitrila. Ispitana je&nbsp;estrogena i antiestrogena aktivnost u eksperimentima <em>in&nbsp;vivo</em>, antiaromatazna aktivnost <em>in vitro</em>, antioksidantna&nbsp;aktivnost DPPH &nbsp;i TBA testom, kao i antiproliferativna&nbsp;aktivnost prema ćelijskim linijama MCF-7 ATCC,&nbsp;MDA-MB-231, HT-29 i MRC-5 novosintetisanih&nbsp;jedinjenja.</p> / <p>Some new compounds, 16- and 17-substituted 16,17-secoestratriene derivatives, as&nbsp; well as D-homoestratriene derivatives, were synthesized, starting from 3-benzyloxy-17-hydroxy-16,17-secoestra-1,3,5 (10)-triene-16-nitrile. The newly synthesized compounds were tested for their <em>in vivo&nbsp;</em>estrogenic and antiestrogenic activity,&nbsp; <em>in vitro&nbsp;</em>antiaromatase activity, antioxidative activity by DPPH and TBA tests, as well as antiproliferative activity against MCF-7 ATCC, MDA-MB-231, HT-29 i MRC-5 cell lines.</p>
104

Antioksidantni, antibakterijski i antimutageni potencijal vrste Myrtus communis L. iz Crne Gore / Antioxidant, antimicrobial andantimutagenic potencial of the Myrtuscomunis L.

Bugarin Dušan 08 June 2010 (has links)
<p>Ispitivanja hemijskog sastava etarskih ulja i<br />ekstrakata izvedena su na vrsti Myrtus communis<br />L. sa pet lokaliteta iz Crne Gore. Pored toga,<br />ispitana je njihova antioksidantna aktivnost u<br />razlicitim in vitro sistemima kako bi se utvrdio<br />uticaj pomenutih ekstrakata i etarskih ulja na<br />neutralizaciju DPPH, NO, OH i 2- radikala, kao<br />i njihov uticaj na lipidnu peroksidaciju u<br />lipozomima i inhibiciju enzima ksantin-oksidaze.<br />Takode, ispitana je i antibakterijska aktivnost<br />etarskih ulja i ekstrakata ove vrste na 9<br />bakterijskih sojeva, kao i njihov antimutageni<br />potencijal na bakterijskom soju Escherichia coli<br />IC 202.</p> / <p> In this tessis the chemical analysis of the<br /> essential oils and methanolic extracts<br /> from five plant samples of Myrtus<br /> communis L., collected from different<br /> localities in Montenegro, have been<br /> investigate. Beside that, their antioxidant<br /> activity in differwnt in vitro systems has<br /> been study to establish their scavenging<br /> potential towards DPPH, NO, OH, and<br /> O2- free radicals, as wel as their effects<br /> on lipid peroxidation in liposoma and<br /> inhibition enzyme XOD. Also, the<br /> antibacterial activity of the essential oils<br /> and methanolic extract has been study on<br /> 9 bacterial strains, as wel as their<br /> antimutagenic effects on bacterial strain<br /> E. Colli IC202.</p>
105

Antioksidantna svojstva lekovitog bilja u hrani / Antioxidant Properties of Medicinal Plants in Food

Mišan Aleksandra 11 December 2009 (has links)
<p>U ovom radu je izvr&scaron;eno kvantitativno&nbsp;određivanje i identifikacija biljnih fenola i&nbsp;<br />flavonoida etanolih ekstrakata ploda per&scaron;una&nbsp;(<em>Petroselini fructus</em>), kore kru&scaron;ine (<em>Frangulae&nbsp;cortex</em>), lista pitome nane (<em>Mentha piperitae&nbsp;folium</em>), ploda kima (<em>Carvi fructus</em>) i lista breze&nbsp;(<em>Betulae folium</em>), kao i komercijalnog preparata Vitalplant<sup>&reg; </sup>((<em>Frangulae cortex</em>(35 %),&nbsp; <em>Mentha&nbsp;piperitae folium</em>(20%),&nbsp; <em>Carvi fructus</em>(20 %),&nbsp;<em>Petroselini fructus&nbsp;</em>(25 %)). U nastavku&nbsp;istraživanja ispitivana je antioksidantna aktivnosti etanolih ekstrakata primenom&nbsp;direktnih, ESR &ldquo;spin trap&ldquo; spektroskopskih&nbsp;metoda određivanja &ldquo;skevindžer&ldquo; aktivnosti na&nbsp;superoksid anjon i &nbsp;hidroksil radikale i&nbsp;indirektnih, spektrofotometrijskih testova za&nbsp;određivanje skevindžer&ldquo; aktivnosti na DPPH˙&nbsp;radikale, redoks potencijala i helatacione&nbsp;aktivnosti, kao i antioksidantne aktivnosti u&nbsp;sistemu&nbsp; &beta;-karoten-linolna kiselina. Osim navedenog, deo istraživanja je posvećen&nbsp;ispitivanju termičke stabilnosti ekstrakata&nbsp;navedenih biljaka i komercijalnog preparata&nbsp;Vitalplant<sup>&reg;&nbsp;</sup>radi sticanja uvida u mogućnost&nbsp;njihove primene u &nbsp;pekarskim proizvodima. U&nbsp;poslednjoj fazi rada, izvr&scaron;eno je određivanje sposobnosti pulvisa i etanolnog ekstrakta komercijalnog &nbsp;preparata Vitalplant<sup>&reg;</sup> da inhibiraju oksidaciju lipida u keksu, primenom spektrofotometrijskih testova &ldquo;skevindžer&ldquo; aktivnosti &nbsp;na DPPH˙ radikale i MDA testa. Ispitane biljne sirovine, kao i komercijalni preparat Vitalplant<sup>&reg;&nbsp;</sup>su bogat izvor jedinjenja iz klase biljnih fenola. Sve ispitane biljne droge poseduju antioksidantnu aktivnost, koja se značajno ne menja usled termičkog tretmana. Dodatak biljne me&scaron;avine Vitalplant<sup>&reg;&nbsp;</sup>, upravo proporcionalno njenom sadržaju, &nbsp;dovodi do povećanja antioksidantne aktivnosti keksa i smanjenja stepena lipidne peroksidacije.&nbsp;</p> / <p>In this paper, quantitative determination and identification of plant phenolics and flavonoids of ethanolic extracts obtained from parsley fruit (<em>Petroselini fructus</em>), buckthorn bark (<em>Frangulae cortex</em>), mint leaves (<em>Mentha piperitae folium</em>), caraway fruit&nbsp; (<em>Carvi fructus</em>), birch leaves (<em>Betulae folium</em>), as well as from commercial preparation Vitalplant&reg; ((<em>Frangulae cortex</em>(35 %), <em>Mentha piperitae folium</em>&nbsp;(20%), <em>Carvi fructus</em>(20 %), <em>Petroselini fructus&nbsp;</em>(25 %)) was performed. In addition, antioxidant&nbsp; activity of ethanolic extracts was tested, by applying direct, ESR &ldquo;spin trap&ldquo; &nbsp;spectroscopic methods for the determination of scavenging activity on superoxide anion and hydroxyl radicals, and indirect, spectrophotometric methods for the determination of DPPH˙ radical scavenging activity, reducing power, chelating activity and antioxidant activity in&nbsp; &beta;-carotene-linoleic acid model system. Moreover, thermal stability of the ethanolic extracts was tested in order to get insight into possible application of the extracts in bakery products. Finally, the ability of the commercial preparation Vitalplant&reg;, in the form of powder and extract, to inhibit oxidative changes of cookies was tested by applying spectrophotometric DPPH radical scavenging and MDA tests.</p><p>According to obtained results, investigated plant samples, including commercial preparation Vitalplant&reg;, are rich source of plant phenolics. Investigated plant drugs possess antioxidant activity, which is not significantly changed after the thermal treatment. Cookie supplementation with commercial preparation Vitalplant&reg; results in&nbsp; better oxidative stability of lipids and enhanced antioxidant activity of the cookies.</p>
106

Activités vasculaires et antioxydantes d'espèces des genres Combretum et Hymenocardia, plantes présumées antihypertensives à Kinshasa et dans le Bas-Congo / Vascular and antioxidant activities of species of the genera Combretum and Hymenocardia, plants presumed antihypertensive in Kinshasa and in Bas-Congo

Nsuadi Manga, Francine 08 May 2013 (has links)
Les maladies cardiovasculaires sont la principale cause de décès dans le monde. Actuellement, leur prévalence croît en Afrique subsaharienne où l'hypertension représente un facteur de risque cardiovasculaire majeur. Différents médicaments sont utilisés pour le traitement de l'hypertension mais dans les pays à revenu faible en général, et en R.D.Congo en particulier, le niveau socio-économique bas de la population pousse cette dernière à faire appel à la médecine traditionnelle. En R.D.Congo, les tradithérapeutes utilisent une multitude de plantes pour traiter l’hypertension. Cependant, les propriétés pharmacologiques de certaines de ces plantes sur la fonctionnalité vasculaire n’ont pas encore été étudiées de manière approfondie.<p>Afin de donner une base scientifique à l’utilisation de ces plantes dans le traitement de l'hypertension artérielle en médecine traditionnelle congolaise, nous avons réalisé dans un premier temps une enquête ethnobotanique. Celle-ci a été menée auprès de tradipraticiens de Kinshasa et du Bas-Congo, dans l'ouest de la R.D.Congo, afin d'obtenir des informations spécifiques sur les plantes qui sont utilisées pour traiter l'hypertension. Suite à cette enquête, trois plantes ont été sélectionnées :les feuilles et les écorces de racines de Combretum racemosum P. Beauv (Combretaceae), les feuilles de Combretum celastroides subsp. laxiflorum Welw (Combretaceae) et les écorces de tronc et de racines d'Hymenocardia acida Tul. (Euphorbiaceae). L'évaluation de l'effet vasorelaxant des extraits polaires issus de ces plantes sur les anneaux d’aorte isolée de rat a montré que les extraits testés ont un effet vasorelaxant endothélium-dépendant. Tous les extraits induisent cet effet via la voie du NO-GMPc alors que ceux de feuilles et d'écorces de racines de Combretum racemosum agissent également via la voie des prostanoïdes. Ces extraits ont aussi une action antioxydante. Enfin, l'administration chronique des extraits polaires de feuilles de Combretum celastroides subsp. laxiflorum et d'écorces de racines d'Hymenocardia acida aux rats spontanément hypertendus a montré que ces deux extraits possèdent une activité antihypertensive. Dans le but de déterminer les composés phytochimiques responsables de l’activité vasorelaxante observée, les extraits polaires de feuilles de Combretum celastroides subsp. laxiflorum et d'écorces de racines d'Hymenocardia acida ont été soumis à un fractionnement sur une colonne de polyamide. Toutes les fractions obtenues ont présenté une activité antioxydante, mais l'activité vasorelaxante était concentrée dans une fraction dont l'analyse par chromatographie liquide couplée à la spectrométrie de masse après thiolyse a indiqué qu'elle était enrichie en procyanidines. En conclusion, notre étude montre l'intérêt de ces plantes dans le traitement de l'hypertension en médecine traditionnelle congolaise, intérêt qui mérite d’être confirmé par des études cliniques rigoureuses./<p><p>Cardiovascular diseases represent a major cause of death in the world. Currently, their prevalence grows in sub-Saharan Africa where hypertension represents a major cardiovascular risk factor. Different drugs are used for the treatment of hypertension, but in low-income countries in general and in the D.R.Congo in particular, low socio-economic level forces the population to frequently recourse to the traditional health systems. In D.R.Congo, the traditional healers use a variety of plants to treat hypertension, but the pharmacological properties of some of these plants on vascular function have not been investigated.<p>To provide a scientific basis for the use of these plants in the treatment of hypertension in Congolese traditional medicine, we first carried out an ethnobotanical survey among traditional healers in some districts of Kinshasa and Bas-Congo, in the west of D.R. Congo, to obtain specific information about the plants that are used as antihypertensive remedies. As a result of this investigation, three plants were selected :leaves and root bark of Combretum racemosum P. Beauv (Combretaceae), leaves of Combretum celastroides subsp. laxiflorum Welw (Combretaceae), and trunk bark and root bark of Hymenocardia acida Tul. (Euphorbiaceae). The evaluation of the vasorelaxant effect of the polar extracts from these plants on isolated rat aorta showed that all extracts have an endothelium-dependent vasorelaxant effect. All extracts induce the vasorelaxant effect through the NO-cGMP pathway while those of Combretum racemosum leaves and root bark also act via the prostanoids pathway. These extracts also showed an antioxidant activity. Chronic administration of polar extracts of Combretum celastroides subsp. laxiflorum leaves and Hymenocardia acida root bark to spontaneously hypertensive rats showed that both extracts have an antihypertensive activity. Both extracts were fractionated on a column of polyamide in order to determine the nature of the compounds responsible for the vasorelaxant activity. All fractions obtained had an antioxidant activity but the vasorelaxant activity was concentrated in one fraction. Analysis of this fraction by liquid chromatography-mass spectrometry after thiolysis indicated that it was enriched in procyanidins. In conclusion, our study shows the interest of these plants in the treatment of hypertension in Congolese traditional medicine, interest which should be confirmed by rigorous clinical studies.<p> <p> / Doctorat en Sciences biomédicales et pharmaceutiques / info:eu-repo/semantics/nonPublished
107

Investigação da atividade antioxidante in vitro e da composição química de diferentes extratos de plantas medicinais / Investigation about in vitro antioxidant activity and chemical composition of different extracts from medicinal

Pereira, Romaiana Picada 18 March 2011 (has links)
Conselho Nacional de Desenvolvimento Científico e Tecnológico / Oxidative stress (OS) is involved in the development of several disorders involving the central nervous system, such as Alzheimer s disease (AD). Considering the limitations of current therapeutics for AD, there is still a great demand for discovery of new medical alternatives. In the first part of the present study it was investigated the antioxidant capacity and the chemical composition of three plants popularly used to treat neurological disorders: Melissa officinalis, Matricaria recutita and Cymbopogon citratus. The antioxidant effect of some phenolic compounds was also examined for comparative purposes. All plant extracts were effective in to combat OS, but Melissa officinalis presented the highest antioxidant effect. Among the purified compounds, quercetin had the highest antioxidant activity followed by gallic acid, quercitrin and rutin. In this work, we have demonstrated that the plant extracts could protect against OS induced by various pro-oxidant agents that induce lipid peroxidation by different process. Based on this study, which indicates that Melissa officinalis could be an effective agent in the prevention of various neurological diseases associated with OS. In the second part of this study, it was investigated the chemical composition and antioxidant activity of different fractions from Melissa officinalis extract. Furthermore, it was verified the effect of the most antioxidant fraction on acethylcholinesterase (AChE) activity and the effect of gallic acid on the matrix metalloproteinase-2 (MMP-2) activity. Ethyl acetate fraction presented the highest flavonoids content as well as antioxidant activity when compared with other tested fractions and also it caused AChE inhibition. Moreover, gallic acid inhibited MMP-2 activity. In conclusion, M. officinalis ethyl acetate fraction is suggested to be further investigated for its possible use in the treatment of AD, due its antioxidant, anticholinesterase activities and the MMP-2 inhibitory capacity of their phenolic compound, gallic acid. / O estresse oxidativo (EO) está envolvido no desenvolvimento de várias doenças relacionadas ao sistema nervoso central, tal como a Doença de Alzheimer (DA). Considerando as limitações da terapia existente para a DA, existe ainda a necessidade de novas alternativas médicas. Na primeira parte deste estudo, foi investigada a capacidade antioxidante e a composição química de três plantas usadas popularmente para tratar desordens neurológicas: Melissa officinalis, Matricaria recutita e Cymbopogon citratus. O efeito antioxidante de alguns compostos fenólicos também foi examinado para fins comparativos. Todos os extratos de plantas foram efetivos no combate ao EO induzido por diferentes agentes, mas o extrato aquoso da Melissa officinalis apresentou o maior efeito antioxidante. Dentre os compostos purificados, a quercetina teve a maior atividade antioxidante seguida pelo ácido gálico, quercitrina e rutina. Neste trabalho, foi mostrado que os extratos de plantas protegeram contra o EO induzido por vários agentes pró-oxidantes que induzem peroxidação lipídica por diferentes processos. Baseado nestes resultados, que indicam que a Melissa officinalis poderia ser um agente efetivo na prevenção de várias doenças neurológicas associadas ao EO, na segunda parte deste estudo, foram investigadas a composição química e a atividade antioxidante de diferentes frações do extrato de Melissa officinalis. Além disso, investigou-se o efeito da fração com maior potencial antioxidante na atividade da acetilcolinesterase (AChE) e o efeito do ácido gálico na atividade da metaloproteinase-2 da matriz (MMP-2). A fração acetato de etila apresentou maior conteúdo de flavonóides associada a uma maior atividade antioxidante quando comparado com as outras frações testadas e causou inibição da AChE. Além disso, o ácido gálico inibiu a atividade da MMP-2. Desta forma, sugere-se que a fração acetato de etila da M. officinalis poderia ser melhor investigada para o seu possível uso no tratamento da DA, devido às suas atividades antioxidante e anticolinesterase e a capacidade do ácido gálico, composto fenólico presente em sua composição, inibir a MMP-2.
108

Síntese e investigação de atividades biológicas de Diidro-Piran-2,4-Dionas / Synthesis and investigation Dihydro-pyron-2,4-dione's biological activities

Souza, Laura Cristiane de 18 December 2007 (has links)
This work presents synthesis of seven dihydro-pyran-2,4-diones and investigation of some of its biological activities (moluscicidal, antiulcer, antioxidant and anticholinesterasic). These compounds were prepared - in yields that had varied of moderate to good (50 - 85%) - through the aldol condensation of β-ketoester’s diânion with an aldehyde or a ketone, basic hydrolysis, followed of lactonization in acid medium. In the first investigation about its biological activities, dihydro-pyran-2,4-diones had been inactive on Biomphalaria glabrata adult, presenting active only on its egg masses. Studies about antiulcer activity were not satisfactory therefore results obtained for dihydro-pyran-2,4-diones were not significantly different of those observed in the control group. For determination of the antioxidant activity, the spectrophotometric assay with stable radical DPPH was chosen. The results obtained for dihydro-pyran-2,4-diones, in this assay, were similar to the observed ones for the positive control used, BHT, and show that these compounds constitute in a promising synthetic antioxidants. Results obtained still point with respect to a possible correlation between enol concentration in the equilibrium, and the capacity of reduction of free radical DPPH. It was verified that electron withdrawing groups increase the activity, whereas introduction of electron donators groups cause a reduction of the activity. When assays were extended for other acyclic 1,3-dicarbonilic compounds, was verified that these don’t present antioxidant activity on free radical DPPH. This fact indicates that conformation also can be decisive for manifestation of the studied activity. The inquiry of the anticholinesterasic activity not yet presented results conclusive, but the preliminary assays showed resulted sufficiently promising, with percentage of inhibition of the enzyme acetylcholinesterase between 50% - 60%. / Fundação de Amparo a Pesquisa do Estado de Alagoas / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Este trabalho apresenta a síntese de sete diidro-piran-2,4-dionas e a investigação de algumas de suas atividades biológicas (moluscicida, antiúlcera, antioxidante e anticolinesterásica). Estes compostos foram obtidos, em rendimentos que variaram de moderados a bons (50 – 85%), através da condensação aldólica do diânion de um β-cetoéster com um aldeído ou uma cetona, seguido de hidrólise básica do éster e lactonização em meio ácido. Na primeira investigação sobre suas atividades biológicas, as diidro-piran-2,4-dionas foram inativas frente ao caramujo adulto da espécie Biomphalaria glabrata, apresentando-se ativo apenas frente à sua desova. Os estudos sobre atividade antiúlcera não foram satisfatórios pois os resultados obtidos para as diidro-piran-2,4-dionas não foram significativamente diferentes daqueles observados no grupo controle. Para a determinação da atividade antioxidante escolheu-se o ensaio espectrofotométrico com o radical estável DPPH. Os resultados obtidos para as diidro-piran-2,4-dionas, neste ensaio, foram similares aos observados para o controle positivo utilizado, BHT, e mostram que estas se constituem numa promissora classe de antioxidantes sintéticos. Os resultados obtidos apontam ainda para uma possível correlação entre a concentração da forma enólica no equilíbrio, o pKa da hidroxila deste enol e a capacidade de redução do radical livre DPPH. Verificou-se que grupos retiradores de elétrons ligados ao anel aumentam a atividade, enquanto que a introdução de grupos doadores de elétrons causa uma redução da atividade. Ao estender os ensaios para outros compostos 1,3-dicarbonílicos acíclicos, verificou-se que estes não apresentam atividade antioxidante frente ao radical livre DPPH. Este fato indica que a conformação também pode ser decisiva para a manifestação da atividade estudada. A investigação da atividade anticolinesterásica ainda não apresentou dados conclusivos, mas os ensaios preliminares mostraram resultados bastante promissores, com porcentagem de inibição da enzima acetilcolinesterase entre 50% - 60%.
109

Criblage d’activités biologiques de plantes endémiques ou indigènes de La Réunion - Recherche de molécules antivirales ciblant le virus du chikungunya / Screening of biological activities of endemic or indigenous plants of La Réunion - Research of antiviral molecules targeting the chikungunya virus

Techer, Sophie 26 April 2013 (has links)
Ce travail de thèse s'attache à identifier des plantes et/ou molécules à activités cytotoxique, antioxydante, anti-inflammatoire et antivirale ciblant le virus du chikungunya (CHIKV) dans le but de trouver des alternatives thérapeutiques vis-à-vis du stress oxydatif et de l'inflammation, mécanismes impliqués dans les maladies chroniques non transmissibles (diabète, obésité…), et de la maladie du chikungunya, maladie vectorielle réémergente. La première partie de ces travaux présente les résultats obtenus lors d'un criblage d'activités biologiques réalisé sur une sélection de dix-huit plantes endémiques et indigènes de La Réunion. Les activités ciblées ont été les activités cytotoxiques sur une lignée cellulaire humaine (cellules THP-1), les activités antioxydantes évaluées par un test in cellulo d'hémolyse et par quatre tests chimiques (TEAC/DPPH/FRAP/ORAC) ainsi qu'une évaluation de la teneur en composés phénoliques (test FOLIN) et les activités anti-inflammatoires testées sur des macrophages murins (cellules RAW-BlueTM). Les résultats obtenus ont permis de mettre, plus particulièrement, en évidence les activités de différents extraits : cytotoxique pour Carissa spinarum, antioxydantes pour Agarista buxifolia et Dryopteris wallichiana et anti-inflammatoire pour Stillingia lineata et Indigofera ammoxylum. La deuxième partie du travail est consacrée à l'étude phytochimique d'une espèce indigène de La Réunion, Stillingia lineata, choisie en raison des résultats obtenus lors de ce criblage biologique préliminaire et de ceux du programme Phytochik. Un fractionnement bioguidé par un test antiviral, réalisé sur des cellules Vero (cellules rénales de singe vert Cercopithecus aethiops) contaminées par le CHIKV, a conduit à l'isolement de trois macrocycles diterpéniques rares de type tonantzitlolone dont l'un présente une structure non caractérisée jusque-là, et d'un pimarane de structure nouvelle. La 4'-acétoxytonantzitlolone a été identifiée comme molécule candidate contre le CHIKV (CE50 = 7 μM). Des relations structure-activité ont pu être définies ; la présence d'un groupement oxygéné sur la chaîne latérale des tonantzitlolones semble jouer un rôle important sur la réponse antivirale de ces squelettes diterpéniques. / The aims of this PhD work were to identify plants and/or molecules with cytotoxic, antioxidant, anti-inflammatory or antiviral (chikungunya virus , CHIKV) activities in order to find therapeutic alternatives towards oxidative stress and inflammation, mechanisms involved in chronic noncommunicable diseases (diabetes, obesity ...), and chikungunya disease, reemerging vector-borne disease. The first part of this work presents the results obtained from a biological screening carried out on a selection of eighteen endemic and indigenous plants of La Réunion. The targeted activities were cytotoxicity on a human cell line (THP-1), antioxidant activities evaluated using an in cellulo hemolysis assay and four chemical tests (TEAC / DPPH / FRAP / ORAC) together with an evaluation of the content of phenolic compounds (FOLIN test) and anti-inflammatory activity tested in murine macrophages (RAW cells-BlueTM). The results allowed to highlight activities of different extracts in particular : cytotoxic for Carissa spinarum, antioxidant for Dryopteris wallichiana and Agarista buxifolia and anti-inflammatory for Stillingia lineata and Indigofera ammoxylum.The second part of this work is devoted to the phytochemical study of Stillingia lineata, an indigenous species of La Réunion chosen because of the results obtained in this preliminary biological screening and those carried out in Phytochik programme. Bioassay-guided fractionation performed on Vero cells (green monkey kidney cells Cercopithecus aethiops) infected with CHIKV led to the isolation of three rare macrocycle-type diterpenes called tonantzitlolone and a new pimarane. The 4'-acetoxytonantzitlolone was identified as a candidate molecule against CHIKV (EC50 = 7 μM). Structure-activity relationships have been defined, the presence of an oxygenated group on the side chain of tonantzitlolones seems to play an important role in the antiviral response of the diterpene skeleton.

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