Le diabète de type 2 est aujourd’hui une maladie de plus en plus répandu. En ce sens il est nécessaire de mettre au point de nouveau composé permettant d’inhiber la gluconéogenèse. C’est pourquoi nous nous sommes intéressé à la synthèse du FR225654 1, décaline présentant une activité hypoglycémiante in vivo après administration par voie orale et inhibiteur de la néoglucogenèse in vitro (IC50 = 1,1.10-7 M). Ce composé, isolé en 2005 du champignon Phoma sp N°00144 et jamais encore synthétisé à ce jour, possède un mécanisme d’action inconnu. La nécessité d’une synthèse par voie chimique convergente et flexible, permettant l’accès à des analogues, est donc évidente. La stratégie consistait à préparer une trans-décaline par le biais d’une réaction de Diels-Alder intramoléculaire à partir d’un triène précurseur. La combinaison de ces travaux a constitué une avancée importante dans le cadre de la synthèse du FR225654, un hypoglycémiant potentiel. La mise au point d’une synthèse convergente du précurseur de la réaction de Diels-Alder permettra notamment d’effectuer par la suite des modifications aisées en vue de la préparation d’une vaste gamme d’analogues simplifiés. A ce jour, le produit de cyclo-addition a été isolé et caractérisé, validant ainsi l’étape clé de la stratégie de synthèse. Ainsi, l’accès rapide au FR225654 est rendu possible et la synthèse d’analogues est maintenant envisageable. Les produits synthétisés feront l’objet d’une évaluation biologique, l’objectif ultime étant d’accéder à de nouveaux médicaments pour le traitement du diabète de type 2. / Type 2 diabetes mellitus (T2DM) is a growing worldwide health concern that is expected to afflict over 366 million people by 2030. FR225654 is a novel gluconeogenesis (GNG) inhibitor recently isolated from the culture broth of Phoma sp.. This compound selectively inhibits GNG of primary rat hepatocytes and shows highly hypoglycemic effects in several in vivo mouse models (80% decrease of glycemia). However, to date, the mechanism of action and molecular target remain unknown. From a structural point of view, FR225654 exhibits a highly oxygenated trans-decalin ring substituted by a β-keto-enol moiety and a side-chain bearing a conjugated carboxylic acid and a trisubstituted olefin. Project specific objectives were to design an efficient total synthesis which could also permit a straightforward access to diverse analogues. This feature would constitute a crucial step for the further understanding of Structure Activity Relationship of FR225654. The work consists in synthesizing separately a side chain and a trans-decalin core by means of an intramolecular Diels-Alder reaction from a precursor. To date, synthesis of the precursor has been achieved in 13 steps as well as the side chain. The Intramolecular Diels-Alder reaction has also been validated in order to accomplish the first total synthesis of FR225654.

Made available in DSpace on 2016-05-02T13:55:25Z (GMT). No. of bitstreams: 1 LucienyOliveiraCosta_dissertacaocompleta.pdf: 360050 bytes, checksum: 8d7f1f64d7adf3c6ec4a39d01097d5a3 (MD5) Previous issue date: 2010-03-04 / Azadirachta indica A. Juss, a tree native to India, commonly Known as neem, characteristic of tropical climate, is virtually non-toxic to humans and does not harm the environment. Boophilus microplus belongs to the family Ixodidae and is a species of tick that undermines cattle productivity. This study determine the effect of two treatments - alcoholic extract of Azadirachta indica and TriatoxTM - on the reproductive parameters and tickcidal actions of the telegenic females of the Boophilus microplus tick. Neem leaf extract was obtained with alcohol 70° GL, according to the technique described by Caceres et al. (1990, 1995). About 200 Boophilus microplus telegenic females were obtained from two naturally infested dairy Holstein cows in a farm of Alfenas, MG, Brazil. The females were analyzed at the Universidade José do Rosário Vellano UNIFENAS Laboratory of Biology and Physiology of Microrganisms. The following preparations were used: neem leaf extract: non-diluted (pure) and diluted to 10-1 and 10-2; distilled water (negative control); and Amitraz, which was diluted according to the manufacturer's recommendation. The telegenic females were submitted to an immersion bath during 30 seconds, and then distributed, one by one, into test tubes capped with gauze and left in a horizontal position at room temperature. The parameters were evaluated only after the death of all the telegenic females in distilled water. The results were analyzed by means of the statistical software Bioestat, and the Kruskal-Wallis test was used to compare the groups (neem, distilled water, and Amitraz) at the 5% significance level. The results showed that Amitraz may be replaced by the Azadirachta indica extract, because the latter was effective against ticks by inhibiting oviposition, increased mortality, reduced survival, producing fewer numbers of fertile and/or infertile eggs and lower weight of egg masses. / A espécie Azadirachta indica A. Juss, popularmente conhecida como nim, é uma árvore nativa da Índia, característica de clima tropical, sendo praticamente atóxica ao homem e não agride ao meio ambiente. O Boophilus microplus é pertencente à família dos Ixodídeos e considerado a principal espécie de carrapato que compromete a produtividade da pecuária bovina. Este trabalho foi conduzido com o objetivo de verificar o efeito do extrato hidroalcoólico de Azadirachta indica e do Amitraz (Triatox®) sobre os parâmetros reprodutivos e suas ações carrapaticidas nas teleógenas do carrapato da espécie Boophilus microplus. O extrato das folhas secas de nim foi obtido através da extração com álcool a 70° GL, conforme técnica descrita por Caceres et al. (1990,1995). Foram coletadas, aproximadamente 200 teleógenas do carrapato Boophilus microplus, de duas vacas leiteiras das raças holandesas, naturalmente infestadas, pertencentes a uma propriedade da cidade de Alfenas MG. As teleógenas foram transportadas para o Laboratório de Biologia e Fisiologia de Microrganismos da Universidade José do Rosário Vellano UNIFENAS Alfenas MG, onde foram realizadas as análises. Foi utilizado o extrato de nim sem diluir (bruto) e diluído a 10-1 e 10-2 mg/L, bem como a água destilada (controle negativo) e o Amitraz, que foi diluído conforme a recomendação do fabricante. As teleógenas foram submetidas ao banho de imersão durante 30 segundos e, em seguida, foram distribuídas unitariamente em tubos de ensaios tampados com gaze e deixados na posição horizontal, em temperatura ambiente. Os parâmetros foram avaliados somente após a quenógena (morte) de todas as teleógenas com água destilada. Para a análise dos resultados, utilizou-se o software estatístico Bioestat e o teste de Kruskal-Wallis foi utilizado para a comparação dos grupos (extrato de nim, água destilada e Amitraz) ao nível de 5% de significância. Os resultados experimentais mostraram que o extrato de Azadirachta indica pode ser substituído pelo Amitraz (produto sintético), pois sua eficácia na inibição da oviposição, menor tempo de mortalidade, menor sobrevivência, menor quantidade de ovos férteis e/ou inférteis e menor peso das massas de ovos das teleógenas submetidas a esse extrato foi comprovada nesse trabalho.

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<p>  </p> <p>Vector-borne diseases (VBDs) represent a significant health burden worldwide, threatening approximately 80% of the global population. Insecticide-based vector control is the most effective method to manage many VBDs, but its efficacy has been declining due to high levels of resistance in vector populations to the main insecticide classes which operate via limited modes of action. Therefore, the discovery of new chemistries from non-conventional chemical classes and with novel modes of action is a priority for the control of vectors and VBDs. Natural products (NPs) are diverse in chemical structures and, potentially, modes of action. They have been used as insecticides for many decades and have inspired the development of multiple synthetic insecticides, suggesting the discovery of novel NPs could lead to the development of highly effective insecticides. </p> <p><br></p> <p>In this thesis, I report two studies with a main goal to identify novel mosquito-active insecticide leads that operate via modes of action distinct from existing insecticides. First, I tested the hypothesis that new mosquito-active insecticide leads with novel chemical structures, possibly operating via novel modes of action, can be identified by high-content larval phenotypic screening against a natural product collection and using novel phenotypic endpoints in addition to mortality endpoints. Here, I performed a high-content larval phenotypic screen using first instar (L1) larvae of <em>Aedes aegypti</em> (Linnaeus, 1762) against 3,680 compounds from the AnalytiCon MEGx Natural Product Libraries and a screening platform developed by Murgia et al., (2022). Compounds were screened in a 384-well plate format using the Perkin Elmer Opera Phenix and larvae were scored for lethal and novel phenotypic endpoints. Screening revealed five chemistries that caused larval mortality, including rotenone and a new NP chemistry, NP-4. The identification of rotenone confirmed the ability of the screen to detect mosquito-active NP chemistries. NP-4 caused high levels of larval mortality in the screen, and toxicity was confirmed in a subsequent concentration-response assay against third instar (L3) larvae of <em>Ae. aegypti</em>. 140 chemistries that caused atypical larval phenotypes, including cuticular pigmentation and morphometric changes relative to negative controls, were also identified by the screen. Some of these chemistries may operate by disruption of pathways regulating melanization, growth and development, and novel targets in the insect nervous systems, thus representing potential leads for further insecticide toxicity and mode of action studies. To facilitate quantitative analyses of atypical phenotypes, an attempt was made to assess the morphometrics of the thorax in larvae exposed to test chemistry, relative to control larvae. However, assessment was limited by the number of larvae images of suitable quality for measurements. </p> <p><br></p> <p>In the second study, I tested the hypothesis that metergoline (Murgia et al., 2022) and NP-4 (this study), two chemistries identified by the HTP phenotypic screen described in this project, operate via disruption of targets in the insect nervous systems that are distinct from the current insecticidal modes of products used in mosquito control programs. Specifically, I explored the hypothesis that metergoline operates via one or more insect orthologs of the mammalian G protein-coupled serotonin and dopamine receptors. An electrophysiology study was performed using the suction electrode technique and ganglia of the German cockroach, <em>Blattella germanica </em>(Linnaeus, 1767). To facilitate the investigation of metergoline agonism/antagonism and disruption of invertebrate GPCR signaling, 5-hydroxytryptamine (5-HT; serotonin) was included as a chemical probe. Electrophysiological recordings showed 5-HT (10µM and 1mM) and metergoline (10µM) caused no significant neurological activity at the tested concentrations in comparison to the saline control. However, a consistent neuro-inhibitory trend was observed, suggesting possible agonism of a 5-HT1-like receptor ortholog and antagonism of a putative 5-HT7-like receptor ortholog in the cockroach, respectively.  NP-4 caused significant neuro-inhibition at the tested concentration of 20µM, in comparison to the negative saline control. Given the demonstration of rapid contact toxicity to <em>Ae. aegypti</em> larvae and neurological inhibition in <em>B. germanica</em>, we propose NP-4 may act at one or more conserved targets in the insect nervous systems, which remain to be elucidated. </p> <p><br></p> <p>The significance of the present study is three-fold. First, this study reports the first high-content phenotypic screen of mosquito larvae against a NP collection and identification of 145 mosquito-active chemistries associated with lethal and phenotypic endpoints. These data confirm that the screening platform provided an innovative and effective system to rapidly identify mosquito-active small molecules with potential novel modes of action. Second, metergoline and NP-4 represent potential novel chemical leads for the development of new insecticides that can be incorporated into vector control programs targeting insecticide-resistant populations. Lastly, the study describes the first electrophysiology study of 5-HT, metergoline, and NP-4 via the suction electrode technique in an insect system and contributes new knowledge to the study of the insect serotonergic system, which represents an expanding area of vector biology research given its roles in feeding regulation.  </p> <p><br></p> <p>Future studies resulting from this thesis might include: (1) development of a set of morphometric criteria for quantitative analyses of atypical larval phenotypes, (2) incorporation of new phenotypic endpoints to expand the capacity of the screen to identify novel mode of action chemistries for insecticide discovery, and (3) identification of chemistry candidates suitable for further development from the 140 chemistries associated with atypical larval phenotypes in the primary screen using chemo-informatic and toxicological studies. In addition, studies using reverse transcription-polymerase chain reaction (RT-PCR), cell-based expression systems, mutant/insecticide resistant strains, and patch clamp electrophysiology could be pursued to further investigate the molecular mode of action of metergoline and NP-4, and potential for vector control.</p>

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Microbial natural products have been a source for new drugs for many decades and are unrivaled in their capacity to generate not only future therapeutic agents, but also providing key agents for agricultural and industrial use. LC-MS/MS based metabolomic tools and technologies have been developed that can rapidly dereplicate nonribosomal peptides and statistically identify related congeners in an automated nontargeted process from complex natural product extracts with nanogram sensitivity. This data-base search approach is designed to handle linear, cyclic and cyclic-branched nonribosomal peptides from proteinogenic and nonproteinogenic amino acids without genomic data or traditional bioactivity directed fractionation. Chemometric work-flows combined with a comprehensive metabolomic guided discovery strategy were used to profile the chemical space of a diverse collection of understudied fungal endophytes from fruiting plants. This approach allowed for the prioritization of unique isolates and for the focused discovery, isolation and characterization of distinct outlier metabolites by LC-SPE, 1D and 2D NMR, HRMS and single crystal X-ray analysis. These metabolomic tools and strategies have led to the discovery and characterization of 35 new and over 40 known natural products, many of which are biologically active. This thesis with enabling metabolomic tools and novel discoveries has demonstrated the utility of these analytical methodologies as an effective strategy for the untargeted discovery of new natural products from bacteria and endophytic fungi. / Thesis / Doctor of Philosophy (PhD)

<p dir="ltr">Cyclic peptides are a growing drug class with over 40 FDA-approved drugs, with natural product cyclic peptides being the inspiration for many of these medicines (e.g., the antibiotic daptomycin, the immunosuppressant cyclosporine A, and the antifungal caspofungin). Two major types of cyclic peptide natural products exist: (1) the ribosomally synthesized and post-translationally modified peptides (RiPPs) and (2) those made by nonribosomal peptide synthetases (NRPSs). Even though many uncharacterized cyclic peptide biosynthetic gene clusters (BGCs) exist, the discovery of new cyclic peptide natural products remains a challenge because many BGCs are cryptic. Herein, we describe the development of a new approach to access the products of these cryptic NRPS BGCs and the discovery of many novel bioactive compounds from this approach. Specifically, we utilized bioinformatics programs to predict the amino acid sequences associated with the multimodular NRPS and the presence of a nearby penicillin-binding protein (PBP)-like thioesterase (TE, PBP-TE) to determine that the predicted peptides are head-to-tail cyclized. Following the bioinformatics-guided predictions, solid phase peptide synthesis (SPPS) followed by solution phase cyclization enabled access to a library of predicted cyclic peptides that we then screened for interesting bioactivities. From this screening, we have identified molecules that stimulate the proteasome, inhibit the growth of free-living amoebas, selectively lyse Gram-negative bacteria, and suppress the immune system. Structure activity relationships for these molecules have been determined, with more potent analogs being discovered. Future directions include mechanism of action studies, as well as expanding the peptide library to include more off-loading methods and tailoring enzymes that might modify the peptide after release from the NRPS.</p>

Leiodolide A is a unique natural product isolated from Pacific marine sponges which has provided an interesting target for total synthesis due to its complex structure and undefined stereochemistry. Although synthetic work towards the synthesis of sister compound leiodolide B has been published, the total synthesis of leiodolide A is yet to be achieved but remains an important target due to high potency against leukaemia, non-small lung and ovarian cancers. The convergent strategy towards the synthesis of leiodolide A involved the synthesis of three subunits; a synthetic route to the C21-C25 vinyl stannane is described, and efforts towards the synthesis of the bidirectional C11-C20 subunit are detailed. Asymmetric vinylogous aldol methodology was developed for the installation of the 1,2-syn propionate motif found in the C1-C10 subunit and in other polypropionate natural products, and was shown to be applicable to a range of substrates in moderate diastereoselectivity and excellent enantioselectivity.