Madeirolide A (1) is a structurally novel polyketide natural product first isolated from the deep-sea sponge Leiodermatium sp. by Wright in 2009. Initial biological investigations of madeirolide A revealed potent inhibition of the fungal pathogen Candida albicans but failed to determine any appreciable cytotoxicity when tested against a limited range of cancer cell lines. The unusual bioactivity of madeirolide A coupled with uncertainty over the true stereostructure of the natural product makes it a compelling target for synthesis. This thesis discloses synthetic efforts towards the total synthesis of madeirolide A with an emphasis on the construction of the all-cis C21 - C27 eastern tetrahydropyran. Chapters 1 and 2 provide an introduction to the importance of natural products in drug discovery and outline the context of this project with details of the isolation and biological activity of madeirolide A. Previous synthetic efforts are also reviewed including those from within the group which formed the basis of the present studies. Chapter 3 describes the synthesis of a fully elaborated C1 - C11 fragment, building upon previously published work in the group. Specifically, it details the successful completion of a modified approach designed to avoid some of the major challenges previously encountered such as undesired migration of protecting groups and challenges in selectively installing an (E)-vinyl iodide. Chapter 4 discusses ongoing efforts towards the challenging C12 - C27 fragment of madeirolide A. The stereocontrolled synthesis of several linear C19 - C27 precursors is outlined, followed by details of screening reactions conducted to affect the desired oxy- Michael cyclisation. Additionally, extensive computational studies have been undertaken in an attempt to rationalise the frustrating lack of reactivity observed with the goal of developing a substrate suitably elaborated to cyclise. Finally, the asymmetric synthesis of the C13 - C17 subfragment is outlined, which will provide eventual access to the eastern tetrahydrofuran. Chapter 5 summarises the synthetic work carried out thus far and explores potential strategies for the future completion of the natural product with a focus on alternative disconnections of the eastern tetrahydropyran.

O presente trabalho descreve o estudo fitoquímico de Dracontium loretense Krause, que ocorre na Amazônia, e, a planta é popularmente usada no tratamento de picada de cobra e de algumas moléstias. O material para a análise fitoquímica foi coletado na selva baixa situada nos arredores de Pucallpa, no Departamento de Ucayali, no Perú. Os rizomas secos e moídos forneceu, após extração com hexano, etanol e etanol aquoso, os respectivos extratos. Estes, submetidos a partição com solventes orgânicos e fracionamentos cromatográficos dos resíduos das fases resultantes, permitiram o isolamento de constituintes apoiares ou semi-polares como sitosterol, estigmasterol, ácido p-hidróxi-benzóico, sitosterol acil-glicosilado, 7-oxo-sitosterol acil-glicosilado e uma mistura de compostos acil-glicosilados. As frações polares foram acetiladas antes do fracionamento, possibilitando o isolamento de uma mistura de carboidratos com predominância de etil-glicosídeo acetilado. A elucidação estrutural das substâncias isoladas foi baseada em métodos espectrométricos: EM, RMN de 1H e de 13C. Os compostos acilados foram hidrolizados e os ácidos graxos resultantes metilados antes de serem submetidos a análise no sistema CG-EM. Os testes biológicos foram realizados com as frações apoiares e polares dos extratos para avaliar a atividade anti-edematogênica. Estes ensaios empregam o veneno de Bothrops atrox (jararaca). Os testes mostraram que ambas as frações inibiam o edema, entretanto com a diferença que a resposta é mais acentuada nas frações polares. / This work describes phytochemical analysis of an araceous species Dracontium loretense, which occurs in Amazon Region and is popularly used the against snakebite and treatment of some diseases. The plant material was collected in the lowland situated around Pucallpa, Ucayali State, Peru. The dried and milled rhizomes were sucessively extracted at room temperature with hexane, alcohol and diluted alcohol, yielding respective extracts after solvent distillation. The solvent partitions and chromatographic separations of extracts afforded sitosterol, stigmasterol, p-hydroxybenzoic acid, sitosterol- and 7-oxo-sitosterol acyl-glucosylated and a mixture of acyl-glucosylated compounds. The polar fractions were acetylated before the purification and the isolation through cromatographic techniques yielded a mixture -of peracetylated carbohydrates and the 2,3,4,6-tetra-acetyl-1-ethyl glucoside. Structure determination of isolated compounds was based on usual spectrometric techniques as Mass Spectrometry and 1H and 13C Nuclear Magnetic Resonance. The natural acylated compounds were submitted to hydrolysis and t-he resulting fat acids were methylated, before submissuion foranalysis on Gas Chromatograph-Mass spectrometer system. Evaluation of anti-edematogenic activity using Bothrops atrox venom was carried out with polar and apolar fractions. It was observed that polar fractions showed higher edema inhibition property.

Esse trabalho descreve o estudo monitorado de extratos de origem microbiológica e vegetal. Com o objetivo de identificar compostos com atividade antioxidante e/ou inibidores da enzima acetilcolinesterase em extratos de origem microbiológica e vegetal do cerrado brasileiro, uma triagem de atividade foi realizada utilizando ensaios simples e rápidos. Nessa triagem dois extratos promissores foram selecionados para os estudos de identificação dos compostos responsáveis pela atividade inicial. O trabalho de purificação foi iniciado com a fração em acetato de etila do extrato etanólico da actinobactéria-36 (50PL), Streptomyces sp., fermentado em meio de canjica amarela que apresentou atividade nos dois ensaios realizados. As atividades antioxidante e anticolinesterásica são relatadas pela primeira vez para essa actinobactéria. Nesse estudo foram identificados dois compostos, o éster metílico do ácido cis-6, cis-8 octadecadienóico e o tetradecanal. Da espécie Psychotria carthagenensis, uma planta da família Rubiaceae, foram objeto de estudo as frações hexânica e acetato de etila oriundas do extrato etanólico das folhas, o extrato hexânico das folhas e o extrato etanólico dos caules. A espécie P. cartahgenensis foi investigada quanto à presença de alcalóides uma vez que é utilizada juntamente com as espécies Psychotria viridis e Banisteriopsis caapi no preparo de uma bebida alucinógena conhecida como ayahuasca. A partir dos extratos etanólicos das sementes, caules e folhas foi realizada uma extração ácido-base resultando em frações ricas em compostos nitrogenados. As frações de alcalóides totais foram analisadas em TLC e revelador específico, o cloro-iodoplatinado, evidenciando a presença de alcalóides. As frações foram analisadas por EM (desreplicação) resultando na identificação de 5 compostos nitrogenados. / This work describes the monitored study of extracts from microbiological and plant origin. In order to identify compounds with antioxidant action and/or inhibitors of acetylcholinesterase enzyme in extracts of microbial and plants of the Brazilian Cerrado vegetation, screening for these activities was performed using simple and rapid tests. From this screening, two promising extracts were selected for identification of the compounds responsible for the initially observed activity. Purification was started with the ethyl acetate fraction in the ethanol extract of actinobacteria-36 (50PL), Streptomyces sp., fermented in a yellow hominy culture medium that displayed activity in both tests. Antioxidant and anticholinesterase activities are reported for this actinobacteria for the first time. Two compounds were identified, namely 6(Z),8(Z)-octadecadienoic acid, methyl ester and tetradecanal. The hexane and ethyl acetate fractions of the ethanol extract of the leaves as well as the ethanol extract of the stems from the Psychotria carthagenensis species, a plant of the Rubiaceae family, were studied. This species was investigated for the presence of alkaloids, because it is used together with the species Psychotria viridis and Banisteriopsis caapi in the preparation of a hallucinogenic drink known as ayahuasca. Acid-base extractions of the ethanol extracts of the seeds, stems, and leaves of this plant were carried out, resulting in fractions rich in nitrogen compounds. The total alkaloids fractions were analyzed by TLC and specific revealing with chlorine-iodoplatinate, which evidenced the presence of alkaloids. The fractions were analyzed by MS (derreplication), which allowed for identification of five nitrogen compounds.

A Química de Produtos Naturais é uma especialidade que procura descrever e mapear os compostos orgânicos provenientes do metabolismo secundário dos seres vivos. Embora essas substâncias não estejam diretamente relacionadas à obtenção de energia e ao crescimento, são detentoras de pronunciadas atividades biológicas, que visam ampliar a sobrevivência e adaptação das espécies que as produzem às condições ambientais em que estão inseridas, desempenhando assim, importantes funções ecológicas. Nesse contexto, a expressiva biodiversidade brasileira contribuiu para o florescimento desse estudo, tornando-se uma produtiva e reconhecida linha de pesquisa no país. Apesar de muito valorizado na pesquisa, ou seja, nos cursos de pós-graduação em Química, dados preliminares apontam que o ensino dos produtos naturais está pouco presente nos cursos de Bacharelado e Licenciatura em Química de diversas universidades públicas brasileiras. Sendo assim, o presente trabalho procura verificar como o conhecimento de Química de Produtos Naturais é expresso nos cursos de graduação em Química, através da análise de sua organização curricular e sob as perspectivas discentes e docentes. Para isso, foi necessário analisar os currículos dos cursos de química (disciplinas e ementas), realizar questionários a alunos de cursos de graduação e entrevistas com professores-pesquisadores da área. Os resultados obtidos têm apontado para a existência de superficialidade na abordagem de conhecimentos acerca dos produtos naturais nos cursos de graduação em Química, mesmo com amplas possibilidades de tratamentos desse tema. Os estudantes de Química confirmaram pouca abordagem da Química de Produtos Naturais em seus cursos, apesar de terem admitido significativo interesse por esse assunto e terem associado seu estudo com uma grande variedade de campos de conhecimento, evidenciando intrínseco caráter interdisciplinar. Além de concordarem com a baixa inserção dos produtos naturais nos cursos de graduação em Química, os docentes têm enfatizado a necessidade de colaboração e integração dos conhecimentos científicos de forma interdisciplinar e a valorização da nossa biodiversidade. / The Chemistry of Natural Products is a science specialty that aims to describe and map the organic compounds from the secondary metabolism of living beings. Although are not directly related to obtaining energy and growth, these substances have pronounced biological activities, which aim to enhance the survival and adaptation of producing species to the environmental conditions in which they live, performing important ecological functions. In this context, the expressive Brazilian biodiversity contributed to the development of this study, becoming a productive and recognized line of research in the country. Although highly valued in research, i.e. in graduate courses in Chemistry, preliminary data indicate that the teaching of natural products is absent from the undergraduate courses in Chemistry from several Brazilian public universities. Thus, this work intends diagnose how the Natural Products Chemistry knowledge is expressed in undergraduate courses in Chemistry, through the analysis of their curricula and under the students and teachers perspectives. For this, we carried out a review of undergraduate chemistry curricula (disciplines and summaries), questionnaires to students of undergraduate courses in chemistry, pharmacy and biotechnology and interviews with chemistry teachers who work as researchers in the area of natural products. The results have highlighted the existence of superficiality in knowledge approach on the natural products in undergraduate courses in chemistry, even with extensive possibilities. Despite associate the study of Natural Products Chemistry with a wide variety of fields of knowledge, (showing intrinsic interdisciplinary character), and admit significant interest in this subject, chemistry graduate students have pointed to little approach in their courses. Teachers agree that there is low insertion of natural products chemistry contents in chemistry courses, emphasizing the necessity to value our biodiversity, establishing collaborations, and promoting the integration of scientific knowledge in an interdisciplinary approach.

Over 4,000 flavonoids have been identified, and among these, many of them are known to possess cardioprotective, anti-inflammatory, antimicrobial, and antitumor effects. However, most of these properties have yet to be fully understood. In this study, extracts from Gnaphalium gracile, thought to possess a mixture of flavonoids, have been tested for cytotoxic activity on pancreatic (MiaPaca, Panc28), colon (HCT-116, Caco-2), and prostate (PC3, LNCaP), cancer cell lines. Polar extracts from the leaves of G. gracile have the most cytotoxic effect on these cancer cell lines, particularly the prostate cancer cell lines PC3 and LNCaP. Evidence suggests the extracts have antineoplastic effects on these cancer cells lines possibly due to differentiation status on pancreatic and colon cancer, but not prostate cancer. Cytotoxic activity is not dependent on tumorigenic potential. Further research is needed to identify the bioactive compounds within these extracts.

No description available.

New antibiotics with novel targets or mechanisms of action are needed to counter the steady emergence of bacterial pathogens that are resistant to antibiotics used in the clinic. MraY, a promising novel target for antibiotic development, initiates the lipid cycle for the biosynthesis of peptidoglycan cell wall, which is essential for the survival of most, if-not-all, bacteria. MraY is an enzyme that catalyzes the transfer and attachment of phospho-MurNAc-pentapeptide to a lipid carrier, undecaprenylphosphate. Muraymycins are recently discovered lipopeptidyl nucleoside antibiotics that exhibit remarkable antibiotic activity against Gram-positive as well as Gram-negative bacteria by inhibiting MraY. We conducted a thorough examination of the metabolic profile of Streptomyces sp. strain NRRL 30473, a known producer of muraymycins. Eight muraymycins were isolated and characterized by a suite of spectroscopic methods, including three new members of muraymycin family named B8, B9 and C5. Muraymycins B8 and B9, which differ from other muraymycins by having an elongated fatty acid side chain, showed potent antibacterial activity against Escherichia coli ∆tolC mutant and pM IC50 against Staphylococcus aureus MraY. Muraymycin C5, which is characterized by an N-acetyl modification of the disaccharide’s primary amine, greatly reduced its antibacterial activity, which possibly indicates this modification is used for self-resistance. In addition to the discovery of new muraymycins, eleven enzymes from the biosynthetic pathway were functionally assigned and characterized in vitro. Six enzymes involved in the biosynthesis of amino ribofuranosylated uronic acid moiety of muraymycin were characterized: Mur16, a non-heme, Fe(II)-dependent α-ketoglutarate: UMP dioxygenase; Mur17, an L-threonine: uridine-5′-aldehyde transaldolase; Mur20, an L-methionine:1-aminotransferase; Mur26, a low specificity pyrimidine nucleoside phosphorylase; Mur18, a primary amine-requiring nucleotidylyltransferase; Mur19, a 5-amino-5-deoxyribosyltransferase. A one-pot enzyme reaction was utilized to produce this disaccharide moiety and its 2′′-deoxy analogue. Two muraymycin-modifying enzymes that confer self-resistance were functionally assigned and characterized: Mur28, a TmrB-like ATP-dependent muraymycin phosphotransferase, and Mur29, a muraymycin nucleotidyltransferase. Notably, Mur28 preferentially phosphorylates the intermediate, aminoribofuranosylated uronic acid, in the muraymycin biosynthetic pathway to produce a cryptic phosphorylated-dissacharide intermediate. Mur23 and Mur24 were assigned as two enzymes that modify the cryptic phosphorylated intermediate by attachment of an aminopropyl group. Mur24 catalyzes the incorporation of butyric acid into the phosphorylated-disaccharide. Following the incorporation, Mur23 catalyzes a PLP-dependent decarboxylation. Finally, Mur15, which belongs to the cupin family, is functionally assigned as a non-heme, Fe(II)-dependent α-ketoglutarate dioxygenase that catalyzes the β-hydroxylation of a leucine moiety in muraymycin D1 to form muraymycin C1. Mur15 can also hydroxylate the γ-position of leucine moiety to muraymycins with fatty acid chain in β-position.

Many years of study have revealed that fungi are excellent sources of novel bioactive secondary metabolites. Some of these secondary metabolites possess therapeutic qualities that improve the quality of life for millions of people. Such metabolites include well known classes such as the penicillins, cephalosporins, and statins, yet many fungi remain underexplored as sources of biologically active metabolites. The research described in this thesis employs an ecology-based approach to targeting fungi for chemical investigation, and describes studies of fungi from two niche groups, fungicolous/mycoparasitic and endophytic fungi, as possible sources of new secondary metabolites with biological activities. In a parallel project, the structures of bioactive compounds isolated from peanut seeds that had been subjected to fungal attack were elucidated in the pursuit of compounds with beneficial bioactivities. Mycoparasitic fungi are those that colonize other fungi by parasitizing the host, often leading to damage to the host fungus. Fungicolous fungi are those that colonize other fungi, but have not been proven to be true mycoparasites. The damage often caused by colonization of host fungi indicates that mycoparasitic and fungicolous fungi can produce antifungal compounds. Chemical investigations of such fungi described in this thesis afforded 37 compounds of various biosynthetic types, seven of which were new. Many of these compounds show antifungal, antimicrobial, and/or cytotoxic effects. Endophytic fungi live asymptomatically within plant tissues and in some cases may provide benefits to the host plant through the production of secondary metabolites. Chemical investigations of corn, wheat, and sorghum endophytes led to the isolation and characterization of 21 compounds, seven of which were new. Many of the endophyte metabolites encountered in this work showed antifungal, antimicrobial, and/or cytotoxic effects. The compounds isolated from peanut seeds were produced in response to fungal attack by an Aspergillus caelatus strain. All of these compounds were stilbene-derived phytoalexins, which are considered to be inducible chemical defenses whose production is elicited or enhanced upon microbial attack. Further studies of these newly identified compounds and their production could lead a a better understanding of how the plant defends itself. Such knowledge could enable researchers to manipulate this mechanism to obtain greater peanut resistance to invasion by pests. Additionally, the health benefits from related stilbene-derived compounds (e.g. resveratrol) from peanuts and other plants have been widely established. Knowledge about the presence of compounds of this type could add to the importance of peanut crop production. The compounds identified in this work were isolated using multiple chromatographic techniques, and the structures were established based on analysis of 1D and 2D NMR data combined with MS, chemical derivatizations, and/or optical measurement data. Absolute configuration assignments were achieved by application of Mosher's Method, CD spectral analysis, and/or chemical derivatizations. Details of the isolation, structure elucidation, and biological activity of these compounds are presented in this thesis.

This thesis describes the chemical investigation of three marine sponges from Antarctica and the total syntheses of natural products erebusinone (12) and its derivative, erebusinonamine (52). Investigation of the yellow Antarctic marine sponge Isodictya setifera resulted in the isolation of two secondary metabolites, purine analog (32) and 3-hydroxykynurenine (24). Chemical investigation of Isodictya setifera led to the isolation of six secondary metabolites which included 5-methyl-2-deoxycytidine (25), uridine (28), 2-deoxycytidine (31), homarine (37), hydroxyquinoline (33), 3-hydroxykynurenine (24). The latter two compounds were found to be intermediates of tryptophan catabolism in crustaceans. From the Antarctic marine sponge Isodictya antractica ceramide analog (39) was isolated and its chemical structure was assigned by a combination of spectroscopic and chemical analyses. Stereochemistry was determined by modified Mosher's method. Erebusinone (12), a yellow pigment isolated from the Antarctic marine sponge Isodictya erinacea has been implicated in molt inhibition and mortality against the Antarctic crustacean amphipod, Orchomene plebs, possibly serving as a precursor of a xanthurenic acid analog. Thought to act as a 3-hydroxykynurenine 24 mimic, erebusinone (12) may be involved chemical defense. This appears to be the first example in the marine realm of an organism utilizing tryptophan catabolism to modulate molting as a defensive mechanism. To further investigate the bioactivity and ecological role of erebusinone (12), the synthesis of this pigment was carried out in an overall yield of 44% involving seven steps which were economical and convenient. Erebusinonamine (52) was also similarly synthesized in eight steps with an overall yield of 45%.

>Magister Scientiae - MSc / The continued emergence of bacterial resistance to the antibiotics currently employed to treat several diseases has added to the urgency to discover and develop novel antibiotics. It is well established that natural products have been the source of the most effective antibiotics that are currently being used to treat infectious diseases and they remain a major source for drug production. Natural products derived from marine microorganisms have received much attention in recent years due to their applications in human health. One of the biggest bottlenecks in the drug discovery pipeline is the rediscovery of known compounds. Hence, dereplication strategies such as genome sequencing, genome mining and LCMS/MS among others, are essential for unlocking novel chemistry as it directs compound discovery away from previously described compounds. In this study, the genome of a marine microorganism, Thalassomonas viridans XOM25T was mined and its antimicrobial activity was assessed against a range of microorganisms. Genome sequencing data revealed that T. viridans is a novel bacterium with an average nucleotide identity of 81% to its closest relative T. actiniarum. Furthermore, genome mining data revealed that 20% of the genome was committed to secondary metabolisms and that the pathways were highly novel at a sequence level. To our knowledge, this species has not previously been exploited for its antimicrobial activity. Hence, the aim of this study was to screen for bioactivity and identify the biosynthetic gene/s responsible for the observed bioactivity in T. viridans using a bioassay-and-genome- guided isolation approach to assess the bioactive agent. The bioassay-guided fractionation approach coupled to LCMS/MS led to the identification of a novel antimicrobial protein, TVP1. Bioinformatic analyses showed that TVP1 is a novel antimicrobial protein that is found in the tail region of a prophage in the T. viridans genome. Phage-derived proteins have previously been shown to induce larval settlement in some marine invertebrates. Since the mechanism of action of TVP1 remains unknown, it remains a speculation whether it may offer a similar function. More research is required to determine the biotechnological application and the role of TVP1 in its host and natural environment.