Thesis (Ph. D.)--University of California, San Diego, 1998. / Vita. Includes bibliographical references (p. 169-179).

Thesis (Ph. D.)--University of Missouri-Columbia, 2002. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2002. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

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Orientador: Vanderlan da Silva Bolzani / Banca: Jairo Kenupp Bastos / Banca: Patrícia Sartorelli / Resumo: O presente trabalho teve como objetivo o estudo químico da fração diclorometânica das folhas de Senna multijuga, visando o isolamento, purificação e elucidação estrutural de alcalóides piridínicos com potencial farmacológico. Inicialmente foi preparado o extrato hidroalcóolico das folhas, o qual foi submetido à partição líquido/líquido com hexano, diclorometano e acetato de etila. As quatro frações obtidas foram avaliadas por CCD, sendo a fração diclorometânica a de maior concentração alcaloídica. Essa fração foi submetida à extração ácido/base e a fração alcaloídica submetida à CCD preparativa de sílica, que foi desenvolvida com uma mistura dos solventes hexano:CHCl3:AcOEt (1,5:2:6,5), de onde foram isolados cinco alcalóides que apresentaram absorção na região do ultravioleta a 254 e 286 nm. Desta separação obteve-se dois alcalóides puros, 7'-multijuguinona (5), 12'-hidroxi-7'-multijuguinona (2), e os demais foram purificados por cromatografia líquida de alta eficiência (CLAE): 4'-multijuguinato de metila (3), 7'- multijuguinol (4a e 4b) e 12'-hidroxi-7'-multijuguinol (1a e 1b). Estas substâncias tiveram suas estruturas elucidadas pelo uso dos experimentos de Ressonância Magnética Nuclear (RMN) e Espectrometria de Massas com ionização por eletrospray (EM). A partir destas análises foi possível determinar a estrutura de sete substâncias, sendo todas inéditas na literatura. As substâncias apresentaram atividade anticolinesterásica moderada, o que justifica a importância de estudos com metabólitos secundários. Os pares 1a e 1b e 4a e 4b isolados apresentam isomeria que ainda não determinada. Pelas análises do perfil alcaloídico determinado no estudo sobre a espécie, pode-se constatar que os demais órgãos também acumulam alcalóides, porém, em concentrações diferentes, prevalencendo um ou dois deles. / Abstract: This present work deals with the chemical study of the dichloromethane fraction of the Senna multijuga leaves, aiming the isolation, purification and structural elucidation of the new bioactive pyridine alkaloids, which can be useful for further pharmacological evaluation. The leaves ethanol extract was subjected a liquid/liquid partitions with hexane, dichloromethane and ethyl acetate, resulting in four fractions, which were evaluated for TLC, being the dichloromethane the fraction with the highest concentration of alkaloids. This fraction was subjected to acid/basic extraction, and the alkaloidal fraction (1.42 g) was subjected to silica preparative TLC, and eluted with a solvent system: n-hexane:CHCl3:AcOEt (1.5:6.5:2), which were isolated five alkaloids. From this procedures were obtained alkaloids, 7'-multijuguinone (5), 12'-hydroxyl-7'- multijuguinone (2) and the resulting mixture was further purified by HPLC yielding methyl 4'-multijuguinate (3), 7'-multijuguinol (4a e 4b) and 12'-hydroxyl-7'- multijuguinol (1a e 1b). The structure of all alkaloids were determined by RMN and mass spectral data analysis resulting in seven new moderate acetylcholinesterase inhibitor derivatives. The alkaloids pairs, 1a;1b and 4a;4b, are isomeric mixtures, not identified yet. Through the alkaloid profile has been established after several data accumulated from this plant, it was observed that others organs also accumulate the same alkaloids, but in different concentration prevailing one or two alkaloids. / Mestre

Orientador: Ian Castro-Gamboa / Coorientador: Márcia Nasser Lopes / Banca: Silvia Noeli López / Banca: Renato Lajarim Carneiro / Resumo: No presente trabalho foram detectados e analisados os metabólitos secundários majoritários das espécies Jatropha multifida L. e J. gossypifolia L., fazendo uso de ferramentas quimiométricas de vanguarda, visando a otimização do processo de extração para, posteriormente, obter cromatogramas de fingerprint através da técnica acoplada CLAE-UV/DAD. Para a espécie J. gossypifolia L. a mistura 1 : 1 clorofórmio : isopropanol apresentou a melhor condição de extração enquanto para J. multifida L. a composição 2/3 : 1/6 : 1/6 de etanol : acetona : 1,4-dioxano foi a que obteve a melhor resposta. Os cromatogramas de fingerprint foram realizados fazendo uso de uma coluna monolítica C-18 (5 µm), como fase estacionária, enquanto a fase móvel para análise da espécie J. gossypifolia L. foi composta por água e uma mistura de solventes orgânicos, MeOH : ACN, na proporção (68 : 32), em gradiente exploratório de 5-100% de fase orgânica. Para a espécie J. gossypifolia L., as condições otimizadas foram: temperatura de coluna de 30 °C, fluxo em 2,0 mL·min-1 e o volume de injeção de 30 µL. Para J. multifida L. a fase móvel foi composta por água e uma mistura MeOH : ACN 1 : 1 em gradiente exploratório 5-100% de fase orgânica. A temperatura de coluna de 40 °C, o fluxo de 2,5 mL·min-1 e o volume de injeção foi de 30 µL. Foram realizados bioensaios in vitro, tais como a redução do reagente DPPH (ação antioxidante), inibição da polimerização da hematina bovina (ação antimalárica), inibição enzimática de acetilcolinesterase (doença de Alzheimer) e o ensaio da inibição do crescimento de fungos fitopatógenos. Nenhum dos extratos brutos avaliados, apresentou atividade significativa quando comparados com os padrões. Quanto à detecção dos metabólitos, a aplicação de métodos de desreplicação aos extratos permitiram a identificação de algumas classes... (Resumo completo, clicar acesso eletrônico baixo) / Abstract: The main goal of this research was to detect and analyze major secondary metabolites from Jatropha multifida L. and J. gossypifolia L. species, using state of art techniques in chemometrics aiming the optimization of the extraction process prior to the acquisition of the fingerprint chromatogram using HPLC-UV/DAD. The optimized extraction condition for Jatropha gossypifolia was the binary mixture 1:1 chloroform:isopropanol, while to Jatropha multifida L. the mixture was ternary consisting of 2/3:1/6:1/6 ethanol:acetone:1,4-dioxane. The fingerprint chromatograms were runned using an exploratory gradient consisting of 5-100% of organic solvent, using a C-18 (5 µm) column, as stationary phase, and then the mobile phase was optimized, through the use of chemometrics for each species. In the case of Jatropha gossypifolia L. the phase consisted in a mixture of 68:32 MeOH:ACN, under a column temperature of 30 oC, injection volume of 30 µL and a flow of 2.0 mL.min-1. For Jatropha multifida L. was 1:1 MeOH:ACN, under column temperature of 40 oC, flow of 2,5 mL.min-1 and an injection volume of 30 µL. Some in vitro bioassays were performed, such as, reduction of the reagent DPPH (antioxidant action), inhibition of polymerization of the haematin bovine (antimalarial), enzymatic inhibition of the acetylcholinesterase (Alzheimer's disease) and the assay of inhibition of the growth of phytopatogenic fungi. None of the crude extracts showed significant activities when compared to the used standards. The application of dereplication methods allowed the identification of some classes of compounds, already reported for Jatropha, such as terpenoids and flavonoids. The strategy developed to performed the dereplication, used an in silico approach through the matching and analysis of the spectrometric and spectroscopic data sets obtained using NMR and HPLC-HRMS(ESI)-MS2 with databases of high... (Complete abstract click electronic access below) / Mestre

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.

Cyclic peptides possess desirable characteristics as potential pharmaceutical scaffolds. The cyanobactin family of cyclic peptide natural products boast diverse structures and bioactivity. Exemplars are the patellamides, which have attracted attention due to their ability to reverse the effects of multi-drug resistance in human leukemia cells. In addition to their macrocyclic architecture patellamides contain azol(in)e heterocycles and d-amino acids. This structural complexity makes them challenging targets for chemical synthesis. Understanding their biosynthesis will enable the development of a biotechnological ‘toolkit' for the synthesis of new pharmaceutical compounds. Patellamides are ribosomally-synthesised and post-translationally modified peptides (RiPPs) and much of their biosynthesis has been elucidated, however there are still elements of their biosynthesis that are not yet fully understood. PatA and PatG contain C-terminal domains of unknown function (DUFs). The crystal structure of PatG-DUF has been solved and subsequent to biochemical and biophysical investigation PatG-DUF was found not to constitute an essential part of the biotechnological ‘toolkit' and can be excluded from in vitro enzyme-based synthesis of cyanobactin-like cyclic peptides. The cyanobactin heterocyclases are able to introduce heterocycles into a peptide backbone, seemingly irrespective of the neighbouring residues; however a molecular rational governing substrate recognition is unknown. Additionally the mechanism of heterocyclisaton is disputed. Analysis of crystal structures of LynD in complex with cofactor and substrate (solved by Dr Jesko Koehnke) enabled the active site and substrate recognition site to be located. A new mechanism for heterocyclisation has been proposed. Guided by the substrate recognition observed in complex structures a constituently active heterocyclase (AcLynD) has been engineered, which is able to process short, leaderless peptide substrates. Epimerisation in cyanobactin biosynthesis is believed to be spontaneous, but its precise timing is uncertain. NMR analysis of selectively labelled peptide substrates processed by the modifying enzymes, identified epimerisation to be spontaneous on the macrocycle, regardless of whether the neighbouring heterocycles have been oxidised. A one-pot in vitro synthesis of cyanobactins has been developed, and employed to create a number of patellamide D analogues to ascertain structural-activity relationships.

The total syntheses of isomeric aglain natural products (±)-foveoglin A and (±)-perviridisin B have been achieved via ESIPT (excited states intramolecular proton transfer)-mediated selective (3+2) photocycloaddition of 3-hydroxyflavone with trans,trans-1,4-diphenyl-1,3-butadiene (DPBD). Using TADDOLs or Pirkle’s alcohol as chiral hydrogen-bonding additives, enantioselective ESIPT photocycloaddition was performed providing access to (+)-foveoglin A which also enabled confirmation of its absolute configuration. Photophysical studies have been conducted for ESIPT photocycloadditions revealing the possibility for exergonic electron transfer from the excited triplet state of 3-hydroxyflavones to dipolarophiles with appropriate redox potentials, which also provided a rationale for the observed selectivity. Further application of ESIPT photocycloaddition using 1-alkyl-2-aryl-3-hydroxyquinolinones (3-HQ’s) to synthesize nitrogen-containing analogues of flavaglines, aza-rocaglates, will be described. Differential photoreactivity between 2-aryl-3-hydroxyquinolinones (N-H-3-HQ’s) and 1-alkyl-2-aryl-3-hydroxyquinolinones (N-alkyl-3-HQ’s) was observed. A rationale for this observation was also provided based on photophysical measurements. A novel method to synthesize N-alkyl-3-hydroxyquinolinones using sodium hydride as base was discovered to overcome limited access to photoreaction substrates. A recirculating photoflow reactor was applied to the ESIPT photocycloaddition to increase the efficiency of the reaction. Initial biological testing indicates that aza-rocaglates do not possess activity in comparison to related rocaglates which also provides further information on the SAR of the natural product scaffold. Computational studies were conducted in collaboration with Prof. David Coker’s group using Metadynamics simulation to study tetrakis-9-phenanthrenyl TADDOL-mediated asymmetric ESIPT photocycloadditions. With a choice of collective variables based on hydrogen-bonding interactions between TADDOL and 3-hydroxyflavone, the free energy surfaces associated with formation of the hydrogen-bonding complexes between TADDOL and the 3-hydroxyflavone/methyl cinnamate or 3-hydroxyflavone/stilebene pairs were obtained. The representative three-component model from the obtained free energy minimum indicate that in addition to hydrogen-bonding interactions, π-π stacking between the phenanthren-9-yl groups of TADDOL and the 3-hydroxyflavone substrate also facilitate the asymmetric photocycloaddition which has provided information for future asymmetric catalyst designs. / 2020-11-06T00:00:00Z

This thesis describes the development of a synthetic route towards daphlongeranine B, an alkaloid isolated from the fruits of Daphniphyllum longeracemosum, by utilising an intramolecular Michael addition to form its unique tricyclic core. <strong>Chapter 1</strong> gives a general introduction to the family of Daphniphyllum alkaloids together with some recent examples, from the literature, illustrating some synthetic attempts towards structurally similar alkaloids. This chapter also features our retrosynthetic analysis of daphlongeranine B. <strong>Chapter 2</strong> details the synthesis of the model spirocyclic enone 72 which was the vital building block needed to investigate the key intramolecular Michael addition. This key reaction was then successfully validated and access to the unique tricyclic core 64 of daphlongeranine B was made possible. <strong>Chapter 3</strong> expands the scope of the key intramolecular Michael addition step. This chapter first describes a synthetic route to the Î2-substituted spirocyclic enone 112 and subsequently validates the key intramolecular Michael addition step to give the tricyclic core 138 of daphlongeranine B. <strong>Chapter 4</strong> details a synthetic route towards the spirocyclic fragment 141 by utilising a Baker's yeast reduction and a tandem addition/cyclisation reaction.