Dissertations / Theses on the topic 'Antitrypanosomal'

The 1,4-benzodiazepin-2-one motif has been taken as a privileged skeleton for making antitrypanosomal agents. A library of over sixty 1,4-benzodiazepin-2-one derivatives has been synthesised employing novel synthetic routes. These derivatives were characterised spectroscopically, by mass spectrometry, and by combustion analysis. Five derivatives were characterised, in the solid state, by single crystal X-ray crystallography. Biological assays of the library of compounds against Trypanosoma brucei brucei (T. b brucei) revealed a range of trypanocidal activities. A first generation library activity showed biological activity as low as 6.25 μM (minimum inhibitory concentration, MIC value). Structure activity relationships in this work revealed that an aromatic substituent at the C3 and N1 positions of the 1,4-benzodiazepin-2-one are important for improved bioactivity. In order to improve biological activity, putative P-2 transporter motifs were exploited in the 1,4-benzodiazepin-2-ones. Structural activity relationships indicate that the inclusion of a guanidine moiety, a putative P-2 transporter motif, can improve the biological activity of these molecules. In vitro screening of these compounds showed a range of antitrypanosomal activities against T. b.brucei, with a number in the low micromolar range (MIC ≥ 0.78 μm) including (S)-1-(4-((3-benzyl-2-oxo-5-phenyl-2,3-dihydro-1H-benzo[e][1,4]diazepin-1-yl)methyl)phenyl)guanidine, (S)-1-(3-((3-benzyl-2-oxo-5-phenyl-2,3-dihydro-1H-benzo[e][1,4]diazepin-1-yl)methyl)phenyl)guanidine, (S)-1-(4-((3-benzyl-5-cyclohexyl-2-oxo-2,3-dihydro-1H-benzo[e][1,4]diazepin-1yl)methyl)phenyl)-guanidine and (S)-1-(1-benzyl-5-cyclohexyl-3-isopropyl-2-oxo-2,3-dihydro-1H-benzo[e][1,4]diazepin-7-yl)guanidine)phenylquanidine.

Le paludisme, la maladie la plus dévastatrice des régions tropicales fait l’objet de nombreuses recherches ayant pour but de trouver des médicaments préventifs, du matériel de protection, de nouveaux traitements, des vaccins, …

Notre travail s’est inscrit dans la recherche des composés naturels actifs sur l’agent pathogène, le Plasmodium. Nos investigations phytochimiques et pharmacologiques ont porté sur Triclisia sacleuxii, une plante utilisée en médecine traditionnelle pour traiter diverses maladies dont deux parasitaires: la schistosomiase et l’ascardiose. Elle est aussi employée dans la préparation du poison de flèche. De plus, T. sacleuxii appartient à la famille des Menispermaceae, une famille riche en alcaloïdes bisbenzylisoquinoléiques (BBIQ). Ces composés ont de nombreuses propriétés biologiques dont l’activité antipaludique et trypanocide. Plusieurs autres espèces appartenant au genre Triclisia sont utilisées en médecine traditionnelle pour traiter la fièvre, le paludisme et d’autres pathologies. Ces éléments ont motivé la recherche dans cette plante des composés à activité antiplasmodiale. En effet, la plupart des composés que nous en avons isolés (p 12) sont actifs aussi bien sur la souche chloroquino-sensible (3D7) que sur la souche chloroquino-résistante (W2) que nous avons testées.

Deux d’entre eux ont en plus une activité plus élevée vis-à-vis de la souche choroquino-résistante.

Les composés actifs sur Plasmodium falciparum ont également montré une toxicité à l’égard de Trypanosoma brucei brucei, une sous-espèce apparentée à celles qui sont à la base de la maladie du sommeil en Afrique Centrale et de l’Est.

A part les usages mentionnés précédemment, T. sacleuxii est en plus employée comme antidote contre les morsures de serpents. Ce qui voudrait dire qu’elle pourrait renfermer des inhibiteurs d’enzymes.

Aussi, des BBIQ ont déjà démontré une activité inhibitrice de l’acétylcholinéstérase (AChE) et des phospholipases A2. Sur base de ces informations, nous avons assigné un troisième objectif à notre investigation qui cible l’AChE en correlation avec la maladie d’Alzheimer (MA). La MA est une pathologie neurodégénérative qui affecte en général les personnes âgées de plus de 60 ans, caractérisée entre autres par une perte progressive de la mémoire, une détérioration de plusieurs fonctions cognitives, de troubles neurologiques et du comportement, … Les différents extraits alcaloïdiques ont montré un degré d’inhibition de l’AChE élevé ( 80 - 90%) à une concentration de 100 μg/ml. Avec les composés purs, l’inhibition est très variable (30 - 90 %) suivant la structure. Enfin, nous avons effectué des investigations pour déterminer le mode d’action antiplasmodiale des BBIQ majeurs isolés de T. sacleuxii. Il apparaît que non seulement toutes les BBIQ n’agissent pas par un même mode d’action, mais aussi un même composé pourrait agir simultanément suivant deux ou plusieurs mécanismes différents.

Malaria, the most devastating disease in tropical areas, is currently a target of numerous researches, aiming to find preventive medicines, protective tools, new treatments and vaccines. In a search for antiplasmodial natural compounds, we have undertaken phytochemical and pharmacological investigations on Triclisia sacleuxii, used in traditional medicine to treat various ailments including two parasitological diseases; schistosomiasis and ascariasis. It is also used as an arrow poison.

Triclisia sacleuxii belongs to the Menispermaceae family, which is known to contain bisbenzylisoquinolines. These components have shown various biological activities among which antimalarial and trypanocidal activity. Furthermore, many Triclisia species are used in traditional medicine for treating fever and malaria along with other disorders.

With this background the research was set out to investigate on possible antiparasitic compounds active against Plasmodium falciparum.

Most of the compounds isolated in this work were active towards both chloroquine sensitive strain (3D7) and chloroquine resistant Plasmodium strain (W2). Interestingly some of them demonstrated selectivity for the resistant strain.

The compounds which displayed antiplasmodial activity also showed toxicity against Trypanosoma brucei brucei, a parasite related to those which cause sleeping sickness.

Besides Triclisia sacleuxii traditional uses mentioned above, it is also used as a snakebites antidote. This suggests that it might contain enzymes inhibitors. Additionally, in previous works, bisbenzylisoquinolines which are believed to be present in T. sacleuxii, have displayed phospholipases A2 and acetylcholinesterase inhibitory activity. On the basis of these informations, the third aim of our investigation targeted acetylcholinesterase (AChE), an enzyme involved in Alzheimer’s disease (AD). AD is a neurodegenerative disease occurring mostly in people aged beyond 60 years, characterised by a progressive loss of memory, impairement of multiple cognitive functions, neurological and behavior disorders, Our results have demonstrated that leaves, stems and roots alkaloidal fractions have high anti-AChE activity. Pure compounds exhibited a structure-dependent activity ranging from 30 up to 90% at a concentration of 100μg/ml).

Finally, we have undertaken an investigation on the antiplasmodial mode of action of the major alkaloids. It appears that not only the BBIQ do not act by a same mechanism, but also a single compound may act by more than one mode of action.
Doctorat en Sciences biomédicales et pharmaceutiques
info:eu-repo/semantics/nonPublished

Specific therapy of chronic Chagas disease aims mainly to reduce parasitemia, besides preventing and reducing symptoms. However, monitoring treatment efficacy still remains unclear due to the lack of laboratorial methods that could certify a complete parasitological cure. Currently, the cure criteria used by various researchers is based on repeated serological and parasitological negative tests. Several studies have shown that serology can remain positive for decades after specific therapeutics. The introduction of highly sensitive techniques such as specific antibodies detection by flow citometry brought new perspectives in Chagas disease cure monitoring. Herein, we developed two studies aiming to evaluate the performance of FC-AFEA and FC-ALTA techniques on post therapeutic evaluation. Our results showed that in a retrospective study using a population with 10 to 15 years of followup after specific therapeutics (n=60), FC-AFEA was capable to segregate cured chagasic patients from non cured ones. Since the method presents a very high sensitivity, some modifications on the original technique, like the utilization of higher dilutions and higher cutoffs, were shown to be necessary. In a prospective study along five years of post therapeutic follow-up (n=44), none of the serological methods used (FC-AFEA, FC-ALTA, IIF, IHA, ELISA, PaGIA) evidenced seronegativity. Nevertheless, we observed that the etiological treatment induced a decrease on FC-AFEA and FC-ALTA reactivity intensity. In addition, in patients presenting post therapy negative hemocultures (TEA), we could identify two subgroups of patients based on their magnitude of reactivity decrease. It is possible that patients with therapeutic success are included in the subgroup presenting higher reactivity decrease. Among the conventional serological tests applied in this study, IHA showed more titer variations, creating difficulties for its use on cure monitoring. IIF was capable to identify reactivity decrease in more than 2 titers in some patients of TEA group. ELISA and PaGIA, in the way they are standardized for diagnostic proposal, were not able to segregate treated and non-treated patients, indicating that modifications on the criterion have to be made for cure monitoring. Therefore, we conclude serology presents important limitations on early cure definition after etiological treatment of chronic Chagas disease. Seroreversion seems to be an inadequate approach for this purpose. Studies should be supported in order to investigate other markers associated to the presence of active infection other than searching for anti-T. cruzi antibodies.
O objetivo da terapeutica especifica da fase cronica da doenca de Chagas e a reducao da parasitemia, alem da prevencao e reducao dos sintomas. Entretanto, a monitoracao da eficacia do tratamento ainda e insatisfatoria, devido a ausencia de metodos laboratoriais que certifiquem a cura. Atualmente, o criterio de cura utilizado por diversos pesquisadores baseiase na negativacao de testes sorologicos e parasitologicos. Diversos estudos mostram que apos a terapia especifica, os testes sorologicos podem permanecer positivos por decadas. A introducao de tecnicas mais sensiveis como a pesquisa de anticorpos por citometria de fluxo trouxe novas perspectivas no monitoramento de cura da doenca de Chagas. Neste contexto, realizamos dois estudos que objetivaram avaliar o desempenho das tecnicas de FC-AFEA e FC-ALTA na avaliacao pos-terapeutica. Nossos resultados mostraram que, em um estudo retrospectivo em uma populacao com 10 a 15 anos de acompanhamento pos-terapeutico (n=60), a FC-AFEA foi capaz de discriminar pacientes chagasicos curados daqueles nao curados. Em virtude da alta sensibilidade do metodo, foram necessarias modificacoes do criterio de positividade da tecnica original utilizado para diagnostico, como o emprego de diluicoes mais altas e elevacao do ponto de corte. Em outro estudo, prospectivo, ao longo de cinco anos de acompanhamento pos-terapeutico (n=44), nenhum dos metodos sorologicos utilizados (FC-AFEA, FC-ALTA, IFI, HAI, ELISA, PaGIA) evidenciou soronegatividade. Entretanto, observou-se que o tratamento etiologico induziu queda na reatividade de FCAFEA e FC-ALTA. Ainda, no grupo de pacientes tratados que apresentavam hemoculturas pos-tratamento negativas (TEA), foi possivel identificar dois subgrupos de pacientes de acordo com a magnitude da queda na reatividade, sendo provavel que pacientes com sucesso terapeutico estejam compreendidos entre aqueles que evoluiram com maior queda de reatividade. Dentre os testes sorologicos convencionais empregados tambem nesta populacao, a HAI mostrou maior variacao dos titulos, dificultando seu emprego na monitoracao recente de cura e mostrando-se insatisfatorio no controle de cura. A IFI foi capaz de identificar queda na reatividade . 2 titulos em alguns pacientes do grupo TEA. A ELISA e o PaGIA, da forma como estao padronizados para uso no diagnostico, nao foram capazes de segregar pacientes tratados ou nao, indicando que para seu uso na monitoracao de cura, os criterios de positividade devam ser adequados. Conclui-se que o uso de testes sorologicos apresenta limitacoes na definicao de cura precoce apos tratamento etiologico da forma cronica da doenca de Chagas. A verificacao de ausencia de anticorpos anti-proteinas derivadas do agente infeccioso parece ser um criterio inadequado de cura. Devem-se incentivar estudos objetivando a procura de outros marcadores associados a presenca ativa da infeccao que nao a presenca de anticorpos anti-T. cruzi.

This PhD thesis is dealing with the bioassay-guided fractionation of a dichloromethane extract of the aerial parts of Achillea fragrantissima with the aim of isolation and structure isolation of the antileishmanial and/or antitrypanosomal principles in the plant
Diese Dissertation beschäftigt sich mit der aktivitätsgeleiteten Fraktionierung eines Dichlormethanextrakts aus den oberirdischen Teilen von Achillea fragrantissima mit dem Ziel der Isolierung und Strukturaufklärung der anti-leishmanialen und/oder anti-trypanosomalen Verbindungen der Pflanze

Yes
Current drugs against human African trypanosomiasis (HAT) suffer from several serious drawbacks. The search for novel, effective, brain permeable, safe, and inexpensive antitrypanosomal compounds is therefore an urgent need. We have recently reported that the 4-aminoquinoline derivative huprine Y, developed in our group as an anticholinesterasic agent, exhibits a submicromolar potency against Trypanosoma brucei and that its homo- and hetero-dimerization can result in to up to three-fold increased potency and selectivity. As an alternative strategy towards more potent smaller molecule anti-HAT agents, we have explored the introduction of ω-cyanoalkyl, ω-aminoalkyl, or ω-guanidinoalkyl chains at the primary amino group of huprine or the simplified 4-aminoquinoline analogue tacrine. Here, we describe the evaluation of a small in-house library and a second generation of newly synthesized derivatives, which has led to the identification of 13 side chain modified 4-aminoquinoline derivatives with submicromolar potencies against T. brucei. Among these compounds, the guanidinononyltacrine analogue 15e exhibits a 5-fold increased antitrypanosomal potency, 10-fold increased selectivity, and 100-fold decreased anticholinesterasic activity relative to the parent huprine Y. Its biological profile, lower molecular weight relative to dimeric compounds, reduced lipophilicity, and ease of synthesis, make it an interesting anti-HAT lead, amenable to further optimization to eliminate its remaining anticholinesterasic activity.
Wellcome Trust

MSc (Chemistry)
Department of Chemistry
Rauvolfia caffra Sond, a species of evergreen trees and shrubs in the dogbane family, (Apocynaceae), is used as a medicinal plant among traditional communities in many countries for the treatment of malaria, diabetes, coughs, gastrointestinal disturbances, skin infections, impotence, insomnia, diarrhoea, dysentery, scabies, worm infections, and both parasitic and microbial infections. Phytochemical studies have revealed that indole alkaloids are the major constituents of the stem bark. However, there are limited studies linking the compounds with the ethnomedicinal uses. The aim of this study is to isolate and characterize bioactive compounds from Rauvolfia caffra Sond. The highest phenolic content found in a fraction was 16.06±0.125 mg GAE/g, while the highest flavonoid content measured was 9.453±0.081 mg QE/g. In the DPPH free radical scavenging activity and reducing power tests, a lowest IC50 value of 0.022±0.003 μg/mL and IC0.5 value 0.518±0.044 μg/mL, respectively, was found. Six compounds were isolated from the stem bark, including lupeol, a pentacyclic tri-terpenoid isolated for the first time from the genus Rauvolfia; raucaffricine, a rare glycoalkaloid of the monoterpenoid indole class; N-methylsarpagine, an indole alkaloid isolated for the time from R. caffra and spegatrine, an indole alkaloid isolated for the first time from R. caffra, respectively. Concerning antimicrobial activity, the highest activity of a fraction was against B. cereus with MIC values as low as 12.5 mg/mL. One fraction at the tested concentration (250 μg/mL) decreased the viability of Plasmodium falciparum (4.149±6.979 %) with an IC50 value of 6.533 μg/mL. The crude extract and some fractions affected the viability of the Trypanosomes at the tested concentration (250 μg/mL), giving -0.133 ± 0.206 %, 11.334 ± 2.692 %, 1.026 ± 0.143 % and 20.769 ± 9.054 % with IC50 values of 18.50 μg/mL, 14.15 μg/mL, 15.58 μg/mL and 34.71 μg/mL, respectively. Furthermore, the fractions did not show significant cytotoxic effects at a concentration of 50 μg/mL.
NRF