The aim of this study was to elucidate the oxidation products of a candidate antimalarial drug, PL69, using a porphyrin system and to determine the accuracy of the oxidation products produced, as compared to what is expected in metabolism. PL69 is a reversed chloroquine (RCQ) that is active against chloroquine resistant malaria. Porphyrin oxidation systems have been shown to mimic in vitro enzymatic metabolism reactions. PL69 and its known metabolite, PL16, were incubated with the porphyrin system, and then the oxidation products were collected and separated by HPLC. The oxidation products were characterized by NMR and mass spectrometry and compared to previous metabolism studies of PL69 with liver microsomes. The results of this research show that this porphyrin system is an acceptable mimic of in vitro metabolism methods for RCQs and provides a good framework for understanding the types of metabolism that will occur in vivo for RCQs.

In spite of great effort aimed at eradication, the malaria epidemic still claims over 600,000 lives each year, and 50% of the world is at risk of contracting the disease. The most deadly form of malaria is caused by Plasmodium falciparum, which is spread from human to human via the female Anopheles mosquito. P. falciparum's lifecycle, which includes both sexual and asexual reproduction, facilitates rapid evolution in response to drug pressure, resulting in the emergence of resistant strains against every antimalarial medication that has been deployed. There is a great need for new antimalarial drugs. Chloroquine (CQ), an aminoquinoline drug deployed in the 1940s, was an inexpensive, effective and safe drug but now has been rendered ineffective throughout much of the tropical regions due to the emergence of CQ-resistant strains of P. falciparum. A new class of hybrid drugs, called Reversed-CQs, has been developed by linking a molecule with a CQ-like moiety to a molecule with a reversal agent (RA) moiety; an RA is a chemosensitizer that can reverse CQ-resistance. The prototype Reversed-CQ, PL01, was shown to be effective in vitro against sensitive and resistant P. falciparum cell cultures, with IC50 values of 2.9 and 5.3 nM, respectively, in comparison to IC50 values for CQ which were 6.9 and 102 nM, respectively. In the course of the Reversed-CQ research, PL74 was synthesized with a pyridine ring replacing the quinoline ring. It was expected that PL74 would display reversal agent activity but would not display antimalarial activity. However PL74 showed antimalarialactivity with IC50 values of 185 and 169 nM in vitro against CQ-sensitive and CQ-resistant strains, respectively. In the investigation of PL74 it has been found that this molecule has a pyridinium salt structure, novel to the Reversed-CQ compounds, and through a structure-activity relationship (SAR) study, it was shown to have activity that may indicate a mode of action different from the Reversed-CQ compounds. A study of the literature revealed that pyridinium salt compounds, with some similarity to PL74, were found to operate as choline analogs inhibiting the biosynthesis of phosphatidylcholine as their main antimalarial mode of action.

An estimated 500 million cases of malaria occur each year. The increasing prevalence of drug resistant strains of Plasmodium in most malaria endemic areas has significantly reduced the efficacy of current antimalarial drugs for prophylaxis and treatment of this disease. Therefore, discovery of new, inexpensive, and effective drugs are urgently needed to combat this disease. Marine biodiversity is an enormous source of novel chemical entities and has been barely investigated for antimalarial drug discovery. In an effort to discover novel therapeutics for malaria, we studied the antimalarial activities of a unique marine-derived peak fraction library provided by Harbor Branch Oceanographic Institute (HBOI). Within this unique library, we have screened 2,830 marine natural product (MNP) peak fractions through a medium throughput screening effort utilizing the SYBR Green-I fluorescence based assay, and have identified 253 fractions that exhibit antimalarial activity. From those inhibiting fractions we have identified twenty species of marine organisms that inhibit Plasmodium falciparum growth, from which thirty-five fractions were selected for further study. Among those thirty-five, eighty-three percent were also found to inhibit the chloroquine resistant strain of P. falciparum, Dd2. The most potent inhibitors were then screened for their cytotoxic properties using the MTT cell viability assay. Among the samples that exhibited potent inhibition of P. falciparum growth were fractions derived from a sponge of the genus Spongosorites sp.. This genus of sponge has been reported to contain the nortopsentin and topsentin class of bis-indole imidazole alkaloids. Nortopsentin A inhibited the parasite growth at the trophozoite stage with an IC50 value of 1.6 µM. This is the first report of antimalarial activity for this class of compound.

Thesis (MSc)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Malaria is a pestilent disease associated with massive socioeconomic burden of sub-Saharan Africa. This disease is caused by a blood infection of the single cellular parasite of the Plasmodium genus. Two enzymes of this parasite have been identified to be essential to the survival of this parasite, notably Spermidine Synthase and Protein Farnesyltransferase. The goal of this dissertation was to search for and synthesise novel inhibitors of these two enzymes with a strong focus towards understanding their structure/activity relationships. To achieve the first goal, molecular modelling was employed. An in-depth discussion is presented to describe the underlying principles relevant to this branch of computational chemistry. This ensures that the experiments using these methods are set-up correctly and results are interpreted within context. Two virtual high-throughput screens were then performed using prepared crystallographic structures of Spermidine Synthase. The first was pharmacophore based method and the second based on LibDock. The database used, containing 7.1 million compounds, was filtered using a custom developed tool prior to screening. Finally, CDOCKER was then used to investigate the activity of potential hit compounds. Spermidine Synthase has a natural affinity for adenosine and this trait was exploited by derivatising analogues to synthesise potential inhibitors of the enzyme. This was to be achieved by the incorporation of both electrophilic and nucleophilic moieties at selected positions, including the use of a high yielding Mitsunobu reaction. A number of additional residues were then synthesised and joined to the adenosine which were proposed to increase the active site occupancy and increase affinity to the enzyme. For the second enzyme targeted for inhibition, Protein Farnesyltransferase, indole was used as a starting scaffold to synthesise potential hits de novo. It was aimed to derivatise the indole at the Nʹ and 3ʹ positions. The crystal structure of one of the intermediates was published. Furthermore, a synthetic sequence which culminated in a palladium catalysed Suzuki coupling was performed. / AFRIKAANSE OPSOMMING: Malaria is ‘n peslike siekte wat geassosieer word met beduinde sosio-ekonomiese implikasies vir sub-Sahara Afrika. Die siekte word veroorsaak deur ‘n bloed infeksie van die enkel sellulêre parasiet van die Plasmodium genus. Twee ensieme, naamlik Spermidien Sintetase en Protein Farnesieltransferase, is geïdentifiseer om noodsaaklik te wees vir die oorlewing van die parasiet. Die doelwit van hierdie verhandeling is die soektog en sintese van oorspronklike inhibeerders van hierdie twee ensieme met ‘n sterk fokus daarop om struktuur/aktiwiteit interaksies te verstaan. Om die eerste doelwit te bereik is molekulêre modellering toegepas. ‘n Indiepte ondersoek word voorgestel om die onderliggende beginsels relevant tot hierdie tak van berekenkundige chemie te beskryf. Dit verseker dat eksperimente wat op hierdie tegnieke berus korrek opgestel word en dat die resultate binne konteks geïnterpreteer word. Twee virtuele hoë-deurset skerms was deurgevoer op voorbereide kristallografiese strukture van Spermidien Sintetase. Die eerste het berus op ‘n pharmakoforiese metode en die tweede op LibDock. ‘n Self-ontwikkelde sagteware gereedskap stuk is gebruik om a databasis van 7.1 miljoen verbindings te filtreer voor dit gebruik is in hoë-deurset skerms. Uiteindelik is CDOCKER gebruik om die potensiele aktiwiteit van “treffer” verbindings te beraam. Spermidien syntetase het ‘n natuurlike affiniteit vir adenosien en hierdie eienskap is benut deur analoeë af te lei na potensiële inhibeerders teen die ensiem. Dit is bewerkstellig deur die insluiting van beide elektrofiliese asook nukleifielese funksionele groepe op gekose posisies. Dit het die gebruik van ‘n hoë opbrengs Mitsunobu reaksie ingesluit. ‘n Aantal ander addisionele residueë is toe gesintetiseer en geheg aan die afgeleide adenosien om die ensiem setel te vul en sodoende die affinitieit te verhoog. Vir die tweede ensiem wat geteiken is vir inhibisie, Protein Farnesieltransferase, is indool benuttig as ‘n begin steier te dien om potensiële treffers de novo te sintetiseer. Dit is geteiken om die indool af te lei op die Nʹ en 3ʹ posisies en die kristal struktuur van een van hierdie tussengangers is gepubliseer. Verder is ‘n sintetiese weg, wat uitgeloop het op ‘n palladium gekataliseerde Suzuki koppeling, uitgevoer.

Diss. (sammanfattning) Stockholm : Karol. inst., 2004. / Härtill 5 uppsatser.

Thesis submitted in fulfilment of the requirements for the Degree of Master of Technology: Organic Chemistry, Durban University of Technology, 2011. / Malaria, the most prevalent parasitic disease, is considered a neglected disease owing to insufficient research and development in synthesis and therapy worldwide. Therapy failures are frequent and are due to a variety of factors such as the intrinsic characteristics of the disease, conditions of transmission, and the difficult control of spreading through tropical areas. Primary factors are the complexity of the parasite life cycle and the development of drug resistance. Another critical factor is the increasing number of immune-compromised patients that suffer from malaria and human immunodeficiency virus (HIV) co-infections. Most of the drugs currently available to treat malaria are quinoline derivatives modelled on the quinine molecule, found in the bark of Cinchona trees. Over the last 50 years the use of quinine has declined owing to the development of synthetic 4-aminoquinolines such as chloroquine. However, the malaria parasite is rapidly becoming resistant to the drugs currently available. Recently bisquinoline compounds were found more potent than chloroquine against both chloroquine-sensitive and resistant strains of malaria; this improved efficacy and prompted an increased interest in the design of these anti-malarial drugs. Although several synthetic methods are available to synthesise bisquinolines, we report the synthesis of bisquinolines from simple, readily available and cost- effective starting compounds. The synthesis was accomplished in four reaction steps using the Claisen condensation, Vilsmeir-Haack reaction, formation of a Schiff base and thermal cyclization, sequentially. We used a conventional energy source and microwave irradiation for the synthesis, wherever possible, of 2, 4-dichloro-3, 4'-biquinoline and 2, 4-dichloro-7'-methoxy-3, 4'-biquinoline. In the first step, 3-acyl-2, 4-dihydroxyquinoline is synthesised from an equimolar mixture of methyl-2-aminobenzoate and ethyl acetoacetate by microwave irradiation for 3 minutes; the yield is 90 % whereas by 6 hours refluxing the yield is 75 %. This is followed by the synthesis of 3-chloro-3-(2,4-dichloroquinolin-3yl) acrylaldehyde, by combining DMF and POCl3 at 00C to form the electrophile which reacts with 3-acyl-2,4-dihydroxyquinoline under microwave irradiation for 5 minutes; the yield is 65 % whereas by 6 hours refluxing the yield is 50 %. In the next step, several protocols to prepare a Schiff base 3-chloro-3-(2, 4-dichloroquinolin-3-yl) allylidene aniline are investigated with the best yield of 75% obtained by microwave irradiation for 5 minutes. Subsequently three aniline derivatives viz, 4-methoxyaniline, 4-chloroaniline and 4-methylaniline, are used as substrate to prepare 3-chloro-3-(2,4-dichloroquinolin-3-yl) allylidene-4-methoxyaniline, 3-chloro-3-(2 ,4-dichloroquinolin-3-yl) allylidene-4-methylaniline and 3-chloro-3-(2, 4-dichloroquinolin-3-yl) allylidene-4-chloro aniline at 68, 78 and 64 % yield, respectively. In the final step, 2, 4-dichloro-3, 4'-biquinoline is prepared; several methods were investigated, however, the best yield is 24 % which is obtained under alkaline conditions in the presence of K2CO3 and DMF by microwave irradiation for 10 minutes. The 2, 4-dichloro-7'-methoxy-3, 4'-biquinoline derivative is also prepared in 18 % yield under the same alkaline conditions. The outline of the total synthesis of bisquinoline is presented graphically below. / National Research Fund.

Thesis (MSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Dichloro-diphenyl-trichloroethane (DDT) was extensively used in agriculture pest control and is still used for indoor residual spraying to control malaria. The lipophylicity of DDT and its breakdown product dichloro-diphenyl-dichloroethylene (DDE) dictates that they associate with membranes, lipids and hydrophobic proteins in the biological environment. Their poor degradable nature causes DDT and DDE to persist for decades in the environment and in individuals who are or were in contact with the pesticide. In many countries the synchronised resistance of the mosquito vector to insecticides and the malaria parasite towards antimalarial drugs led to a drastic rise in malaria cases and to malaria epidemics. This study assesses the influence of low level exposure of DDT and DDE on chloroquine (CQ) resistance of the dire human malaria parasite, Plasmodium falciparum. The in vitro activity of p,p’-DDT and p,p’-DDE towards blood stages of chloroquine sensitive (CQS) P. falciparum D10 and chloroquine resistant (CQR) P. falciparum Dd2 was determined using two complementary in vitro assays (Malstat and SYBR Green 1). The 50% inhibition concentrations (IC50s) of p,p’-DDT and p,p’-DDE were found to be ±14 to 38 μM (5-12 μg/mL) and highly similar towards CQS and CQR P. falciparum strains. This result indicated that the proteins involved in CQ resistance have no effect on the activity of the insecticide DDT and it breakdown product DDE. In order to assess the influence of DDT and DDE on CQ activity, in vitro fixed ratio drug combination assays were performed, as well as isobologram analysis. We found that CQ works in synergy with p,p’-DDT and p,p’-DDE against CQS P. falciparum D10. However, both p,p’-DDT and p,p’-DDE were antagonistic toward CQ activity in CQR P. falciparum Dd2. This indicated that p,p’-DDT and p,p’-DDE do have an effect on CQ resistance or on the action of CQ via a target other than hemozoin polymerization. The observation of reciprocal synergism of p,p’-DDT and p,p’-DDE with CQ against CQS D10 and antagonism against CQR Dd2 strain is highly significant and strongly indicates selection of CQ resistant strains in the presence of p,p’-DDT and p,p’-DDE. People who have low levels of circulating DDE and/or DDT could be at a high risk of contracting CQR malaria. However, medium term (nine days) DDE exposure of CQS P. falciparum D10 did not induce resistance, as no significant change in activity of CQ, p,p’-DDT and p,p’-DDE towards blood stages the CQS strain was observed. This exposure was, however, shorter than expected for a malaria infection and would be addressed in future studies. From our results on the interaction of CQ with p,p’-DDT and p,p’-DDE, it was important to assess the residual DDT and DDE variable and how much of residual p,p’-DDT and/or p,p’- DDE would enter into or remain in the different compartments (the RPMI media, erythrocytes and infected erythrocytes) over time. In combination with liquid-liquid extraction, we developed a sensitive GC-MS analyses method and a novel HPLC-UV analysis method for measuring DDT and DDE levels in malaria culturing blood and media. Whilst the HPLC-UV method was relatively cheaper, faster, and effective in determining high DDT and DDE concentrations, the optimised GC-MS method proved to be effective in detecting levels as low as 78 pg/mL (ppt) DDE and 7.8 ng/mL (ppb) DDT in biological media. Using both the HPLC and GC-MS methods we observed that malaria parasites influence distribution of the compounds between the erythrocytic and media fractions. P. falciparum D10 infection at ±10% parasitemia lead to must faster equilibration (less than 8 hours) between compartments. Equimolar distribution of p,p’-DDE was observed, but the parasites lead to trapping of the largest fraction of p,p’-DDT in the erythrocyte compartment. These results indicate that a substantial amount would reach the intra-erythrocytic parasite and could influence the parasite directly, possibly leading to either synergistic or antagonistic drug interactions. This study is the first to illustrate the “good and bad” of the insecticide DDT in terms of CQ resistance and sensitivity toward the human malaria parasite P. falciparum. These results will hopefully have an important influence on how future policies on malaria control and treatment particularly in endemic areas will be addressed and could also have an impact on the anti-malarial drug discovery approach. / AFRIKAANSE OPSOMMING: Dichlorodifenieltrichloroetaan (DDT) is op groot skaal in landbouplaagbeheer gebruik en word nog steeds gebruik vir binnenshuise oppervlakbespuiting om malaria te beheer. Die lipofilisiteit van DDT en sy afbraakproduk dichlorodifenieldichloroetileen (DDE) dikteer dat hulle met membrane, lipiede en hidrofobiese proteïene in die biologiese omgewing assosieer. Stadige afbraak veroorsaak dat DDT en DDE vir dekades in die omgewing agterbly, asook in individue wat in kontak is, of was met die insekdoder. In baie lande het gesinkroniseerde weerstand van die muskietvektor teenoor insekdoders en die malariaparasiet teenoor antimalariamiddels gelei tot 'n drastiese styging in malariagevalle en tot malariaepidemies. In hierdie studie word die invloed van lae vlak blootstelling van DDT en DDE op chlorokien (CQ) weerstand van die mens malariaparasiet, Plasmodium falciparum, geëvalueer. Die in vitro aktiwiteit van p,p'-DDT en p,p'-DDE teenoor die bloedstadia van chlorokiensensitiewe (CQS) P. falciparum D10 en chlorokien-weerstandbiedende (CQW) P. falciparum Dd2 is bepaal deur gebruik te maak van twee komplementêre in vitro toetse (Malstat en SYBR Groen toetse). Die 50% inhibisie konsentrasies (IC50s) van p,p'-DDT en p,p'-DDE is bepaal as ±14 to 38 μM (5-12 μg/mL) en was hoogs vergelykbaar tussen CQS en CQW P. falciparum stamme. Hierdie resultaat het aangedui dat die proteïene betrokke by CQ weerstand geen effek op die aktiwiteit van die insekdoder DDT en die afbraakproduk DDE het nie. Om die invloed van DDT en DDE op CQ aktiwiteit te evalueer, is die aktiwiteit van kombinasies van die verbindings in vaste verhoudings getoets, tesame met isobologram ontleding. Ons het gevind dat CQ sinergisties saam met p, p'-DDT en p, p'-DDE teen CQS P. falciparum D10 werk. Daarteenoor het beide p, p'-DDT en p, p'-DDE antagonistiese werking getoon teenoor CQ aktiwiteit met CQW P. falciparum Dd2 as teiken. Dit het aangedui dat p,p'-DDT en p, p'-DDE wel 'n invloed op CQ weerstand het of ‘n aktiwiteit van CQ, anders as hemozoin polimerisasie, beïnvloed. Die waarneming van resiproke sinergisme en antagonisme van p, p'-DDT en p, p'-DDE in kombinasie met CQ teenoor die CQS D10 en CQW DD2 stamme respektiewelik, is hoogs betekenisvol en dui op seleksie van CQweerstandige stamme in die teenwoordigheid van p, p'- DDT en p, p'-DDE. Mense wat lae vlakke van sirkulerende DDE/DDT het, het dus 'n hoër risiko om CQW malaria te kry. Verder is gevind dat medium termyn (nege dae) DDE blootstelling van CQS P. falciparum D10 nie weerstand nie veroorsaak nie, want geen beduidende verandering in die aktiwiteit van CQ, p,p'-DDT en p,p'-DDE teenoor die bloed stadiums van die CQS stam is waargeneem nie. Hierdie blootstelling is egter korter as in 'n malaria-infeksie en sal verder bestudeer word in toekomstige studies. Vanuit die interaksie resultate van CQ met p, p'-DDT en p, p'-DDE was dit belangrik om die residuele DDT en DDE veranderlike te evalueer, asook die distribusie van p,p'-DDT en p,p'- DDE tussen die verskillende kompartemente (die kultuurmedium, eritrosiete en geïnfekteerde rooibloedselle) oor verloop van tyd. In kombinasie met vloeistof-vloeistof ekstraksie, het ons 'n sensitiewe GC-MS en nuwe HPLC-UV analisemetode ontwikkel vir die meet van DDT en DDE-vlakke in bloed (normale en geïnfekteerde eritrosiete) en die kultuurmedium. Terwyl die HPLC-UV metode relatief goedkoper, vinniger en effektief in die bepaling van hoë DDT en DDE-konsentrasies is, was die geoptimaliseerde GC-MS metode doeltreffend in die opsporing van vlakke so laag as 78 pg/mL (dpt) DDE en 7.8 ng/mL (dpb) DDT in biologiese media. Met behulp van beide die HPLC-UV en GC-MS metodes is waargeneem dat die malariaparasiet die ekwilibrasie van die verbindings tussen die eritrosiet- en media kompartemente beïnvloed. P. falciparum D10 infeksie met ± 10% parasitemia lei tot vinniger ekwilibrasie (minder as 8 uur) tussen die kompartemente. Ekwimolêre verspreiding van p,p'- DDE is waargeneem, maar die parasiete het die grooste fraksie van p,p'-DDT in die eritrosiet kompartement vasgevang. Hierdie resultate wys dat 'n aansienlike fraksie die intraeritrositiese parasiet kan bereik en sodoende die parasiet direk kan beïnvloed en moontlik kan lei tot sinergistiese of antagonistiese middel interaksies. Hierdie studie is die eerste om die "goed en sleg" van die insekdoder DDT in terme van CQ weerstand en sensitiwiteit teenoor die menslike malariaparasiet P. falciparum te illustreer. Hierdie resultate sal hopelik 'n belangrike invloed hê op die toekomstige beleid oor die beheer van malaria en behandeling, veral in endemiese gebiede, en mag ook 'n impak hê op die antimalariamiddel navorsing.

Intermittent fevers caused by Plasmodium parasites have been known for millennia, and have caused untold human suffering. Today, millions of people are afflicted by malaria each year, and hundreds of thousands die. Historically, the most successful synthetic antimalarial drug was chloroquine, as it was safe, inexpensive, and highly efficacious. However, plasmodial resistance to chloroquine now greatly limits its utility. Previously in our laboratories it has been shown that attachment of a "reversal agent moiety" to the side chain of chloroquine can result in the restoration of activity against chloroquine-resistant strains of P. falciparum malaria. In the first part of the work presented here, a study has been made of the importance of the quinoline ring substitution pattern to the activity of such reversed chloroquines. The compounds presented here include those bearing a substituent in the 2-, 5, 6-, 7-, and/or 8- position, and include those with chloro, bromo, iodo, fluoro, nitro, trifluoromethyl, methyl, and methoxy substituents. For reversed chloroquines, 2-, 5-, and 8- substituents have been found to decrease in vitro antiplasmodial activity against P. falciparum relative to 7-chloro substitution, whereas 6- and 7- substituted compounds with various substituents have in many cases similar activity to that of 7-chloro substituted compounds. Little difference has been observed between 6- and 7- substitution, or between chlorine and a methyl group in position 6. In most cases these effects on activity are directionally similar to those observed for chloroquine analogs without an attached reversal agent, but the magnitude of the effect is generally smaller, suggesting that the activities of reversed chloroquines are less affected by modifications to the quinoline ring system than is true for chloroquine analogs without an attached reversal agent. The second portion of this work presents an asymmetrical bis-quinoline (PL241) that is highly active against P. falciparum malaria, with an IC50 of less than 0.1 nM for all strains tested. Mechanistic studies have been performed in which the substitution patterns of the two quinoline rings of PL241 are modified in ways that indicate that either ring system is equally capable of participating in the antimalarial activity of these compounds. The excellent in vitro antiplasmodial activity of PL241 makes this a compound of great interest for further development as a potential antimalarial drug. In the third part of this work, a survey has been made of antimalarial treatments recommended in the European medical literature from the time of Pliny the Elder (active in the first century A.D.) through the advent of modern malaria chemotherapy in the early twentieth century. In the fifteen primary sources utilized in this study, 251 distinct substances - primarily plants - were identified as having likely been used in the treatment of malaria. Of the 38 substances that were described in three or more sources, at least fifteen have been examined by other workers for antiplasmodial activity; in many cases, they were found to have antiplasmodial activity in vitro or in vivo. However, the majority of the phytotherapies for malaria identified in this project have not yet been tested against Plasmodium species, and may provide valuable leads in the search for new compounds active against drug-resistant malaria.

La nécessité de garantir la qualité des médicaments antipaludiques disponibles sur le marché pharmaceutique d'Afrique subsaharienne est l'une des stratégies mises en œuvre pour réduire les taux élevés de morbidité et de mortalité liés au paludisme. L'objectif de ce travail de thèse était de proposer des méthodes de dosage par électrophorèse capillaire (EC) de combinaisons antipaludiques à base de sulfadoxine/pyriméthamine (SDX/PYR), artésunate/amodiaquine (AS/AQ) et artéméther/luméfantrine (AM/LUM) retenues dans le schéma thérapeutique ivoirien et commercialisées sous forme de comprimés.Cet objectif a été atteint en employant trois modes de séparation : l'électrophorèse capillaire de zone (CZE) pour SDX/PYR, la chromatographie électrocinétique micellaire (MEKC) pour AS/AQ et la chromatographie électrocinétique par microémulsion (MEEKC) pour AM/LUM. Les méthodes développées ont été validées selon les règles d'ICH et appliquées à des comprimés provenant d'officines ou vendues sur les marchés de rue en Côte d'Ivoire. Elles présentent une répétabilité satisfaisante (CV < 3%, n = 7 procédures analytiques). La méthode de CZE qui utilise un tampon pH 7 pour la séparation de SDX et PYR a donné des résultats de dosage concordants avec la méthode de chromatographie liquide décrite dans l'USP-NF. Sur les neuf formulations de comprimés analysées, une formulation prélevée dans le marché de rue s'est révélée sous-dosée en SDX. La méthode MEKC utilisant le dodécylsulfate de sodium (SDS) dans un tampon borate pH 9,2 a permis le dosage d'AS et AQ. L'application à l'analyse de quatre formulations issues de l'officine a donné des teneurs en AS et AQ conformes aux teneurs déclarées. Enfin, la microémulsion octane-butanol-SDS-tampon borate en MEEKC s'est révélée appropriée au dosage d'AM et LUM, molécule très hydrophobe. L'application à l'analyse de quatre formulations prélevées à l'officine a révélé des teneurs conformes aux teneurs déclarées et la présence dans une formulation d'un ingrédient non déclaré. Le potentiel de screening de cette méthode MEEKC, évalué sur 22 antipaludiques et la sulfaméthoxazole et la triméthoprime, a donné une résolution partielle ou totale pour 17 composés.L'EC peut être utilisée comme technique alternative à la chromatographie liquide pour le contrôle des antipaludiques retenus dans le schéma thérapeutique ivoirien. / The need to ensure the quality of antimalarials available on the pharmaceutical market in sub-Saharan Africa is one of the strategies implemented to reduce the high morbidity and mortality rates associated with malaria. The aim of this thesis was to propose capillary electrophoresis (CE) methods for the determination of combinations of antimalarials containing sulfadoxine/pyrimethamine (SDX/PYR), artesunate/amodiaquine (AS/AQ) and artemether/lumefantrine (AM/LUM) recommended in the Côte d'Ivoire therapeutic protocol and marketed as tablets.The objective was achieved by employing three separation modes: capillary zone electrophoresis (CZE) for SDX/PYR, micellar electrokinetic chromatography (MEKC) for AS/AQ and microemulsion electrokinetic chromatography (MEEKC) for AM/LUM. The developed methods were validated according to ICH rules and were applied to various tablet formulations bought in pharmacies or on the street-market in Côte d'Ivoire. The methods presented satisfactory repeatability values (CV <3%, n = 7 analytical procedures). CZE method used a buffer of pH 7 for the simultaneous separation of SDX and PYR and gave results that were compliant with the dosage by the liquid chromatography method described in the U.S. Pharmacopoeia. Of the nine tablet formulations analyzed, one formulation bought on the street-market had a low SDX content. An MEKC method using SDS in a borate buffer pH 9.2 allowed the determination of AS and AQ in bilayer tablets. Application to four commercial formulations with different dosages gave a content in good agreement with the declared content. Finally, butanol-octane-SDS-borate buffer microemulsion in MEEKC was found to be suitable for the determination of AM and LUM, a very hydrophobic compound. Application to four commercial tablet formulations gave a content in good agreement with the declared content and evidenced the presence in a formulation of an undeclared ingredient. The potential screening capacity of this MEEKC method was evaluated on 22 antimalarials and on sulfamethoxazole and trimethoprim. Partial or complete resolution of 17 compounds was obtained.CE can be used as an alternative technique to liquid chromatography for the control of antimalarial drugs recommended in the national therapeutic protocol against malaria.

A thesis submitted to the Faculty of Science University of the Witwatersrand Johannesburg in fulfillment for the requirements of the degree of Master of Science. 14 May 2015. / Peptidomimetic compounds have been shown to exhibit both anti-HIV and anti-malarial activity. A multicomponent reaction was used to create a library of peptidomimetic compounds with an α-hydroxy-β-amino acid unit. The Passerini reaction between an aldehyde, carboxylic acid and isocyanide was used to prepare compounds containing both ester and amide functionalities. These compounds were then subjected to a deprotection-acyl migration strategy giving rise to the target compounds. This approach, known as the Passerini Amine Deprotection Acyl Migration (PADAM) sequence was successfully used to create a library of novel peptidomimetic compounds. From this library, 22 compounds were tested for activity against HIV and malaria. The Passerini reaction gives rise to a product containing a new stereogenic centre, and as the starting aldehyde used (N-Boc-phenylalaninal) has a stereogenic centre, the products were isolated as a mixture of diastereomers. Our research was also focused on finding ways of influencing the stereoselectivity of the reaction and the separation of the resulting diastereomers. The diastereomeric ratio of the Passerini products was found to be approximately 2:1 for all the reactions performed. This ratio could be modified slightly when using certain carboxylic acids and isocyanides that were either very bulky or had a stereogenic centre. Attempts to enzymatically resolve the diastereomeric products were not successful after trials using a library of 25 lipase enzymes. However, use of preparative HPLC enabled the successful separation of most of the diastereomeric mixtures, affording compounds with high purity. X-ray crystallography enabled us to identify the major diastereomers as having the R,S configuration, whilst the minor diastereomers had the S,S configuration at the two stereogenic centres. A possible explanation for the observed stereoselectivity is based on the Felkin-Anh chelation control model. It suggests that mono-protected amino aldehydes follow a chelation controlled mechanism in nucleophilic addition reactions. Chelation occurs, albeit in the form of hydrogen bonding, between the NH and carbonyl oxygen. The library of compounds was tested for activity against both HIV-1 and malaria. Only three compounds showed moderate activity against the malaria parasite, inhibiting parasitic growth by 37-42% at 5 μM respectively. Significantly, all of the active compounds contained an adamantyl moiety. Unfortunately no anti-HIV activity was seen for any of the compounds tested in the HIV-assay.