Thesis (Ph.D. in Neuroscience) -- University of Colorado at Denver and Health Sciences Center, 2006. / Typescript. Includes bibliographical references (leaves 108-118). Free to UCD Anschutz Medical Campus. Online version available via ProQuest Digital Dissertations;

Submitted by Jos? Henrique Henrique (jose.neves@ufvjm.edu.br) on 2017-09-20T20:31:49Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) gabriele_azevedo_cardoso.pdf: 4324631 bytes, checksum: 3efd70a64b9fe1de1234371d61299990 (MD5) / Approved for entry into archive by Rodrigo Martins Cruz (rodrigo.cruz@ufvjm.edu.br) on 2017-10-09T13:35:54Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) gabriele_azevedo_cardoso.pdf: 4324631 bytes, checksum: 3efd70a64b9fe1de1234371d61299990 (MD5) / Made available in DSpace on 2017-10-09T13:35:54Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) gabriele_azevedo_cardoso.pdf: 4324631 bytes, checksum: 3efd70a64b9fe1de1234371d61299990 (MD5) Previous issue date: 2017 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico (CNPq) / Funda??o de Amparo ? Pesquisa do Estado de Minas Gerais (FAPEMIG) / A necessidade de desenvolvimento de novos agentes antimicrobianos cresce ? medida que se torna maior a resist?ncia de microrganismos aos antibi?ticos usualmente empregados. Nesse sentido, os pept?deos antimicrobianos (PAMs) surgem como uma excelente alternativa para o desenvolvimento de novos antibi?ticos. O presente trabalho prop?s a s?ntese do pept?deo antimicrobiano LyeTx-I para estudos de mecanismo de a??o em membranas bacterianas, empregando diferentes t?cnicas biof?sicas e estruturais. O pept?deo LyeTx-I, composto por 24 res?duos de amino?cidos, foi isolado pela primeira vez do veneno de aracn?deos da esp?cie Lycosa erythrognata. Utilizando como t?cnicas principais a ITC e a RMN para obten??o de par?metros cin?ticos, termodin?micos e da intera??o pept?deo-membrana, foi poss?vel avaliar a rela??o estrutura e atividade do pept?deo LyeTx-I. Foram utilizadas ainda, t?cnicas complementares de CD, extravasamento de CF, fluoresc?ncia de Trp, DLS e, potencial zeta para obter informa??es adicionais acerca do modo de intera??o do pept?deo. Observou-se a predomin?ncia de conforma??o helicoidal do pept?deo LyeTx-I, tanto em meios biomim?ticos zwitteri?nicos, quanto em meios ani?nicos. Em meios ani?nicos, observou-se maior conte?do de ?-h?lice, bem como maior constante de intera??o, enquanto que em presen?a de ambientes zwitteri?nicas foram observadas menor helicidade e constante de intera??o. Os dados termodin?micos, obtidos para ambos os meios, mostraram que o processo de intera??o pept?deo-membrana ? dirigido principalmente pela componente entr?pica, uma vez que a componente ent?lpica ? menor. Os dados estruturais e termodin?micos foram coerentes com os demais estudos biof?sicos. Foi observada a partir da an?lise de extravasamento de CF maior capacidade de forma??o de poros no meio ani?nico. Os dados de fluoresc?ncia intr?nseca de Trp e de supress?o de fluoresc?ncia por acrilamida mostraram maior mudan?a de ambiente qu?mico para apolar, do res?duo de Trp-2, quando em presen?a de meio biomim?tico ani?nico. Dessa forma, o pept?deo apresenta maior capacidade de permeabilizar a membrana ani?nica. Al?m disso, o estudo comparativo entre os meios zwitteri?nicos e ani?nicos, permitiu verificar que, embora a intera??o eletrost?tica seja importante para a intera??o pept?deo-membrana, a permeabiliza??o do LyeTx-I na membrana fosfolip?dica ? fundamental para a lise celular. Dessa forma, este estudo mostra que o pept?deo LyeTx-I apresenta elevada prefer?ncia por intera??o com bicamadas fosfolip?dicas ani?nicas, o que faz dele um potencial agente bactericida. / Disserta??o (Mestrado) ? Programa de P?s-Gradua??o em Qu?mica, Universidade Federal dos Vales do Jequitinhonha e Mucuri, 2017. / The demand for the development of new antimicrobial agents increases in line with the resistance of microorganisms to the antibiotics usually employed. In this sense, antimicrobial peptides (AMPs) appear as an alternative to the classical antibiotics. The present work proposed the synthesis of the antimicrobial peptide LyeTx-I for studies of mechanism of action in bacterial membranes using a set of biophysical and structural techniques. LyeTx-I peptide is composed of 24 amino acid residues and was isolated for the first time from the venom of the Lycosa erythrognata arachnid species. In order to evaluate the structure-activity relationship of the LyeTx-I, we have employed ITC and NMR as main techniques to obtain the kinetic, thermodynamic and structural parameters of the peptide-membrane interaction. Complementary measurements of CD, CF extravasation, Trp fluorescence, DLS and zeta potential were also used as additional information about the mode of action of the peptide. The ?-helical conformation of the LyeTx-I peptide was observed either in presence of zwitterionic and anionic biomimetic media. Nevertheless, a higher ?-helix content and interaction constant was observed for LyeTx-I in all anionic media when compared to the zwitterionic environments. The thermodynamic data gathered in both media, showed that the peptide-membrane interaction is driven mainly by the entropic contributions, since the enthalpic component is smaller. The structural and thermodynamic data were consistent with the complementary biophysical experiments. It was observed from the CF extravasation a greater capacity of pore formation in the anionic medium. Intrinsic Trp fluorescence showed also a greater change of the residue of Trp-2 to the apolar chemical environment in the presence of anionic biomimetic medium. In this way, the peptide presents a higher capacity to permeabilize the anionic membrane. In addition, the comparative study between the zwitterionic and anionic media, reveals that, although the electrostatic interaction is important to the peptide-membrane interaction, the permeabilization of the LyeTx-I peptide in the phospholipid membrane is fundamental for the cellular lysis. Finally, the study clearly shows the high preference of LyeTx-I for interacting anionic phospholipid bilayers, which makes it a potential bactericidal agent.

Le glutamate est le principal neurotransmetteur excitateur du système nerveux central. Il est responsable de la majorité des transmissions synaptiques. En revanche, cet acide aminé naturel est aussi impliqué dans de nombreuses neuropathologies notamment en cas de surconcentration au niveau des synapses. Les récepteurs métabotropiques du glutamate, capables de moduler la transmission synaptique, constituent des cibles thérapeutiques prometteuses. Ces récepteurs sont divisés en trois groupes et notre laboratoire s’est focalisé sur ceux du groupe III et particulièrement le sous-type 4 qui présente des caractéristiques intéressantes dans le traitement symptomatique de la douleur et de la maladie de Parkinson. Le manque d’outils pharmacologiques de ce récepteur nous a poussé à synthétiser de nouveaux agonistes orthostériques à partir du composé référence, le LSP4-2022. Cette molécule est issue de nombreuses optimisations chimiques du (S)-PCEP provenant lui d’un screening virtuel. Durant ces trois années de doctorat, nous avons pu peaufiner la relation structure-activité autour du LSP4-2022 en synthétisant des nouveaux analogues fluorés et hétérocycliques. En parallèle, une seconde étude nous a permis d’attribuer la configuration des deux diastéréomères constituants tous les composés testés à ce jour / Glutamate is the major excitatory neurotransmitter in the central nervous system. It is responsible of the majority of synaptic transmissions. In contrast, this natural amino acid is also involved in numerous neuropathologies and particularly in case of glutamate overconcentration in the synapse. Metabotropic glutamate receptors, that can modulate synaptic transmission, thus constitute promising therapeutic targets. These receptors are divided in three groups and our laboratory has been focused in group III and especially subtypes 4 which own interested properties in symptomatic treatment of pain and Parkinson Disease. The lack of pharmacological tools targeting this receptor prompts us to synthesize novel orthosteric agonist from the hit compound LSP4-2022. This molecule was obtained after several chemical optimizations from (S)-PCEP discovered from virtual screening. During my Ph.D., we could refine the structure-activity relationship of LSP4-2022 synthesizing new fluorinated and heterocyclic derivatives. Besides, a second study was carried out to identify the configuration of the two diastereomers which form tested compounds

The war between human and malaria has never stopped, and the development and application of antimalarial drugs has not eradicated this terrible disease. To fight drug-resistant malaria, many leads have been studied over the years. (1S,3R)-MMV008138 and MMV1803522 are two compounds that have been studied in the Carlier Group. My research focused on the structural variation of each of these compounds, in the hope that greater potency could be realized. Chapter 2 describes my work on (1S,3R)-MMV008138, which inhibits the enzyme PfIspD in the methylerythritol phosphate (MEP) pathway. This compound shows good in vitro potency against the drug resistant Dd2 strain of Plasmodium falciparum. However, this lead showed no activity in mouse models. This lack of activity may be due to poor metabolic stability of the compound. However, a significant increase in in vitro potency could also improve in vivo activity. Towards that end, I focused on further variation of the D-ring and A-rings. With the regard to the D-ring, we made five analogs of MMV008138 that replaced the 2,4-dichlorophenyl ring with dihalogenated thiophen-3-yl and thiophen-2-yl rings. We also explored the effect of installing a cyano group on the A-ring of MMV008138. Unfortunately, none of these new compounds were potent growth inhibitors of Dd2 strain P. falciparum. We conclude that the lead goes into a well-defined pocket within the PfIspD enzyme that only accommodates 2,4-dihalogenated phenyl D-rings. This pocket also cannot accept any substitution larger than F on the A-ring. Interestingly, the crystal structure of 5-cyano-substituted MMV008138 was obtained ((±)-2-50c). This is the first compound out of more than 100 analogs of MMV008138 family to be amenable to crystallization. The solid state conformation of the (±)-2-50c revealed that the C3-carboxyl group was in a pseudoequatorial orientation, and the C1-aryl group was thus in a pseudoaxial orientation. 1H NMR spectroscopic studies in CD3OD-D2O were carried out to determine the solution conformation. As expected from previous studies of ester derivatives of MMV008138, these studies indicated that in solution, 2-5 would adopt both the C3-carboxyl pseudoequatorial and pseudoaxial conformations. In Chapter 3, I describe the synthesis of analogs of the antimalarial drug candidate MMV1803522. This β-carboline-3-carboxamide shows good in vitro growth inhibition potency of Dd2 strain P. falciparum, operating by a still unknown mechanism. To investigate the pharmacophore of this lead, I first sought to determine whether the pyridine N (i.e. N2) of the β-carboline was important for in vitro potency. I prepared series of carbazole analogs of MMV1803522, which replace N2 with a CH. These compounds potently inhibited the growth of Dd2 strain P. falciparum. These results suggest that N2 of MMV1803522 is not involved in any energetically significant interactions with its target protein. To further identify the pharmacophore, we prepared truncated analogs lacking the A- and B- rings (biphenyl analogs), and tricyclic analogs that feature a reversed indole moiety. Unfortunately, the biphenyl analogs and reversed indole analogs show no growth inhibition at 10,000 nM the highest concentration tested. Lastly, I describe analogs of MMV1803522 in which the 3,4-dichlorophenyl ring of MMV1803522 was replaced with halogenated thiophene. This substitution was tolerated, but compounds were roughly half as potent as MMV1803522. / Doctor of Philosophy / Malaria, mainly caused by the infection of P. falciparum, is a serious worldwide disease. In 2020, there were 241 million cases of malaria infections and over 600,000 deaths from malaria. Combinations of commercially available antimalarial compounds, such as chloroquine, mefloquine and artemisinin, are commonly used as combination therapies to treat malaria. Since different antimalarial compounds have different mechanisms of action, this combination strategy can greatly slow down the spread of drug-resistant parasites. However, multiple drug-resistant strains of P. falciparum have been reported. Therefore, there is an urgent need for new antimalarial compounds with novel mechanisms of action. This dissertation involves my research on the investigation and optimization of two novel antimalarial compounds, MMV008138 and MMV1803522. MMV008138 is an inhibitor of the MEP pathway, which is an essential metabolic pathway and attractive target for antimalarial therapies, in malaria parasites. The parasites cannot survive, with the MEP pathway inhibited. Since the MEP pathway is not present in human, the MMV008138 molecule is unlikely to have toxicity to human. The MMV008138 molecule has been demonstrated to have great in vitro performance of inhibiting the MEP pathway in several studies, however, the in vivo performance in mouse models is yet to improve. This may be due to the poor metabolic stability of this compound. The compound decomposes in the mouse body before it takes effect. To enhance the metabolic stability and potency, I performed chemical modifications on the A- and D-rings of the MMV008138 compound. An X-ray crystal structure was obtained to help elucidate the conformer distribution of MMV008138. This crystal structure can be used to guide our understanding of the docking of this compound to the target enzyme in the future. MMV1803522 is another compound that shows great potency in vitro and in vivo. This compound is fully oxidized and contains four aromatic rings. However, the target enzyme and the mechanism of action of MMV1803522 is yet to be discovered, and the structure-activity relationship between the chemical structure and the biological activity of this molecule is still unknown. Therefore, I have developed synthetic methods to synthesize a series of compounds that are structurally similar to the MMV1803522 and found that potency of this molecule is not due to the nitrogen on the C-ring. Also, the number and size of the ring structures in the MMV1803522 may be crucial for this molecule to exhibit great potency in vitro and in vivo.

No description available.

No description available.

Binding of the Rev protein with Rev Response Element (RRE) RNA present in singly- and unspliced mRNA transcripts is necessary for the replication of HIV-1. This interaction transports the mRNA transcripts from the nucleus to the cytoplasm for translation of the necessary structural and enzymatic proteins for the newly budding virus as well as for providing its genetic material. Given the high rate of mutation in HIV-1, the highly conserved and pertinent RRE RNA is of high interest for pharmaceutical intervention. Consequently, a branched peptide library containing unnatural amino acids was developed to target RRE RNA with the goal of increasing stability, potency, selectivity, and in vivo activity for RRE RNA. An unnatural amino acid branched peptide library (46,656 sequences) was synthesized and screened against RRE IIB and several hits in the sub-micromolar regime were found. A number of hits demonstrated selectivity in the presence of other RNAs in addition to two hits, 4A5 and 4B3, significantly inhibiting HIV-1 growth in vitro. These peptides inhibited HIV-1 replication in a concentration dependent manner and were demonstrated to be non-toxic. Further analysis of 4A5 and 4B3 via footprinting and SHAPE-MaP experiments determined that these peptides blocked binding of Rev through binding at the primary and secondary binding sites of RRE RNA. Sphingosine 1-phosphate (S1P) is a signaling molecule that plays a role in various biological processes including immunity, neurogenesis, and angiogenesis. The role S1P plays is largely determined by its location, in which Spinster homolog 2 (spns2) and mfsd2b are the two known transporters. The two transporters exist in different cell types and cellular localizations, with spns2-produced S1P being responsible for trafficking of lymphocytes. As such, spns2 has become of interest for therapeutic targeting in autoimmune and inflammatory diseases. To validate spns2 as a target in pharmaceutical intervention, a series of spns2 inhibitors were developed. A screening of a library of inhibitors found that compound SLP7120922 demonstrated inhibition of spns2 transport activity. The design, synthesis, and biological evaluation of inhibitors based on SLP7120922 is described. Modifications to the lipophilic tail region were performed with one compound 4.40f discovered to be potent, minimally toxic, and active in vivo. A series of modifications to the head region were then conducted that evaluated linear head derivatives with alkyl-, amide-, and amino acid-based groups. A number of compounds are reported that demonstrate good in vitro activity and minimal toxicity with two compounds, 4.48b and 4.52c, showing favorable in vivo activity in mice. / Doctor of Philosophy / Human immunodeficiency virus (HIV-1) has a high rate of mutation, which commonly leads to the need for many types of medications throughout the lifetime of a patient. In order to design a therapeutic that the virus has a low chance of growing resistance to, a target needs to be chosen with a low mutation rate. One such target is the Rev Response Element (RRE) RNA and it is necessary for the virus to replicate. A protein named Rev binds to RRE RNA in order for RRE to carry out its pertinent function. To block this function we have chosen branched peptides to target the RNA. Peptides are made of the same building blocks of proteins, but are much shorter than proteins. The peptides described here are made up of modified building blocks, called unnatural amino acids. This work describes the generation of an unnatural amino acid branched peptide library and how it was screened in order to find branched peptides that bind RRE RNA. Many peptides were found to bind RRE RNA but two in particular, 4A5 and 4B3, were the best binders that inhibited HIV-1 growth. The remainder of the work describes how these peptides bind to RRE RNA, while demonstrating that they are non-toxic and bind HIV-1 in a concentration dependent manner. A transporter protein termed Spinster homolog 2 (spns2) transports a signaling molecule known as sphingosine 1-phosphate (S1P). For our immune system to function properly, spns2 has to transport S1P to the appropriate places to signal to immune cells. Unfortunately, this is a problem in autoimmune and inflammatory diseases, such as multiple sclerosis, due to these diseases having an overactive immune system. A potential way to treat these diseases would be by inhibiting spns2. This work describes the design, synthesis, and biological evaluation of spns2 inhibitors. Many compounds were found to inhibit spns2 to a degree, but three compounds, in particular, show potent and effective inhibition in mice.

Doctor of Philosophy / In healthy individuals, the autoimmune system is the body's natural defense against foreign materials and organisms. The main tools utilized for this defense mechanism are immune cells. However, in patients suffering from autoimmune diseases, the autoimmune system is overactive resulting in its attack on healthy cells, which leads to reduced or eliminated function of the targeted organs. To suppress these overreactive immune responses, pharmaceutical intervention is needed. An integral part of autoimmune response is the lipid sphingosine-1-phosphate (S1P). Interactions of S1P with its response-inducing receptors prompts the release of immune cells, lymphocytes in particular, from lymph tissue to migrate and participate in the invoked immune response. The pharmaceutical industry has produced five FDA approved drugs that disrupt this S1P-receptor interaction by blocking the receptor to reduce the autoimmune response in patients suffering from autoimmune diseases such as multiple sclerosis and ulcerative colitis. However, these treatments had adverse side effects on the cardiovascular system due to the presence of S1P receptors in the heart. Due to this, there is attraction to target a different node of the S1P signaling pathway to avoid these side effects while still suppressing the immune response. A node that is a viable target for therapeutic target that has recently become the focus of medicinal chemistry campaigns is the transporter protein spinster homolog 2 (Spns2). This protein is responsible for the transport of S1P from intracellular space to extracellular space to interact with its receptors and induce the immune response. Recently, our group has developed several effective inhibitors of Spns2. In this dissertation, several improvements of previously reported inhibitors are revealed. The pinnacle of this work is the development of 4.22v that is optimized to have drug-like properties for testing in mice. Administration of 4.22v to mice resulted in reduced circulating lymphocytes and without showing signs of toxicity following chronic dosing for 14 days. These results suggest that 4.22v is a potential drug candidate and is currently undergoing further biological evaluation.

Diseases such as malaria and dengue impose great economic burdens and are a serious threat to public health, with young children being among the worst affected. These diseases are transmitted by mosquitoes, also called disease vectors, which are able to transmit both parasitic and viral infections. One of the most important strategies in the battle against mosquito-borne diseases is vector control by insecticides and the goal is to prevent people from being bitten by mosquitoes. Today’s vector control methods are seriously threatened by the development and spread of insecticide-resistant mosquitos warranting the search for new insecticides. This thesis has investigated the possibilities of vector control using non-covalent inhibitors targeting acetylcholinesterase (AChE); an essential enzyme present in mosquitoes as well as in humans and other mammals. A key requirement for such compounds to be considered safe and suitable for development into new public health insecticides is selectivity towards the mosquito enzyme AChE1. The work presented here is focused on AChE1 from the disease transmitting mosquitoes Anopheles gambiae (AgAChE1) and Aedes aegypti (AaAChE1), and their human (hAChE) and mouse (mAChE) counterparts. By taking a medicinal chemistry approach and utilizing high throughput screening (HTS), new chemical starting points have been identified. Analysis of the combined results of three different HTS campaigns targeting AgAChE1, AaAChE1, and hAChE allowed the identification of several mosquito-selective inhibitors and a number of compound classes were selected for further development. These compounds are non-covalent inhibitors of AChE1 and thereby work via a different mechanism compared to current anti-cholinergic insecticides, whose activity is the result of a covalent modification of the enzyme. The potency and selectivity of two compound classes have been explored in depth using a combination of different tools including design, organic synthesis, biochemical assays, protein X-ray crystallography and homology modeling. Several potent inhibitors with promising selectivity for the mosquito enzymes have been identified and the insecticidal activity of one new compound has been confirmed by in vivo experiments on mosquitoes. The results presented here contribute to the field of public health insecticide discovery by demonstrating the potential of selectively targeting mosquito AChE1 using non-covalent inhibitors. Further, the presented compounds can be used as tools to study mechanisms important in insecticide development, such as exoskeleton penetration and other ADME processes in mosquitoes.

Parkinson’s disease (PD) is an age-related neurodegenerative disorder. The degeneration of the neurons of the substantia nigra in the midbrain leads to the loss of dopamine from the striatum, which is responsible for the motor symptoms of PD. In the brain, the enzyme, monoamine oxidase B (MAOB), An analysis of the Lineweaver-Burk plots indicated that 7-(3-bromobenzyloxy)-3,4-dihydro-2(1H)- quinolinone inhibits MAO-B with a Ki value of 2.7 nM. An analysis of the structure-activity relationships for MAO-B inhibition shows that substitution on the C7 position of the 3,4-dihydro- 2(1H)-quinolinone moiety leads to significantly more potent inhibition compared to substitution on C6. In this regard, a benzyloxy substituent on C7 is more favourable than phenylethoxy and phenylpropoxy substitution on this position. In spite of this, C6-substituted 3,4-dihydro-2(1H)-quinolinone with potent MAO-B inhibitory activities were also identified. An analyses of selected properties of the 3,4-dihydro-2(1H)- quinolinones showed that the compounds are highly lipophilic with logP values in the range of 3.03- 4.55. LogP values between 1 and 3 are, however, in the ideal range for bioavailability. The compounds synthesised have logP values higher than 3, which may lead to lower bioavailability. Laboratory data further showed that none of the 3,4-dihydro-2(1H)-quinolinones are highly toxic to cultured cells at the concentrations, 1 μM and 10 μM, tested. For example, the most potent MAO-B inhibitor, 7-(3-bromobenzyloxy)-3,4-dihydro-2(1H)-quinolinone, reduced cell viability to 88.11% and 86.10% at concentrations of 1 μM and 10 μM, respectively. These concentrations are well above its IC50 value for the inhibition of MAO-B. At concentrations required for MAO-B inhibition, the more potent 3,4-dihydro-2(1H)-quinolinones are thus unlikely to be cytotoxic. It may thus be concluded that C7-substituted 3,4-dihydro-2(1H)-quinolinones are promising highly potent and selective MAO-B inhibitors, and thus leads for the therapy of Parkinson’s disease. represents a major catabolic pathway of dopamine. Inhibitors of MAO-B conserve the depleted supply of dopamine and are thus used in the therapy of PD. In the present study, a series of 3,4- dihydro-2(1H)-quinolinone derivatives were synthesized and evaluated as inhibitors of recombinant human MAO-A and MAO-B. These quinolinone derivatives are structurally related to a series of coumarin (1-benzopyran-2-one) derivatives, which has been reported to act as MAO-B inhibitors. C6- and C7-substituted 3,4-dihydro-2(1H)-quinolinone derivatives were synthesized by reacting 6- or 7- hydroxy-3,4-dihydro-2(1H)-quinolinone with an appropriately substituted alkyl bromide in the presence of base. To evaluate the MAO inhibitory properties (IC50 values) of the quinolinone derivatives the recombinant human MAO-A and MAO-B enzymes were used. The reversibility of inhibition of a representative 3,4-dihydro-2(1H)-quinolinone derivative was examined by measuring the recovery of enzyme activity after the dilution of the enzyme-inhibitor complexes, while the mode of MAO inhibition was determined by constructing Lineweaver-Burk plots. To determine the lipophilicity of the 3,4-dihydro-2(1H)-quinolinone derivatives, the logP values were measured. The toxicity of the 3,4-dihydro-2(1H)-quinolinone derivatives towards cultured cells (cytotoxicity) was also measured. The results document that the 3,4-dihydro-2(1H)-quinolinone derivatives are highly potent and selective MAO-B inhibitors with most homologues exhibiting IC50 values in the nanomolar range. The most potent MAO-B inhibitor, 7-(3-bromobenzyloxy)-3,4-dihydro-2(1H)-quinolinone, exhibits an IC50 value of 2.9 nM with a 2750-fold selectivity for MAO-B over the MAO-A isoform. As a MAO-B inhibitor, this compound is approximately equipotent to the most potent coumarin derivative (IC50 = 1.14 nM) reported in literature. Since MAO-B activity could be recovered after dilution of enzyme-inhibitor mixtures, it may be concluded that 7-(3-bromobenzyloxy)-3,4-dihydro-2(1H)- quinolinone is a reversible MAO-B inhibitor. The Lineweaver-Burk plots constructed for the inhibition of MAO-B by 7-(3-bromobenzyloxy)-3,4-dihydro-2(1H)-quinolinone were linear and intersected on the y-axis. These data indicated that this compound also is a competitive MAO-B inhibitor. / MSc (Pharmaceutical Chemistry), North-West University, Potchefstroom Campus, 2014