La diffusion Raman exaltée de surface (SERS) est utilisée pour la mise au point d’un biocapteur capable de détecter des pesticides dans l’eau, en se basant sur le suivi de l’activité enzymatique de l’Acétylcholinestérase (ACHE). Les nanoparticules d’or sont utilisées comme substrats SERS actifs. Le signal Raman exalté de l’analyte est optimisé en testant plusieurs types de nanoparticules.Le Raman SERS a permis la détection directe du Paraoxon (PO) et du carbaryl (CA) et la possibilité de suivi de l’activité de l’ACHE. En absence d'inhibiteurs, la molécule d’acétylcholine (ATC) est transformée en acide acétique et en choline par l’enzyme ACHE. La mesure de l’activité de l’ACHE repose sur le suivi des concentrations en ATC car sa transformation est inhibée en présence de pesticides. Il a été ainsi possible d’établir une relation linéaire entre la concentration de pesticides et l’exaltation du signal Raman de l’ATC non transformé. La méthode a permis la détection du PO et du CA, avec une limite de détection beaucoup plus faible que la détection directe. Ce biocapteur basé sur l’activité de l’ACHE a ensuite été utilisé pour l'évaluation d’autres polluants (inhibiteurs d’ACHE) comme les additifs contenus dans les plastiques notamment. Enfin, nous avons développé une seconde approche qui consistait à mesurer l’activité de l’ACHE en utilisant la diffusion dynamique de la lumière. En effet, nous avons montré que les paramètres physicochimiques (agrégation) des AuNPs en contact avec certaines molécules, sont fortement influencés par l’activité enzymatique de l’ACHE. C’est ce phénomène d’instabilité qui nous a permis de distinguer entre les deux cas : absence et présence de PO. / Surface-enhanced Raman scattering (SERS) was used to develop a biosensor for the detection of pesticides through the monitoring of the enzymatic activity of acetylcholinesterase (ACHE). Gold nanoparticles (AuNPs) were used as an active SERS substrate. The enhanced Raman signal of the analyte is optimized by testing several types of nanoparticles. Raman SERS allowed the direct detection of Paraoxon (PO) and carbaryl (CA) pesticides and the possibility of follow-up of the activity of the ACHE. In the absence of inhibitors, the acetylcholine (ATC) is transformed into acetic acid and choline by the enzyme ACHE. The measurement of ACHE activity is performed through the monitoring of ATC concentrations because its transformation is inhibited in the presence of pesticides. Results showed a linear correlation between the concentration of pesticides and the SERS signal of the untransformed ATC. The method was optimized for the quantification of paraoxon and carbaryl with a limit of quantification much lower than the one obtained with a direct detection. Their identification was also possible using chemometrics. This biosensors, based on the ACHE activities, was applied to the evaluation of emergent pollutants: additives of commercial polymers. Our results suggested that most of the tested polymers contained molecules that act as inhibitors of the ACHE. Finally, we propose another very simple approach to measure the ACHE activity using dynamic light scattering measurements. We found that the physicochemical parameters (aggregation) of AuNPs were strongly influenced by the enzymatic activity of ACHE when in contact with specified molecules, allowing to detect the presence of PO.

Submitted by Maria Medeiros (maria.dilva1@ufcg.edu.br) on 2018-07-27T15:07:10Z No. of bitstreams: 1 DAYVISON JOSÉ NUNES DO NASCIMENTO - DISSERTAÇÃO (PPGECA) 2016.pdf: 2467199 bytes, checksum: 6112558d9b477651302684cf6df39802 (MD5) / Made available in DSpace on 2018-07-27T15:07:10Z (GMT). No. of bitstreams: 1 DAYVISON JOSÉ NUNES DO NASCIMENTO - DISSERTAÇÃO (PPGECA) 2016.pdf: 2467199 bytes, checksum: 6112558d9b477651302684cf6df39802 (MD5) Previous issue date: 2016-08-26 / Capes / Corpos hídricos superficiais são mais susceptíveis à contaminação por agrotóxicos devido às atividades agrícolas desenvolvidas em suas áreas de recarga. Este trabalho avaliou a presença de agrotóxicos do grupo carbamato e piretróide em águas brutas e tratadas dos reservatórios Epitácio Pessoa (Boqueirão), a montante, e Argemiro de Figueiredo (Acauã), a jusante da região hidrográfica do médio curso do rio Paraíba, por meio de metodologia analítica por cromatografia líquida de alta eficiência. Os resultados indicaram que as metodologias apresentaram seletividade, linearidade (R² ≥ 0,9982), precisão e exatidão (DPR ≤ 4,27 %) e robustez, dentro das especificações estabelecidas pela ANVISA e Inmetro. Do grupo químico carbamato, foram detectados os agrotóxicos aldicarbe sulfona, carbaril e metiocarbe no reservatório de montante e aldicarbe sulfona no reservatório de jusante. Todas as concentrações mantiveram-se dentro dos limites exigidos pelos padrões de potabilidade de água de consumo humano, nacional e/ou internacionais. Apenas o agrotóxico carbaril não apresentou conformidade com a Resolução CONAMA 357/2005, que define as concentrações máximas permitidas para enquadramento de águas superficiais. Do grupo químico piretróide foram detectados os agrotóxicos ciflutrina e flumetrina em ambos os reservatórios estudados. A concentração do agrotóxico cilfutrina manteve-se dentro do padrão de potabilidade internacional, no entanto o princípio ativo flumetrina não apresenta valores limites indicados nos padrões de potabilidade nacional e internacionais. O tratamento convencional para potabilização de água empregado na área de estudo não se mostrou eficiente para a remoção de agrotóxicos. / Superficial water bodies are more susceptible to pesticide contamination due to agricultural activities in their recharging areas. This study evaluated the presence of carbamate and pyrethroid pesticides group in raw and treated waters from the upstream reservoir Epitácio Pessoa (Boqueirão) and the downstream reservoir Argemiro de Figueiredo (Acauã), in the hydrographic region of the middle course of Paraiba River, northern Brazil, through an analytical methodology by high-performance liquid chromatography. Results indicated that the methodology presented selectivity, linearity (R² ≥ 0.9982), accuracy and precision (RSD ≤ 4.27%) and robustness within the specifications set by ANVISA and Inmetro. Of Chemical group carbamate, the pesticides aldicarb sulfone, carbaryl and methiocarb were detectes in the upstream reservoir and aldicarb sulfone was detectes in the downstream reservoir. All concentrations have remained within the limits required by the national and/or international drinking water standards. Only the pesticide carbaryl did not show compliance with Resolution 357/2005, of Brazilian Environment Ministry, which defines the maximum allowable concentrations for classification of surface waters. The pyrethroid chemical group the cyfluthrin and flumethrin pesticides were detected in both studied reservoirs. The concentration of the pesticide cilfutrina remained within the international potability standard, however the active flumethrin principle has no limits indicated in the standards of national and international potability. Conventional water treatment applied in the study area did not show ability for the removal of carbamate pesticides.

The submitted thesis deals with determination of selected pesticides in water samples by gas chromatography. The target pesticides belong to the group of organophosphates (chlorpyrifos, diazinon, parathion, dimethoate, phosmet) and carbamates (carbofuran, aldicarb, methiocarb, pirimicarb, and propamocarb). In the theoretical part, the division of pesticides is stated, and their properties are described, as well as their fate in the environment and their negative effects. Then, the possibilities of analytical determination based on gas chromatography are characterized. The experimental part describes the treatment of the samples and their subsequent analysis. Solid phase extraction was chosen as the extraction technique. Two kinds of cartridges were optimized (Oasis HLB and Supelclean ENVI-18) in combination with various elution reagents. The most suitable combination was then used for processing of real samples of waste-water, which was taken from WWTP in Brno Modřice. For the final determination of the target compounds by gas chromatography, two types of detectors were used: mass spectrometer and an electron capture detector.

Indiana University-Purdue University Indianapolis (IUPUI) / Histones are highly basic proteins which when digested by trypsin are hard to analyze using mass spectrometry. Because histones are basic nuclear proteins, a nuclei prep followed by acid extraction is the best purification strategy to increase overall abundance of purified histones. Blocking the lysine residues and cleaving with trypsin is a useful technique to increase detection of histone peptides using MudPIT. In particular, carbamylation and propionylation are the best two methods to block lysine residues. Using both propionylation and carbamylation along with no treatment has been shown to increase the identification of unmodified and modified histone peptides when coupled with MudPIT analysis.

Worldwide, malaria is one of the deadliest diseases. In 2016 it sickened 216 million people and caused 445,000 deaths. In order to control the spread of this deadly diseases to human, we can either target the mosquito vector (Anopheles gambiae) or the parasite (Plasmodium falciparum). Due to recent emergence of resistance to current insecticides and antimalarial drugs there is a pressing need to discover and develop new agents that engage new targets in these organisms. To circumvent the effect of resistance to pyrethroid insecticides on the efficacy of insecticide treated nets (ITNs), the use of acetylcholinesterase (AChE) inhibitors on ITNs has drawn attention. In the first project, we explored a small library of γ- substituted oxoisoxazole- 2(3H)-carboxamides and isoxazol-3-yl carbamates, and nitriles as AChE inhibitors targeting wild- type (G3) and resistant (Akron) An. gambiae mosquito. In total 23 compounds were synthesized and evaluated. Both carbamates and carboximides with a 2-cyclopropylethyl side chain (1-87a and 1-88a) were extremely toxic to Akron mosquitos, yet these compounds did not exhibit appreciable selectivity between human and An. gambiae AChE. Unfortunately, none of the nitriles showed appreciable toxicity to G3 strain of the mosquitoes, nor did they inhibit An. gambiae AChE. In the second project, conducted in collaboration with Professor Michael Klemba, we focused on the mode of action of an established antimalarial drug, Mefloquine (MQ). Dr. Klemba's recently developed amino acid efflux assay was used to determine the effect of MQ and its open-ring analogs on hemoglobin endocytosis and catabolism in P. falciparum-infected erythrocytes. In total 26 MQ analogs were synthesized and 18 were studied in depth to determine their potency to inhibit leucine (Leu) efflux and parasite growth (SYBR Green). An excellent correlation (R² = 0.98) over nearly 4 log units was seen for these 18 compounds in the two assays. These data are consistent with the hypothesis that the antimalarial action of these compounds principally derives from inhibition of hemoglobin endocytosis. After this observation, a number of photo-affinity probes were designed and synthesized in hopes of isolating the molecular target of MQ. These analogs are currently being used by Dr. Klemba in pull-down experiments. In the third project, conducted in collaboration with Professor Belen Cassera, we sought to optimize a new antimalarial drug lead that would circumvent current resistance mechanisms. In Plasmodium parasites, the methylerythritol phosphate (MEP) pathway is known to be essential for its growth. This pathway is absent in humans, presenting the opportunity to develop potentially safe and effective therapeutic candidates. Previous work in the Cassera and Carlier lab had established that MMV008138 was the only compound in the Malaria Box that targeted the MEP pathway and that it was (1R,3S)-configured. My research expanded previous efforts in the Carlier group and produced synthesis of 73 analogs of MMV008138 (3-21a'1) that were tested for growth inhibition. These analogs featured variation at the A-, B-, C- and D-ring. In the process, a novel Pictet-Spengler ring expansion reaction of ortho-substituted acetphenones was discovered. The ring-expanded products were identified by means of 1D and 2D NMR experiments, HRMS, and X-ray crystallography. Among the 73 analogs prepared, four compounds showed similar growth inhibition potency to the lead 3-21a'1. In particular, the methoxyamide 3-80a, and the fluorinated A-ring analogs 3-124a, 3-124c and 3-124d all showed excellent (500-700 nM) growth IC₅₀ values against P. falciparum. All four showed full rescue upon co-application of IPP (200 μM), confirming that they target the MEP pathway. ADME-Tox evaluation of these new analogs will soon be underway. / PHD / Malaria is a severe and potentially fatal mosquito-borne disease. The continuous emergence of insecticide-resistant mosquitoes and drug-resistant parasite strains necessitates the development of novel antimalarial agents, notably those that engage new targets in these organisms. Herein we present three projects in which the synthesis and characterization of new malaria insecticide and therapeutic candidates are described. Our aim in the first project was to synthesize acetylcholinesterase (AChE) inhibitors as potential mosquitocides to be deployed on insecticide-treated nets. Three different classes of compounds were synthesized and characterized. Their potency to inhibit the wild-type and insecticide-resistant mosquito AChE, and their corresponding mosquito toxicities were assessed. Mosquito-toxic compounds were identified, but they did not show appreciable selectivity between mosquito and human AChEs. The second project was directed toward finding the biological target of a known antimalarial drug; mefloquine (MQ). Numerous different MQ analogs were synthesized, and their potency was assessed in two biochemical assays. The results of this study strongly suggest that MQ kills malaria parasites by preventing them from ingesting the red blood cell hemoglobin. The third project was concerned with the optimization of a compound (MMV008138) that kills malaria parasites by preventing it from synthesizing a key biochemical building block (IPP). Several new compounds were prepared that had similar antimalarial activity to MMV008138, of which many have better potential to serve as antimalarial drugs. In addition, these studies provided valuable insights for the design of further improved analogs.

L'étude porte sur une électrode à butyrylcholinestérase immobilisée, destinée à la détection de pesticides et insecticides inhibiteurs de cette enzyme, en particulier les organophosphorés et les carbamates. Les conditions optimales de mise au point et d'utilisation de cette électrode sont étudiées, ainsi que son comportement en présence d'inhibiteurs solubles dans l'eau, représentés, par le paraoxon. La détection d'inhibiteurs insolubles dans l'eau est effectuée dans un mélange tampon phosphate-éthanol ou méthanol. Le champ des interférences connues est élargi aux sels d'halogénures, et les possibilités de régénération de la butyrylcholinestérase inhibée optimisées. La détection en routine d'inhibiteurs dans les eaux exposées à des risques de pollution accidentelle est mise au point grâce à un ensemble automatisé, dont le fonctionnement est explicité. Un modèle théorique permet d'expliciter certains résultats de l'expérience.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-05-04T12:42:14Z No. of bitstreams: 1 angelinamariadealmeida.pdf: 23133254 bytes, checksum: 7560d658fe12ed7f6166fc99ab314157 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-05-17T13:30:51Z (GMT) No. of bitstreams: 1 angelinamariadealmeida.pdf: 23133254 bytes, checksum: 7560d658fe12ed7f6166fc99ab314157 (MD5) / Made available in DSpace on 2017-05-17T13:30:51Z (GMT). No. of bitstreams: 1 angelinamariadealmeida.pdf: 23133254 bytes, checksum: 7560d658fe12ed7f6166fc99ab314157 (MD5) Previous issue date: 2016-07-29 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Os valores terapêuticos do ouro são conhecidos desde a China antiga e, atualmente, complexos de ouro são empregados no tratamento da artrite reumatóide. Outras propriedades biológicas relativas aos complexos de ouro(I) vêm sendo reportadas na literatura, como atividade antitumoral, antibacteriana, antiviral e antifúngica. A primeira parte dessa tese descreve a síntese de novos complexos lipofílicos de ouro(I) contendo núcleo 1,3,4-oxadiazol-2-tiona ou 1,3-tiazolidina-2-tiona, além de serem constituídos por fosfinas terciárias, como trifenilfosfina ou trietilfosfina. Após caracterização através de métodos espectroscópicos usuais (RMN de 1H, 13C, 31P, IV e EMAR), foram realizadas avaliações biológicas in vitro para todos os complexos de ouro(I) e seus respectivos ligantes orgânicos. Os resultados citotóxicos frente a linhagens tumorais (CT26WT e B16F10) e normais (BHK21) indicam acentuada atividade antitumoral devido aos baixos valores de IC50 quando comparados aos valores obtidos para os ligantes orgânicos e para a Cisplatina. A atividade antibacteriana dos complexos de ouro(I) contra as bactérias Gram-positivas Staphylococcus aureus e Staphylococcus epidermidis também mostrou-se satisfatória, uma vez que os complexos exibem baixos valores de CIM comparados aos resultados obtidos para os ligantes orgânicos e cloranfenicol. O desenvolvimento de metodologias de catálise por metais de transição, em especial o uso de paládio, tem atraído considerável atenção no meio acadêmico e industrial. Assim, a segunda parte do trabalho aborda o desenvolvimento de um método geral de preparação de ésteres ativos via alcoxicarbonilação catalisada por paládio e o acoplamento carbonilativo entre haletos de arila, cianato de potássio, álcoois e monóxido de carbono catalisada por paládio. Em ambos os casos, verifica-se a generalidade dos protocolos devido à diversidade e aos bons rendimentos do escopo obtido a partir de diferentes nucleófilos e haletos aromáticos e heteroaromáticos. / Therapeutic gold values are known since ancient China and gold complexes are currently employed in the treatment of rheumatoid arthritis. Other biological properties relative to the complexes of gold(I) have been reported in the literature, such as antitumor activity, antibacterial, antiviral and antifungal. The first part of this thesis describes the synthesis of novel lipophilic complexes of gold(I) containing core 1,3,4-oxadiazol-2-thione or 1,3-thiazolidine-2-thione, and they are constituted by tertiary phosphines, such as triphenylphosphine or triethylphosphine. After characterization using usual analythical methods (NMR 1H, 13C, 31P, IR and HRMS) the biological evaluations were performed in vitro for all complexes of gold(I) and their organic ligands. The cytotoxic results against tumor cells (CT26WT and B16F10) and normal cells (BHK21) show pronounced antitumor activity due to low IC50 values compared to the values obtained for the corresponding ligands and Cisplatin. The antibacterial activity for the complexes of gold(I) against Gram-positive bacteria Staphylococcus aureus and Staphylococcus epidermidis also proved to be satisfactory, since the complexes exhibit low MIC values compared to the results obtained for the ligands and chloramphenicol. The development of catalytic methodologies by transition metals, in particular the use of palladium, has attracted considerable attention in the academia and industry. Thus, the second chapter covers the development of a general method for preparation of active esters via palladium catalyzed alkoxycarbonilation and carbonilative coupling of aryl halides, potassium cyanate, alcohols and carbon monoxide. In both cases the generality of the protocols is confirmed by the diversity and good yields obtained to the scope from different nucleophiles and aromatic and heteroaromatic halides.

The increased use of pesticides has resulted in a corresponding increase in concern for the effect they may have on the health of humans and other non-target organisms. The two main areas of concern are the toxicological effects that mixtures of pesticides may have as well as the endocrine disrupting effects. Although the individual pesticides may be present at concentrations below the levels deemed to be detrimental to health, it has been argued that their combined effect may still result in elevated health risks. Another important aspect of pesticide risk assessment requires a consideration of the breakdown products of pesticides and their effect on human health. There has been very little research into the effects of degradation products and this issue should be addressed as these could potentially pose a higher risk than their parent compounds. One of the most important bio-markers available for use is the ubiquitous enzyme acetylcholinesterase (AChE). This enzyme is responsible for one of the most important functions in the body; namely nerve impulse transmission, upon which all life depends. The inhibition of this enzyme indicates toxicity and as a subsequence, a threat to the organism’s well-being. Bioassays have also recently been developed to test chemicals for endocrine disrupting effects. These tests rely on a dose response equivalent to that of the most potent well known estrogen 17-β estradiol. Any chemical that has a measurable response is deemed to display endocrine disrupting effects. This first aim of this study was to investigate the toxicological and endocrine disrupting effects of three organophosphorus pesticides; aldicarb, parathion and demeton-S-methyl, in addition to two breakdown products; aminophenol and p-nitrophenol. Two carbamate pesticides; carbaryl and carbofuran were also analysed. The toxicological effects of mixtures of the parent pesticide compounds were tested to assess if any antagonistic, additive or synergistic effects were observed. This data was then used in conjunction with an artificial neural network to assess if individual pesticides could be distinguished from mixtures of pesticides. A final objective was to sample various Eastern Cape water sources, utilising the enzymatic assay to determine the presence of any of these pesticides in these samples. There were several conclusions drawn from this study. AChE was successfully used as an assay to test the toxicity of the pesticides under investigation, based on their inhibition of this enzyme. An important factor for consideration throughout the study was the need to establish basal and monitor AChE activity (i.e. the need to monitor AChE activity in the absence of any pesticide). This ensured accurate comparison of the results obtained. It was found that demeton-S-methyl was the most potent of these pesticides followed by carbaryl, parathion, aldicarb and finally carbofuran, and that carbofuran could potentiate AChE. The results indicated that pesticide mixtures generally exhibited an additive inhibitory effect on AChE, although at some concentrations of pesticides, synergistic and antagonistic effects were noted. From the data using mixtures of pesticides, a feed forward neural network was created that was successfully able to distinguish individual pesticides from mixtures within its training parameters. None of the pesticides tested displayed endocrine disrupting properties in the Yeast Estrogen Screen (YES), T47D-KBluc and MDA-kb2 bio-assays. Other studies reported mixed results in this regard and thus no final conclusions could be drawn. The Blaauwkrantz River, Kariega River, Sundays River, Swartkops River and Kowie River were all tested for pesticides and although positive results were recorded, conventional methods indicated that there were no pesticides in the rivers. There were, however, trace metals present which are known to inhibit AChE, thus causing a false positive result. These results indicated that AChE can be used as a high throughput initial pre-screening tool, but that it cannot serve as a substitute for more accurate conventional testing methods.

Les prodrogues sont des dérivés biologiquement inactifs d’un principe actif qui, après administration à un organisme, subissent une transformation chimique ou enzymatique pour libérer le principe actif au site d’action. Elles améliorent les propriétés physicochimiques du principe actif pour permettre un meilleur transport à travers les barrières biologiques et pour augmenter l’activité in vivo. Elles sont utilisées pour améliorer la formulation et l’administration, accroître la perméabilité et l’absorption, modifier le profil de distribution et éviter le métabolisme et la toxicité. Cette approche est très utile pour améliorer l'administration de principes actifs. Il existe deux types de prodrogues : les prodrogues liées à un transporteur et les bioprécurseurs. Dans le premier cas, la molécule active est liée par une liaison covalente à un groupement temporaire, ce qui fournit une nouvelle molécule, qui est inactive. Le groupement temporaire libéré ne doit pas avoir, par lui-même, d'action pharmacologique ni de toxicité. Dans le second cas, le principe actif est transformé métaboliquement ou chimiquement par réaction d’hydratation, d’oxydation ou de réduction. Les azapeptides sont des mimes peptidiques dans lesquels un ou plusieurs carbones de la chaîne peptidique sont remplacés par des atomes d’azote. Ce remplacement augmente la rigidité de la chaîne peptidique et favorise le repliement de type β. Le repliement β des azapeptides est associé à plusieurs propriétés thérapeutiques. Certains azapeptides ont montré une meilleure activité, une meilleure sélectivité et une plus grande stabilité comparativement aux peptides parents ce qui prolonge leur durée d'action et les rend plus résistants aux dégradations métaboliques. Ce mémoire s’intéresse particulièrement à l’azapeptide : [aza(p-MeO)F⁴]-GHRP-6. Celui-ci est un analogue du peptide sécréteur d’hormone de croissance 6 (GHRP-6, H-His-D-Trp-Ala-Trp-D-Phe-Lys-NH₂), qui possède une affinité pour deux récepteurs distincts : les récepteurs de growth hormone secretagogue receptor 1a (GHS-R1a) et le récepteur cluster of differentiation 36 (CD36). L’[aza(p-MeO)F⁴]-GHRP-6 démontre une sélectivité envers le récepteur CD36 offrant des possibilités de traitement de maladies telles que l’athérosclérose et la dégénérescence maculaire liée à l’âge (DMLA). De plus, le récepteur CD36 peut interagir avec un corécepteur toll-like receptor 2 (TLR2), et l’[aza(p-MeO)F⁴]-GHRP-6 peut réduire des réponses immunitaires innées. La stratégie des prodrogues a été utilisée dans ce mémoire pour augmenter la durée d’action de l’azapeptide [aza(p-MeO)F⁴]-GHRP-6. Plus précisément, cinq analogues des prodrogues α-acyloxyéthylcarbamates de l’aza(p-MeO)F⁴-GHRP-6 ont été synthétisées. Ce mémoire présente la première synthèse de prodrogues α-acyloxyéthylcarbamates à caractère PEG de l’[aza(p-MeO)F⁴]-GHRP-6. / A prodrug is a biologically inactive derivative of a drug which after administration undergoes chemical or enzymatic modification to release the active drug at targeted sites of activity. Prodrugs improve physicochemical properties to enable better transport through biological barriers and enhance activity. They are used to improve formulation and administration, to enhance permeability and absorption, to modify distribution profiles and to avoid metabolism and toxicity. The prodrug approach is useful for improving drug delivery. Prodrugs are classified into two types: carrier-linked prodrugs and bio-precursors. In the first case, the parent drug is linked by a covalent bond to an inert carrier or transport moiety. The carrier should not be active or toxic. The active drug is released by a chemical or enzymatic cleavage in vivo. In the second case, the parent drug is converted metabolically or chemically by hydration, oxidation or reduction reactions. Azapeptides employ a semicarbazide as an amino amide surrogate in a peptide analog in which the backbone α-CH is replaced by nitrogen. Through electronic interactions, the semicarbazide favors backbone β-turn geometry due to a combination of urea planarity and hydrazine nitrogen lone pair – lone pair repulsion. Azapeptides have proven therapeutic utility. Some of them exhibit better selectivity, activity and stability than the parent peptides with increased duration of action and improved metabolic stability. Growth hormone releasing peptide-6 (GHRP-6, H-His-D-Trp-Ala-Trp-D-Phe-Lys-NH₂) is a synthetic peptide possessing an affinity for two different receptors: growth hormone secretagogue receptor 1a (GHS-R1a) and cluster of differentiation receptor 36 (CD36). The GHRP-6 azapeptide analogue, [aza(p-MeO)F⁴]-GHRP-6, has exhibited good affinity for CD36 and reduced nitric oxide overproduction in macrophage cells stimulated with the TLR-2 agonist R-FSL-1. Azapeptide ligands of CD36, such as [aza(p-MeO)F⁴]-GHRP-6, offers potential as prototypes for developing treatments of diseases such as atherosclerosis and age-related macular degeneration. A prodrug strategy has been pursued to improve the pharmacokinetic properties, such as duration of action, of [aza(p-MeO)F⁴]-GHRP-6. The first examples of α-acyloxyethyl carbamate peptides have been prepared. Five α-acyloxyethyl carbamate analogues of [aza(p-MeO)F⁴]-GHRP-6 have been synthesized by routes featuring acylation of the resin-bound peptide using different activated α-acyloxyethyl carbonates prior to resin cleavage and side chain deprotection. The evaluation of the activity of the pharmacokinetic properties of the [aza(p-MeO)F⁴]-GHRP-6 prodrugs is currently in progress and will be reported in due time.

No description available.