Methyldopa (L-alpha-Methyl-3,4-dihydroxyphenylalanine) is a catecholamine used as an antihypertensive agent.1 Alpha-Methyldopa is not used as frequently anymore due to side effects, but it is still used especially in developing countries due to its low cost. Indications are mostly for the management of pregnancyinduced hypertension (PIH), as it is relatively safe in pregnancy compared to other antihypertensive drugs. This project is intended to increase the already-existing knowledge base of the mechanism of pharmacological action and to stimulate further investigation through research. The sympathetic nervous system is a division of the autonomic nervous system and it is responsible for the “flight-or-fight” response. It is involuntary and constantly active to maintain homeostasis in the human body. Sympathetic responses include an increase in heart rate, blood pressure and cardiac output, dilation of pupils and bronchioles, constriction of blood vessels, contraction of sphincters and inhibition of gut motility and secretions. The purpose of this study is to evaluate the activity of the sympathetic nervous system of volunteers by three different techniques (QT interval and Heart rate variability and Skin conductance) after a week of a bi-daily dosage of alphamethyldopa. All volunteers received either 250mg alpha-methyldopa orally or a placebo tablet in a randomized, double blind, placebo controlled study design. The correlation between the following techniques was also evaluated: Skin conductance as measured by the ProComp Infiniti Biofeedback apparatus, QT interval on ECG and HRV measured with Viport apparatus. A salivary sample was collected to evaluate the effect of alpha-methyldopa on salivary cortisol using an ELISA kit for analysis. / Dissertation (MSc)--University of Pretoria, 2013. / gm2014 / Pharmacology / unrestricted

The metabolism of tyrosine is essential for many critical biochemical events including catecholamine synthesis, melanogenesis and insect cuticle sclerotization. These pathways are highly regulated in both insects and mammals by many well-characterized enzymes including dopa decarboxylase and tyrosine hydroxylase. On the other hand, there are still many enzymes involved in these processes that we know very little about. Dopachrome tautomerase (DCT), dopachrome conversion enzyme (DCE) and α-methyldopa resistant protein (AMD) fall into the category of the less characterized enzymes. Dopachrome is a pivotal intermediate in melanogenesis. Mammalian DCT and insect DCE both use dopachrome as a substrate. DCE catalyzes a decarboxylative structural rearrangement of dopachrome to 5,6-dihydroxyindole (DHI), whereas DCT mediates the isomerization/tautomerization of dopachrome to 5,6-dihydroxyindole-2-carboxylic acid (DHICA). DHI is oxidized easily, leading to the production of melanin, as well as reactive oxygen species (ROS). DHICA is less reactive, relative to DHI, and consequently produces less toxic byproducts during melanogenesis; therefore DCT plays an important role in detoxification of DHI and ROS. Purification and MS analysis of DCE and DCT determined that N-glycosylation is a primary post-translational modification. Q-TOF mass spectrometry was used to determine N-glycosylation patterns from Aedes aegypti DCE and MALDI-TOF/TOF was used to determine multiple glycosylation sites in DCT. N-glycosylation is critical for the folding and trafficking of secreted proteins in the endomembrane system. The analysis of glycosylation sites in DCE and DCT therefore is essential toward achieving a comprehensive understanding of their structure and function. Like DCT, AMD also plays a protective role. The AMD protein was originally identified in Drosophila mutants hypersensitive to α-methyldopa, an inhibitor of dopa decarboxylase (DDC). Production of dopamine by DDC is critical for developing insects because dopamine conjugates are used as crosslinking agents for cuticle sclerotization. Although there has been much discussion into the function of AMD, what exactly this protein does has been unknown. AMD shares 48% sequence identity with DDC, however we have found that AMD is an enzyme, which possesses a different catalytic activity. GC-MS analysis of AMD enzymatic reaction components revealed that AMD catalyzes the oxidative decarboxylation of L-DOPA to DOPAL, and also the oxidative decarboxlation of α-methyldopa to 3,4-dihydroxyphenylacetone. In summary, multiple N-glycosylation sites were characterized in DCT and DCE, furthermore a new protein function has been demonstrated for AMD. These experiments were performed using classical biochemistry techniques in combination with mass spectrometry. / Ph. D.

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-06-28T14:51:48Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) UNIVERSIDADE FEDERAL DE PERNAMBUCO (Salvo Automaticamente)_correto.pdf: 1889034 bytes, checksum: eb0752322509ac8a41b42b336e30870a (MD5) / Made available in DSpace on 2016-06-28T14:51:48Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) UNIVERSIDADE FEDERAL DE PERNAMBUCO (Salvo Automaticamente)_correto.pdf: 1889034 bytes, checksum: eb0752322509ac8a41b42b336e30870a (MD5) Previous issue date: 2014-05-30 / A metildopa (a-metil-3, 4-dighidro-l-fenilalanina) é um agente hipotensor de ação central, é uma pró-droga, que exerce sua ação anti-hipertensiva através de um metabólito ativo. A estabilidade é um importante parâmetro para avaliar a segurança, eficácia e qualidade exigidas para o registro sanitário de produtos farmacêuticos. Vários países publicam diretrizes para estabilidade farmacêutica. No Brasil, estes estudos devem ser conduzidos segundo o Guia para a Realização de Estudos de Estabilidade, publicada na resolução - RE n.01 de 29 de julho de 2005 e a RDC 58 de 20 de dezembro de 2013 que estabelece parâmetros para a notificação, identificação e qualificação de produtos de degradação em medicamentos com substâncias ativas sintéticas e semissintéticas, classificados como novos, genéricos e similares e dá outras providências. O objetivo desse trabalho foi desenvolver um método indicativo de estabilidade para comprimidos revestidos de metildopa 500mg, avaliando a especificidade e a seletividade deste método. Para avaliação da especificidade e seletividade do método foram mantidas amostras da metildopa matéria-prima, comprimido revestido 500mg e placebo nas seguintes condições de estresse: hidrólises (ácida, básica e neutra), oxidação e temperatura; as amostras também foram submetidas ao teste de fotoestabilidade. A seletividade do método também foi demonstrada após realização de testes com o padrão primário de metildopa contaminado com a impureza 3-O-metil-metildopa. Os resultados foram analisados segundo dados gerados por cromatografia líquida de alta eficiência (CLAE) com detector de arranjo de diodos (DAD). A 3-O-metildopa apresenta tempo de retenção relativo (TRR) de 1,37 frente à metildopa. A metildopa mostrou-se estável nas hidrólises neutras e ácida menos concentradas bem como na degradação térmica, oxidativa e na fotoestabilidade. Apresentou um decaimento muito acentuado nas condições básicas (NaOH 0,1 e 1,0M), sendo inadequado para o estudo de métodos indicativos de estabilidade como indica a RDC 58 de 2013. A condição mais severa da hidrolise ácida (HCl 5,0M) apresentou um teor de 77,80% para a matéria-prima e 82,99% para o comprimido revestido em comparação com o padrão de trabalho após 72 horas de estudo, ambos apresentaram um pico de degradação com TRR de aproximadamente 2,00. Na condição de hidrólise alcalina menos concentrada (NaOH 0,01M) apareceram produtos de degradação tanto na matéria-prima como para o comprimido revestido de metildopa, porém, o pico que apresenta área significativa apresenta TRR de 0.38 e o teor do fármaco foi de 73,49% para a matéria-prima e 74,48% para o comprimido revestido em comparação com o padrão de trabalho após 72 horas de estudo. Através das análises dos resultados obtidos utilizando as ferramentas de integração e de análise espectral para avaliação da similaridade e pureza dos picos, verifica-se que o método utilizado consegue detectar os produtos de degradação que venham a surgir durante os estudos de estabilidade. O método posteriormente foi validado utilizando como referências a RE 899 de 2003 e a norma técnica da ICH Q2 R1. O método desenvolvido e validado foi utilizado no estudo de estabilidade de um comprimido revestido de metildopa 500mg similar constante no mercado brasileiro, apresentando resultados dentro da especificação exigida para o produto. / Methyldopa (a-methyl-3,4-dihydro-l-phenylalanine) is a centrally acting antihypertensive agent, is a prodrug, which exerts its antihypertensive action through an active metabolite. Stability is an important parameter to evaluate the safety, efficacy and quality required for sanitary registration of pharmaceutical products. Several countries publish guidelines for pharmaceutical stability. In Brazil, the stability studies should be conducted according to the guide on conducting stability studies, published in the resolution RE 01 of July 29, 2005 and RDC 58 of December 20, 2013 laying down parameters for notification, identification and qualification of degradation products in medicine with synthetic and semi synthetic active substances classified as new, generic and similar and other measures. The aim of this study was to develop a stability indicating method for coated tablets 500mg of methyldopa following and evaluating the specificity and selectivity of this method. To assess the specificity and selectivity of the method of methyldopa samples were stored raw material, coated tablet 500mg and placebo in the following stress conditions: hydrolysis (acidic, basic and neutral), oxidation, light and temperature. The selectivity of the method was demonstrated after testing with the primary pattern methyldopa contaminated with impurity 3-O-methyl-methyldopa. The results were analyzed according to data generated by high performance liquid chromatography (HPLC) with diode array detector (DAD). 3-O-methyl-methyldopa has RRT 1.37 front methyldopa. Methyldopa was stable in neutral and acidic hydrolysis less concentrated as well as thermal, oxidative degradation and photostability. Showed a dramatic decay in basic conditions (NaOH 0,1 and 1,0M) and unsuitable for the study of stability indicating methods as shown in the RDC 58/ 2013. The most severe conditions of acid hydrolysis (5,0M HCl) showed a content of 77.80 % for the raw material and 82.99 % for the coated tablet compared the standard of work after 72 hours of study, both showed a peak of degradation with TRR approximately 2,00. In the condition of less concentrated alkaline hydrolysis (0,01M NaOH) appeared both in the degradation products as raw material for the coated tablet methyldopa, however, the peak that shows significant area RRT 0,38 and shows content of the drug was 73,49% for raw and 74,48% for the coated tablet compared the standard of work after 72 hours of study. Through the analysis of the results obtained using the tools of integration and spectral analysis for assessing similarity and purity of the peaks, it is found that the method can detect possible degradation products that arise during the stability studies . The method was subsequently validated using as references to RE 899 2003 and the technical standards of the ICH Q2 R1. The developed and validated method was used on a tablet stability study coated methyldopa 500mg similar constant in the Brazilian market, presenting results within the specification required for the product.