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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

The Use of MM/QM calculations of 13C chemical shifts in the analysis of Edaravone tautomers

Abraham, R.J., Cooper, M.A., Aghamohammadi, Amin, Afarinkia, Kamyar, Liu, Xiangli 07 March 2024 (has links)
Yes / The 13C NMR chemical shifts of the three Edaravone tautomers (keto, enol, and amine) were calculated using a combined molecular mechanics (Pcmod 9.1/MMFF94) and ab initio (GIAO (B3LYP/DFT, 6–31 + G(d)) model. This method gave such good agreement with experiment that the assignment of the complex spectrum of Edaravone in solution, which is a mixture of the three tautomers could be made. This has been attempted previously by various methods with diverse results. In CDCl3 solution, the observed spectra show only one form, the keto tautomer, and this is also the case with acetonitrile solvent. Acetone solvent reacts with Edavarone in the NMR tube. In the other solvents studied, methanol, pyridine, DMSO, trifluoroethanol (TFE), there is a mixture of the tautomers with populations which vary with the solvent. The application of the shift predictions allows the assignment of the 13C spectra to the three tautomers and from this the proportions of the tautomers in the solution. The results at times differ significantly from previous studies, and this is discussed.
42

Influência da rutina na fotoestabilização da avobenzona (filtro UVA) e do ρ-metoxicinamato de octila (filtro UVB) / Influence of rutin in photostabilization of avobenzone (UVA filter) and octyl methoxycinnamate (UVB filter)

Pinto, Claudinéia Aparecida Sales de Oliveira 29 May 2014 (has links)
Com o intuito de promover proteção de amplo espectro, na maioria dos protetores solares estão associados pelo menos dois filtros orgânicos (UVA e UVB). A combinação da avobenzona (BMBM), filtro UVA, e do p--metoxicinamato de octila (EHMC), filtro UVB, é conhecida e muito utilizada em formulações manipulas e industrializadas, porém apresenta alteração na absorção espectral após exposição à radiação UV. A estratégia empregada com maior frequência para reduzir a instabilidade da combinação é baseada na adição de agentes fotoestabilizadores. A adição de substâncias naturais em formulações fotoprotetoras vem sendo explorada, especialmente o grupo dos flavonoides, como a rutina, que apresenta resultados positivos em relação à eficácia fotoprotetora. O objetivo principal desta pesquisa foi avaliar o potencial da rutina como substância fotoestabilizadora dos filtros EHMC e BMBM. Foram desenvolvidas formulações contendo os dois filtros associados ou não com rutina de acordo planejamento fatorial em três níveis. As formulações foram avaliadas quanto a eficácia fotoprotetora in vitro aplicadas em placas de PMMA e analisadas por espectrofotometria de refletância com esfera de integração antes e após a exposição à radiação UV. As interações moleculares dos filtros com a rutina foram avaliadas por 1H RMN, DSC, TG e análise qualitativa da supressão do estado energético singleto. A adição de rutina nas formulações contendo 5,0% (p/p) de BMBM e 10,0% (p/p) de EHMC promoveu elevação na conservação do FPS in vitro de 53,9% para 65,8 (0,1% de rutina) e 70,8% (1,0% de rutina). As curvas DSC e TG da rutina apresentaram alterações promovidas pela presença dos filtros BMBM e EHMC, indicando interação entre o flavonoide e os filtros. Após dose de 5760 J cm-2 de radiação UV o valor da razão trans/cis para o filtro EHMC em solução adicionado do filtro BMBM foi elevado de 5,5±0,1, sem adição de rutina, para 12,6±0,4, com adição da rutina. A análise qualitativa da supressão do estado singleto indicou que um dos mecanismos envolvidos na fotoestabilização dos filtros BMBM e EHMC é a supressão do estado energético singleto. Os resultados reportados neste estudo indicaram que a adição da rutina em formulações fotoprotetoras representa um caminho simples e efetivo para elevar a fotoestabilidade da combinação dos filtros BMBM e EHMC. A adição da rutina em formulações fotoprotetoras representa uma estratégia promissora, pois aliada a ação fotoestabilizadora, verificada nesse estudo, esse flavonoide possui propriedades antioxidante e quelante de metais que podem colaborar para o desenvolvimento de formulações fotoprotetoras de amplo espectro com aumento da segurança e eficácia. / In order to promote broad-spectrum protection, most sunscreens are associated with at least two organic filters (UVA and UVB). The combination of avobenzone (BMBM), UVA filter, and octyl methoxycinnamate (EHMC), UVB filter, is well known and widely used in industrial formulations and pharmaceutical compounding, but shows alteration in spectral absorption after UV radiation exposure. The most commonly used strategy to reduce the instability of the combination is based on the addition of photostabilizer agents. The addition of natural substances in sunscreen formulations has been explored, especially the group of flavonoids such as rutin, which shows positive results regarding photoprotective efficacy. The main objective of this research was to evaluate the potential of rutin as a photostabilizer substance of EHMC and BMBM. Formulations were developed containing the two filters associated or not with rutin, according to factorial design at three levels. The formulations were evaluated for in vitro photoprotective efficacy applied on PMMA plates and analyzed by spectrophotometer with integrating sphere reflectance before and after exposure to UV radiation. Molecular interactions of filters with rutin were evaluated by 1H NMR, DSC, TG and qualitative analysis of the suppression of singlet energy state. The addition of rutin in the formulations containing 5.0 % (w/w) BMBM and 10.0 % (w/w) EHMC promoted an increase in the preservation of in vitro SPF of 53.9% to 65.8 (0.1 % rutin) and 70.8 % (1.0% rutin). The DSC and TG curves of rutin showed changes promoted by the presence of BMBM and EHMC filters, indicating interaction between the flavonoid and filters. After 5760 J cm-2 of UV radiation the value of the trans/cis ratio for the EHMC filter added from the BMBM filter was increased from 5.5 ± 0.1 without addition of rutin, to 12.6 ± 0 4,with the addition of rutin. Qualitative analysis of the suppression of the singlet state indicated that one of the mechanisms involved in the photostabilization BMBM and EHMC filters is suppression of singlet excited state.The results reported in this study indicate that the addition of rutin in sunscreen formulations is a simple and effective way to increase the photostability of the combination of BMBM and EHMC. The addition of rutin in sunscreen formulations represents a promising strategy, for allied with the photostabilization action, observed in this study, this flavonoid has antioxidant and chelating properties of metals that can contribute to the development of broad-spectrum sunscreens formulations with increased safety and efficacy.
43

Functionalization Of Saturated Hydrocarbons: High Temperature Bromination

Gunbas, Duygu Deniz 01 June 2006 (has links) (PDF)
ABSTRACT FUNCTIONALIZATION OF SATURATED HYDROCARBONS: HIGH TEMPERATURE BROMINATION G&uuml / nbaS, Duygu Deniz M.S., Department of Chemistry Supervisor: Prof. Dr. Metin Balci June 2006, 174 pages Although saturated hydrocarbons are readily available and extremely cheap starting materials, they can not be used in synthetic chemistry without prior activation. Efficient functionalization of alkanes leading to the production of useful organic chemicals in an industrial scale is of considerable interest for the chemical and pharmaceutical industries and remains a long-term challenge for chemists. In this respect, halogenations of hydrocarbons which leads to a variety of useful synthetic intermediates is an open avenue which deserves special attention. It is also noteworthy to mention that efficient methods for selective functionalization of saturated bicyclic hydrocarbons still remains elusive, albeit a number of methods employing various reagents have been developed for the C&amp / #8211 / H bond activation of open chain and monocyclic alkanes. Herein, we will investigate the high temperature bromination reactions as a method for functionalization of saturated bicyclic hydrocarbons such as octahydropentalene (1), octahydro-1H-indene (2) and 1a,2,7,7a-tetrahydro-1H-cyclopropa[b]naphthalene (3). The scope and the limitations of the reaction will reveal the regio-and stereoselectivity. Furthermore, formation mechanism of the products will be discussed and the chemistry of these compounds will be extended for further functionalization
44

Studium dynamického chování a interakcí během teplotně indukované fázové separace v polymerních roztocích / The Study of Dynamic Behaviour and Interactions During the Temperature-Induced Phase Separation in Polymer Solutions

Kouřilová, Hana January 2011 (has links)
Title: The Study of Dynamic Behaviour and Interactions During the Tempera- ture-Induced Phase Separation in Polymer Solutions Author: Hana Kouřilová Department / Institute: Charles University in Prague, Faculty of Mathemat- ics and Physics, Department of Macromolecular Physics Supervisor of the doctoral thesis: doc. RNDr. Lenka Hanyková, Dr. Abstract: 1 H and 13 C high-resolution NMR spectroscopies were used for the phase separation investigation in three types of polymer solutions: i) poly(N -isopropylmethacrylamide)/D2O/ethanol with or without negatively charged comonomer sodium methacrylate, ii) random copolymers poly(N -isopro- pylmethacrylamide-co-acrylamide) in D2O, D2O/ethanol and D2O/acetone and iii) D2O solutions of polymer mixtures poly(N -isopropylmethacrylamide)/poly(N - vinylcaprolactam). For i) cononsolvency effect and influence of temperature on the phase separation was studied. Differences between mesoglobules formed as a consequence of cononsolvency effect and of temperature were found. While inside the cononsolvency-induced mesoglobules no bound ethanol molecules were detect- ed, in the mesoglobules formed by the effect of temperature ethanol molecules were present. The charge introduced into the polymer chains strenghtens polymer- solvent interactions. For ii) mesoglobules were found to be...
45

Síntese de 1h-1,2,3-triazóis trialoacetil substituídos análogos estruturais da rufinamida / Synthesis of the trihaloacetil substituted 1h-1,2,3-triazoles structural analoguesof rufinamide

Moraes, Maiara Correa de 15 February 2013 (has links)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The present dissertation describes a chemical methodology for the synthesis of three series containing fourteen new molecules of trifluoro(chloro)methyl substituted 1H-1,2,3-triazoles, which are structural analogues to the antiepileptic drug Rufinamide. The protocol used consisted in reactions of 1,3-dipolar cycloaddition of 2,6-difluorobenzyl azide and 4-alkoxy-4-alkyl(aryl/heteroaryl)-1,1,1-trifluoro(chloro)-3-alken-2-ones, where the 4-substituents are H, Me, Ph, 4-OMeC6H4, 4-NO2C6H4,4-FC6H4,2-Thienyle 4,4 -Biphenyl. The optimized reactios were carried-out in absense of solvente, in reaction times of 48 to 96 hours at 100-150°C and in yields of 30-75%. The reactions employing the 4-alkoxy-4-aryl(heteroaryl)-1,1,1-trifluoro-3-alken-2-ones 1and 2,6-difluorobenzyl azidedemonstrated a 4-substituent dependency of the enones precursors (above mentioned) and conducted to the formation of isomeric mixtures of 4-trifluoroacetyl substituted and/or 5-trifluoromethyl substituted triazoles in varying proportions, which were separated and purified by chromatographic columns. On the other hand, the reactions employing the 4-alkoxy-4-alkyl(aryl/heteroaryl)-1,1,1-trichloro-3-alken-2-ones and the same 2,6-difluorobenzyl azide produced exclusively a series of 4- trichloroacetyl substituted triazoles without the detection of the respective 5-trichloromethyl substituted regioisomer. The synthesized triazoles were characterized by 1H, 13C, uni- and two-dimensional NMR Spectroscopy techniques as HMQC, gas chromatography coupled to mass spectrometry (GC-MS), mono-crystal X-ray diffraction, high resolution mass spectrometry (HRMS) and their purity determined by CHN Elemental Analysis. / A presente dissertação descreve uma metodologia química para a síntese de três séries de 1H-1,2,3-triazóis trifluor(cloro)metil substituídos, totalizando quatorze moléculas inéditas, as quais são análogas estruturais do fármaco antiepiléptico Rufinamida. O protocolo consistiu na realização de reações de cicloadição 1,3-dipolares envolvendo 2,6-difluorbenzil azida e 4-alcóxi-4-alquil(aril/heteroaril)-1,1,1-trifluor(cloro)-3-alquen-2-onas, sendo os substituintes 4-alquila(arila/heteroarila) iguais a H, Me, Ph, 4-OMeC6H4, 4-NO2C6H4,4-FC6H4,2-Tienila e 4,4 -Bifenila. As reações otimizadas se processaram na ausência de solvente, em tempos reacionais de 48 a 96 horas a 100-150°C e levaram a rendimentos na faixa de 30-75%. As reações que utilizaram 4-alcóxi-4-aril(heteroaril)-1,1,1-triflúor-3-alquen-2-onase 2,6-difluorbenzil azida apresentaram uma dependência quanto a substituição da posição 4 das enonas precursoras (acima descritos) e conduziram à formação de misturas isoméricas de triazóis 4-trifluoracetil substituídos e/ou 5-trifluormetil substituídos em proporções variadas, as quais foram passíveis de separação e purificação por cromatografia em coluna. Por outro lado, as reações empregando 4-alcóxi-4-alquil(aril/heteroaril)-1,1,1-tricloro-3-alquen-2-onas e a mesma 2,6-difluorbenzil azida produziram, exclusivamente, uma série de triazóis 4-tricloroacetil substituídos sem a detecção dos respectivos regioisômeros 5-triclorometil substituídos. Os triazóis sintetizados foram caracterizados por espectroscopia de RMN de 1H, 13C por técnicas uni- e bidimensionais (HMQC), cromatografia a gás acoplada à espectrometria de massas (GC-MS), difração de raios-X em mono-cristal, espectrometria de massas de alta resolução (HRMS) e a sua pureza determinada através de análise elementar CHN.
46

Influência da rutina na fotoestabilização da avobenzona (filtro UVA) e do ρ-metoxicinamato de octila (filtro UVB) / Influence of rutin in photostabilization of avobenzone (UVA filter) and octyl methoxycinnamate (UVB filter)

Claudinéia Aparecida Sales de Oliveira Pinto 29 May 2014 (has links)
Com o intuito de promover proteção de amplo espectro, na maioria dos protetores solares estão associados pelo menos dois filtros orgânicos (UVA e UVB). A combinação da avobenzona (BMBM), filtro UVA, e do p--metoxicinamato de octila (EHMC), filtro UVB, é conhecida e muito utilizada em formulações manipulas e industrializadas, porém apresenta alteração na absorção espectral após exposição à radiação UV. A estratégia empregada com maior frequência para reduzir a instabilidade da combinação é baseada na adição de agentes fotoestabilizadores. A adição de substâncias naturais em formulações fotoprotetoras vem sendo explorada, especialmente o grupo dos flavonoides, como a rutina, que apresenta resultados positivos em relação à eficácia fotoprotetora. O objetivo principal desta pesquisa foi avaliar o potencial da rutina como substância fotoestabilizadora dos filtros EHMC e BMBM. Foram desenvolvidas formulações contendo os dois filtros associados ou não com rutina de acordo planejamento fatorial em três níveis. As formulações foram avaliadas quanto a eficácia fotoprotetora in vitro aplicadas em placas de PMMA e analisadas por espectrofotometria de refletância com esfera de integração antes e após a exposição à radiação UV. As interações moleculares dos filtros com a rutina foram avaliadas por 1H RMN, DSC, TG e análise qualitativa da supressão do estado energético singleto. A adição de rutina nas formulações contendo 5,0% (p/p) de BMBM e 10,0% (p/p) de EHMC promoveu elevação na conservação do FPS in vitro de 53,9% para 65,8 (0,1% de rutina) e 70,8% (1,0% de rutina). As curvas DSC e TG da rutina apresentaram alterações promovidas pela presença dos filtros BMBM e EHMC, indicando interação entre o flavonoide e os filtros. Após dose de 5760 J cm-2 de radiação UV o valor da razão trans/cis para o filtro EHMC em solução adicionado do filtro BMBM foi elevado de 5,5±0,1, sem adição de rutina, para 12,6±0,4, com adição da rutina. A análise qualitativa da supressão do estado singleto indicou que um dos mecanismos envolvidos na fotoestabilização dos filtros BMBM e EHMC é a supressão do estado energético singleto. Os resultados reportados neste estudo indicaram que a adição da rutina em formulações fotoprotetoras representa um caminho simples e efetivo para elevar a fotoestabilidade da combinação dos filtros BMBM e EHMC. A adição da rutina em formulações fotoprotetoras representa uma estratégia promissora, pois aliada a ação fotoestabilizadora, verificada nesse estudo, esse flavonoide possui propriedades antioxidante e quelante de metais que podem colaborar para o desenvolvimento de formulações fotoprotetoras de amplo espectro com aumento da segurança e eficácia. / In order to promote broad-spectrum protection, most sunscreens are associated with at least two organic filters (UVA and UVB). The combination of avobenzone (BMBM), UVA filter, and octyl methoxycinnamate (EHMC), UVB filter, is well known and widely used in industrial formulations and pharmaceutical compounding, but shows alteration in spectral absorption after UV radiation exposure. The most commonly used strategy to reduce the instability of the combination is based on the addition of photostabilizer agents. The addition of natural substances in sunscreen formulations has been explored, especially the group of flavonoids such as rutin, which shows positive results regarding photoprotective efficacy. The main objective of this research was to evaluate the potential of rutin as a photostabilizer substance of EHMC and BMBM. Formulations were developed containing the two filters associated or not with rutin, according to factorial design at three levels. The formulations were evaluated for in vitro photoprotective efficacy applied on PMMA plates and analyzed by spectrophotometer with integrating sphere reflectance before and after exposure to UV radiation. Molecular interactions of filters with rutin were evaluated by 1H NMR, DSC, TG and qualitative analysis of the suppression of singlet energy state. The addition of rutin in the formulations containing 5.0 % (w/w) BMBM and 10.0 % (w/w) EHMC promoted an increase in the preservation of in vitro SPF of 53.9% to 65.8 (0.1 % rutin) and 70.8 % (1.0% rutin). The DSC and TG curves of rutin showed changes promoted by the presence of BMBM and EHMC filters, indicating interaction between the flavonoid and filters. After 5760 J cm-2 of UV radiation the value of the trans/cis ratio for the EHMC filter added from the BMBM filter was increased from 5.5 ± 0.1 without addition of rutin, to 12.6 ± 0 4,with the addition of rutin. Qualitative analysis of the suppression of the singlet state indicated that one of the mechanisms involved in the photostabilization BMBM and EHMC filters is suppression of singlet excited state.The results reported in this study indicate that the addition of rutin in sunscreen formulations is a simple and effective way to increase the photostability of the combination of BMBM and EHMC. The addition of rutin in sunscreen formulations represents a promising strategy, for allied with the photostabilization action, observed in this study, this flavonoid has antioxidant and chelating properties of metals that can contribute to the development of broad-spectrum sunscreens formulations with increased safety and efficacy.
47

Vliv teploty a času na podíl krystalické a amorfní fáze v polypropylenu / Temperature and Time Influence on Crystalline and Amorphous Phase Content in Polypropylene

Vilč, Ladislav January 2010 (has links)
is is a study of the relationship between structure, mechanical properties and relaxing behavior of the polypropylene. The structure was evaluated by the quantity the solid phase content (SPC). This was defined as mathematical result of free induction decay (FID) signal from pulsed 1H-NMR. The solid phase content is a quite new structural parameter representing the quantity for description of semi-crystalline polymers. Whereas pulsed 1H-NMR is non-destructive, accurate and repeatable, it becomes a unique tool for a description of mechanical, structural, physical-mechanical changes of polypropylene within the time and temperature. Particularly, this method registers the small changes in the time-dependant shipments during secondary crystallization with small structure changes.
48

INTERAKCE V ROZTOCÍCH A GELECH NA PODNĚTY REAGUJÍCICH POLYMERNÍCH SYSTÉMŮ STUDOVANÝCH NMR SPEKTROSKOPIÍ / Interactions in solutions and gels of stimuli-responsive polymer systems investigated by NMR spectroscopy

Konefał, Rafał January 2018 (has links)
Stimuli-responsive (stimuli-sensitive, intelligent, or smart) polymers are polymer materials which, after small external stimuli, evidently change their physical or chemical properties. Smart polymers can be classified according stimuli they respond to such as: temperature changes, mechanical stress, light irradiation, ultrasonic treatment, application of external magnetic as well as electric field, changes of pH, ionic strength, addition of the chemical agents and presence of biomolecules and bioactive molecules. Stimuli-responsive synthetic polymer systems has attracted considerable attention due to wide range of applications, i.e. controlled drug delivery and release systems, diagnostics, tissue engineering and 'smart' optical systems, as well as biosensors, microelectromechanical systems, coatings, and textiles. Among the types of stimuli for this dissertation temperature, pH and reactive oxygen species (ROS) responsive polymer systems were studied. In case of thermoresponsive polymers, when polymer chains are molecularly dissolved in a good solvent, changes (increasing or decreasing) of temperature result in insolubility (globular nanoparticles formation) of polymer chains, called temperature induced phase-separation. pH responsive polymers change properties such as: solubility, volume (gels),...
49

Monoamine oxidase inhibition by novel quinolinones / Letitia Meiring

Meiring, Letitia January 2014 (has links)
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
50

Produção de biodiesel empregando biocatálise via reações de esterificação e transesterificação / Biodiesel production employing biocatalysis by esterification and transesterification reactions

Rosset, Isac George 14 March 2011 (has links)
Neste trabalho prepararam-se ésteres de ácidos graxos por esterificação do ácido oléico e transesterificação do óleo de soja e do triéster oléico via catálise enzimática. Determinou-se a composição dos produtos obtidos por RMN 1H e CG-FID. Os padrões dos ésteres do ácido oléico via esterificação ácida foram preparados empregando ácido sulfúrico, os padrões dos ésteres do óleo de soja por transesterificação básica com hidróxido de sódio e o padrão do triéster oléico foi sintetizado utilizando ácido p-tolueno sulfônico como catalisador. A melhor enzima para essas reações foi determinada através de reações de esterificação do ácido oléico e transesterificação do óleo de soja com etanol na ausência de co-solventes, sendo que foi selecionada a lipase de Candida antarctica. A mesma enzima foi empregada nas esterificações enzimáticas do ácido oléico com diversos alcoóis (metanol, etanol, n-propanol e n-butanol), na transesterificação enzimática do óleo de soja e do triéster oléico com etanol. Em ambos os estudos, foram avaliados os fatores que influenciam as reações: quantidade de enzima; tempo de reação; água adicionada ao álcool e reuso do biocatalisador. Na esterificação enzimática do ácido oléico, o uso do etanol forneceu o melhor rendimento (96,5%) com 5,0% (m/m) de enzima em 24 horas de reação. Quando uma quantidade de 4,0% de água foi adicionada ao álcool, a reação utilizando metanol mostrou maior eficiência (98,5%) e os rendimentos com os outros alcoóis não foram alterados significativamente (acima de 90%). Também foi possível utilizar a enzima por até 10 ciclos sem perda de rendimento, com exceção do metanol, onde ocorreu um decréscimo acentuado de rendimentos nos ciclos seguintes. Na transesterificação enzimática do óleo de soja, os mesmos fatores foram avaliados e com 5,0% de enzima, após 24 horas, foi obtido um rendimento de 84,1% e com a adição de água o rendimento não foi significativamente alterado (83%). Na transesterificação, os métodos de quantificação por RMN 1H e CG-FID foram comparados sendo que uma maior diferença foi observada para as reações com baixos rendimentos por RMN 1H, porém em altos rendimentos a diferença entre os dois métodos não foi significativa. Monoglicerídeos e diglicerídeos foram quantificados por CG-FID e por RMN 1H onde foi possível calcular a razão dos produtos formados através de uma equação desenvolvida, sendo que a diferença entre esses tipos de análises foi pequena, de apenas 1,4%. A transesterificação enzimática do triéster oléico foi obtida em bom rendimento (90,4%) e uma pequena quantidade de mono- e diglicerídeos foi produzida. Em todas as reações de transesterificação, o glicerol não foi detectado após a lavagem dos produtos. A metodologia empregando a lipase de Candida antarctica mostrou-se eficiente para a produção de biodiesel a partir do óleo de soja e do ácido oléico com diferentes tipos de alcoóis. / In this work, it was prepared esters of the fatty acid by esterification of the oleic acid and transesterification of the soy oil through enzymatic catalysis. It was determined the composition of the products obtained by 1H NMR and GC-FID. The standards of esters of the oleic acid by acid esterification was prepared employing sulfuric acid, the standards of esters of the soy oil by alkaline transesterification with sodium hydroxide and the standard of the oleic triester was synthesized employing p-toluene sulfonic acid as catalyst. The best enzyme for those reactions was determined through reactions of esterification of the oleic acid and transesterification of the soy oil with ethanol and free co-solvents, and lipase from Candida antarctica was selected. The same enzyme was employed in the enzymatic esterifications of the oleic acid with various alcohols (methanol, ethanol, propanol and butanol), in the enzymatic transesterification of soy oil and the oleic triester with ethanol. In both studies, was assessed the factors that influence the reactions: amount of catalyst, reaction time, water added in the alcohol and the turnover of biocatalyst. In the enzymatic esterification of the oleic acid, the ethanol showed the better yield (96,5%) with 5,0% (m/m) of enzyme at 24 hours of reaction. When 4,0% of water was added to the alcohol, the methanol showed the high efficiency (98,5%) and the yield with another alcohols were not affected. It was also possible to use the enzyme for 10 cycles without lose yield, except for the methanol. In the enzymatic transesterification of the soy oil, the same factors were assessed using 5,0% of enzyme, after 24 hours, a yield of 84,1% was obtained and with the water addition the yield was not modified (83%). On the transesterification, 1H NMR and GC-FID were compared and a great difference was observed for low yields, but on high yields, the difference between methods was small. Monoglycerides and diglycerides were quantified by GC-FID and detected by 1H NMR, it was possible to calculate the ratio between them on the products formed through an equation developed and the difference for this type of analysis was small, only 1.4% . The enzymatic transesterification of the oleic triester was obtained with good yield (90,4%) and a small amount of the monoglycerides and diglycerides was produced. In all the transesterifications reactions, glycerol was not detected after washing mixture of products. The methodology employing Candida antarctica lipase was efficient for biodiesel production by soybean oil and oleic acid with different alcohols.

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