No description available.

Thesis (doctoral)--University of Helsinki, 2007. / Includes bibliographical references. Also available on the World Wide Web.

Diss. (sammanfattning) Umeå : Univ., 2007. / Härtill 5 uppsatser.

Orientadores: Priscila Gava Mazzola, Carlos Emílio Levy / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas / Made available in DSpace on 2018-08-17T05:25:26Z (GMT). No. of bitstreams: 1 Amaral_LilianFerreiraBarbosa_M.pdf: 1912127 bytes, checksum: 32484facc8e6b93417ada30bacc332ce (MD5) Previous issue date: 2010 / Resumo: A contaminação microbiológica apresenta um risco potencial à qualidade do produto, mas, sobretudo pode afetar a saúde do consumidor. Conservantes são substâncias adicionadas a produtos cosméticos, farmacêuticos, de limpeza e alimentícios com o objetivo de inibir o desenvolvimento de microrganismos, durante sua fabricação e estocagem, bem como proteger o consumidor de contaminação inadvertida durante o uso do produto. Embora alguns conservantes já estejam consagrados na literatura, os mesmos têm sido relacionados ao desencadeamento de reações alérgicas, motivando a procura do conservante ideal. O Xilitol é um açúcar natural proveniente de plantas, frutas e vegetais, que possui propriedades antimicrobianas descritas na literatura. O presente trabalho teve como objetivo avaliar a eficácia antimicrobiana do monoéster de C-8 Xilitol (patente PCT/IB 2008/054321), visando sua utilização como conservante em bases cosméticas, através de testes de desafio conservante (challenge test) e determinação da concentração inibitória mínima (CIM). Os resultados obtidos na determinação da concentração mínima inibitória estão entre 1,0 e 1,25 % para Staphylococcus aureus, Escherichia coli e Candida albicans e entre 1,0 e 1,5% para Pseudomonas aeruginosa e Aspergillus niger, indicando a faixa de concentração do monoéster de C-8 Xilitol que inibiu totalmente o crescimento do microrganismo, no teste de diluições. A loção hidratante utilizada no teste de desafio foi conservada com a concentração de 1% do monoéster de C-8 Xilitol, verificando-se um rápido declínio na contagem de UFC/g nos primeiros tempos de avaliação após a contaminação do produto, para todas as bactérias testadas. Após o período de avaliação, incluindo a reinoculação do produto, o monoéster de C-8 Xilitol mostrou-se eficaz frente às bactérias P. aeruginosa, E. coli e S. aureus, atendendo à especificação de redução de 99,9% do número de células viáveis estabelecida em compêndios oficiais. O mesmo ocorre em relação à C. albicans que apresenta uma redução de 90% do número de células viáveis e também em relação ao A. niger, quando o pH da loção testada é ajustado de 5,5 para 7,0. Nas condições em que os testes foram conduzidos, podemos concluir que o monoéster de C-8 Xilitol, apresenta atividade antimicrobiana frente aos microrganismos testados e atende aos requisitos de uma substância dotada de atividade conservante, podendo ser considerado uma alternativa conservante para produtos cosméticos / Abstract: Microbiological contamination presents a potential risk to product quality, but specially can affect the health of consumers. Preservatives are substances added to cosmetic, pharmaceuticals, cleaning agents and food in order to inhibit growth of microorganisms during product manufacturing and storage and to protect consumers from inadvertent contamination during the use of the product. Although some preservatives are already well established in the literature, they have been linked to the allergic reactions, motivating the search for the ideal preservative. Xylitol is a natural sugar derived from plants, fruits and vegetables, which antimicrobial properties are described in the literature. This study aimed to evaluate the antimicrobial effectiveness of C-8 Xylitol monoester (patent pending PCT/IB 2008/054321), for its use as a preservative in cosmetic formulations. The minimum inhibitory concentration (MIC) was determined by the broth macrodilution method and the antimicrobial effectiveness of C-8 Xylitol monoester was determined by using challenge test method. The results obtained in the determination of minimum inhibitory concentration are between 1.0 and 1.25% for Staphylococcus aureus, Escherichia coli and Candida albicans and between 1.0 and 1.5% for Pseudomonas aeruginosa and Aspergillus niger. The amount of 1% of C-8 Xylitol monoester was added to the lotion used in the challenge test, observing a rapid decline in the number of CFU/g in stages of evaluation after contamination of the product by all bacteria. After the evaluation period, including reinoculation product, the C-8 xylitol monoester was effective against P. aeruginosa, E. coli and S. aureus, according to the specification of 99.9% reduction in the number of viable cells established in the official compendia. The same occurs in relation to C. albicans, which shows a 90% reduction in the number of CFU/g. Regarding A. niger, similar reduction is observed when pH value of the lotion is adjusted from 5.5 to 7.0. Under the tests conditions used, we concluded that C-8 Xylitol monoester has antimicrobial activity and could be considered as an alternative preservative for cosmetic formulations / Mestrado / Ciencias Biomedicas / Mestre em Ciências Médicas

Abstract The purpose was to evaluate the microbiological mechanism of action of xylitol and to assess its use in clinical practice for preventing acute otitis media (AOM). To test whether the effect of xylitol on S. pneumoniae is inhibited by fructose, a total of 20 strains of S. pneumoniae were exposed to xylitol in the presence of fructose and other carbon sources. Addition of 5% xylitol to the media resulted in marked growth inhibition, an effect which was totally eliminated in the presence of 1%, 2.5% or 5% fructose but not in the presence of 1% or 5% glucose, 1% galactose or 1% sucrose. The inhibition of pneumococcal growth is probably mediated via a fructose phosphotransferase system in a similar manner to that seen in mutans streptococci. Sorbitol alone did not affect the growth of pneumococci, and thus sorbitol is unlikely to provide any clinical benefit in the prevention of AOM. To evaluate the effect of xylitol on the ultrastructure of S. pneumoniae and Haemophilus influenzae (H. influenzae) and on the pneumococcal phenotype, five strains of S. pneumoniae and one strain of H. influenzae were examined by electron microscopy after xylitol exposure. Xylitol damaged the ultrastructure of the pneumococci. Some of the bacteria were lysed and the cell wall of the remaining ones became more diffuse and the polysaccharide capsule was ragged. The resulting morphology was identical to that of the transparent pneumococcal phenotypic variant. The properties of the transparent variants of pneumococci could explain the clinical efficacy of xylitol in preventing AOM despite the lack of effect on the nasopharyngeal carriage of pneumococci. The cell wall of H. influenzae became slightly thicker, but the morphology remained otherwise unchanged. To evaluate the pharmacokinetics of xylitol locally in the nasopharynx, xylitol concentrations were measured in the saliva of 65 children by enzymatic assay after giving them xylitol chewing gum or syrup at doses equal to those used in clinical trials. Concentrations high enough to have an antimicrobial effect were attained, but the xylitol disappeared from the saliva within 15 minutes, which indicates that high peak concentrations may be more important for efficacy than the time for which the concentration exceeds the level needed for an antimicrobial effect. To find a more convenient dosing regime for xylitol prophylaxis, xylitol was administered to 1277 children only during an acute respiratory infection (ARI) in a randomised placebo-controlled trial. The occurrence of AOM during ARI was 34/166 (20.5%) in the xylitol mixture group as compared with 32/157 (20.4%) among the children receiving the control mixture. Among older children receiving control chewing gum, xylitol chewing gum or xylitol lozenges, AOM was experienced by 24/218 (11.0%), 31/220 (14.1%) and 34/219 (15.5%) respectively. None of the differences between the groups was statistically significant. Xylitol should be used continuously in AOM prophylaxis, as it proved ineffective when used only during URI.

The first section of this dissertation (Chapter I-III) describes the development of new methodologies to prepare uracil and arylidenehydantoin derivatives. A regioselective synthesis of 6-alkyl- and 6-aryluracils was developed by the dimerization of 3-alkyl- and 3-aryl-2-propynamides promoted by either Cs2CO3 or K3PO4. A range of 3-aryl-2- propynamides, with both electron-deficient and electron-rich 3-aryl substituents, were successfully reacted in high yields. A synthetic route to prepare arylidenehydantoins was developed using the Pd-catalyzed dimerization of 3-aryl-2-propynamides. Both electron rich and electron deficient 3-aryl-2-propynamides were dimerized successfully to produce the desired arylidenehydantoins in moderate to excellent yields. The second section of this dissertation (Chapter IV and V) describes the development of a reliable low-cost method to determine amounts of xylitol in sugar free gum samples to predict dangerous exposure levels for dogs. Xylitol is generally considered safe for human consumption and is frequently used in sugar free gum, however, it is extremely toxic to dogs. It is unknown if partially consumed chewing gum is also dangerous. A method to determine xylitol content of these sugar free gum samples employing GC-MS with direct aqueous injection (DAI) is presented. This method was successfully applied to over 120 samples including, fresh gum, 5 min, 15 min, and 30 min chewed gum samples. Further extension of this work resulted in the development of an undergraduate laboratory experiment for upper-level undergraduate chemistry students which teaches calibration methods, xylitol extraction, sample preparation for GC-MS analysis, and data analysis.

No description available.

Xylitol can be produced from xylose or hemicellulose hydrolysates by either chemical reduction or microbial fermentation. Current technology for commercial production is based on chemical reduction of xylose or hemicellulose, and xylitol is separated and purified by chromatographic methods. The resultant product is very expensive because of the extensive purification procedures. Microbial production of xylitol is being researched as an alternative method for xylitol production. Apart from the chromatographic separation method and activated carbon treatment, no other separation method has been proposed for the separation of xylitol from the fermentation broth. Membrane separation was proposed as an alternative method for the recovery of xylitol from the fermentation broth because it has the potential for energy savings and higher purity. A membrane separation unit was designed, constructed, tested, and successfully used to separate xylitol from the fermentation broth. Eleven membranes were investigated for xylitol separation from the fermentation broth. A 10,000 nominal molecular weight cutoff (MWCO) polysulfone membrane was found to be the most effective for the separation and recovery of xylitol. The membrane allowed 82.2 to 90.3% of xylitol in the fermentation broth to pass through while retaining 49.2 to 53.6% of the Lowry's method positive material (such as oligopeptides and peptides). Permeate from the 10,000 MWCO membrane was collected and crystallized. Crystals were analyzed by HPLC for xylitol and impurities and determined to have purity up to 90.3%. / Master of Science

Bibliography: leaves 133-148 / x, 148 leaves, [3] leaves of plates : ill ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, 1984

O presente estudo foi dividido em quatro etapas distintas. A primeira etapa teve por objetivo avaliar a liberação de xilitol na saliva de humanos ao longo do tempo após aplicação de verniz controle e contendo 10% e 20% de xilitol. Um estudo cruzado foi realizado pela aplicação de 32 mg de cada verniz sobre as superfícies vestibulares de todos os incisivos centrais de 10 voluntários. Amostras salivares foram coletadas no baseline e após 5 min, 10 min, 15 min, 30 min, 1 h, 1 h 30 min, 2 h, 4 h e 8 h da aplicação dos vernizes para posterior análise da concentração de xilitol na saliva. Um estudo clínico foi realizado na segunda etapa com o objetivo de verificar a influência do verniz contendo xilitol a 20% sobre a contagem de estreptococos do grupo mutans provenientes de biofilme dentário. Semanalmente, 32 mg de verniz controle (grupo G1) ou verniz contendo xilitol a 20% (grupo G2) foram aleatoriamente aplicados sobre as superfícies vestibulares dos incisivos centrais de 67 crianças. Após quatro semanas de procedimento, amostras de biofilme dentário foram coletadas do terço cervical de todos os dentes presentes na cavidade bucal e a contagem relativa e absoluta dos microrganismos foi determinada. A terceira etapa objetivou analisar a influência do xilitol sobre a ultra-estrutura de Streptococcus mutans ATCC 33478 e Streptococcus sobrinus ATCC 25175. Além disso, a capacidade do xilitol e do flúor em promover estresse celular em S. mutans UA 159 geneticamente modificados (deleção do gene vicK) foi determinada na quarta etapa. As concentrações de xilitol na saliva (F=5,228, p=0,024) em diferentes tempos de coleta (F=18,24, p<0,0001) foram estatisticamente diferentes após aplicação dos vernizes contendo 10% e 20% do açúcar (etapa 1). Na etapa 2, contagens absolutas inicial e final de estreptococos do grupo mutans (Teste-t, p=0,4192) e de estreptococos totais (Teste-t, p=0,3506) não foram significativamente diferentes nos indivíduos pertencentes ao grupo G2. No entanto, uma redução significativa na porcentagem relativa inicial e final de estreptococos do grupo mutans em relação aos estreptococos totais foi observada (Teste-t, p= 0,0095). Xilitol a 20% promoveu alterações na morfologia de S. mutans ATCC 33478 e S. sobrinus, ATCC 25175, resultando em paredes celulares mais difusas e menos definidas, cápsulas 24 polissacarídicas mais dispersas e irregulares em relação ao grupo controle (etapa 3). Os tratamentos envolvendo xilitol a 1,25% e 2,5% mostraram-se capazes de produzir maior estresse celular à S. mutans geneticamente modificados quando comparados aos tratamentos com NaF a 22,5 mM e 45 mM em todos os tempos analisados (ANOVA a um critério, Teste de Tukey, p<0,05). Portanto, o verniz contendo xilitol pode ser considerado um interessante veículo para a administração do açúcar, uma vez que demonstrou propiciar uma liberação mais lenta do poliol na cavidade bucal. Além disso, a significativa redução da contagem relativa de estreptococos do grupo mutans em relação aos estreptococos totais pode auxiliar na prevenção de cárie dentária. Este estudo também demonstrou a habilidade do xilitol em produzir alterações ultra-estruturais de S. mutans ATCC 33478 e S. sobrinus, ATCC 25175, além de ser capaz de produzir estresse celular em S. mutans UA159 com deleção do gene vicK. / This study was divided in four distinct stages. The first one aimed to assess the xylitol release in human saliva along time after application of control, 10% or 20% xylitol varnishes. A cross-over design study was performed by application of 32 mg of each varnish on buccal surfaces of all incisors of 10 volunteers. Salivary samples were collected to analyze the xylitol concentration in baseline and after 5 min, 10 min, 15 min, 30 min, 1 h, 1 h 30 min, 2 h, 4 h and 8 h from varnishes application. A clinical study was executed in the second stage aiming observe the influence of 20% xylitol varnish on mutans streptococci counts from dental plaque. Weekly, 32 mg of control varnish (group G1) or 20% xylitol varnish (group G2) were randomly applied on buccal surfaces of central incisors of 67 children. After 4 weeks of procedures, dental plaque samples were collected from cervical of all teeth and relative and absolute counts of microorganisms were determined. The third stage aimed to analyze the effect of xylitol on the ultrastructure of Streptococcus mutans ATCC 33478 and Streptococcus sobrinus ATCC 25175. Moreover, the capacity of xylitol and fluoride to promote cellular stress in S. mutans UA 159 knockout vick gene was determined in the fourth stage. Salivary xylitol concentrations (F=5,228, p=0,024) in different collection times (F=18,24, p<0,0001) were statistically different after 10% and 20% varnishes application (stage 1). In stage 2, initial and final absolute mutans streptococci (Teste-t, p=0,4192) and total streptococci counts (Teste-t, p=0,3506) did not differ significantly in volunteers from group G2. However, a significant reduction of initial and final relative mutans streptococci counts was observed in relation to total streptococci (Teste-t, p= 0,0095). 20% xylitol promoted alterations in morphology of S. mutans ATCC 33478 and S. sobrinus, ATCC 25175, resulting in more diffuse and less defined cellular wall, more dispersive and irregular polysaccharidic capsules in comparison to control group (stage 3). 1.25% and 2.5% xylitol treatments were able to produce higher cellular stress to genetically modified S. mutans when compared to 22.5 mM and 45 mM NaF treatments throughout the time (ANOVA, Tukeys test, p<0.05). Therefore, xylitol varnish can be regarded as interesting vehicle to administer the polyol because it achieved a slower xylitol release into the oral cavity. Furthermore, a significant reduction of relative mutans streptococci counts in relation to total streptococci can aid in prevention of dental caries. The present study also demonstrated the ability of xylitol in producing ultrastructural alterations in S. mutans ATCC 33478 and S. sobrinus, ATCC 25175, besides generating cellular stress to S. mutans UA159 knockout vicK gene.