Thesis (Ph. D.)--Illinois State University, 2005. / Title from title page screen, viewed September 26, 2006. Dissertation Committee: David Williams (chair), Craig Gatto, Radheshyam Jayaswal, Wade Nichols, Laura Vogel, Brian Wilkinson. Includes bibliographical references (leaves 150-166) and abstract. Also available in print.

Thesis (M.Sc.) - University of Queensland, 2005. / Includes bibliography.

Thesis (M.S. in food science)--Washington State University, August 2007. / Includes bibliographical references.

Thesis (Ph.D.)--Baylor University, 2006. / Includes bibliographical references (p. 131-139).

Thesis PlanA (M.S.)--University of Wisconsin--Stout, 2006. / Includes bibliographical references.

Thesis PlanB (M.S.)--University of Wisconsin--Stout, 2006. / Includes bibliographical references.

Orientador: Olga Maria Mascarenhas Faria de Oliveira / Coorientador: José Carlos Rebuglio Vellosa / Banca: Taís Maria Bauab / Banca: Mariza Pires de Melo / Resumo: O excesso na geração de espécies reativas como os radicais livres pode resultar num desequilíbrio que, embora benéfico em situações como o combate a micro-organismos patógenos, está implicado com diversas patologias crônicas e com o envelhecimento. Assim é comum a indicação de compostos antioxidantes para a prevenção destas patologias e inclusive, algumas pesquisas com substâncias antioxidantes já resultaram no desenvolvimento de novos medicamentos. Desta forma, o estudo de fontes naturais que apresentam substâncias ativas sobre as diferentes espécies oxidantes geradas em nosso organismo é de grande importância, visto as implicações destas em várias patologias. Entre estas fontes, Agaricus blazei Murrill é um cogumelo comestível e medicinal, popularmente utilizado na prevenção do envelhecimento e no tratamento de diversas doenças, como câncer, artrite reumatóide, artrose, aterosclerose, diabetes e hipertensão. Tem sido relatado também, o uso de outros cogumelos como Agaricus bisporus (champignon), Lentinus edodes (shiitake) e Pleurotus ostreatus (shimeji ou hiratake), de forma similar ao Agaricus blazei. Além da função nutricional desse cogumelo é importante verificar possíveis atividades biológicas, o que poderia render novos produtos com alegações de propriedades funcionais ou terapêuticas, como as já existentes para o A. blazei. Assim, este projeto objetivou o estudo do perfil de atividade antioxidante (químico, enzimático e ex vivo) e análise de atividade antibacteriana de três cogumelos cultivados no Brasil em comparação com o Agaricus blazei Murrill. Foram utilizadas metodologias de análise de atividade antioxidante como os ensaios de ação scavenger do DPPH·, ABTS·+, O2 ·-, NO, H2O2 e HOCl, e também por análise do sistema oxidativo catalisado por mieloperoxidase (MPO) e... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The excessive generation of reactive oxygen species, like free radicals, can lead to an imbalance which, although benefical in such situations to combat pathogenic microorganisms, is involved with various chronic diseases and aging. Thus, it is common to indicate the use of antioxidants for prevention of these diseases, and some research about antioxidant products have already resulted in the development of new medicines. Thus, the study of natural sources that contain active compounds over the different oxidant species, generated in our bodies, is of great importance, due their implications in various pathologies. Among these sources, Agaricus blazei Murrill is an edible and medicinal mushroom, commonly used in the prevention of aging and the treatment of various diseases such as cancer, rheumatoid arthritis, osteoarthritis, atherosclerosis, diabetes and hypertension. It has also been reported, the use of other Agaricus bisporus (champignon), Lentinus edodes (shiitake) and Pleurotus ostreatus (shimeji or hiratake), similar to Agaricus blazei. Besides its nutritional properties, it is important to check possible biological activities, which could render functional property claims as those existing for the A. blazei. Thus, mushrooms such as this project aims to study the profile of antioxidant activity (chemical, enzymatic and ex vivo) of mushrooms cultivated in Brazil, comparing to Agaricus blazei Murrill. Antioxidant activities were evaluated through DPPH·, ABTS·+, O2 ·-, NO, H2O2 and HOCl and also by analysis of the oxidative system catalyzed by myeloperoxidase (MPO) and horseradish peroxidase (HRP). In relation to cellular analysis and antibacterial, it was determined toxicity erythrocytes and neutrophils, and activity in relation to Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa... (Complete abstract click electronic access below) / Mestre

No description available.

>Magister Scientiae - MSc / Fucoidan is a marine-derived sulphated polysaccharide with bioactive properties ideal for the food, chemical and pharmaceutical industries. The polysaccharide consists largely of L-fucose, has a highly heterogeneous structure and is of diverse origin. Fucoidan was extracted from Ecklonia maxima, Laminaria pallida and Splachnidium rugosum and the effect of different extraction methods on fucoidan heterogeneity was assessed. Extraction methods employed hot water, hydrochloric acid or calcium chloride salt. Fucoidan yield and purity were determined by various colorimetric assays. Highest fucoidan yield was obtained with the hot water extraction method as seen by highest L-fucose content. Splachnidium rugosum extracts contained ~5 times more L-fucose than Ecklonia maxima and Laminaria pallida extracts. The salt extraction method yielded extracts free of contaminants, however L-fucose content in all extracts was >20 times lower. Acid extraction yielded highest levels of uronic acid contamination and liberated sulphate from the fucoidan polysaccharide. The fucose-to-sulphate ratio for Ecklonia maxima was approximately 1:5, whilst the ratios for Splachnidium rugosum and Laminaria pallida were approximately 1:1 and 1:2, respectively. The acid and salt extraction methods removed all traces of protein contaminants, while the hot water method retained very low levels of protein. The extraction method used to isolate fucoidan was a determining factor in yield and purity. Chemical compositional analyses of hot water extracts were assessed by gas chromatography mass spectroscopy. Splachnidium rugosum and Laminaria pallida extracts consisted largely of L-fucose, while Ecklonia maxima fucoidan was characterized with high glucose abundance. Crude hot water and acid extracts from Splachnidium rugosum tissue were fractionated and purified by (anionic) ion exchange chromatography as bioactivity has been correlated to lower molecular weight forms. In water extracts, ion exchange chromatography resulted in close to 90% decrease in L-fucose, sulphate and uronic acid, while protein content increased by 57%. Similar results were reported for acid extracts; however protein content did not change significantly. These results show that method of extraction may affect the composition of fucoidan post-purification. Hot water extraction is recommended due to higher fucoidan yield, as reflected by L-fucose content, and higher sulphate-to-fucose ratio. High protein content after ion exchange chromatography was however of concern. Since mucilage in Splachnidium rugosum thallus was free of protein, fucoidan was precipitated from mucilage with ethanol. Fucoidan yield of mucilage was >15-fold higher than content in purified hot water extracts with a sulphate-to-fucose ratio of ~1:1. The average molecular weight of native fucoidan in mucilage was estimated at 2367 kDa. The polysaccharide was hydrolysed by gamma-irradiation levels of 10-50 kGy to fractions ranging between 60 and 15.5 kDa. Hot water crude fucoidan extracts from Ecklonia maxima, Laminaria pallida, and Splachnidium rugosum were assessed for anti-oxidant activity by measuring the ability to scavenge free radicals and the capacity to reduce copper ions with 2,2-Diphenyl-1-picrylhydrazyl and Cupric Reducing Anti-oxidant Capacity assays, respectively. Ecklonia maxima crude fucoidan displayed highest anti-oxidant activity and capacity, having the potential to scavenge reactive oxygen species as well as the capacity to reduce copper to less toxic forms in mammalian systems. Splachnidium rugosum showed weakest anti-oxidant activity and lowest reducing capacity. The anti-cancer activity of crude and purified hot water Splachnidium rugosum extracts, as well as non-irradiated (native) and gamma-irradiated fucoidan, and commercially procured fucoidan were assessed for anti-cancer activity against MCF-7 breast cancer cells. Splachnidium rugosum crude and purified fucoidan displayed a half maximal inhibitory concentration of 0.7 mg/mL and 0.029 mg/mL, respectively. Low cytotoxicity of crude and purified Splachnidium rugosum fucoidan against non-cancerous breast epithelial cell line MCF-12A was observed, as seen by half maximal inhibitory concentration values of 2 mg/mL and 0.663 mg/mL, respectively. The cancer specific selectivity of purified Splachnidium rugosum fucoidan was therefore much higher as reflected by 10-fold higher selectivity index than that of crude fucoidan. Native and low molecular weight gamma-irradiated fucoidan also showed bioactive properties including anti-cancer activity as seen by the reduction of cell proliferation in vitro, whereas crude fucoidan showed the ability to scavenge free radicals, and the capacity to reduce copper ions. / National Research Foundation (NRF)

Amine and nitroxide based radical-trapping antioxidants (RTAs) have long been known to display remarkable efficacy as inhibitors of hydrocarbon autoxidation. Their unique ability to catalytically trap the chain-carrying peroxyl radicals responsible for oxidative degradation of organic materials has led to their widespread use in petroleum-derived materials. While a great deal of research has been done to understand and expand upon this reactivity, little improvement in the chemistry behind diarylamine and nitroxide RTAs has emerged. In recent years our group has established that heterocyclic analogues of phenolic and diarylaminic RTAs are more stable to one-electron oxidation than the equivalent phenyl derivatives. This has allowed substitution of these RTAs with strong electron donating groups without compromising their stability to oxidation, and has led to the development of some of the most effective RTAs ever reported – compounds which often have reactivities ca. 200-fold greater than the current industrial standards. Herein, we describe the development of novel fluorometric and spectrophotometric methods to measure the reactivities of these RTAs, which replace more traditional approaches that are often laborious and require highly specialised equipment. Co-autoxidations with the highly absorbent probes PBD-BODIPY and STY-BODIPY allow for rapid and convenient measurement of RTA activity under a wide variety of conditions by UV/Vis spectrophotometry. Similarly, the high temperature activity of these RTAs can be measured in heavy hydrocarbon autoxidations, where hydroperoxide formation is monitored through the use of a pro-fluorescent phosphine. The key step in Korcek’s proposed diarylamine catalytic cycle has been studied and found to proceed through different mechanisms depending on the structure of the intermediate N,N-diarylalkoxyamine. While unactivated alkoxyamines widely react through N-O homolysis/disproportionation to regenerate the diarylamine RTA, activation of either the aryl or alkyl fragments allows regeneration through a more efficient, pericyclic retro-carbonyl-ene (RCE) reaction. Additionally, the mechanism behind the high temperature RTA activity of dialkylnitroxides – key intermediates in the activity of hindered amine light stabilizers (HALS) – has been evaluated and found to be dependent on in situ formation of carboxylic acids. Upon protonation by these acids, dialkylnitroxides become potent RTAs capable of trapping oxygen-centered radicals. The oxoammonium ions arising from this reaction then oxidize alkyl radicals competitively with O2 addition to regenerate the nitroxide. Lastly, we have extended the strategy used for heterocyclic phenols and diarylamines to the development of highly reactive azaphenoxazine and azaphenothiazine RTAs. While synthesis of these compounds is complicated by the presence of a favorable smiles rearrangement, synthesis of the ‘correct’ isomers yields extremely potent RTAs, capable of trapping peroxyl radicals under diffusion control. Applying these compounds in both ambient and high temperature autoxidations reveals that they may be some of the most effective RTAs ever reported, outperforming even the most reactive of the heterocyclic diarylamines previously studied.