The marama bean is an underutilised legume growing wild in the arid and semi arid regions of Southern Africa. Sorghum is an important cereal crop in arid regions of the world. The seed coats of marama beans and bran of sorghum contain antioxidant phenolic compounds with potential health benefits. Aqueous extracts for possible use as antioxidant functional food ingredient were prepared from seed coats of marama beans and bran of condensed tannin sorghum by extracting with water (water extract) or with water acidified to pH 2 (acidified water extract). Aqueous extraction was used in order to obtain an extract free from organic solvents, safe for human consumption, and containing compounds representative of those that are available under aqueous conditions of the gastrointestinal tract. The extracts were analysed for total phenolic content, total flavonoid content, condensed tannin content and protein precipitation capacity using spectrophotometric methods and for individual phenolic compounds using HPLC-MS. Proanthocyanidins were characterised using thiolysis degradation in conjunction with HPLC-MS. The antioxidant activities of the extracts were measured using ABTS, DPPH and ORAC assays. Extracts were also evaluated for protective effect against free radical induced human erythrocytes haemolysis, oxidative DNA damage and human LDL oxidation. Extracts from marama bean seed coats had significantly higher total phenolic content, total flavonoid content, condensed tannin content, protein precipitation capacity and phenolic compound concentration than equivalent extracts from condensed tannin sorghum bran. Three phenolic acids and three flavonols esterified to gallic acid were identified in the extracts from marama bean seed coats. Extracts from condensed tannin sorghum bran had six major phenolic acids, two phenolic aldehydes and three flavanones. Proanthocyanidins in extracts from marama bean seed coats were predominantly highly galloylated prodelphinidins while those in extracts from condensed tannin sorghum bran were procyanidins. Extracts from marama bean seed coats had higher antioxidant activity and protective effects against free radical induced erythrocyte haemolysis and LDL oxidation compared to equivalent extracts from condensed sorghum bran. Extracts from condensed tannin sorghum bran showed some protective effect against oxidative DNA damage. However, extracts from marama bean seed coats gave inconclusive results probably due to prodelphinidins binding to DNA. Extraction of marama bean seed coats under acidic condition resulted in reduction in phenolic compound content, antioxidant activity and protective effect against erythrocyte haemolysis, possibly due to co-precipitation of phenolic compounds with interpolymer complex precipitate formed between highly galloylated condensed tannins and cell wall polysaccharides at pH 2. In contrast, extraction of condensed tannin sorghum bran under the acidic condition resulted in an extract with significantly higher phenolic content and protective effect against erythrocyte haemolysis than the water extract possibly due to enhanced extraction of free and esterified phenolics and release of bound phenolic compounds. Water extracts and acidified water extracts (from marama been seed coats or sorghum bran) did not show significant differences in their protective effect against oxidative DNA damage and LDL oxidation. Extraction under acidic condition may be the preferred method for sorghum bran because it increases recovery of phenolic compounds, but not for marama bean seed coats because it causes reduction in phenolic compound content. The findings of this study show that the extracts have a potential to reduce oxidative stress which is implicated in many chronic diseases such as neurodegenerative diseases, cancer and cardiovascular disease. The extracts can be used in the development of functional foods with potential health benefits. / Thesis (PhD)--University of Pretoria, 2012. / Food Science / unrestricted

Au cours de ce travail, différents glucosylamines et aminodésoxyglucoses ont été synthétisés et caractérisés par différentes méthodes spectroscopiques dont l’IRTF, la RMN 1H, 13C et MALDI-Tof MS. L’étude des propriétés biologiques de ces molécules réalisée, d’une part, avec deux champignons du bois, Coriolus versicolor et Poria placenta, et d’autre part, avec trois microorganismes potentiellement rencontrés dans des aliments, Listeria innocua, Salmonella typhimurium et Fusarium proliferatum ont indiqué une contribution positive de la N-alkylation, du degré de N-substitution et de la quaternisation sur l’inhibition de leur croissance. Par ailleurs, l’impact sur la bioactivité, de la position du groupe amine sur le sucre, a été étudié. Il a été montré que la position du groupe amine sur le C-1 du glucose conduisait à une activité antifongique contre C. versicolor et P. placenta plus prononcée alors que la position C-3 du glucose était favorable à une activité antimicrobienne contre L. innocua et S. typhimurium. / In this study different glucosylamines and amino desoxyglucoses were synthesized and characterised using various spectroscopic methods including IRFT, both 1H and 13C NMR spectroscopy and MALDI-Tof MS. Biological assessment of these compounds realised with two wood decay fungi, Coriolus versicolor and Poria placenta on one hand, and with three food microorganisms Listeria innocua, Salmonella typhimurium and Fusarium proliferatum on other hand, indicated a positive impact of both N-alkylation and degree of N-substitution and quaternisation on their growth inhibition. Furthermore, a biological impact of the amine position on sugar was studied. It was found that amine function attached to the C-1 of glucose conducted to the best antifungal activity against both C. versicolor and P. placenta while that fixed on the C-3 of glucose was indicated for antibacterial activity against L. innocua and S. typhimurium.

A soja e seus produtos são ricos em isoflavonóides, estes possuem a concentração aumentada após a fermentação microbiana, devido à liberação de fenólicos, através da conversão das formas glicosídicas em agliconas. O processo fermentativo em estado sólido por fungos filamentosos tem sido amplamente empregado como uma estratégica biotecnológica na busca de agregar valores aos produtos e subprodutos agroindustriais, principalmente elevando os teores de compostos bioativos. No presente estudo, foram avaliados o aumento dessas propriedades, como antioxidante e anti-inflamatória em diferentes substratos utilizando linhagens fúngicas do gênero Rhizopus sp. As 17 linhagens testadas foram capazes de elevar o potencial antioxidante dos grãos de soja. A fermentação de soja e arroz utilizando o R. oligosporus NRRL 2710 resultou em um incremento de 26,5 vezes o potencial antioxidante e 9,33 vezes o teor de compostos fenólicos nos extratos etanólicos, em 72 horas de processo. Além disso, mostraram resposta positiva para a atividade antiinflamatória, apresentando capacidade de inibição máxima de 70,75% e concentração inibitória de 4,2 mg mL. Os produtos fermentados pelo R. oligosporus NRRL 2710 foram submetidos a diferentes processos de extração: Soxhlet com diferentes solventes e supercrítica de CO2 + etanol (scCO2 + EtOH), o que permitiu verificar a relação entre a polaridade e o rendimento de extração. As extrações de Soxhlet foram realizadas usando amostras fermentadas secas e úmidas, os maiores valores de rendimento obtidos foram 42,09% e 32,84%, respectivamente. Este tipo de extração permitiu obter valores de atividade antioxidante na concentração inibitória (IC50) de 0,55 e 0,67 g g-1 e compostos fenólicos de 1,30 e 1,05 mg EAG g-1. Diferentes condições foram testadas no processo de extração com fluido comprimido (scCO2 + EtOH), para estudar a influência da pressão e temperatura no rendimento da extração. Os resultados mostraram que ambas as variáveis influenciam o rendimento do processo. Os extratos deste processo apresentaram um valor de IC50 de 0,17 g g-1, inibindo 94,05% do radical DPPH. Quanto aos compostos fenólicos, estes extratos apresentaram 1,39 mg EAG g-1. / The soybean and its products are rich in isoflavonoids, these have the increased concentration after the microbial fermentation, due to the release of phenolics, through the conversion of the glycosidic forms into aglycones. The solid state fermentative process by filamentous fungi has been widely used as a biotechnological strategy in the search of aggregating values to agroindustrial products and byproducts, mainly raising the levels of bioactive compounds. In the present study, the increase of these antioxidant and anti-inflammatory properties in different substrates using fungal strains of the genus Rhizopus sp. The 17 lines tested were able to raise the antioxidant potential of the soybean grains. The fermentation of soybean and rice using R. oligosporus NRRL 2710 resulted in an increase of 26.5 times the antioxidant potential and 9.33 times the content of phenolic compounds in the ethanolic extracts, in 72 hours of process. In addition, they showed a positive response to anti-inflammatory activity, with a maximum inhibitory capacity of 70.75% and an inhibitory concentration of 4.2 mg mL. The products fermented by R. oligosporus NRRL 2710 were submitted to different extraction processes: Soxhlet with different solvents and supercritical CO2 + ethanol (scCO2 + EtOH), which allowed to verify the relationship between polarity and extraction yield. Soxhlet extractions were performed using dry and wet fermented samples, the highest values of yield obtained were 42.09% and 32.84%, respectively. This type of extraction allowed to obtain values of antioxidant activity at the inhibitory concentration (IC50) of 0.55 and 0.67 g g-1 and phenolic compounds of 1.30 and 1.05 mg GAE g-1. Different conditions were tested in the compressed fluid extraction process (scCO2 + EtOH) to study the influence of pressure and temperature on extraction yield. The results showed that both variables influence the yield of the process. The extracts from this procedure had an IC50 value of 0.17 g g-1, inhibiting 94.05% of the DPPH radical. As for phenolic compounds, these extracts presented 1.39 mg GAE g-1.