Characterization of cereal arabinoxylans and their health benefits

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dc.contributor.authorMalunga, Lovemore Nkhata
dc.contributor.examiningcommitteeEck, Peter (Human Nutritional Sciences) Jones, Peter (Food Science) Friel, James (Human Nutritional Sciences) Slavin, Joanne (University of Minnesota)en_US
dc.contributor.supervisorBeta, Trust(Food Science)en_US
dc.date.accessioned2016-09-01T17:05:33Z
dc.date.available2016-09-01T17:05:33Z
dc.date.issued2015en_US
dc.date.issued2015en_US
dc.date.issued2016en_US
dc.date.issued2016en_US
dc.degree.disciplineFood Scienceen_US
dc.degree.levelDoctor of Philosophy (Ph.D.)en_US
dc.description.abstractConsumption of whole grain cereals is associated with decreased risk of colorectal cancers and diabetes but the underlying mechanism still remain unclear. Oxidative damage is involved during initial or developmental stages of colorectal cancers whereas diabetes is typified by high concentration of plasma glucose. Thus the main objective of this research was to understand the role feruloyl arabinoxylan (AX) and oligosaccharides (AXOS) play in maintenance of gut health and digestion and absorption of dietary carbohydrates in order to propose an alternative mechanism through which cereals exerts their perceived health benefits. Investigation into the antioxidant potential of water extractable arabinoxylans from wheat, barley, and corn revealed that AXs are capable of donating both electron and hydrogen atom during redox reactions. Their antioxidant potential was highly influenced by ferulic acid content, degree of xylose substitution, and pattern of substitution. The factors influencing antioxidant capacity of AXOS were also investigated. AXOS with higher content of esterified ferulic acid and degree of substitution are better antioxidants. Investigation into the presence of feruloylated AXOS in maize and wheat showed that only feruloyl arabinose and feruloyl arabinosyl xylose are present. The levels of feruloyl arabinose increase during gastric digestion due to low pH. The amount of resultant feruloylated AXOS during gastric digestion is dependent on the content of insoluble bound ferulic acid. Feruloylated oligosaccharides were found to inhibit both mammalian intestinal α-glucosidase and glucose transporter 2 (GLUT2) activities. Ferulic acid bound to the oligosaccharides was responsible for their inhibition properties. On the other hand, AX polysaccharides did not affect starch hydrolysis to maltose regardless of concentration or type. However, the polysaccharides were capable of significantly inhibiting intestinal α-glucosidase activity (noncompetitively) when maltose was used as a substrate. Thus based on our results, the following mechanism may be involved for AX to exert their perceived health benefits: a) water extractable AXs donate electrons or hydrogen atoms to neutralize dietary free radicals (implicated in the initiation and/or development of chronic diseases) as they traverse through the gastrointestinal tract; and b) AXs noncompetitively inhibit intestinal α-glucosidase and/or AXOS inhibit intestinal α-glucosidase and glucose transporter thereby attenuating postprandial blood glucose levels.en_US
dc.description.noteOctober 2016en_US
dc.identifier.citationAPAen_US
dc.identifier.citationCereal Chemistryen_US
dc.identifier.citationNutrition & metabolismen_US
dc.identifier.citationAPAen_US
dc.identifier.urihttp://hdl.handle.net/1993/31620
dc.language.isoengen_US
dc.publisherELSEVIER BVen_US
dc.publisherAMERICAN ASSOCIATION OF CEREAL CHEMISTSen_US
dc.publisherBIOMED CENTRAL LTDen_US
dc.publisherELSEVIER BVen_US
dc.rightsopen accessen_US
dc.subjectFood scienceen_US
dc.subjectNutritionen_US
dc.subjectArabinoxylanen_US
dc.subjectFeruloylated arabinoxylansen_US
dc.subjectDietary fiberen_US
dc.subjectColon cancersen_US
dc.subjectDiabetesen_US
dc.subjectGlucose absorptionen_US
dc.subjectAntioxidanten_US
dc.subjectAlpha - glucosidaseen_US
dc.titleCharacterization of cereal arabinoxylans and their health benefitsen_US
dc.typedoctoral thesisen_US
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