Functional and bioactive properties of flaxseed proteins and peptides

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dc.contributor.authorNwachukwu, Ifeanyi
dc.contributor.examiningcommitteeAukema, Harold (Food and Human Nutritional Sciences) Nyachoti, Martin (Animal Science) Udenigwe, Chibuike (Food and Human Nutritional Sciences) Tsopmo, Apollinaire (Carleton University)en_US
dc.contributor.supervisorAluko, Rotimi (Food and Human Nutritional Sciences)en_US
dc.date.accessioned2019-01-07T19:35:22Z
dc.date.available2019-01-07T19:35:22Z
dc.date.issued2018-12en_US
dc.date.submitted2019-01-01T02:47:27Zen
dc.date.submitted2019-01-07T19:04:54Zen
dc.date.submitted2019-01-07T19:25:53Zen
dc.degree.disciplineFood and Human Nutritional Sciencesen_US
dc.degree.levelDoctor of Philosophy (Ph.D.)en_US
dc.description.abstractThe aim of this thesis was to determine flaxseed protein functionality and confirm the bioactive properties of the enzymatic protein hydrolysates using in vitro and in vivo methods. Flaxseed albumins and globulins were extracted using NaCl and then separated by membrane dialysis. SDS-PAGE analyses showed that the globulin fraction consisted of polypeptides in the 10-50 kDa range while the albumin fraction mainly contained a 10 kDa polypeptide. Amino acid analysis revealed significantly (p<0.05) higher levels of hydrophobic amino acids in the globulin when compared to the albumin, which also corresponded to globulin’s higher surface hydrophobicity. A systematic evaluation of methods to determine the protein content of enzymatic protein hydrolysates suggests HPLC amino acid analysis as the most accurate. Subsequent hydrolysis of flaxseed proteins was carried out using thermoase GL-30, a food grade protease, in order to produce flaxseed protein hydrolysates (FPH), which were then fractionated by means of ultrafiltration into peptide fractions ranging in size from <1-10 kDa. When tested for in vitro antihypertensive and antioxidant properties, the FPH and its membrane fractions were found to scavenge free radicals, chelate metal ions, and reduce ferric iron, in addition to inhibiting the activities of angiotensin converting enzyme and renin. The flaxseed proteins also reduced systolic blood pressure in spontaneously hypertensive rats after oral administration by up to 37 mmHg within 8 h of administration. Finally, this work demonstrated the capacity of calmodulin-dependent phosphodiesterase (CaMPDE)-inhibitory flaxseed-derived peptides to be transported across the intestinal epithelium, and to influence activity of the target enzyme following absorption. Initial cell culture experiments using Caco-2 cells confirmed cell membrane permeation by the peptides in addition to absence of cytotoxicity. After individual oral administration of six CaMPDE-inhibitory peptides, two were detected in the blood of Wistar rats up to 90 min while all six peptides each inhibited plasma CaMPDE activity with AGA being the most effective. In addition to the discovery of several novel antioxidant flaxseed peptide sequences, this work demonstrated the antihypertensive properties of flaxseed protein hydrolysates, and provided novel information on the bioavailability and in vivo efficacy of flaxseed-derived CaMPDE-inhibitory peptides.en_US
dc.description.noteFebruary 2019en_US
dc.identifier.citationNwachukwu, I.D., and Aluko, R.E. (2018) Physicochemical and emulsification properties of flaxseed (Linum usitatissimum) albumin and globulin fractions. Food Chemistry, 255: 216-225.en_US
dc.identifier.citationNwachukwu, I.D., and Aluko, R.E. (2019) A systematic evaluation of various methods for quantifying food protein hydrolysate peptides. Food Chemistry, 270: 25-31en_US
dc.identifier.citationNwachukwu, I.D., Girgih, A.T., Malomo, S.A., Onuh, J.O., and Aluko, R.E. (2014) Thermoase-derived flaxseed protein hydrolysates and membrane ultrafiltration peptide fractions have systolic blood pressure-lowering effects in spontaneously hypertensive rats. International Journal of Molecular Sciences, 15(10):18131-18147.en_US
dc.identifier.citationNwachukwu, I.D., and Aluko, R.E. (2018) Antioxidant properties of flaxseed protein hydrolysates: influence of hydrolytic enzyme concentration and peptide size. Journal of the American Oil Chemists Society, 95(8):1105-1118.en_US
dc.identifier.urihttp://hdl.handle.net/1993/33635
dc.language.isoengen_US
dc.rightsopen accessen_US
dc.subjectFlaxseeden_US
dc.subjectAntihypertensive bioactive peptidesen_US
dc.subjectProtein determinationen_US
dc.subjectAmino acid analysisen_US
dc.subjectHypertensionen_US
dc.subjectAngiotensin converting enzymeen_US
dc.subjectUltrafiltrationen_US
dc.subjectSpontaneously hypertensive raten_US
dc.subjectCalmodulinen_US
dc.subjectPhosphodiesteraseen_US
dc.subjectCaco-2 cellsen_US
dc.subjectPeptide transporten_US
dc.subjectIntestinal epitheliumen_US
dc.titleFunctional and bioactive properties of flaxseed proteins and peptidesen_US
dc.typedoctoral thesisen_US
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