title: Effect of peptide size on antioxidant properties of African yam bean seed (Sphenostylis stenocarpa) protein hydrolysate fractions.
abstract: Enzymatic hydrolysate of African yam bean seed protein isolate was prepared by treatment with alcalase. The hydrolysate was further fractionated into peptide sizes of <1, 1-3, 3-5 and 5-10 kDa using membrane ultrafiltration. The protein hydrolysate (APH) and its membrane ultrafiltration fractions were assayed for in vitro antioxidant activities. The <1 kDa peptides exhibited significantly better (p < 0.05) ferric reducing power, diphenyl-1-picryhydradzyl (DPPH) and hydroxyl radical scavenging activities when compared to peptide fractions of higher molecular weights. The high activity of <1 kDa peptides in these antioxidant assay systems may be related to the high levels of total hydrophobic and aromatic amino acids. In comparison to glutathione (GSH), the APH and its membrane fractions had significantly higher (p < 0.05) ability to chelate metal ions. In contrast, GSH had significantly greater (p < 0.05) ferric reducing power and free radical scavenging activities than APH and its membrane fractions. The APH and its membrane fractions effectively inhibited lipid peroxidation, results that were concentration dependent. The activity of APH and its membrane fractions against linoleic acid oxidation was higher when compared to that of GSH but lower than that of butylated hydroxyl toluene (BHT). The results show potential use of APH and its membrane fractions as antioxidants in the management of oxidative stress-related metabolic disorders and in the prevention of lipid oxidation in food products.
authors.affiliation: Department of Food Science and Technology, Federal University of Technology, Akure, Nigeria; E-Mail:  comfort.funmilayo@yahoo.com  (C.F.A.).
authors.forename: Comfort F
authors.initials: CF
authors.lastname: Ajibola
authors.forename: Joseph B
authors.initials: JB
authors.lastname: Fashakin
authors.forename: Tayo N
authors.initials: TN
authors.lastname: Fagbemi
authors.forename: Rotimi E
authors.initials: RE
authors.lastname: Aluko
mesh_terms: D000596:Amino Acids / Q000032:analysis; D000975:Antioxidants / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D005978:Glutathione / Q000378:metabolism; D010084:Oxidation-Reduction; D010455:Peptides / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D012639:Seeds / Q000378:metabolism; D031303:Sphenostylis / Q000378:metabolism*; D013381:Subtilisins / Q000378:metabolism; D014462:Ultrafiltration
chemical_list: D000596:Amino Acids; D000975:Antioxidants; D010455:Peptides; D013381:Subtilisins; D005978:Glutathione
references.citation: Bioresour Technol. 2008 Apr;99(6):1690-8
references.pmid: 17512726
references.citation: Anal Biochem. 1978 Jun 15;87(1):206-10
references.pmid: 98070
references.citation: J Nutr Biochem. 2005 Sep;16(9):562-9
references.pmid: 16115545
references.citation: J Chromatogr. 1984 Dec 7;336(1):93-104
references.pmid: 6396315
references.citation: Food Chem. 2008 Nov 15;111(2):370-6
references.pmid: 26047437
references.citation: Curr Pharm Des. 2003;9(16):1297-308
references.pmid: 12769738
references.citation: J Food Sci. 2008 May;73(4):C249-55
references.pmid: 18460118
references.citation: Int J Mol Sci. 2011;12(5):3148-61
references.pmid: 21686175
references.citation: J Agric Food Chem. 2003 Jun 4;51(12):3661-7
references.pmid: 12769542
references.citation: J Sci Food Agric. 1974 Aug;25(8):919-22
references.pmid: 4411930
references.citation: J Agric Food Chem. 2008 Apr 23;56(8):2714-21
references.pmid: 18376842
references.citation: J Sci Food Agric. 2010 Aug 30;90(11):1855-60
references.pmid: 20602516
references.citation: J Nutr Biochem. 2007 Jan;18(1):31-8
references.pmid: 16563720
references.citation: Compr Rev Food Sci Food Saf. 2004 Jan;3(1):21-33
references.pmid: 33430557
references.citation: J Agric Food Chem. 2010 Apr 28;58(8):4712-8
references.pmid: 20359226
references.citation: Food Chem. 2008 Jul 1;109(1):144-8
references.pmid: 26054275
references.citation: Crit Rev Food Sci Nutr. 2008 May;48(5):430-41
references.pmid: 18464032