Purification and characterisation of antioxidative peptides from unfractionated rice bran protein hydrolysates

Abstract

Crude rice bran protein (CRBP) was prepared by alkaline extraction and then treated with 0.6 m HCl to remove phytic acid. The phytate-free rice bran protein (PFRBP) was hydrolysed with proteases M, N, S, P and pepsin under optimal conditions. Hydrolysates obtained from various hydrolysis periods were subjected to analysis for their degree of hydrolysis (DH) and functional properties. The hydrolysates were fractionated by reversed-phase column chromatography on Kaseigel ODS resin (120-140 lm) using a stepwise gradient of aqueous ethanol, and their activities were measured. The 40% ethanol fraction of protease P 4 h-hydrolysate was separated by successive reversed-phase high-performance liquid chromatography and the amino acid sequences of isolated antioxidative peptides were determined by a protein sequencer and matrix-assisted laser desorption ionisation-time of flight mass spectrometry. Crude rice bran protein had higher antioxidative activity than PFRBP, due to the presence of phytic acid. Phytate contents of rice bran, CRBP and PFRBP were 2.5%, 1.42% and 0%, respectively. The activity of PFRBP increased upon protease digestion. Protease M hydrolysates showed the highest DH, but the lowest antioxidative activity. Hydrolysates with DH below 10% had higher antioxidative activity than those above 20%. This result indicates that the antioxidative activity of the hydrolysates is inherent to their characteristics amino acid sequences of peptides depending on the protease specificities.

Antioxidant activity of hydrolysates and peptide fractions derived from porcine hemoglobin

“…However, there was no correlation (p>0.05) between hydrolysis time and antioxidant activity. The result was also found in the process of alcalase-hydrolyzed silver carp protein (Dong et al 2008), Protease P-hydrolyzed sericin (Wu et al 2008) and five proteases hydrolyzed rice bran protein (Adebiyi et al 2007). This result indicates that the antioxidant activity of the hydrolysates is inherent to their characteristics amino acid sequences of peptides depending on protease specificities.…”

In vitrocytoprotection of modified casein hydrolysates by plastein reaction on rat hepatocyte cells

“…Food proteins can be digested by proteases or fermented by edible microorganisms to produce protein hydrolysates, which are more active than the parent proteins. Many of these hydrolysates or the purified peptides, such as those from soybean (Moure, Domínguez, & Parajo, 2006), rice (Adebiyi, Adebiyi, Ogawa, & Muramoto, 2008), and animal-origin (Hernández-Ledesma, Miralles, Amigo, Ramos, & Recio, 2005;Lin, Guo, You, Yin, & Liu, 2012;Tavares et al, 2011;Zhuang & Sun, 2011) proteins, were found to have antioxidant properties, and thus received increasing attention in the recent years (Elias, Kellerby, & Decker, 2008). Among the milk protein products, caseinate and whey products are now produced in large quantities as protein ingredients for food industry.…”

Manufacturing of peptides exhibiting biological activity

“…The consequence of the proteolytic action is the change in molecular conformation of native proteins and production of functional and bioactive products (Panyam and Kilara 1996; Adebiyi et al 2008). Enzymatic hydrolysis is a process conducted under mild conditions which can be easily controlled and allows one to obtain products with well-defined features (Clemente 2000; FitzGerald and O’Cuinn 2006).…”