Purification and Characterization of Antioxidant Peptides and Enzymatic Hydrolysates from Rice Bean (Vigna umbellata)

Abstract

Higher intake of plant protein is associated with lower risk in degenerative diseases caused by oxidative stress, thereby placing enormous demand in the identification of plant-based sources of protein like legumes. Rice bean (Vigna umbellata) is known to be a great source of low-cost and good nutritional quality protein for utilization in food products. This study characterized the soluble and hydrolyzed proteins from rice beans and assessed their antioxidant properties in vitro. The total soluble proteins from the rice bean were extracted using 35 mM potassium phosphate buffer (pH 7.2 M, 0.40 M NaCl) affording a concentration of 1.23 mg/mL. The isolated proteins were purified by a combination of gel filtration chromatography, ammonium sulfate precipitation and dialysis. SDS-PAGE was performed to monitor the changes in the protein profile after every purification step. Enzyme hydrolysis was also done using pepsin and a mixture of trypsin, chymotrypsin and thermolysin. The antioxidant activity of the protein extract and digest after 4 h of hydrolysis were determined using 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging assay, and found to be 35.11% and 19.68%, respectively. The results indicate that rice beans can be utilized as a rich source of protein with antioxidant properties and can be a rich source of functional foods.