Study on Antioxidant Activity and Amino Acid Analysis of Rapeseed Protein Hydrolysates

Alkaline extraction followed by acid precipitation were employed to extract rapeseed protein and, Alcalase 2.4 L was used to obtain rapeseed protein hydrolysates. Three groups of rapeseed protein hydrolysates were obtained by purifying with membrane ultrafiltration and a Sephacryl S-100HR gel column. The antioxidant activities were then determined. Group 3 had the best antioxidant activities according to the oxygen radical absorbance capacity, peroxyl radical-scavenging capacity, and cellular antioxidant activity assays, with the following antioxidant values: an oxygen radical absorbance capacity value of 1610 +/- 113 mu mol TE/(g sample), a peroxyl radical-scavenging capacity value of 622 +/- 30 mg VC/(100 g sample), and a cellular antioxidant activity value of 25 +/- 2 mu mol QE/(g sample) and corresponding EC50 value of 58 +/- 3 mu g/mL. Six peaks of group 3 were collected and well separated by reversed phase-high-performance liquid chromatography. Peak 5 were identified to exhibit a higher antioxidant activity, the amino acid sequence of which was found to be Trp-Ile (Leu)-Tyr, as determined by liquid chromatography-mass spectrometry.