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Optimization of purification of angiotensin I-converting enzyme inhibitory peptide derived from walnut protein by size exclusion chromatography

In order to obtain the novel angiotensin I–converting enzyme(ACE) inhibitory peptides,walnut protein hydrolysates prepared with Alcalase 2.4 L were isolated by size exclusion chromatography. Firstly,the operation parameters of size exclusion chromatography such as the eluent,the flow rate and the sample concentration were investigated. Furthermore,the ACE inhibitory activity of different parts were assessed before and after the purification. Additionally,the RP–HPLC map and amino acid composition of the ACE inhibitory peptides were determined. The results showed that the distilled water was the best eluent,the elution rate was 0.4 m L/min,the sampling volume was 1.5 m L,the sampling concentration was 150 mg/m L,the purification effect was the best under this condition. Also,walnut protein hydrolysates can be divided into the four different components by Sephedax G–15,the highest components of ACE inhibitory activity was 90.35±0.25%,whose IC50 value was 0.158 mg/m L. It found that the peptides effectively purified when comparing the peptides map by RP–HPLC and they were mainly concentrated on the 10,13,17,21 min location. The hydrophobic amino acids were significantly enriched by the size exclusion chromatography,from which the value of the aromatic acids Tyr,Phe were 10.46% and 20.15% respectively.