Enzymatic Preparation of Quinoa Protein Peptides and Its Lipid-lowering and Uric Acid-Lowering Activity in Vitro

To study the optimal enzymatic hydrolysis conditions and uric acid-lowering activity of lipid-lowering peptides from quinoa protein, this study used quinoa as raw material to extract protein, and used pancreatic lipase inhibition rate as the activity index. The enzymatic hydrolysis process of lipid-lowering peptides was optimized by single factor experiment and response surface analysis. The pancreatic lipase inhibitory activity, sodium taurocholate binding activity, cholesterol esterase inhibitory activity, xanthine oxidase inhibitory activity and amino acid composition of quinoa protein peptides were analyzed and characterized. The results showed that the optimal enzymatic hydrolysis conditions of lipid-lowering peptides from quinoa were as follows: pH1.6, enzymatic hydrolysis temperature 42.9 ℃, substrate concentration 3.03%, enzymatic hydrolysis time 1 h and enzyme to substrate ratio 0.2%. The theoretical value of inhibition rate of pancreatic lipase was 90.43%, and the actual value was 90.93%±0.10%. The optimal enzymatic hydrolysates showed excellent effect of lowering lipid in vitro. The IC₅₀ of pancreatic lipase inhibition rate and cholesterol esterase inhibition rate were 7.49 μg/mL and 4.73 mg/mL, respectively. Meanwhile, the EC₅₀ of taurocholic sodium binding rate was 0.53 mg/mL. In addition, the optimal enzymatic hydrolysates showed good xanthine oxidase inhibition effect (IC₅₀=5.97 mg/mL), indicating that it had the uric acid-lowering effect in vitro. Amino acid analysis showed that quinoa protein peptides were rich in essential amino acids (34.23%), and the percentage of hydrophobic amino acid and acidic amino acid were 34.11% and 31.66%, respectively. The quinoa protein peptides had high lipid-lowering and uric acid-lowering activities in vitro, which provided a theoretical basis for the high-value application of quinoa protein peptides.