Antioxidant and antihyperglycemic potential of soybean hydrolysates

Protein hydrolysates are considered as a potential dietary source of natural antioxidants with important antihyperglycemic activity. This study was conducted to understand the effect of conventional and low-glycinin soy cultivars on the protein profiles and antioxidant capacity (AC) of their alcalase hydrolysates. The cultivars were grown in three different locations to identify which cultivar(s) exhibited the highest AC across multiple growing regions after alcalase hydrolysis. The peroxyl radical scavenging AC of soy peptides were also compared against purified β-conglycinin and glycinin hydrolysates. Another part of the study was conducted to understand the effect of in vitro simulated digestion of protein-based beverages and ingredients on the production of peptides with potent AC as well as α-glucosidase and α-amylase inhibitory activities. Nine protein-based beverages and ten functional ingredients (I-5 to 14) were analyzed for their AC and starch-hydrolyzing enzymes inhibitory activity. Four beverages and four protein-based ingredients were selected for in vitro digestion using pepsin and pancreatin. Statistical differences were observed in the protein profiles and AC among the different cultivars tested (p0.05). Purified GL hydrolysate had an AC of 28.5 µM TE/µg soluble protein which was significantly different than low glycinin soybean hydrolysates (p<0.05). All beverages showed no inhibition of α-amylase activity and only commercial 1, regular soymilk and low-glycinin soymilk beverages inhibited α-glucosidase by 9.8, 9.4 and 10.2%, respectively. Non-protein based ingredients 8 and 14 exhibited α-glucosidase inhibitory activity with IC50 of 16.7 and 88.5 µg/mL, respectively and α-amylase inhibitory activity with IC50 of >2,500.0 and 325.1 µg/mL, respectively. After pepsin-pancreatin hydrolysis, the AC and α-glucosidase inhibitory activity of protein-based beverages and ingredients increased significantly (p