Angiotensin-converting enzyme (ACE)-inhibitory activity of boza, a traditional fermented beverage

Background In this study the angiotensin-converting enzyme (ACE)-inhibitory activity of boza and protein fractions of boza separated according to molecular weight was determined. In addition, the effect of in vitro digestion on ACE-inhibitory activity was investigated. Results The protein content, ACE-inhibitory activity and IC50 value of boza were 1.0896 +/- 0.08%, 76.76 +/- 14.93% and 7.2 +/- 0.28 mu g protein mL-1 respectively. The protein hydrolysate was separated into three fractions according to molecular weight (MW), i.e. MW < 5000 Da, 5000 < MW < 10 000 Da and 10 000 < MW < 20 000 Da. The lowest IC50 value (0.268 +/- 0.07 mu g protein mL-1) was found for the fraction with 5000 < MW < 10 000 Da (P < 0.05). After in vitro digestion the ACE-inhibitory activities of stomach and intestine dialysates were almost the same (P > 0.05). The IC50 value of stomach digest was determined as 2.06 +/- 0.32 (mu g protein mL-1). However, the IC50 value of intestine digest could not be determined, because all dialysates with different protein concentrations displayed ACE-inhibitory activity greater than 50%. Conclusion The findings indicate that boza, protein hydrolysate, fractionated hydrolysates and dialysates obtained after in vitro digestion contain bioactive compounds with different ACE-inhibitory activities. Based on these results, boza can be considered as a good source of ACE-inhibitory peptides. (C) 2012 Society of Chemical Industry