A peptidomic approach for the identification of antioxidant and ACE-inhibitory peptides in sardinelle protein hydrolysates fermented by Bacillus subtilis A26 and Bacillus amyloliquefaciens An6

Antioxidant and angiotensin I-converting enzyme (ACE)-inhibitory activities of sardinelle (Sardinella aurita) protein hydrolysates (SPHs) obtained by fermentation with Bacillus subtilis A26 (SPH-A26) and Bacillus amyloliquefaciens An6 (SPH-An6) were investigated. Both hydrolysates showed dose-dependent antioxidant activities evaluated using various in vitro antioxidant assays. Further, they were found to exhibit ACE-inhibitory activity. Peptides from SPH-A26 and SPH-An6 were analyzed by nESI-LC-MS/MS and approximately 800 peptides were identified. Identified peptides derived mainly from myosin (43% and 31% in SPH-An6 and SPH-A26, respectively). Several peptides identified in both hydrolysates were found to share sequences with previously identified antioxidant and ACE-inhibitory peptides based on Biopep database. Some of these peptides were selected for synthesis and their biological activities were evaluated. Among the synthesized peptides, NVPVYEGY and ITALAPSTM were found to be the most effective ACE-inhibitors with IC50 values of 0.21 and 0.23mM, respectively. On the other hand, NVPVYEGY, which exhibited the highest ACE-inhibitory activity, showed the highest reducing power and peroxyl radical scavenging activities, followed by SLEAQAEKY and GTEDELDKY. The results of this study suggest that fermented sardinelle protein hydrolysates are a good source of natural antioxidant peptides and could have the potential to act as hypotensive nutraceutical ingredients.