Peptide identification in a salmon gelatin hydrolysate with antihypertensive, dipeptidyl peptidase IV inhibitory and antioxidant activities.

Salmon gelatin (Salmo salar, SG) enzymatic hydrolysates were generated using Alcalase 2.4L, Alcalase 2.4L in combination with Flavourzyme 500L, Corolase PP, Promod 144MG and Brewer's Clarex. The hydrolysate generated with Corolase PP for 1h (SG-C1) had the highest angiotensin converting enzyme (ACE, IC50=0.13±0.05mgmL(-1)) and dipeptidyl peptidase IV (DPP-IV, IC50=0.08±0.01mgmL(-1)) inhibitory activities, and oxygen radical absorbance capacity (ORAC, 540.94±9.57μmolTEg(-1)d.w.). The in vitro bioactivities of SG-C1 were retained following simulated gastrointestinal digestion. Administration of SG and SG-C1 (50mgkg(-1) body weight) to spontaneously hypertensive rats (SHR) lowered heart rate along with systolic, diastolic and mean arterial blood pressure. The SG-C1 hydrolysate was fractionated using semi-preparative RP-HPLC and the fraction with highest overall in vitro bioactivity (fraction 25) was analysed by UPLC-MS/MS. Four peptide sequences (Gly-Gly-Pro-Ala-Gly-Pro-Ala-Val, Gly-Pro-Val-Ala, Pro-Pro and Gly-Phe) and two free amino acids (Arg and Tyr) were identified in this fraction. These peptides and free amino acids had potent ACE and DPP-IV inhibitory, and ORAC activities. The results show that SG hydrolysates have potential as multifunctional food ingredients particularly for the management of hypertension.