Kinetics of in vitro renin and angiotensin converting enzyme inhibition by chicken skin protein hydrolysates and their blood pressure lowering effects in spontaneously hypertensive rats

Chicken skin protein hydrolysates (CSPHs) and their membrane ultrafiltration fractions were investigated for their blood pressure lowering effects. Chicken skins from thigh or breast muscles were hydrolyzed with 3% Alcalase or 1% pepsin/pancreatin, respectively; hydrolysates were then fractionated into <1, 1-3, 3-5, and 5-10 kDa peptide sizes. Chicken breast skin hydrolysate (CBSH) and peptide fractions inhibited angiotensin converting enzyme (ACE) with IC50 values of 0.36-0.64 mg/mL, which were significantly (p < 0.05) higher than the 0.42-0.75 mg/mL values obtained for chicken thigh skin hydrolysate (CTSH) and peptide fractions. Results suggest that a high content of branched-chain amino acids contributed to the significantly (p < 0.05) higher ACE-inhibition by <1 kDa peptide fraction. All the samples with exception of the CBSH 3 kDa fraction had similar renin inhibitory values. Kinetics studies revealed that enzyme inhibition pattern was mostly of the mixed-type for ACE and renin. Oral administration of 100 mg peptides/kg body weight to spontaneously hypertensive rats led to maximum systolic blood pressure reduction of −32.67 and −31.33 mmHg after 6 h for CTSH and CBSH, respectively. We conclude that the CSPHs have potential use as active ingredients to formulate antihypertensive functional foods and nutraceuticals.