Isolation of Peptides with Angiotensin I-converting Enzyme Inhibitory Effect Derived from Hydrolysate of Upstream Chum Salmon Muscle

In order to utilize upstream chum salmon as a component of nutraceutical food, their defatted muscle proteins were hydrolyzed with 5% thermolysin. The resulting hydrolysate showed high inhibitory activity against angiotensin I‐converting enzyme (inhibitory concentration₅₀= 27.9 protein μg/mL) in vitro. A significant reduction of systolic blood pressure was observed when 500 and 2000 mg/kg of body weight were orally administered into spontaneously hypertensive rats. Angiotensin I‐converting enzyme inhibitory peptides contained in the hydrolysate were isolated with various chromatographs. These 6 active peptides were Trp residue‐containing dipeptides: Trp‐Ala, Val‐Trp, Trp‐Met, Met‐Trp, Ile‐Trp, and Leu‐Trp. The inhibitory concentration₅₀ values of these dipeptides ranged from 2.5 μM to 277.3 μM.