Article Title

Hydrolysates from tuna cooking juice as an anti-hypertensive agent


Tuna cooking juice containing 4% protein was hydrolyzed using a commercial protease, Orientase from Bacillus subtilis, to prepare hydrolysate (OAH) that inhibits angiotensin I-converting enzyme (ACE). The systolic blood pressure (SBP) dropped by 18 mmHg in spontaneously hypertensive rats (SHR) 2hr after being orally administered the hydrolysate at 0.25g hydrolysate/kg body weight, and reduced, from 172 mmHg to 150 and 142 mmHg for those administered with lyophilized OAH at 0.5 and 1.0 g/kg body weight, respectively. This indicated that the lowering effect on SBP was dose-dependent. Constituents derived from the gel filtration of OAH with molecular weight ranging from 240-565 Da exerted an obvious effect on SBP. Although the reduced SBP in SHR gradually returned to the original level, the reduction effect lasted for 2-10 hr, depending on the dose. The SBP of SHR fed on a normal diet increased gradually to 215 mmHg by the age of 15 weeks, while it decreased, then increased to and stayed at, respectively, 200, 205 and 215 mmHg for those fed on diets containing 2.5, 1.25 or 0.25% lyophilized OAH. This result showed that proteins in tuna cooking juice are potential source of ACE-inhibiting agent, and thus may be useful to regulate the blood pressure.

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