Angiotensin I-converting enzyme inhibitory peptides derived from wakame (Undaria pinnatifida) and their antihypertensive effect in spontaneously hypertensive rats

Seven kinds of angiotensin I-converting enzyme (ACE) inhibitory peptides were isolated from the hydrolysates of wakame (Undaria pinnatifida) by Protease S "Amano" (from Bacillus stearothermophilus) by using three-step high-performance liquid chromatography (HPLC) on a reverse-phase column. These peptides were identified by amino acid composition analysis, sequence analysis, and liquid chromatography-mass spectrometry (LC-MS), as Val-Tyr (IC50 = 35.2 muM), Ile-Tyr (6.1 muM), Ala-Trp (18.8 muM), Phe-Tyr (42.3 muM), Val-Trp (3.3 muM), Ile-Trp (1.5 muM), and Leu-Trp (23.6 muM). These peptides have resistance against gastrointestinal proteases in vitro. Each peptide was determined to have an anti hypertensive effect after a single oral administration in spontaneously hypertensive rats (SHR). Among them, the blood pressure significantly decreased by Val-Tyr, Ile-Tyr, Phe-Tyr, and Ile-Trp in a dose of 1 mg/kg of body weight (BW). The present study showed that antihypertensive effect in the hydrolysates of wakame by Protease S "Amano" was attributed to these peptides.