Novel casein-derived peptides with antihypertensive activity

In this study, we report novel casein-derived peptide sequences with angiotensin converting enzyme (ACE)-inhibitory activity and antihypertensive activity demonstrated in spontaneously hypertensive rats (SHR). The peptides were obtained by enzymatic hydrolysis of total isoelectric casein with pepsin. To identify ACE-inhibitory peptides, the casein hydrolysate was fractionated by semi-preparative high performance liquid chromatography, and 44 (CN) peptides contained in the active fractions were sequenced by using an ion trap mass spectrometer. Among the identified peptides, three sequences, that corresponded to αs1-CN f(90–94) (RYLGY), αs1-CN f(143–149) (AYFYPEL), and αS2-CN f(89–95) (YQKFPQY), showed IC50 values as low as 0.71 μm, 6.58 μm, and 20.08 μm, respectively. These three peptides also exerted antihypertensive activity when they were orally administered to SHR at a dose of 5 mg kg−1 of body weight. The activity of peptides RYLGY and AYFYPEL in SHR was similar to that found for tripeptide VPP when orally administered at the same dose.