Angiotensin-Converting Enzyme-Inhibitory Peptides Isolated from Pepsin Hydrolyzate of Apios americana Tuber and Their Hypotensive Effects in Spontaneously Hypertensive Rats

With the aim of elucidating the hypotensive effects of Apios americana Medikus tuber, active ingredients with angiotensin-converting enzyme (ACE)-inhibitory activity were identified and their hypotensive effects in spontaneously hypertensive rats (SHR) were investigated. From a pepsin digest of A. americana showing strong activity, two ACE-inhibitory peptides were isolated and identified as YRLPNL and YQLP. Although the ACE-inhibitory activity of YQLP was weak, YRLPNL showed strong ACE-inhibitory activity (IC50 value 7.7 nM) equal to those of lisinopril and captopril. After a single oral administration of YRLPNL, SHR showed a significant decrease in blood pressure. These results suggest that YRLPNL, isolated from A. Americana, is a hypotensive peptide having ACE-inhibitory activity. This is the first report of a food peptide having ACE-inhibitory activity equal to that of pharmaceuticals.