New antihypertensive peptides isolated from rapeseed

Four potent angiotensin converting enzyme (ACE) inhibitory peptides, IY, RIY, VW and VWIS, were isolated from subtilisin digest of rapeseed protein. Among them RIY and VWIS are new peptides With IC50 28 and 30 muM, respectively. All isolated peptides lowered blood pressure of spontaneously hypertensive rats (SHR) following oral administration. The maximum effect in the case of RIY was observed 4 h after administration, while maximum effect of other peptides on blood pressure occurred 2 h after administration. Furthermore, the antihypertensive effect of RIY was observed even in old rats, in which ACE inhibitors become less effective, suggesting that a different mechanism other than ACE inhibition is also involved in lowering blood pressure by this peptide. Subtilisin digest of rapeseed protein also significantly lowered blood pressure of SHR after oral administration of a single dosage 0.15 g/kg, exerting maximum antihypertensive effect 4 h after administration. This digest appears promising as a functional food, which may be useful in the prevention and treatment of hypertension. (C) 2003 Elsevier Inc. All rights reserved.