Antihypertensive effect of rapeseed peptides and their potential in improving the effectiveness of captopril

BACKGROUND: The main objective of this study was to evaluate the safety and antihypertensive activity of rapeseed peptides and to investigate their potential synergy with captopril. Rapeseed peptides did not have a synergistic effect with captopril on inhibiting ACE activity in simulated digestion tests in vitro. But in vivo they could synergistically augment the amplitude range of lowering blood pressure with captopril by approximately 9% and prolong the antihypertensive effect duration time by over 20% in antihypertension tests of spontaneously hypertensive rats. In addition, the inhibiting effect of rapeseed peptides on ACE activity was noticeable in some rat organs in vivo. Nevertheless, when compared to captopril group, the potential synergy of rapeseed peptides with captopril did not cause a further decrease in ACE activity in the organs but their synergy further improved levels of NO (12.7%) and endothelial nitric oxide synthase (74.1%) in rat serum. Further studies of some peptides identified from rapeseed peptides showed that some of the rapeseed peptides (Cys-Leu, Val-Ala-Pro) could markedly increase contents of NO and endothelial nitric oxide synthase. CONCLUSIONS: Rapeseed peptides have antihypertensive activity and they showed potential synergy with captopril in antihypertensive performance in vivo. The synergy was not from ACE inhibition but from other pathways, like improvement in endogenous vasodilator contents.