Blood pressure lowering effects of Australian canola protein hydrolysates in spontaneously hypertensive rats

- Inhibition of both renin and ACE activities using enzyme hydrolysed canola proteins.
- Australian canola exhibited antihypertensive effects in hypertensive rats.
- Canola protein isolate had the most prolonged antihypertensive effect in vivo.
- Smaller sized peptides contributed to a faster rate of blood pressure decrease.

The in vitro and in vivo antihypertensive activities of canola protein hydrolysates and ultrafiltration membrane fractions (< 1, 1-3, 3-5, & 5-10 kDa) were examined in this study. The hydrolysates were obtained after 4 h enzyme hydrolysis of canola protein isolate (CPI) using each of Alcalase, chymotrypsin, pepsin, trypsin and pancreatin. The hydrolysates had significantly (p < 0.05) reduced (35-70%) surface hydrophobicity when compared to the CPI. Alcalase hydrolysate contained the highest level of low molecular weight peptides and produced highest (p < 0.05) in vitro inhibition of angiotensin converting enzyme (ACE) activity. However, pancreatin hydrolysate was the most effective (63.2%) in vitro renin inhibitor. Membrane fractionation of pancreatin hydrolysate led to a 15% reduction in renin inhibition by the 1-3 kDa peptide fraction. In contrast, ACE and renin inhibitions were significantly (p < 0.05) increased by 10-20% after membrane ultrafiltration fractionation of the trypsin hydrolysate. Trypsin hydrolysate was ineffective at reducing hypertension in spontaneously hypertensive rats after oral administration (200 mg/kg body weight). However, Alcalase and pepsin hydrolysates showed appreciable antihypertensive effects, with Alcalase hydrolysate producing the greatest (− 34 mm Hg) and fastest (4 h) decrease in systolic blood pressure (SBP). CPI had the most prolonged (24 h) SBP-reducing effect, which is attributable to the extensive protein hydrolysis in the GIT. We conclude that the Alcalase and pepsin hydrolysates may serve as useful ingredients to formulate antihypertensive functional foods and nutraceuticals.