According to findings published online in the Journal of Functional Foods, flaxseed meal contains peptide amino acid sequences that may be exploited as potential food sources for lowering blood pressure based on their angiotensin converting enzyme (ACE)-inhibitory activity.
ACE inhibitors work by inhibiting the conversion of angiotensin I to the potent vasoconstrictor, angiotensin II, thereby improving blood flow and blood pressure.
“The results of this study clearly indicate that flaxseed protein hydrolysates possess potential as a food source of anti-hypertensive agents,” wrote the researchers, led by Rotimi Aluko from the University of Manitoba.
“This will contribute towards increased value-added utilization of flaxseed meal, currently a low-value by-product of the oilseed processing industry,” they added.
High blood pressure (hypertension),defined as having a systolic and diastolic blood pressure (BP) greater than 140 and 90 mmHg, is a major risk factor for cardiovascular disease (CVD) - a disease that causes almost 50 per cent of deaths in Europe, and reported to cost the EU economy an estimated €169bn ($202bn) per year.
The Manitoba-based researchers prepared different protein hydrolysates using different enzymes, including pepsin, ficin, trypsin, papain, thermolysin, pancreatin and Alcalase.
The ACE-inhibitory activity was then tested in vitro using N-(3-[2-furyl]acryloyl)-phenylalanylglycylglycine, and the hydrolysate from thermolysin and the cationic peptide fraction from Alcalase “showing the most potent activity”, said the researchers.
The researchers also noted that some of the peptides had additional benefits by acting on the activity of renin, an enzymes produced in the kidney that converts angiotensinogen to angiotensin I, and then to angiotensin II. Therefore, renin inhibition is seen as a method of reducing blood pressure.
Of note, the cationic peptide fraction was found to inhibited renin in uncompetitively.
“The flaxseed peptide fractions that inhibited both ACE and renin activities possess better prospects, and potentially could provide better in vivo lowering of blood pressure when compared to peptides that inhibit ACE alone,” wrote the researchers.
“Further work is needed to characterize the effects of these flaxseed protein hydrolysate and cationic peptide fractions in lowering of blood pressure, and to identify their constituent bioactive peptides,” they concluded.
The study was funded by the Advanced Foods and Materials Network of Centre of Excellence (AFMnet) and the Natural Sciences and Engineering Research Council of Canada (NSERC).
Source: Journal of Functional Foods Published online ahead of print, doi: 10.1016/j.jff.2009.01.009“Kinetics of the inhibition of renin and angiotensin I-converting enzyme by flaxseed protein hydrolysate fractions” Authors: C.C. Udenigwe, Y.-S. Lin, W.-C. Hou, R.E. Aluko