Journal of Functional Foods (Apr 2013)
Purification and hypotensive activity of rapeseed protein-derived renin and angiotensin converting enzyme inhibitory peptides
Abstract
Rapeseed protein isolate (RPI) was hydrolyzed with Alcalase followed by reverse-phase high performance liquid chromatography (RP-HPLC) purification of bioactive peptides. The rapeseed protein hydrolysate (RPH) obtained after 4 h digestion with Alcalase had a degree of hydrolysis (DH) of ∼11%. Gel permeation chromatography separation showed high contents of low molecular weight peptides in the RPH when compared to the RPI. After preparative and analytical RP-HPLC separations, three peptides (LY, TF and RALP) were purified and amino acid sequence determined by tandem mass spectrometry. LY (IC50, 0.11 mM) was the most potent (p < 0.05) against ACE activity when compared to TF (IC50, 0.81 mM) and RALP (IC50, 0.65 mM). However, RALP (IC50, 0.97 mM) was the most potent (p < 0.05) against renin activity when compared to LY (IC50, 1.87 mM) and TF (IC50, 3.1 mM). Single oral administration (30 mg/kg body weight) to spontaneously hypertensive rats showed LY and RALP to be the more effective hypotensive agents with maximum blood pressure reduction of −26 and 16 mmHg, respectively when compared to TF (−12 mmHg). The results suggest that the higher number of hydrophobic amino acid residues LY and RALP contributed to their higher in vitro and in vivo activities when compared to TF.