Antioxidant properties, ACE/renin inhibitory activities of pigeon pea hydrolysates and effects on systolic blood pressure of spontaneously hypertensive rats

Legumes are rich sources of protein in human diet and their consumption has been associated with the prevention of chronic diseases attributable to their bioactive components. Pigeon pea (Cajanus cajan) is an underutilized legume with relatively high protein content (similar to 24%). Protein hydrolysates were prepared from pea isolate by enzymatic hydrolysis using pepsin and pancreatin. Hydrolysates were evaluated for their amino acid composition, antioxidant properties, in vitro and in vivo antihypertensive properties. The hydrolysates had high hydrophobic amino acids, especially isoleucine, phenylalanine, and leucine. Pepsin-pancreatin-hydrolyzed pea protein (PPHPp) showed significantly higher ability to scavenge DPPH center dot while pancreatin-hydrolyzed pea protein (PPHPa) had higher (OH)-O-center dot, ABTS(center dot+) scavenging, Fe3+ reducing and linoleic acid peroxidation inhibition. PPHPp exhibited superior angiotensin-converting enzyme inhibition (61.82%) while PPHPa showed higher renin inhibition (14.28%). PPHPp exhibited strong antihypertensive effect, showing an instantaneous systolic blood pressure lowering effect (-26.12 mmHg) within 2-h post-oral administration. Pigeon pea protein hydrolysate (especially from pancreatin digest) could therefore, be a promising source of bioactive peptides and potential ingredient for formulation of functional foods against oxidative stress and hypertension.