Antioxidant and renin-angiotensin system inhibitory properties of cashew nut and fluted-pumpkin protein hydrolysates

Abstract

Antioxidant and renin-angiotensin system (RAS)-inhibitory protein hydrolysates derived from the enzymatic hydrolysis of cashew nut (CNP) and fl uted pumpkin (FPP) proteins were investigated. The CNP and FPP hydrolysates (CNPH and FPPH) from pepsin or Alcalase treatments were subjected to membrane ultrafi ltration using different MWCOs to obtain <1, 1-3, 3-5, 5-10, and >10 kDa peptide fractions. Hydrolysis of protein isolates at similar enzyme levels allowed obtaining peptic hydrolysates with a lower degree of hydrolysis (46.7-48.0%) when compared to the Alcalase- -produced hydrolysates (47.7-50.3%). Amino acid composition revealed that CNPH had 28% hydrophobic residues when compared to higher contents (32-35%) in the 3-10 kDa peptide fractions. In contrast, aromatic residues increased from 8% in the FPPH to 9-13% in the peptide fractions. The in vitro OH and DPPH scavenging activities were signifi cantly (p<0.05) enhanced by ultrafi ltration but potency was inversely related to peptide size. The ferric-reducing power was the highest for the <1 kDa CNPH (2.47) when compared to 1.33 for CNPH and other peptide fractions. Metal chelation ability was signifi cantly (p<0.05) enhanced by ultrafi ltration only for the CNPH with 21% compared to ∼96% for the peptide fractions. ACE inhibition was signifi cantly (p<0.05) lower for the Alcalase CNPH and peptide fractions (∼87%) compared to ∼92% of pepsin-CNPH. However, renin inhibition was signifi cantly (p<0.05) increased by ultrafi ltration from 45.7 and 62.1% to ∼82.4 and 96.5% for FPPH and CNPH, respectively. We conclude that the strong antioxidant properties coupled with RAS inhibition make CNPH and FPPH as well as their low molecular weight peptides potential ingredients to formulate health-promoting foods.