Kidney bean protein products as potential antioxidative and antihypertensive alternatives for non-pharmacological inhibition of angiotensin-converting enzymes

Kidney bean protein (KBP) albumin (KBPA) and globulin (KBPG) were produced by salt extraction method while the isolate (KBPI) was prepared by alkaline extraction followed by isoelectric precipitation. Furthermore, enzymatic hydrolysates of KBPI were prepared by treatment with alcalase (KBPH-A) and pepsin+pancreatin (KBPH-PP) respectively, while the antioxidant and angiotensin-converting enzyme (ACE) inhibiting activities of KBP products were evaluated after determining their amino acid (AA) composition profile. The result of the AA profile showed that while the hydrophobic amino acid (HAA) of KBPG (41%) was higher than KBPA (39%) and KBPI (36%) respectively, they however had similar (11%) aromatic amino acids (AAA). In addition, enzymatic hydrolysis resulted in increased contents of HAA and AAA of KBPH-A and KBPH-PP (42–45%; 14%), respectively. The KBPG had the highest OH− and ABTS− scavenging activities (40 and 45%) among the non-hydrolyzed fractions, which increased (70 and 75%) after hydrolysis by alcalase and PP. The KBPG had higher bioactivities (antioxidant and ACE inhibition) than the KBPA, which might be due to more hydrophobic character resulting from the higher disulfide bond present in globulin compared to the glycoprotein albumin. The hydrolyzed proteins had significantly higher (p