In vitro and in vivo antihypertensive activity of palm kernel cake protein hydrolysates: Sequencing and characterization of potent bioactive peptides

This study was aimed to generate a valuable protein hydrolysate and bioactive peptides with strong ACE-inhibitory activity in vitro and in vivo from palm kernel cake (PKC) protein. PKC protein was independently hydrolyzed by seven different proteases to produce PKC protein hydrolysates. Among those investigated, papain-produced hydrolysate revealed the highest ACE-inhibitory activity (70.9%). When normotensive rats induced with hypertension were fed the hydrolysate at a dose of 75 mg/kg body weight, their blood pressures stabilized considerably. Fractionation of the protein hydrolysate using RP-HPLC revealed a direct relationship between hydrophobicity and ACE-inhibitory activity. The fractions with relatively higher ACE-inhibitory activity were further fractionated by isoelectric focusing, out of which fractions having neutral and basic charges showing higher ACE-inhibitory activities (77% and 75%, respectively). Nine peptide sequences were identified by Q-TOF mass spectrometry, and their respective ACE-inhibitory activities evaluated. The peptide sequences YLLLK, YGIKVGYAIP, and LPWRPATNVF showed ACE-inhibitory activities of 100%; however, the best IC50 values were observed for YGIKVGYAIP, GIFE and LPWRPATNVF at 1 μM, 3 μM and 20 μM, respectively.