Microencapsulation and modification of synthetic peptides of food proteins reduces the blood pressure of spontaneously hypertensive rats.

Synthetic peptides were microencapsulated into liposomes, cycled with a disulfide bond or modified with d-phenylglycine (d-phg) at the N-terminal, and their antihypertensive effects as orally administered (0.18 mM/kg body weight) to spontaneously hypertensive rats (SHR) were measured. The microencapsulated Leu-Lys-Pro reduced significantly the systolic blood pressures of SHR by 45 mmHg and showed a prolonged duration, revealing the significant protective effect of encapsulation. d-phg-Leu-Arg-Pro showed a duration about 2 h shorter than that of the peptide without modification. In addition, cyclic Leu-Arg-Pro peptide with a disulfide bond between the N- and C-terminal amino acids reduced the systolic blood pressure of SHR by 35 mmHg and displayed a lengthy duration.