Preparation of liposome encapsulating angiotensin-I-converting enzyme inhibitory peptides from sunflower protein hydrolysates.

Liposomal angiotensin-I-converting enzyme inhibitory (ACEI) peptides were prepared from sunflower protein hydrolysates by the thin‑film ultrasonic method. Response surface methodology (RSM), in combination with fractional factorial designs and central composite design methods were utilized to optimize entrapment efficiency and balance the drug release. We found that the ratio of phospholipids to cholesterol, ultrasound time and the ratio of phospholipids to ACEI peptides were significant factors affecting entrapment efficiency (P<0.001). Optimal preparation conditions of liposomal‑ACEI peptides were the ratio of soybean phospholipids to cholesterol (w/w) of 4.1:1, PEG‑2000 dosage (%) of 4, NaCl concentration in PBS (mM) of 50, hydration temperature of 45˚C, ultrasound time of 8.05 min and the ratio of soybean phospholipids to ACEI peptides of 15:1 (w/w). The experimental entrapment efficiency of liposomal‑ACEI peptides was (91.25±0.182%). Moreover, the balanced release rate of liposome encapsulated ACEI in phosphate buffer was 77.83% after 12 h.