The feasibility of antihypertensive oligopeptides encapsulated in liposomes prepared with phytosterols-β-sitosterol or stigmasterol

The feasibility of liposomes with cholesterol substituted by phytosterols and the effect of antihypertensive oligopeptides encapsulated in liposomes on blood pressure of spontaneously hypertensive rats (SHRs) were investigated. β-Sitosterol or stigmasterol was used as a substitute for cholesterol to prepare liposomes. OA3, angiotensin-I-converting enzyme (ACE) inhibitory oligopeptides derived from tuna cooking juice, was the agent used to lower the blood pressure in SHRs. Results indicated that sterol contained in liposomes showed better effect for OA3 encapsulation. The highest efficiency was observed when the molar ratio of lecithin/phytosterols was 1/0.5. Encapsulation efficiencies were 50% and 49% for β-sitosterol and stigmasterol, respectively. Furthermore, stabilities of storage, pH, oxidation and gastrointestinal enzyme exhibited no significant difference irrespective of sterol composition. Liposomes containing cholesterol or phytosterol all lowered blood pressure slowly as evaluated in vivo in SHRs. Therefore, replacing cholesterol with phytosterols in preparing liposomes is feasible and recommended.