Preparation and Physicochemical Properties of Total Flavonoids Liposomes from the Stems and Leaves of Astragalus membranaceus
The preparation conditions of total flavonoids liposomes from the stems and leaves of Astragalus membranaceus by ethanol injection method was optimized.The effects of mass ratio of lecithin to cholesterol,mass ratio of total flavonoids extract to lecithin,the amount of ethanol,hydration pH,hydration temperature and ultrasonic time on the encapsulation efficiency of liposomes were investigated,and the process was further optimized by response surface methodology.Finally,the physicochemical properties of the liposomes prepared by the optimal technology were analyzed.The results showed that the optimum preparation conditions of total flavonoids liposomes were as follows:the mass ratio of lecithin to cholesterol was 4∶1,the mass ratio of total flavonoids extract to lecithin was 1:25,the amount of ethanol was 20 mL,the hydration pH was 7.2,the hydration temperature was 40 ℃,and the ultrasonic time was 11 min.Under these conditions,the encapsulation efficiency was 89.98％,the particle size was 236.35 nm,the polydispersity index was 0.252,and the zeta potential was-52.1 mV.The mid-infrared spectroscopy suggested that total flavonoids were successfully encapsulated into the lipid material through intermolecular forces without the formation of new chemical bonds.Stability tests showed that leakage rates of liposomes under such conditions as the temperature below 60 ℃ and the pH close to neutral and weakly alkaline were small,indicating that the liposomes had good thermal stability and suitable acid-base stability.This study lays a theoretical foundation for the application of total flavonoids from the stems and leaves of Astragalus membranaceus in the development of healthy food.
stems and leaves of Astragalus membranaceustotal flavonoidsliposomesethanol injection methodpreparationphysicochemical properties
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