Supercritical Extraction Of Propolis And Preparation Of Propolis Extract Liposomes

Propolis and its flavonoids exhibit strong antioxidant and anti-tumor effects, as well as anti-inflammatory and anti-microbial activities, which shows the bright future of propolis as a valuable remedy substance. However, the biological functions of propolis and its flavonoids depend much on their concentration. Furthermore, propolis and its flavonoids are unstable to such physicochemical factors as light, heat, oxygen, and metallic ions, etc. This research is aimed to establish an optimized process for maximum concentration and protection of propolis and its flavonoids.The supercritical CO2 extraction process of propolis was optimized via orthogonal design, and the optimum conditions were chosen as follows: extraction temperature 50℃, extraction pressure 25MPa, entrainer 95% ethanol, propolis/ethanol 6:1(w/v); and the supercritical CO2 propolis extract thus obtained contained a flavonoids concentration of 14.8g/100g.The influences of various conditions were studied on the encapsulation efficiency of supercritical CO2 propolis extracts obtained as above. Among the methods evaluated, the rotary evaporated film ultrasonication method showed better encapsulation efficiency for propolis flavonoids. And the ranges of the prepartion conditions of propolis liposomes were determined relevant to the rotary evaporated film ultrasonication method. With the mean diameter of propolis liposomes, the encapsulation efficiency, and the percentage encapsulation efficiency retention rate of the liposomes chosen as controlling indexes, non-linear multi-function regression and computerized optimization were performed to obtain the optimum preparation process of propolis liposomes. Two sets of process conditions were thus chosen for further evaluation.The in vitro release characteristics of the two propolis liposome preparations obtained under optimized conditions were tested by dissolution trials. Both liposome preparations exhibited better sustained-release characteristics relative to the unprotected supercritical CO2 propolis extract. The preparation process pertaining to the propolis liposomes preparation showing better in vitro release characteristics were determined as the final optimum conditions: Egg lecithin 500mg, cholesterol 80mg, propolis 100mg, rotary evaporating temperature 45℃, phosphate buffer solution (pH7.4) 25mL, and ultrasonic treatment time 25min. The propolis liposomes prepared under these conditions showed an encapsulation efficiency of 86.6% with a mean diameter of 104.78nm and a percentage encapsulation efficiency retention rate of 77.0%.