Abstract: Favonoids have low solubility, poor alkali resistance and photolysis resistance, and are very unstable in chemical properties, thereby limiting their application in foods. Microemulsion is a good carrier that can solve the problem that favonoids are difficult to utilize due to incompatibility and oxidization. By drawing pseudo-ternary phase diagrams using the titrimetric method, the influence of surfactants, cosurfactants, surfactant/cosurfactant ratio (Km, m/m), and oil phases on the formation of microemulsion was investigated in order to determine the best microemulsion formulation. The morphology and size distribution of microemulsions were explored by a transmission electron microscope (TEM) and a particle size analyzer. Furthermore, a microemulsion system containing flavoinoids from Acanthopanax senticosus leaves was prepared and its antioxidant capacity was evaluated by the scavenging activity against superoxide anion, hydroxyl and 1,1-diphenyl-2-picrylhydrazyl radicals. Its antibacterial activity was studied by measuring the diameter of the inhibition zones. Untreated flavoinoids were employed as control. The results showed that the greatest microemulsion area was obtained using isopropylmyristate as oil phase, Tween-80 as surfactant, and anhydrous alcohol as cosurfactant (Km = 2) . The average particle size of the microemulsion was about 18.3 nm. After high-speed centrifugation and standing for a long time, the system was still uniformed, transparent and without stratification. The antioxidant tests indicated that the antioxidant capacity of the flavonoid microemulsion was better than that of the control. In the antibacterial tests, the flavonoid microemulsion was more effective against Escherichia coli, Staphylococcus aureus, Salmonella and Pseudomonas fluorescens than the control.

Key words: microemulsion, pseudo-ternary phase diagrams, flavonoid, antioxidant capacity, antibacterial property