Preparation Of W/O/W Multiple Emulsion Encapsulating Vitamin C And Its Application In Whitening Cosmetics

Vitamin C is a kind of whitening active substance commonly used in whitening cosmetics,which has whitening,anti-oxidation and anti-wrinkle properties.However,The structure of vitamin C is unstable and it is easy to be oxidized and lose its activity.As a novel carrier,multiple emulsions can not only protect the encapsulated active substances,but also slow down the release rate and prolong the action time of the active compounds.In this paper,the W/O/W multiple emulsions encapsulating vitamin C was prepared by two-step emulsification method.The photostability,controlled release in vitro,anti-oxidation and whitening performances were tested.Finally,it was used in the formula of whitening milk.The main research results of this thesis are as follows:1.W/O/W multiple emulsions were prepared by two-step emulsification method.Five factors affecting the stability of the emulsion were investigated by orthogonal test,including the concentration of Span80,as a lipophilic emulsifier in the first step emulsification,the amount of Tween80,as a hydrophilic emulsifier in the second step emulsification,the oil-water ratio of W/O emulsions,the emulsion-water ratio of W/O/W double emulsions and the amount of xanthan gum in external water phase.The optimal formulation conditions of W/O/W multiple emulsions were determined as follows: the ratio of oil-water was 7: 4,the ratio of emulsion-water was 3: 2,the concentration of Span80 was 6 %,the concentration of Tween80 was 3 % and the concentration of xanthan gum was 1.5 %.2.By comparing the UV stability of vitamin C in aqueous solution,W/O emulsion and W/O/W multiple emulsion,we obtained that the content of vitamin C after UV irradiation for 21 days was 0,37.2 % and 71.7 %,respectively.3.By testing the drug content of transdermal diffusion,we obtained that the maximum release rate of aqueous solution has reached 94.7 % in 18 hours,and the maximum release efficiency of W/O emulsion is 88.3 % in 24 hours.The release efficiency of W/O/W multiple emulsion was 64.1 % in 48 hours,and the release was slow and sustained.4.The oxidation resistance model of DPPH free radical and the inhibition rate of tyrosinase were measured under the condition of accelerated oxidation of vitamin C at high temperature.After 3 weeks,W/O/W multiple emulsion still maintained 68.7 % DPPH elimination rate and 68.8 % tyrosinase inhibition rate,which was much higher than that of W/O emulsion 36.7 % DPPH elimination rate and 54.7 % tyrosinase inhibition rate.5.The formula of W/O/W multiple emulsion whitening milk was prepared by encapsulating vitamin C in the inner phase.The stability of the product was proved by centrifugal test,heat resistance test,cold resistance test,freeze-thaw test and static test.There is no irritation or allergic reaction to the skin.