2002 ANNUAL SCIENTIFIC SEMINAR 295 Simple multiphase POW emulsions were produced, and their physical and chemical stability tested, on the basis of the theoretical considerations discussed so far. I would not like to say a few things about the stability of these emulsion, using encapsulated Vitamin C and polyphenols as my examples. The chemical stability of ascorbic acid was studied over a period of 450 days with polarimetric methods. The samples examined were stored under normal conditions at room temperature. Parallel to this, a sample of this emulsion was stored at 40øC and the ascorbic acid concentration determined over a 90-day period. In the sample stored at room temperature, an ascorbic acid concentration of 83.9% was measured after a storage period of 450 days. The ascorbic acid concentration of this sample after a 90-day storage period at 40øC was 71.4 %. If the samples are stored in PET or aluminum packages, 91.2% of the original ascorbic acid concentration is measured after 450 days at room temperature and 81.9% after 450 days at 40øC. Emulsions containing polyphenols or green tea as active substances are known to discolor very rapidly even under normal storage conditions. We can make use of this phenomenon to study the stability of encapsulated polyphenol over time with purely optical methods. As can be seen in Fig ..... , an emulsion containing 1% polyphenol in encapsulated form does not display any discoloration after 180 days of storage at room temperature. In contrast, the comparison sample, in which the same account ofpolyphenol has been worked into the corresponding OW emulsion, exhibited marked discoloration. ow cream containing 1%wt green tee POW cream containing 1%wt encapsulated green tee Following this discussion of the physical and chemical stabilization of multiple POW emulsions, two questions worthy of exploration are: a) in what way are the encapsulated active substances released on the skin and b) what effect can we expect them to exert there? The above model emulsion containing 1.1% of ascorbic acid in encapsulated form will serve as the basis for this discussion. Efficacy of POW Emulsions The question of whether ascorbic acid is released on the skin by multiple emulsions, as well as the extent of such release, can be answered quite accurately on the basis of the known anti-oxidative effect of this substance. If we expose the skin to UVA radiation, squalene peroxide is formed on the skin surface. If free ascorbic acid is present on the skin during UVA irradiation, the formation of lipid peroxide is suppressed as a function of the ascorbic acid concentration (1-3). It could be demonstrated that even low concentrations of vitamin C delivered by multiple phase emulsions reduce significantly the formation of the harmful lipid peroxides on the skin. The obtained data demonstrating the reduction of lipid peroxide formation on human skin are in ideal correlation to the anti-wrinkling effects of other studies using ascorbic acid on hairless mice.

296 JOURNAL OF COSMETIC SCIENCE Protection against radical formation under UVA radiation [%] 80 70 60 50 40 30 20 10 0 0 2 4 6 8 10 12 Concentration of Vitamin C in Emulsion The extent to which the released ascorblc ac•d can be transported to deeper skin layers by the multiple emulsion was tested on human skin as well. 1oo 6o 4o Strip layer AS ascorblc ac•d •s able to penetrate deeper skin layers, we can expect It to &splay well known effects such as reducing the occurrence of age-related ptgment spots or promoting heahng processes m damaged skin. Several screening tests were camed out to explore these questions as well. The effect of the simple POW emulsion described above on the occun'ence of age-related p•gment spots xvas also •nvesugated m the follo•vmg experimental model. ,•, lOO.O c• • 80.0 ._ c• 60.0 -- .=_ • 40.0 5 10 15 20 25 30 35 40 Application [ days ] Th•s test also showed clearly that even small amounts ofascorblc acid can exert an unexpected positive cfI•:ct Furthermore, hght-mduced erythema disappears rapidly when treated with a multiple POW emulsion containing ascorblc ac•d, as •s shown by the lbilowmg test. Up to now this effect has appeared to be due solely to the action ofascorb•c ac•d. To show that th•s is m fact not the case, I would also hke to present an example using retmol •nstead ol'ascorb•c ac•d.