PURPLE SWEET POTATO EXTRACTS IN UV PROTECTION 339 ingredients for absorbing UV radiation. Without the addition of anthocyanin extracts, the UV-A and UV-B absorption ability of the cosmetic cream was low. Figure 5 shows the fraction of incident UV radiation that is absorbed by the cosmetic cream. Without the addition of anthocyanin extract, the cosmetic cream absorbed ap- proximately 30% of the UV radiation. When 5 ml of the anthocyanin extract (0.61 mg of Figure 4. The UV absorbance of a cosmetic cream with the UV-A and UV-B regions measured by the spec- trophotometric method ( : no anthocyanin extract added : 0.61 mg/100 g anthocyanin extract added : 1.22 mg/100 g total anthocyanins added). Figure 5. The infl uence of anthocyanin extract on the percentage UV radiation absorbed.

JOURNAL OF COSMETIC SCIENCE 340 total anthocyanins) was added to 100 g of the cosmetic cream, the UV absorption ability of the cosmetic cream was signifi cantly improved, reaching 46%. When 10 ml of the antho- cyanin extract (1.22 mg of total anthocyanins) was added, 50% of the UV radiation was absorbed. Based on Figure 5, anthocyanin extract contributed to the absorption of UV ra- diation. However, the relationship between UV absorption and anthocyanin extract content was not linear. The improvement in UV absorption ability became less signifi cant as more anthocyanin extract was added. The optimal anthocyanin extract content is dependent on practical application and requires further study. Generally speaking, a small amount of an- thocyanin extract was adequate for signifi cant enhancement of UV absorbing ability. The recipe provided in this study was designed to show the effect of adding purple sweet po- tato extract to a cosmetic cream. The UV-absorbing ability of anthocyanin extracts was mea- sured by using a UV spectrophotometer without running expensive human tests. Although the UV spectrophotometric methodology is a convenient tool for preliminary evaluation, hu- man tests are still required to confi rm the infl uence of anthocyanins on humans. The next step of this study is to get governmental permission for running SPF analysis on humans. CONCLUSIONS TNG73 purple sweet potato extracts were an excellent anthocyanin source for preparing UV-protective cosmetic cream. The acidic ethanol-extracted anthocyanins had better radical scavenging ability, higher total phenolic content, and stronger reducing ability than anthocyanins extracted using acidic water. Based on these results, we recommended the use of acidic ethanol-extracted anthocyanins as additives in UV-protective cosmetic cream. The UV absorption ability of the cosmetic cream was successfully improved by the addition of anthocyanin extract. The difference in UV absorption ability arising from the addition of anthocyanin extract was more signifi cant for UV-B rays. However, the opti- mal anthocyanin extract content remains dependent on practical application, and requires further study. ACKNOWLEDGMENTS This research was funded by Chang Gung Institution of Technology, grant no. EZRPF380141. REFERENCES (1) H. Hidaka, S. Horikoshi, N. Serpone, and J. Knowland, In vitro photochemical damage to DNA, RNA and their bases by an inorganic sunscreen agent on exposure to UVA and UVB radiation, J. Photochem. Photobiol. A: Chem., 111, 205–213 (1997). (2) A. Ouhtit and H. N. Ananthaswamy, A model for UV-induction of skin cancer, J. Biomed. Biotech., 1, 5–6 (2001). (3) H. Soehnge, A. Ouhtit, and H. N. Ananthaswamy, Mechanisms of induction of skin cancer by UV ra- diation, Frontiers in Biosci., 2, 538–551 (1997). (4) D. Moyal, How to measure UVA protection afforded by sunscreen products. Expert Rev. Dermatol., 3, 307–313 (2008). (5) N. Serpone, A. Salinaro, S. Horikoshi, and H. Hidaka, Benefi cial effects of photo-inactive titanium di- oxide specimens on plasmid DNA, human cells and yeast cells exposed to UVA/UVB simulated sun- light, J. Photochem. Photobiol. A: Chem., 179, 200–212 (2006).