J. Cosmet. Sci., 61, 333–341 (September/October 2010) 333 Infl uence of purple sweet potato extracts on the UV absorption properties of a cosmetic cream CHIN-FENG CHAN, CHING-YI LIEN, YUNG-CHANG LAI, CHE-LUN HUANG, and WAYNE C. LIAO, Department of Applied Cosmetology, Hung Kuang University, Taichung (C.-F.C.), Department of Applied Chemistry, National Chia-Yi University, Chia-Yi (C.-Y.L.), Agricultural Research Institute, Chia-Yi Agricultural Experiment Station, Chia-Yi (Y.-C.L., C.-L.H.), and Department of Nursing, Chang Gung Institution of Technology, Chia-Yi (W.C.L.), Taiwan. Accepted for publication June 30, 2010. Synopsis Anthocyanins were added to a cosmetic cream to provide additional protection against UV radiation. The infl uence of anthocyanins on UV absorption ability was carefully evaluated. Anthocyanins were successfully extracted from TNG73 purple sweet potato using acidic ethanol and acidic water. Acidic ethanol-extracted anthocyanins had better radical scavenging ability, higher total phenolic content, and stronger reducing abil- ity than acidic water-extracted anthocyanins. The cosmetic cream with 0.61 mg of total anthocyanins (per 100 g cream) absorbed approximately 46% of the incident UV radiation. Although the anthocyanins ab- sorbed both UV-A and UV-B radiation, they were particularly effective against UV-B rays. This study dem- onstrates that the addition of anthocyanin extracts of purple sweet potato to a cosmetic cream improves the cream’s UV absorption ability. INTRODUCTION The sun’s rays contain ultraviolet light that can be classifi ed as UV-A (320~400 nm), UV-B (290~320 nm), or UV-C (200~290 nm) radiation. Ultraviolet rays can penetrate into skin tissues and destroy skin cells (1). As a result, ultraviolet rays cause a number of serious problems including visible aging, wrinkling of the skin, damage to the immune system, and skin cancer (2,3). The use of sunscreen products to protect skin from ultra- violet radiation is strongly recommended. The ability of sunscreen to protect against UV radiation is measured by two factors, the sun protection factor (SPF) and the protection factor of UV-A (PFA). The SPF number indicates the protection from sunburn caused by UV-B, while the PFA number indicates the protection against UV-A (4). In both cases, a higher number indicates stronger protection. Sunscreens work by chemical (absorbing) and/or physical (refl ecting and scattering) methods to protect the skin from ultraviolet Address all correspondence to Wayne C. Liao.

JOURNAL OF COSMETIC SCIENCE 334 radiation. Some organic materials like octyl dimethyl para-aminobenzoic acid (PABA) and salicylate are used to absorb ultraviolet radiation, while some inorganic particles like zinc oxide and titanium dioxide are used to refl ect the ultraviolet rays (5–8). Both chem- ical and physical methods use active ingredients to insulate the skin from ultraviolet ra- diation, but unfortunately some ingredients may act as allergens to the skin. In addition, the active ingredients may break down after hours of exposure to the sun. This decompo- sition raises questions about how long the UV protective ability of sunscreens will last. Consumers demand comfortable, stable, and safe sunscreen ingredients (9). The current trend in the sunscreen market is towards using ingredients extracted from natural prod- ucts, which are generally considered safe (10–13). Anthocyanins are good anti-oxidative compounds (14–16). Since anthocyanins have been reported to have the ability to absorb UV-A and UV-B radiation (17,18), they can also protect skin against wrinkling and other aging effects. Although anthocyanins are ideal ingredients for making sunscreens, it is important to maintain an acidic environment to avoid degradation of anthocyanins (19). Anthocyanins are pH-sensitive (20,21), and their color changes with pH. The effect of pH on the UV absorption ability of anthocyanins requires further study. Anthocyanins can be found in many deep-colored vegetables and fruits such as grapes, cherries, plums, eggplants, and caulifl ower (22–25). Anthocyanins and their derivatives are widely used as natural pigments and food additives. Crop scientists at the Agricul- tural Research Institute (ARI), Chia-Yi Agricultural Experiment Station, have been working on a sweet potato breeding program to create new cultivars. A newly cultivated purple sweet potato, named Tainung No. 73 (TNG73), has reddish-purple root fl esh. TNG73 is the fi rst sweet potato variety developed by a Taiwanese breeder with high an- thocyanin content. It was proven that the anthocyanins extracted from purple sweet po- tato have increased stability during thermal treatments (26). Anthocyanins can be directly extracted from purple sweet potato using acidic ethanol and acidic water. Although new extraction methods have been developed, acidic-solvent extraction is still preferred due to its relatively low cost. The main goal of this study was to incorporate TNG73 purple sweet potato extract into a cosmetic cream and analyze the infl uence of anthocyanins on the apparent UV protec- tion. The DPPH radical scavenging activity, total phenolic content, and the reducing ability of the anthocyanin extracts were also carefully evaluated. MATERIALS AND METHODS TNG73 purple sweet potatoes provided by the Agricultural Research Institute (ARI), Chia-Yi Agricultural Experiment Station, Taiwan, were used as the anthocyanin source in this study. TNG73 was extracted with either acidic ethanol (1.5 N HCl in ethanol 15:85 (v/v)) or acidic water (1.5 N HCl in water 15:85 (v/v)) to provide anthocyanin solutions. The extracted anthocyanin solutions were purifi ed using resins, then freeze-dried to col- lect the reddish-purple powders. The total anthocyanin content, expressed as cyanidin- 3-glucoside, was determined by the following equation (27): ε − × × × 1.0 4.5 ( ) Total anthocyanin content (mg/l)= pH pH A A MW DF1000× d (1)