TEST FOR ANTIOXIDANT ACTIVITY 239 Zoom ZoomOut Trace fluLoscale flnnotate Print 8.58088 [Abs] 8.88888 8.8888 ........................... : ........................... : .......................... : ........................... • .......................... : : sec 188.88 Figure 1. Kinetic plot of the increase in absorbance at 600 nm over time. (-I•-): Vehicle formulation was 0.126 dA/min. (-(2)-): Antioxidant formulation was 0.011 dA/min. product, 0.7 mg is multiplied by 100 in order to determine that 0.07 gm of the cosmetic product is equivalent to 50% inhibition in this assay. In this way, relative measurements of effectiveness can be calculated and used for comparison to other products. Based on regression analysis from the standard curve and end-point assay analysis, the relative antioxidant activity concentration that was determined for this product was 52.7 nmoles/mg (+ SD 1.7) of material. In contrast the placebo contained only 11.4 nmoles/ mg (+ SD 1.2), although when compared to a blank, there appeared to be some background antioxidant activity by the formulation itself. These data are summarized in Figure 2. 40 20 lO blank vehicle vehicle + antioxidants Figure 2. Increase in the amount of nmoles/mg of antioxidant activity in cosmetic formulations as deter- mined by standard curve and end-point assay measurements.

240 JOURNAL OF COSMETIC SCIENCE DISCUSSION Antioxidants in skin care products have been found to be effective protectants against free radical-mediated oxidative damage in skin. Also, due to the rise in photodamage in an aging population, the topical application of cosmetic products that contain antioxi- dants has become an important area of research in skin care products. Thus, the need to measure the activity of antioxidants in a finished product is of critical importance. In this report we describe a novel and simple technique to quickly assess the relative antioxidant potential of whole product formulations. Additionally, it can be utilized for stability studies and, since the chromogen develops in the visible region, perhaps even a quali- tative result can be obtained by workers in the field who lack spectrophotometers but need to assay the antioxidant activity of a product. REFERENCES (1) B. A. Gilchrest, Skin and Aging Processes (CRC Press, Boca Raton, FL, 1989), pp. 97-116. (2) A. V. Benedetto, The environment and skin aging, Clin. Dermatol., 16, 129-139 (1998). (3) J. Fuchs and L. Packer, Eds., Oxidative Stress in Dermatology (Marcel Dekker, New York, 1993). (4) E. Pelle, D. Maes, G.A. Padulo, E-K. Kim, and W. P. Smith, An in vitro model to test relative antioxidant potential: Ultraviolet-induced lipid peroxidation in liposomes, Arch. Blochem. Biophys., 283, 234-24O (1990). (5) E. Pelle, N. Muizzuddin, T. Mammone, K. Marenus, and D. Maes, Protection against endogenous and UVB-induced oxidative damage in stratum corneum lipids by an antioxidant-containing cosmetic formulation, Photodermatol. Photoimm•nol. Photoreed., 15, 115-119 (1999).