AN IN VITRO METHOD TO EVALUATE THE ANTIOXIDANT EFFICACY OF TOPICAL FORMULATIONS.

We have developed a method of evaluating antioxidant efficacy in vitro using a three dimensional epidermal construct (MatTek EPI-100, MatTek Corpora-tion, Ashland, MA) which contains a well defined stratum corneum with a lipid profile similar to human skin. The EPI-100 allows direct application of test products to the stratum corneum. This method was used to evaluate the antioxidant potential of a new alpha hydroxy acid (AHA) lotion with vitamins E, C, and A. Two indicators of oxidative stress, lipid hydroperoxides and prostaglandin E-2 (PGE-2), were measured using three distinct techniques to assess antioxidant activity. Oxidative stress was induced in the tissue system by irradiating with UVA/B irradiation (1.5 and 3.0 MED/hr/cm2) using a solar simulator. After irradiation, test material was applied and the tissues were incubated at 37 degrees C in 5% CO2 for 2 hours for lipid hydroperoxides or overnight for PGE-2. The lipid hydroperoxides were then extracted from the tissues and their levels quantitated by HPLC post column chemiluminescence. The PGE-2 levels were quantified from the media underneath the tissue substrate. The ratio of lipid hydroperoxides to total phospholipids decreased from 31.7 (3 MED irradiated control) to 15.9 for irradiated tissue treated with the AHA lotion. Cellular antioxidant protection was also indicated by a decrease in PGE-2 level from 18.3 K (pg/ml) for the 1.5 MED irradiated control, to 7.1 K (pg/ml) for the irradiated tissue treated with the AHA lotion buffered to a neutral pH. This test method simulates in vivo use conditions, and indicates that the test AHA formulation provides antioxidant protection.

AHA, Alpha hydroxy acids, Antioxidant potential, Antioxidants, Ascorbic acid, Endpoints, Prostaglandin E-2 (PGE-2), Epi-100, EpiDerm, Lipids, ceramides, PGE-2, Phototoxicity, Profiles/Analyses, Prostaglandin E-2, Sun screens, Tocopherol, Tocopheryl acetate, UVA, UVB, Ultra-violet radiation (UV), Vitamin A