In vivo and in vitro evaluation of phytic acid as topical antioxidant

The use of locally applied antioxidants has been shown as an effective approach for the skin photo-protection. In a previous investigation we have demonstrated that phytic acid (PA), a component of most cereal grains and seeds, is able to reduce the erythemal response to UV-exposure when applied 30 minutes before UV-radiation. PA was used at 0.5 % concentration in a O/W emulsion containing also inositol at 2.0 % concentration. Before the test and 24 and 48 h after irradiation the extent of the reaction was evaluated with visual scoring as well as with instrumental measurement of skin redness,TEWL and hydration. In this study we have evaluated the ability of PA to protect human keratinocytes cultures against UV exposure. PA extracted from the rice bran was used at 100 μM. The experiments were performed also on ascorbic acid at the same concentration. Human HaCaT keratinocytes were grown in 3,5 cm2 plates containing complete medium (DMEM with 10% fetal calf serum). Thirty minutes before UV radiation, medium was removed and replaced by PBS with or without the antioxidants. The light source was a 150-Watt xenon arc solar simulator. Series of cultures were irradiated with scalar UV-doses ranging from 11,56 to 92,48 mJ/cm2. After irradiation PBS solution with or without antioxidants was removed and replaced with fresh medium. The antioxidant activity was evaluated by MTT assay after 24 hrs. The solutions containing the active ingredients demonstrated a protective ability stronger than that of the controls. Particularly PA showed an ability to protect the keratinocytes against UV damage more pronounced than vitamin C. Our investigation has proved that phytic acid is able to protect human keratinocytes against UV radiation. This means that epidermal cells are involved in the PA-mediated photoprotection in vivo and represents a fur-ther support for the use of PA as topical photoprotective agent