Phenols from olive mill wastewater and other natural antioxidants as UV filters in sunscreens

Antioxidants are frequently used in sunscreen formulations to complement UV filter photo-protection of synthetic compounds. The current study investigates the application of phenols (recovered from olive mill wastewater) as UV filter in comparison to other natural antioxidants (ascorbic acid and α-tocopherol). The spectrums (220-400 nm) of all assayed antioxidants alone or in combination with synthetic sunscreen agents (Benzophenone-3, Uvinol A, Tinosorb M, TiO2, Octocrylene, OMC and OC-PABA) were obtained and the respective in vitro SPF of the solutions was calculated. Olive phenols were more active UV filters in a broader region of UVB and UVA compared to ascorbic acid and α-tocopherol. However, they were not so active against synthetic compounds especially in the UVB region. The fact that olive phenols absorb in both UV regions of interest allow their application as UV-protection booster in particular cases, e.g. to enhance the absorption of Tinosorb M and Uvinul A solutions in the UVB region and to increase the absorption of Octocrylene, OD-PABA and OMC in the UVA region.