Effect of propylene glycol and ethanol on the UVB-induced peroxidation of linoleic acid and lipids of porcine skin, in the presence of different TiO₂ specimens

Titanium dioxide is a sunscreen pigment with photocatalytic activity. We studied the behavior of different TiO₂ specimens used in cosmetic products on the UVB-induced peroxidation of linoleic acid as model substrate and of porcine skin, at different pH values. Lipoperoxidation of linoleic acid occurred to a lower extent with the coated compared to the uncoated TiO₂, and it decreased at pH 7.0 compared to 4.0. The addition of organic additives such as propylene glycol and ethanol induced a significant reduction of the lipoperoxidation activity, particularly with the most reactive TiO₂ specimens. Similar results were obtained with the porcine skin.