A novel characteristic of salicylate UV absorbers: suppression of diethylhexyl 2,6-naphthalate (Corapan TQ)-photosensitized singlet oxygen generation

2-Ethylhexyl salicylate (EHS, octyl salicylate) and homomenthyl salicylate (HMS, homosalate) are UV-B absorbers used in cosmetic sunscreens. Diethylhexyl 2,6-naphthalate (DEHN, tradename Corapan TQ) used as a mildly effective photostabilizer for labile butylmethoxydibenzoylmethane, the most widely used UV-A absorber, is an efficient singlet oxygen photosensitizer with a high quantum yield of singlet oxygen generation Φ Δ = 0.44 in ethanol. The effects of EHS, HMS, l -ascorbic acid (AA, vitamin C), 3- O -ethyl- l -ascorbic acid (3-EtAA) and Trolox (TX, a water-soluble analogue of vitamin E) on DEHN-photosensitized singlet oxygen generation have been studied through measurements of time-resolved near-infrared phosphorescence in ethanol. These compounds suppress DEHN-photosensitized singlet oxygen generation. 40% of Φ Δ is decreased by adding 32 mmol dm −3 EHS or HMS. Φ Δ is decreased to a half by adding 3.0 mmol dm −3 TX. Fluorescence and transient absorption measurements suggest that the observed suppression is due to the quenching of the excited singlet state of DEHN by EHS, HMS, AA and 3-EtAA. These compounds do not quench the excited triplet state of DEHN. On the other hand, TX quenches both the excited singlet and triplet states of DEHN. It was shown that these UV-B absorbers have a novel characteristic as a suppressor of photosensitized singlet oxygen generation. Suppressing singlet oxygen generation is an important method for the prevention of skin damage. To the best of our knowledge, this is the first report on the suppression of photosensitized singlet oxygen generation by UV absorbing molecules. 40% of the quantum yield of DEHN-photosensitized singlet oxygen generation is decreased by adding 32 mmol dm −3 EHS.