A Blocked Diketo Form of Avobenzone: Photostability, Photosensitizing Properties and Triplet Quenching by a Triazine‐derived UVB‐filter

Abstract

Novel sunscreens are required providing active protection in the UVA and UVB regions. On the other hand, there is an increasing concern about the photosafety of UV filters, as some of them are not sufficiently photostable. Avobenzone is one of the most frequently employed sunscreen ingredients, but it has been reported to partially decompose after irradiation. In the present work, photophysical and photochemical studies on a methylated avobenzone-derivative have shown that the diketo form is responsible for photodegradation. A transient absorption was observed at 380 nm after laser flash photolysis excitation at 308 nm. It was assigned to the triplet excited state of the diketo form, as inferred from quenching by oxygen and b-carotene. This transient also interacted with key building blocks of biomolecules by triplet-triplet energy transfer (in the case of thymidine) or electron transfer processes (for 2¢-deoxyguanosine, tryptophan and tyrosine). Irradiation of the avobenzone derivative in the presence of a triazine UV-B filter (E-35852) diminished the undesirable effects of the compound by an efficient quenching of the triplet excited state. Thus, sunscreen formulations including triplet quenchers could provide effective protection from the potential phototoxic and photoallergic effects derived from poor photostability of avobenzone.

Combination of retinyl palmitate and UV-filters: Phototoxic risk assessment based on photostability and in vitro and in vivo phototoxicity assays

“…However, avobenzone photoprotective effects are reduced when the compound is under UV radiation due to tautomerization, fragmentation and generation of photoproducts (Damiani et al, 2006;Paris et al, 2009;Schwack and Rudolph, 1995). The difficulty to obtain broad spectrum sunscreens containing avobenzone justifies the search by the scientific community and the Research & Development centers in the industry for new UV-filters and molecules able to improve avobenzone photostability.…”

Filter-filter interactions. Photostabilization, triplet quenching and reactivity with singlet oxygen

“…8 More recently, interaction between the keto form of BM-DBM and a new broadband triazine filter, namely E-35852, has been considered both from a photophysical and a photochemical point of view. 11 In this study, the efficient triplet state quenching ability of the triazine derivative has been correlated with its photostabilizing properties.…”

Cyanobacterial metabolites as a source of sunscreens and moisturizers: a comparison with current synthetic compounds

“…A multicentre photopatch test study on 1031 patients across 12 European countries indicated that this oil-soluble UV filter, along with OCR and benzophenone-3, was the most frequent sunscreen absorber that led to photoallergic contact dermatitis (Kerr et al, 2012). The reactive nature of BM-DBM has been reported by several groups, with Paris et al (2009) finding that UV irradiation of BM-DBM results in an increase in the keto isomer and reactivity with key biomolecules such as nucleosides, tryptophan and tyrosine. Similarly, Stiefel & Schwack (2013) showed that the carbonyl group of BM-DBM and other related UV filters have a high tendency to form adducts with free amino acids or peptides, and suggest that such reactions can occur within the skin layer.…”