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A Blocked Diketo Form of Avobenzone: Photostability, Photosensitizing Properties and Triplet Quenching by a Triazine‐derived UVB‐filter
Author(s) -
Paris Cecilia,
LhiaubetVallet Virginie,
Jiménez Oscar,
Trullas Carles,
Miranda Miguel Ángel
Publication year - 2009
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.2008.00414.x
Subject(s) - photochemistry , chemistry , triplet state , photodegradation , quenching (fluorescence) , uv filter , flash photolysis , excited state , fluorescence , triazine , organic chemistry , kinetics , molecule , photocatalysis , reaction rate constant , physics , optics , catalysis , quantum mechanics , nuclear physics
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 β‐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.