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Suppression of menthyl anthranilate (UV-A sunscreen)-sensitized singlet oxygen generation by Trolox and α-tocopherol

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Abstract

Menthyl anthranilate (MA, tradename meradimate) is a UV-A absorber. The interactions of ground-state molecular oxygen with the long-lived triplet state of MA produce singlet oxygen through energy transfer. The quantum yield of singlet oxygen generation is 0.12 in air-saturated ethanol. Kinetic traces of the near-IR phosphorescence of singlet oxygen generated by MA-photosensitization have been measured in the absence and presence of Trolox (a water-soluble analogue of vitamin E and a quencher of singlet oxygen) and α-tocopherol (vitamin E, a natural antioxidant) in ethanol. Fluorescence and transient absorption measurements suggest that Trolox and α-tocopherol quench the lowest excited singlet and triplet states of MA. As a result, Trolox and α-tocopherol suppress MA-photosensitized singlet oxygen generation. Not only the quenching of singlet oxygen but also the suppression of singlet oxygen generation is the mechanism of antioxidant properties of Trolox and α-tocopherol for MA. The ability of α-tocopherol to suppress the MA-photosensitized singlet oxygen generation in isododecane, used as a solvent for an oil-soluble UV absorber, is close to that in ethanol. Suppression of sunscreen-photosensitized singlet oxygen generation is an important method for the formulation of safe cosmetic sunscreens.

Graphical abstract: Suppression of menthyl anthranilate (UV-A sunscreen)-sensitized singlet oxygen generation by Trolox and α-tocopherol

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Supplementary files

Article information


Submitted
28 Jan 2020
Accepted
28 May 2020
First published
29 May 2020

Photochem. Photobiol. Sci., 2020, Advance Article
Article type
Paper

Suppression of menthyl anthranilate (UV-A sunscreen)-sensitized singlet oxygen generation by Trolox and α-tocopherol

S. Kitasaka, M. Yagi and A. Kikuchi, Photochem. Photobiol. Sci., 2020, Advance Article , DOI: 10.1039/D0PP00023J

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