Department of Chemistry, Graduate School of Engineering Science, Yokohama National University, 240-8501, Tokiwadai, Hodogaya-ku, Yokohama, Japan.
Photochem Photobiol Sci. 2020 Jul 15;19(7):913-919. doi: 10.1039/d0pp00023j.
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.
Menthyl anthranilate (MA, 商标名 meradimate) 是一种 UV-A 吸收剂。基态分子氧与 MA 的长寿命三重态之间的相互作用通过能量转移产生单线态氧。在空气饱和的乙醇中，单线态氧的生成量子产率为 0.12。已经在乙醇中测量了 MA 光敏化产生的单线态氧的近红外磷光的动力学轨迹，在不存在和存在 Trolox（维生素 E 的水溶性类似物和单线态氧的猝灭剂）和 α-生育酚（维生素 E，一种天然抗氧化剂）的情况下。荧光和瞬态吸收测量表明 Trolox 和 α-生育酚猝灭 MA 的最低激发单线态和三线态。结果，Trolox 和 α-生育酚抑制 MA 光敏化的单线态氧生成。不仅单线态氧的猝灭，而且单线态氧生成的抑制都是 Trolox 和 α-生育酚对 MA 的抗氧化性能的机制。α-生育酚在用作油溶性紫外线吸收剂溶剂的异十二烷中抑制 MA 光敏化单线态氧生成的能力接近于在乙醇中的能力。抑制防晒霜光敏化单线态氧生成是安全化妆品防晒霜配方的重要方法。
