A UVA filter (4-tert-butyl-4′-methoxydibenzoylmethane): photoprotection reflects photophysical properties

Abstract A dibenzoylmethane-based UVA sunscreen, 4- tert -butyl-4′-methoxydibenzoylmethane has been shown to protect human lymphoid cells efficiently when present in high concentration (10 −2 M). The molecular mechanisms of this behaviour are proposed to be related to a mixture based on enol-transient-keto forms. At much lower sunscreen concentrations (10 −5 –10 −10 M) a switch from UVA to UVB protection is observed. This supports the theory of a conversion to a transient species absorbing in the UVB.