A UVA filter (4-tert-butyl-4'-methoxydibenzoylmethane): Photoprotection reflects photophysical properties

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.