Evaluating\nthe Fluorescence Quenching of Troxerutin\nfor Commercial UV Sunscreen Filters

2-Phenylbenzimidazole-5-sulfonic acid (PBSA) and disodium\nphenyl\ndibenzimidazole tetrasulfonate (DPDT) are commercially available ultraviolet\n(UV) sunscreen filters that are known to undergo radiative relaxation\nfollowing the absorption of UV light. The release of high-energy photons\nfrom this relaxation can be detrimental to human health; therefore,\nfluorescence quenchers need to be incorporated in commercial sunscreen\nformulations containing PBSA or DPDT. Troxerutin is a fluorescence\nquencher utilized for DPDT commercially. Here, its ability to quench\nthe fluorescence of both PBSA and DPDT is evaluated using a dual-pronged\napproach by breaking down the multicomponent problem into its constituent\nparts. First, PBSA and DPDT’s femtosecond to nanosecond photodynamics\nare uncovered in solution and on the surface of a human skin mimic\nto ascertain a benchmark. Second, these results are compared to their\nphotodynamics in the presence of troxerutin. A significant reduction\nin the fluorescence lifetime is observed for both PBSA and DPDT on\na human skin mimic with the addition of troxerutin, which is attributed\nto a Dexter energy transfer (DET) or Förster resonance energy\ntransfer (FRET) quenching mechanism. This finding demonstrates the\nhitherto unseen fluorescence quenching mechanism of troxerutin on\na human skin mimic and its role in quenching the fluorescence of commercial\nUV sunscreen filters through a DET or FRET mechanism.