Singlet molecular oxygen quenching by the antioxidant dimethylmethoxy chromanol in solution and in ex vivo porcine skin

Singlet‐oxygen is a non‐radical reactive oxygen species believed to play a major role in many photooxidation processes in connection with diverse photo‐biological processes such as skin ageing or photocarcinogenesis. Dimethylmethoxy chromanol (3,4‐dihydro‐6‐hydroxy‐2,2‐dimethyl‐7‐methoxy‐1(2H)‐benzopyran) is a potent antioxidant used in cosmetic and pharmaceutical formulations. We have assessed the singlet oxygen quenching ability of dimethylmethoxy chromanol, by monitoring the near‐IR phosphorescence of singlet‐oxygen in solution and in ex vivo porcine skin samples. Dimethylmethoxy chromanol quenches singlet oxygen with a rate constant of (1.3 ± 0.1) × 10⁸ M^?1 s^?1 in solution. Consistent with this, a clear reduction in the singlet oxygen lifetime and emission intensity was observed when ex vivo porcine skin samples were treated with dimethylmethoxy chromanol.