Lycopene is more potent than beta carotene in the neutralization of singlet oxygen: Role of energy transfer probed by ultrafast Raman spectroscopy

Energy transfer processes between beta carotene, lycopene, and singlet oxygen (¹O₂) have been studied by ultrafast Raman spectroscopy. Our experimental results demonstrate that during the neutralization of singlet oxygen by beta carotene the excitation energy of singlet oxygen is transferred directly to the first excited electronic state S₁ of beta carotene. In contrast, the excitation energy of singlet oxygen is transferred directly to the ground excited vibronic state S0 of lycopene. Our data not only provide the first direct experimental elucidation of energy transfer processes in such important biological systems but also help explain why lycopene is a more potent antioxidant than beta carotene in the neutralization of singlet oxygen.