Real time detection of reactions between radicals of lycopene and tocopherol homologues

Laser flash photolysis of lycopene in homogeneous chloroform solution together with tocopherol homologues results in rapid formation of the lycopene radical cation and slower formation of tocopheroxyl radicals. Time-resolved detection by absorption spectroscopy of decay of the lycopene radical cation, of formation of the tocopheroxyl radicals, and of bleaching of lycopene has shown that alpha-tocopherol is able to reduce the lycopene radical cation and thereby partially regenerate lycopene on a ms timescale. In contrast, lycopene is able to reduce the delta-tocopheroxyl radical, whereas an equilibrium exists between the lycopene radical cation and beta- or gamma-tocopherol. The relative stability of these antioxidant radicals is hence: alpha-tocopheroxyl > lycopene radical cation similar to beta-tocopheroxyl similar to gamma-tocopheroxyl > delta-tocopheroxyl.