Riboflavin photosensitized singlet oxygen oxidation of vitamin D

Samples containing various levels of vitamin D and riboflavin, with and without ascorbic acid or a-tocopherol were prepared in a model system. Samples were stored in the light or in the dark at 45 degrees C for up to 8 h. Headspace oxygen was determined by gas chromatography with thermal conductivity detection. Oxidation of vitamin D was not observed In samples without riboflavin stored in the light nor in samples with riboflavin stored in the dark. Vitamin D with riboflavin was oxidized under right. alpha-Tocopherol quenched singlet oxygen at a rate of 2.52 x 10(8) M-1 sec(-1), whereas ascorbic acid quenched singlet oxygen at a rate of 2.23 x 10(7) M-1 Sec(-1).