Riboflavin‐photosensitized singlet oxygen oxidation product of vitamin D 2

The riboflavin‐photosensitized singlet oxygen oxidation of vitamin D 2 in a model system of 12% water and 88% acetone was studied to understand the possible oxidation of fortified vitamin D in milk. Only the samples containing vitamin D 2 and riboflavin under light storage showed two new peaks in the HPLC chromatogram, indicating that singlet oxygen oxidation of vitamin D 2 had occurred. UV analysis indicated that a new compound was formed from the reaction of the triene of vitamin D 2 with oxygen. The mass spectrum showed that one of the two compounds had a molecular ion at m/z =412, which was an increase of the mass of vitamin D 2 by the mass of exactly one oxygen. The IR spectrum suggested the presence of a hydroxyl group and no carbonyl group in the product. The combned information from UV, MS, and FTIR spectra and the chemical mechanisms of singlet oxygen oxidation of vitamin D 2 indicated that a 5,6‐epoxide of vitamin D 2 was formed from vitamin D 2 in the presence of riboflavin under light.