PHOTOOXIDATIONS AND PHOTOSENSITIZED OXIDATIONS OF VITAMIN-A AND ITS PALMITATE ESTER

Photo-oxidation of vitamin A with UV light gave retinal and a mixture of epoxy derivatives of the vitamin; however, vitamin A palmitate gave anhydrovitamin A and fragments derived from cleavage of the side-chai n double bonds. The rate of oxidation and the type of oxidation produc ts produced by photosensitized oxidation of vitamin A and its palmitat e ester with visible light depended on the sensitizer. The vitamin gav e epoxides, peroxides and cleavage products, while the palmitate gave mainly cleavage products. Some of the oxidation products were isolated and identified; many others were too unstable and decomposed during w ork-up. The photosensitized processes are considered to be initiated b y singlet oxygen.