ON THE OPTICAL SPECTRA OF SOLID FILMS OF RETINYL POLYENES. ISOMERIZATION DURING THE AUTOXIDATION?

Abstract— The UV spectra of solid amorphous films of all-trans retinyl polyenes. i. e. retinyl acetate, retinyl palmitate, axerophtene and retinal, on supports are investigated. It is shown that in the absence of oxygen the spectra of the films do not change at room temperature; in the presence of O₂ the fast oxidation of the polyenes occurs which in the case of retinol esters and axerophtene is accompanied by the shift of the absorption maxima to the shorter wavelengths. Consequently, the interpretation of blue shift of UV spectra of retinyl polyene films given by Hotchandani and Leblanc (1976) is incorrect. The formation of the only compound is shown to occur during the first stage of the oxidation of retinyl acetate and retinyl palmitate films. Proceeding from IR spectra of oxidized films the compound is assigned to the corresponding 11-cis isomer.