Portal de Periódicos da CAPES

[27] Analysis of geometrically isomeric vitamin A compounds

1980; Academic Press; Linguagem: Inglês

10.1016/s0076-6879(80)67029-3

1557-7988

G.W.T. Groenendijk, P.A.A. Jansen, S.L. Bonting, F.J.M. Daemen,

Retinal Development and Disorders

This chapter explains the analysis of geometrically isomeric vitamin A compounds. Geometric isomers of vitamin A compounds play an essential role in the visual process. Both the 11-cis and all-trans configurations of vitamin A aldehyde (retinal, retinaldehyde), vitamin A alcohol (retinol), and vitamin A ester (retinyl ester) have been shown to occur in the visual cycle. In different systems used in this study, it is found that the retinols move slower than the retinals, whereas the retinyl esters move relatively close to the solvent front, even in almost pure hexane. With increasing polarity of the elution solvent, the mobility of all vitamin A compounds increases. The data obtained indicate that the common geometric isomers of the vitamin A compounds can in principle be separated by thin-layer chromatography. In general, the method works satisfactorily when a single geometric isomer is to be identified. However, with retinyl esters and with 11-cis and 13-cis retinal, no reliable separation seems possible. In the latter case, modification with hydroxylamine to retinal oximes appeared to facilitate their identification, because each isomer gives two spots, a syn- and an anti-form. It was shown by means of NMR spectroscopy that the slower moving spots represent the anti-isomers.