Trennung und Charakterisierung von β‐Carotin‐Isomeren

Separation and Characterization of the cis ‐Isomers of β,β‐Carotene A stable HPLC. system is described allowing the excellent separation of 11 different cis ‐isomers of β,β‐carotene from the all‐ trans compound. The system is applied to the analysis of cis/trans mixtures obtained from plant extracts and by photoisomerization of the all‐ trans isomer. Al 2 O 3 is used as the stationary phase while hexane with controlled H 2 O content is utilized as the mobile phase. With the aid of the optimum conditions 8 sufficiently stable cis isomers were isolated and their structures shown to be the 9‐, 13‐ and 15‐ cis , the 9,9′‐, 9, 13‐, 9, 13′‐ and 13,13′‐di‐ cis and, tentatively, the 9,13,13′‐tri‐ cis β,β‐carotenes by application of 270‐MHz‐FT.‐ 1 H‐NMR. spectroscopy.